Omega Owners Forum
Chat Area => General Car Chat => Topic started by: Auto Addict on 02 August 2017, 12:55:47
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"Current MB's use the alternator differently to older models.
Most have variable output alternators to help reduce fuel consumption.
In most cases once a battery is fully charged they hold battery voltage between 12.6v-13v to reduce fuel consumption. If you apply the brakes then the voltage may increase to as much as 15v to recoup the "free" energy, if accelerating then it may drop as low as 12v. The engine ECU determines what voltage it wants to maintain at the battery based on load/temps/electrical consumers etc.
All Bluefficiency models have this, and most other current models."
So, the leisure battery on my caravan may not always be at full charge, if I read the above correctly, as it will be balanced to the car battery.
If this is true, is there a way around the problem.
Car electric experts your thoughts please.
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you know there is ;)
https://caravanchronicles.com/2017/07/21/is-a-euro-6-engine-killing-your-leisure-battery/ :y
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
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you know there is ;)
https://caravanchronicles.com/2017/07/21/is-a-euro-6-engine-killing-your-leisure-battery/ :y
Well yes, apart from it's out of stock, and no-one knows the price of it.
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
Need it fully charged to run the fridge whilst on the move, and again, to use the mover when I get home, as it's too tight a turn to reverse into it's parking slot.
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
Need it fully charged to run the fridge whilst on the move, and again, to use the mover when I get home, as it's too tight a turn to reverse into it's parking slot.
The fridge should be run from the vehicle battery when on the move :y
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
Need it fully charged to run the fridge whilst on the move, and again, to use the mover when I get home, as it's too tight a turn to reverse into it's parking slot.
The fridge should be run from the vehicle battery when on the move :y
Agreed, but my point is the leisure battery will only be maintained at the same voltage as the car battery, i.e. 80%.
Not enough to use the mover.
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
Need it fully charged to run the fridge whilst on the move, and again, to use the mover when I get home, as it's too tight a turn to reverse into it's parking slot.
The fridge should be run from the vehicle battery when on the move :y
Agreed, but my point is the leisure battery will only be maintained at the same voltage as the car battery, i.e. 80%.
Not enough to use the mover.
are you sure about the 80%? the caravan battery is in parallel with the car battery so should end up in the same state of charge as the car batt. are euro 6 cars in normal use really leaving their battery at only 80% charge? if so it's good news for battery manufacturers. :o
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
Need it fully charged to run the fridge whilst on the move, and again, to use the mover when I get home, as it's too tight a turn to reverse into it's parking slot.
The fridge should be run from the vehicle battery when on the move :y
Agreed, but my point is the leisure battery will only be maintained at the same voltage as the car battery, i.e. 80%.
Not enough to use the mover.
are you sure about the 80%? the caravan battery is in parallel with the car battery so should end up in the same state of charge as the car batt. are euro 6 cars in normal use really leaving their battery at only 80% charge? if so it's good news for battery manufacturers. :o
Apparently so ... reason is, I believe, to allow "space" for the regenerative braking to put the elecktrickery it makes .. so the alternators "backoff" saving power (fuel) and the braking tops up the battery instead ..... :(
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
Need it fully charged to run the fridge whilst on the move, and again, to use the mover when I get home, as it's too tight a turn to reverse into it's parking slot.
The fridge should be run from the vehicle battery when on the move :y
Agreed, but my point is the leisure battery will only be maintained at the same voltage as the car battery, i.e. 80%.
Not enough to use the mover.
Not if you use a voltage sensing relay. This will connect the leisure battery only when the alternator is kicking out a decent voltage, so the battery will be charged when the car decides to pump charge into the vehicle battery, and left standing when it isn't.
You would need to arrange for the fridge to get power from the car whenever the engine is running, however.
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
Need it fully charged to run the fridge whilst on the move, and again, to use the mover when I get home, as it's too tight a turn to reverse into it's parking slot.
The fridge should be run from the vehicle battery when on the move :y
Agreed, but my point is the leisure battery will only be maintained at the same voltage as the car battery, i.e. 80%.
Not enough to use the mover.
Not if you use a voltage sensing relay. This will connect the leisure battery only when the alternator is kicking out a decent voltage, so the battery will be charged when the car decides to pump charge into the vehicle battery, and left standing when it isn't.
You would need to arrange for the fridge to get power from the car whenever the engine is running, however.
If you read some of the article I linked to, the gist of it is that the smart alternator sees the leisure battery's voltage & tries to balance it out with the car's battery. I think a VSR is too simplistic ......
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If you read some of the article I linked to, the gist of it is that the smart alternator sees the leisure battery's voltage & tries to balance it out with the car's battery. I think a VSR is too simplistic ......
Yes, but I don't think he's 100% correct. The two batteries' states of charge will track each other if they are simply in parallel all the time, of course. With a VSR, it won't pull in while the car's alternator is allowing the vehicle battery to discharge, because the terminal voltage will sink too low, so the leisure battery won't discharge.
During periods of regenerative braking or when the car decides the battery has got a bit low, the voltage will rise, the relay will pull in and the leisure battery will receive charge. The car will probably monitor charging current as an additional indicator of the state of the battery, so it may well see the extra current drain into the leisure battery and decide extra charging is required.
Once it's happy with the state of charge of the battery, or the opportunity for regenerative charging has passed, the voltage will drop once again, the leisure battery will be disconnected and it will retain its' new charge level. I think it would work.
As an alternative, however, a charge controller that can boost the car's output voltage and inherently blocks any discharge path back from the leisure battery would also do the job.
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Back in the days before this alternator complexity took hold, people used two fat diodes in a "bean tin" to split the charge between the two batteries; the diode voltage drop was hardly significant and the laisure battery could not discharge to the car.....happy, simple days! ;D
Ron.
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Back in the days before this alternator complexity took hold, people used two fat diodes in a "bean tin" to split the charge between the two batteries; the diode voltage drop was hardly significant and the laisure battery could not discharge to the car.....happy, simple days! ;D
Ron.
Yep, before they decided that it's preferable to shorten the life of the battery, starter, alternator, etc. with all the environmental consequences of their manufacture and disposal, to achieve an extra femtomile-per-gallon. ::)
A bit like the recent U-turn on speed humps, really, give it a few years and we'll have revolutionary new vehicles that save the planet by not stalling at every set of traffic lights. ;D
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If you read some of the article I linked to, the gist of it is that the smart alternator sees the leisure battery's voltage & tries to balance it out with the car's battery. I think a VSR is too simplistic ......
Yes, but I don't think he's 100% correct. The two batteries' states of charge will track each other if they are simply in parallel all the time, of course. With a VSR, it won't pull in while the car's alternator is allowing the vehicle battery to discharge, because the terminal voltage will sink too low, so the leisure battery won't discharge.
During periods of regenerative braking or when the car decides the battery has got a bit low, the voltage will rise, the relay will pull in and the leisure battery will receive charge. The car will probably monitor charging current as an additional indicator of the state of the battery, so it may well see the extra current drain into the leisure battery and decide extra charging is required.
Once it's happy with the state of charge of the battery, or the opportunity for regenerative charging has passed, the voltage will drop once again, the leisure battery will be disconnected and it will retain its' new charge level. I think it would work.
As an alternative, however, a charge controller that can boost the car's output voltage and inherently blocks any discharge path back from the leisure battery would also do the job.
I don't think that would solve the fridge problem when running on 12v, as I believe, the fridge only works when the alternator is charging.
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If you use a voltage sensing relay to switch it in, it should just get disconnected when the car's battery is not being charged and it means it won't be discharged by the car's systems. That behaviour is probably OK unless you're relying on it to be charged heavily while on the move.
Need it fully charged to run the fridge whilst on the move, and again, to use the mover when I get home, as it's too tight a turn to reverse into it's parking slot.
The fridge should be run from the vehicle battery when on the move :y
Agreed, but my point is the leisure battery will only be maintained at the same voltage as the car battery, i.e. 80%.
Not enough to use the mover.
are you sure about the 80%? the caravan battery is in parallel with the car battery so should end up in the same state of charge as the car batt. are euro 6 cars in normal use really leaving their battery at only 80% charge? if so it's good news for battery manufacturers. :o
Apparently so ... reason is, I believe, to allow "space" for the regenerative braking to put the elecktrickery it makes .. so the alternators "backoff" saving power (fuel) and the braking tops up the battery instead ..... :(
yes i got that. it's simply the car telling the alternator when it's braking and the alternator then putting max load on the belt. no electicity actually comes directly from the brakes/wheels. I can see the car would do that when loads are on, i.e. supply the load more from the alternator while braking and the battery when not. i don't see the need to not keep the battery 100% charged though.
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I don't think that would solve the fridge problem when running on 12v, as I believe, the fridge only works when the alternator is charging.
The fridge might struggle if it is driven by the VSR, as it might not be "on" for a sufficient proportion of the time to maintain temperature. In that case, it would need to be controlled by an ignition switched feed, I think.
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i think there may be a misunderstanding here. regenerative braking to my mind means an electric car getting amps by using the electric motors to slow the car. in a fossil fuelled euro 6 car surely all it means is the alternator maxes its load on the fan belt when the car is braking and outputs high amps to the battery and any other electrical load needing it. fossil euro 6 cars have no other source of amps than the alternator and the battery, i.e. they have no electric motors driving/taking energy from the wheels.
i don't think euro 6 cars would deliberately run with the battery off charge (i.e. below 12.75V). has anyone with such a car done a voltage reading while running?
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Is there any room to fit a second, conventional, alternator to power the trailer?
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Manufacturer specific tow electrics should disable the 'smart' part of the smart alternator when it senses that the caravan is plugged in. It also disables the stop start to maintain the battery power for the fridge and the Al-ko Trailer Control (ATC).
Assume yours is not manufacturer specific towbar and electrics so maybe a voltage booster within the van may work, but fitting one of those may come close to buying the specific electrics pack. :-\
Alternatively, always tow with your lights on. :)
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i think there may be a misunderstanding here. regenerative braking to my mind means an electric car getting amps by using the electric motors to slow the car. in a fossil fuelled euro 6 car surely all it means is the alternator maxes its load on the fan belt when the car is braking and outputs high amps to the battery and any other electrical load needing it. fossil euro 6 cars have no other source of amps than the alternator and the battery, i.e. they have no electric motors driving/taking energy from the wheels.
i don't think euro 6 cars would deliberately run with the battery off charge (i.e. below 12.75V). has anyone with such a car done a voltage reading while running?
Yes, it's simply offsetting the load on the alternator until such time as it comes "for free", such as when engine braking is in use. In order to achieve this you need to maintain the battery in a state of partial discharge so that it is able to take advantage of such opportunities as they arise, hence, in the normal scheme of things, it's maintained at less than 100% fully charged.
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i think there may be a misunderstanding here. regenerative braking to my mind means an electric car getting amps by using the electric motors to slow the car. in a fossil fuelled euro 6 car surely all it means is the alternator maxes its load on the fan belt when the car is braking and outputs high amps to the battery and any other electrical load needing it. fossil euro 6 cars have no other source of amps than the alternator and the battery, i.e. they have no electric motors driving/taking energy from the wheels.
i don't think euro 6 cars would deliberately run with the battery off charge (i.e. below 12.75V). has anyone with such a car done a voltage reading while running?
Yes, it's simply offsetting the load on the alternator until such time as it comes "for free", such as when engine braking is in use. In order to achieve this you need to maintain the battery in a state of partial discharge so that it is able to take advantage of such opportunities as they arise, hence, in the normal scheme of things, it's maintained at less than 100% fully charged.
yes but you could still keep the battery at full charge and use the surplus amps to power everything else . if euro 6 cars don't do that then the battery will inevitably be left at less than full charge, resulting in early replacement.
i suspect euro 6 cars do leave their batteries fully charged and claims they don't may be marketing hype to sell unnecessary devices. OP where is your opening quote from? i can't see any mention on http://techcenter.mercedes-benz.com/en/blueefficiency/detail.html
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yes but you could still keep the battery at full charge and use the surplus amps to power everything else .
That's exactly what a conventional alternator does. Floating the battery at 13.8-14.4 V = keeping it fully charged and powering everything else from the alternator - all of the time the engine is running.
What a "smart" alternator does is to allow the engine ECU to reduce this voltage to perhaps 12.5V during cruising and acceleration conditions. Not low enough to seriously deplete the battery, but low enough that the battery will take no charge whatsoever unless it's pretty flat and, if it's fully charged, it will supply the car electrical loads. When braking, the voltage can be raised higher than the normal alternator output, to perhaps 15 volts or so, rapidly charging the battery and taking over all electrical load.
Don't forget that such a vehicle will probably be cursed with "stop-start" technology, so the loads on the battery are going to be quite high during normal driving as the battery repeatedly starts the engine and runs the accessories while the engine is stopped. By only replenishing such loads when the car is braking or when the battery does get low enough to cause concern, you save a little fuel.
Granted, the battery is going to keep getting cycled between partially discharged and fully charged, which will shorten its life, but since when have environmentalists been able to see the big picture? ;)
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And the silly Jag system periodically purposely discharges the battery a fair way to test it. Because that is going to be contusive to battery longevity, isn't it.
Bloody do-gooders. The cull needs to start, as silliness is taking over.
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yes but you could still keep the battery at full charge and use the surplus amps to power everything else .
That's exactly what a conventional alternator does. Floating the battery at 13.8-14.4 V = keeping it fully charged and powering everything else from the alternator - all of the time the engine is running.
no i meant at full charge i.e. 12.75V not on charge (13.8-14.4V) which agreed is what a conventional set up does.
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Manufacturer specific tow electrics should disable the 'smart' part of the smart alternator when it senses that the caravan is plugged in. It also disables the stop start to maintain the battery power for the fridge and the Al-ko Trailer Control (ATC).
Assume yours is not manufacturer specific towbar and electrics so maybe a voltage booster within the van may work, but fitting one of those may come close to buying the specific electrics pack. :-\
Alternatively, always tow with your lights on. :)
That makes sense for such cars.....id imagine it would make the ecu to get the alternator to produce a high enough output all the time :y
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And the silly Jag system periodically purposely discharges the battery a fair way to test it. Because that is going to be contusive to battery longevity, isn't it.
Bloody do-gooders. The cull needs to start, as silliness is taking over.
I knew you're tempted, but don't tow a caravan with Jag ;)
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yes but you could still keep the battery at full charge and use the surplus amps to power everything else .
That's exactly what a conventional alternator does. Floating the battery at 13.8-14.4 V = keeping it fully charged and powering everything else from the alternator - all of the time the engine is running.
no i meant at full charge i.e. 12.75V not on charge (13.8-14.4V) which agreed is what a conventional set up does.
But unless you allow the battery to discharge to some extent, there is no benefit, because you're not shifting any of the load to a later period of braking. If the alternator is chucking out 12.75, it'll be powering all of the car's systems, the only difference is that it won't be charging the battery much if it's depleted.
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And the silly Jag system periodically purposely discharges the battery a fair way to test it. Because that is going to be contusive to battery longevity, isn't it.
Bloody do-gooders. The cull needs to start, as silliness is taking over.
I knew you're tempted, but don't tow a caravan with Jag ;)
Oh, I'm devastated, I can't tow a burger wagon. Oh well ;D
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Oh, I'm devastated, I can't tow a burger wagon. Oh well ;D
It's not that you can't, just that your burgers will defrost in the 'fridge. ;)
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Oh, I'm devastated, I can't tow a burger wagon. Oh well ;D
It's not that you can't, just that your burgers will defrost in the 'fridge. ;)
No, I'm pretty sure the man who lives in the glovebox that fixes everything said not to use for towing.
Camping is fine, as the fridge can plug into any of the 12v sockets scattered throughout the car.
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Cars that have this variable voltage alternators and risk running the van battery low during towing surely the option would be to leave the 12S socket not connected... :-\
Ok the fridge wont be working during towing but is that really necessary if you put some ice blocks in there for the journey. :-\
For vans like AA's with a power mover, surely if the van battery is fully charged at the beginning of each trip, then the battery must have enough juice to move the van at each end of the trip I would have thought....if you have a high enough power rated one :y
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Cars that have this variable voltage alternators and risk running the van battery low during towing surely the option would be to leave the 12S socket not connected... :-\
Chances are if a car is new enough to have a 'smart' alternator, then it'll have a 13 pin socket
Ok the fridge wont be working during towing but is that really necessary if you put some ice blocks in there for the journey. :-\
Depends how long the journey is ::)
For vans like AA's with a power mover, surely if the van battery is fully charged at the beginning of each trip, then the battery must have enough juice to move the van at each end of the trip I would have thought....if you have a high enough power rated one :y
that's part of the problem .... a 'flatter' battery won't move the caravan as far ;)
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The solution, I suppose, would be to isolate the caravan battery, from the cars 12v system.
That way it would be fully charged when I left home, get charged up again on site, and would still be fully charged when I got home.
This would allow me to use the mover to put it onto my drive.
The fridge could possibly be able to look after itself, I always get it cold before the star of a journey by running it on mains for 24 hrs plus.
Probably have to forget about taking frozen stuff with us.
Any ideas on a suitable relay to stop the feed going back to the car?
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Would a suitable (20 amp?) diode upset your car's charging system?
Ron.
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yes but you could still keep the battery at full charge and use the surplus amps to power everything else .
That's exactly what a conventional alternator does. Floating the battery at 13.8-14.4 V = keeping it fully charged and powering everything else from the alternator - all of the time the engine is running.
What a "smart" alternator does is to allow the engine ECU to reduce this voltage to perhaps 12.5V during cruising and acceleration conditions. Not low enough to seriously deplete the battery, but low enough that the battery will take no charge whatsoever unless it's pretty flat and, if it's fully charged, it will supply the car electrical loads. When braking, the voltage can be raised higher than the normal alternator output, to perhaps 15 volts or so, rapidly charging the battery and taking over all electrical load.
Don't forget that such a vehicle will probably be cursed with "stop-start" technology, so the loads on the battery are going to be quite high during normal driving as the battery repeatedly starts the engine and runs the accessories while the engine is stopped. By only replenishing such loads when the car is braking or when the battery does get low enough to cause concern, you save a little fuel.
Granted, the battery is going to keep getting cycled between partially discharged and fully charged, which will shorten its life, but since when have environmentalists been able to see the big picture? ;)
I would love to know how much, but I suspect very very very little...
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Is there any room to fit a second, conventional, alternator to power the trailer?
:-\
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You cant be the first to be trying to fix this? Have the caravan club or similar got any advice?
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....... Have the caravan club or similar got any advice?
You must be joking ..... they cant manage a decent web site
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Does the fridge really need to be cold upon arrival?
Get the fridge powered up on arrival, nip to supermarket for supplies, it should be cool by the time you're back.
This caravanning malarkey seems a hell of a lot more effort than camping, for the gain of being more cramped, restricted on travel speed/distance, drink huge amounts of fuel, and storaing the bloody thing ::)
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Does the fridge really need to be cold upon arrival?
Get the fridge powered up on arrival, nip to supermarket for supplies, it should be cool by the time you're back.
This caravanning malarkey seems a hell of a lot more effort than camping, for the gain of being more cramped, restricted on travel speed/distance, drink huge amounts of fuel, and storaing the bloody thing ::)
Fridge is not really a problem, we get it cold before we set off, and will probably get the odd current from the alternator on the journey.
The main problem would be the caravan battery draining to the same voltage as the car battery.
I think the simple solution would be to fit a battery isolator switch (caravan battery end) to stop this happening as you don't need the 12v system on the caravan whilst towing.
Err cramped? Don't think so, fixed bed, all mod cons, hot & cold water on tap, waste straight into drain, central heating if it gets cold, own spacious shower, loads of storage space, never gets damp in the pouring rain, I could go on............
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I could go on............
... and toilet for those night time visits :y
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I could go on............
... and toilet for those night time visits :y
I said I could go on ;)
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I could go on............
... and toilet for those night time visits :y
I said I could go on ;)
Don't you just love watching people putting up/taking down large tents in the pouring rain from the comfort of your caravan :D
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A quick google and I found this article.....tho they aint cheap...
http://www.12voltplanet.co.uk/battery-to-battery-chargers.html
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A quick google and I found this article.....tho they aint cheap...
http://www.12voltplanet.co.uk/battery-to-battery-chargers.html
Err yes, have you seen the price of them, seems like overkill :o
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Ouch, those prices! Gold plated? :o
Ron.
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' VSRs are not suitable for use with 'smart' alternators.' ..... ;)
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I could go on............
... and toilet for those night time visits :y
I'm not old enough yet ;)
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A quick google and I found this article.....tho they aint cheap...
http://www.12voltplanet.co.uk/battery-to-battery-chargers.html
Err yes, have you seen the price of them, seems like overkill :o
Yes....hence my comment
However those ones are quite heavy duty....I guess you could get away with a 10amp one...not sure what power rating your fridge is but I doubt the combined power consumption of the fridge and a fully charged battery is going to be more than 10A.
10A ones are cheaper ;)
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I could go on............
... and toilet for those night time visits :y
I'm not old enough yet ;)
:( I am
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I could go on............
... and toilet for those night time visits :y
I'm not old enough yet ;)
Your not trying to tell us you don't need a night time bathroom visit after 10 tinnies of wife basher ::) ;D
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Your not trying to tell us you don't need a night time bathroom visit after 10 tinnies of wife basher ::) ;D
If you've got to get up anyway, you might as well walk a decent distance away rather than do it in your wardrobe, as far as I'm concerned. :o
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Your not trying to tell us you don't need a night time bathroom visit after 10 tinnies of wife basher ::) ;D
If you've got to get up anyway, you might as well walk a decent distance away rather than do it in your wardrobe, as far as I'm concerned. :o
Strange habits you've got KW, you keep a toilet in your wardrobe :o
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Is there not a 12V to 12V DC to DC converter available for battery charging purposes (may be as per used on solar panels)?
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Is there not a 12V to 12V DC to DC converter available for battery charging purposes (may be as per used on solar panels)?
The caravan fridge when on 12v is controlled by a relay that only activates when the alternator is charging the main car battery, not worried about that as it can look after itself.
The caravan battery is on a direct feed from the car battery, and as such can give a reverse drain back to the car battery if the alternator ecu is not charging.
This feed also provides power to the Al-Ko ATC system, but is isolated from the caravan battery.
I need to isolate that feed to stop this happening, the caravan does not draw any power from its own battery whilst towing and will remain fully charged if not connected to the car allowing me to use the mover.
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Why not use a conventional voltage sensing relay? That will connect the caravan battery when the vehicle electrical system is at a high voltage and disconnect it when the voltage drops. You'll get some charging of the caravan battery when the vehicle battery is being charged and it will protect the caravan battery from being discharged.
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Why not use a conventional voltage sensing relay? That will connect the caravan battery when the vehicle electrical system is at a high voltage and disconnect it when the voltage drops. You'll get some charging of the caravan battery when the vehicle battery is being charged and it will protect the caravan battery from being discharged.
That seems to be the best option, if I could find one.
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I think I may have one in the junk box. Came with some towbar electrics but surplus to requirements. :y
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Why not use a conventional voltage sensing relay? That will connect the caravan battery when the vehicle electrical system is at a high voltage and disconnect it when the voltage drops. You'll get some charging of the caravan battery when the vehicle battery is being charged and it will protect the caravan battery from being discharged.
http://www.12voltplanet.co.uk/voltage-sensitive-relay-12v-140a.html
Would this do the trick?
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I think I may have one in the junk box. Came with some towbar electrics but surplus to requirements. :y
:y
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Why not use a conventional voltage sensing relay? ......
I've not had any if these problems yet so haven't really looked into it myself. But they've used VSRs for years now due to their ease of fitting/wiring & tend to think that if the answer was so simple there would never have been a problem in the first place :-\
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Why not use a conventional voltage sensing relay? That will connect the caravan battery when the vehicle electrical system is at a high voltage and disconnect it when the voltage drops. You'll get some charging of the caravan battery when the vehicle battery is being charged and it will protect the caravan battery from being discharged.
http://www.12voltplanet.co.uk/voltage-sensitive-relay-12v-140a.html
Would this do the trick?
Your issue is that under normal operation the output volts from the battery changes considerably and such a relay will keep dropping out, potentially for long periods.
Hence why I suggested the solar charging type, this will take the varying alternator output and convert it into a controlled charging supply for the leisure battery, couple this with an (ideally adjustable voltage sensing or ignition controlled relay) and you will get a nicely topped up pikey supply.
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Why not use a conventional voltage sensing relay? That will connect the caravan battery when the vehicle electrical system is at a high voltage and disconnect it when the voltage drops. You'll get some charging of the caravan battery when the vehicle battery is being charged and it will protect the caravan battery from being discharged.
http://www.12voltplanet.co.uk/voltage-sensitive-relay-12v-140a.html
Would this do the trick?
Your issue is that under normal operation the output volts from the battery changes considerably and such a relay will keep dropping out, potentially for long periods.
Hence why I suggested the solar charging type, this will take the varying alternator output and convert it into a controlled charging supply for the leisure battery, couple this with an (ideally adjustable voltage sensing or ignition controlled relay) and you will get a nicely topped up pikey supply.
Not bothered about it being topped up when towing, as there will not be a drain on it if its isolated from the car battery ;)
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Customer service!
I decided to phone the towbar electrics manufacturer to see if they could throw any light on the matter, in case they had something inbuilt to stop reverse drain.
Spoke to a technical bloke who said he hadn't heard of that, when I started to explain the different voltages of the two batteries he said 'Get a life' and hung up on me.
Perhaps I should ::)
;D
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Customer service!
I decided to phone the towbar electrics manufacturer to see if they could throw any light on the matter, in case they had something inbuilt to stop reverse drain.
Spoke to a technical bloke who said he hadn't heard of that, when I started to explain the different voltages of the two batteries he said 'Get a life' and hung up on me.
Perhaps I should ::)
;D
Towbar fitters. If only their legs were long enough to stop their knuckles dragging on the ground. ;D
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Well that definitely proves it, plugged the 'van into the car, and the leisure battery voltage started to drop like a stone!
Where to mount a split charge relay though, it's got to be on the caravan, after the Al-Ko ATC system.
No wiring diagram came with the caravan.
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I know that I suggested this earlier and I'm prepared to be shot down in flames, but why won't a suitably rated diode feeding the caravan's battery do the job? This will allow it to be charged and prevent reverse drain. It shouln't affect the "smart" alternator, as it won't be able to see it as anything other than extra capacity of the main battery. You would, of course, lose about 0.7 Volt across the diode - not a worry, surely?
Ron.
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I know that I suggested this earlier and I'm prepared to be shot down in flames, but why won't a suitably rated diode feeding the caravan's battery do the job? This will allow it to be charged and prevent reverse drain. It shouln't affect the "smart" alternator, as it won't be able to see it as anything other than extra capacity of the main battery. You would, of course, lose about 0.7 Volt across the diode - not a worry, surely?
Ron.
Or I could just disconnect the caravan battery whilst towing :-\
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I know that I suggested this earlier and I'm prepared to be shot down in flames, but why won't a suitably rated diode feeding the caravan's battery do the job? This will allow it to be charged and prevent reverse drain. It shouln't affect the "smart" alternator, as it won't be able to see it as anything other than extra capacity of the main battery. You would, of course, lose about 0.7 Volt across the diode - not a worry, surely?
Ron.
0.7V drop is quite a reasonable amount when considering lead acid battery charge voltages.....made worse with the Mercs operating system :y
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Understood, Mr. Fuse, but it will still keep the caravan's battery relatively happy. If it really is a worry, spend a little more on a power Schottky diode which will have a 0.1 - 0.2 volt drop across it?
RS Components, Farnell, Rapid Electronics and Maplins for sources.
Ron.
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Why not use a conventional voltage sensing relay? That will connect the caravan battery when the vehicle electrical system is at a high voltage and disconnect it when the voltage drops. You'll get some charging of the caravan battery when the vehicle battery is being charged and it will protect the caravan battery from being discharged.
http://www.12voltplanet.co.uk/voltage-sensitive-relay-12v-140a.html
Would this do the trick?
Did you read this bit??
IMPORTANT NOTE: These relays are not suitable for vehicles with 'smart' or 'intelligent' alternators. As a guide this applies to vehicles having engines that comply with Euro5 emissions standards and onward, often also incorporating regenerative braking (if in doubt please consult your vehicle manufacturer to confirm). If your vehicle has a smart alternator then you will need to use a battery-to-battery charger instead of a VSR
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I know that I suggested this earlier and I'm prepared to be shot down in flames, but why won't a suitably rated diode feeding the caravan's battery do the job? This will allow it to be charged and prevent reverse drain. It shouln't affect the "smart" alternator, as it won't be able to see it as anything other than extra capacity of the main battery. You would, of course, lose about 0.7 Volt across the diode - not a worry, surely?
Ron.
Or I could just disconnect the caravan battery whilst towing :-\
You should have fuses for the charging electrics from the vehicle into the caravan,just pull the ones relevent to charging and battery to isolate car from van
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Understood, Mr. Fuse, but it will still keep the caravan's battery relatively happy. If it really is a worry, spend a little more on a power Schottky diode which will have a 0.1 - 0.2 volt drop across it?
RS Components, Farnell, Rapid Electronics and Maplins for sources.
Ron.
So Schottky diodes have a habit of not lasting on what is considered 'the worst power supply in the world' (automotive) as they do not tolerate reverse voltage and the spikes seen tend to age them quickly and 'pop' them (hence why Schottky barriers are not used nearly as often as you may think)
What you have to think of is that the difference between a 90% charged battery and one that is 60% charged is about 0.6V so yes, the V drop has a big impact and any battery below 90% charged will tend to sulphate to.
The main issue is if the leisure battery will charge at all connected to the car due to the way the alternator output varies, the setup is totally focused on the state of the vehicle battery and nothing else plus, they have current sensing on the battery lead just to make matters worse.
Hence why I suggested the solar type charger, it prevents back feeding and takes what ever supply voltage is given to it and tailors it to what the leisure battery needs, plus it gives current limiting to.....
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... Hence why I suggested the solar type charger, it prevents back feeding and takes what ever supply voltage is given to it and tailors it to what the leisure battery needs, plus it gives current limiting to.....
Yep, that would undoubtedly be the best solution if you actually need to deliver charge to the caravan battery reliably. It just becomes another load on the car's electrical system, regardless of voltage, until the battery is satisfied and it stops drawing significant current.
I suspect, for AA's scenario, just disconnecting the caravan battery from the towing connector and ensuring it is fully charged before a trip would probably be the simplest solution.
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I did say that I expected to get flamed and I am nicely toasted now; thanks gents! :-X :-X
Ron.
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I did say that I expected to get flamed and I am nicely toasted now; thanks gents! :-X :-X
Ron.
No intention to flame, just a case of passing on a bit of knowledge :y
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And it was appreciated, thanks. I have worked with Schottky technology often, but never in the hostile automotive environment.
I agree that pulling the appropriate fuse would be simplest, but what are your thoughts on putting one of those 1-2 Farad capacitors so loved by the gullible teenage go-faster crowd across the leisure battery to deal with the harmful spikes?
Ron.
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Or fit a second alternator for the caravan. Won't suggest it again if anyone can provide a sensible reason why not.
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Or fit a second alternator for the caravan. Won't suggest it again if anyone can provide a sensible reason why not.
I'd guess lack of space under the bonnet on most cars these days would prevent you fitting one.
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Or fit a second alternator for the caravan. Won't suggest it again if anyone can provide a sensible reason why not.
I'd guess lack of space under the bonnet on most cars these days would prevent you fitting one.
Nah! Loadsaroom!
(http://doctorgrooveband.com/WEBMetal-ALT.jpg)
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Or fit a second alternator for the caravan. Won't suggest it again if anyone can provide a sensible reason why not.
I'd guess lack of space under the bonnet on most cars these days would prevent you fitting one.
I've always wondered why caravans don't incorporate one driven by the wheels. It's self-contained then, close to the load it needs to power and the whole issue of towing electrics is completely sidestepped.
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And it was appreciated, thanks. I have worked with Schottky technology often, but never in the hostile automotive environment.
I agree that pulling the appropriate fuse would be simplest, but what are your thoughts on putting one of those 1-2 Farad capacitors so loved by the gullible teenage go-faster crowd across the leisure battery to deal with the harmful spikes?
Ron.
Ineffective (in the same way they are for the audio systems!)
When I did a bit of audio design, the large capacitors work well for handling slow(er) changing fluctuations in the supply voltage but not fast transients (consider an equivalent model of a capacitor with some series resistance, L and a bloody big C and all becomes clear). To deal with faster spikes you need low capacity parts or ideally, a multitude of values......but the optimum will be dependent on the source resistance and on cars, that varies.
To protect a Schottky barrier (as they are not really a diode being a metal semiconductor interface), you need a capacitor (or two) in parallel and ideally some sort of clamp (once made a good one with a FET triggered by a Zener) so again, far from easy.
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Or fit a second alternator for the caravan. Won't suggest it again if anyone can provide a sensible reason why not.
I'd guess lack of space under the bonnet on most cars these days would prevent you fitting one.
I've always wondered why caravans don't incorporate one driven by the wheels. It's self-contained then, close to the load it needs to power and the whole issue of towing electrics is completely sidestepped.
Something for you to invent & patent. ;) Plenty of electric driven cars on the road that you can nick a wheel off for its motor
..... or how about like a bicycle's dynamo of old ;D
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Or fit a second alternator for the caravan. Won't suggest it again if anyone can provide a sensible reason why not.
I'd guess lack of space under the bonnet on most cars these days would prevent you fitting one.
Nah! Loadsaroom!
(http://doctorgrooveband.com/WEBMetal-ALT.jpg)
That's a fair old serpentine 'fan' belt ;D :y
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To clarify my earlier post, the manufacturer specific tow pack on the Beemer was wired so that it sensed the caravan plug was in and disabled the 'smart' Ecu function to the alternator and switched off the stop-start function. Had no issues with the fridge or charging. On my lads Nissan it was the same, although I believe that some models require reprogramming.
On the Nissan, with the caravan on tow the voltage was a steady 14.2 and with the van unplugged the voltage varied from 12.4 to 14.8 depending on acceleration or deceleration.
So, manufacturers are aware of it and have responded to it, albeit at a price, but the after-market fitters seem to go down the ignition switched relay route to overcome the issue.
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Never towed a caravan with my E Class, but it had the factory folding tow hitch 8) Cost the original owner a few quid... Well into four figures iirc :o
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Customer service!
I decided to phone the towbar electrics manufacturer to see if they could throw any light on the matter, in case they had something inbuilt to stop reverse drain.
Spoke to a technical bloke who said he hadn't heard of that, when I started to explain the different voltages of the two batteries he said 'Get a life' and hung up on me.
Perhaps I should ::)
;D
He must have seen this thread! :-X ;D
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Never towed a caravan with my E Class, but it had the factory folding tow hitch 8) Cost the original owner a few quid... Well into four figures iirc :o
I saw one for the first time a few weeks ago, looking at it you wouldn't want to get the trailer nose weight to wrong!
And yes, it looked dam over complicated and expensive!
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If you can't get nose weight right then you shouldn't be towing in the first place ;) In fact, you should have your license removed (I'll stop short of suggesting a TB-like cull ;D)
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I wonder where I stand if I tried to argue that the towing electrics are 'not fit for purpose'?
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Never towed a caravan with my E Class, but it had the factory folding tow hitch 8) Cost the original owner a few quid... Well into four figures iirc :o
I saw one for the first time a few weeks ago, looking at it you wouldn't want to get the trailer nose weight to wrong!
And yes, it looked dam over complicated and expensive!
of course it is, it's German. There's no way they would use the American method of removable tow bars: a length of square tube attached to the car, and another that slides into it retained with a pin. They'll tow much heavier loads with that arrangement than we are allowed to.
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.....
looking at it you wouldn't want to get the trailer nose weight to wrong!
.....
You could think that about a detachable bar too .... there doesn't seem to be much holding them in place ???
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...... There's no way they would use the American method of removable tow bars: a length of square tube attached to the car, and another that slides into it retained with a pin. They'll tow much heavier loads with that arrangement than we are allowed to.
They look sh1t though ::)
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...... There's no way they would use the American method of removable tow bars: a length of square tube attached to the car, and another that slides into it retained with a pin. They'll tow much heavier loads with that arrangement than we are allowed to.
They look sh1t though ::)
not when the registration plate covers them
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
When I start the car and put my foot on the brake, the eco systems will be cancelled, and the car will operate normally, controlling the fridge relay and charging of the leisure battery.
If it doesn't, then I'm to go back to them as the car will not have been re-programmed correctly.
Thank goodness I used one of their approved fitters.
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
.....
Nice one, I knew it was possible. :y
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.....
looking at it you wouldn't want to get the trailer nose weight to wrong!
.....
You could think that about a detachable bar too .... there doesn't seem to be much holding them in place ???
Considerably more support on the bayonet type fitting then the electric item that pivots in the direction (well almost) of where the force is being transmitted through the tow ball. They only have a very minimal type solenoid lock pin from what I could see (god help you if that fails to engage!)
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.....
looking at it you wouldn't want to get the trailer nose weight to wrong!
.....
You could think that about a detachable bar too .... there doesn't seem to be much holding them in place ???
Considerably more support on the bayonet type fitting then the electric item that pivots in the direction (well almost) of where the force is being transmitted through the tow ball. They only have a very minimal type solenoid lock pin from what I could see (god help you if that fails to engage!)
There is a light to tell you, and there's a reassuring clunk as it latches... good for 2100kgs too :D
Is there any reason why an US spec towbar cannot be used here? Obviously if fitted to a car which is sold in both markets...
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...
Is there any reason why an US spec towbar cannot be used here? Obviously if fitted to a car which is sold in both markets...
Do they use 50 mm balls or are they 2" :-\
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Is there any reason why an US spec towbar cannot be used here? Obviously if fitted to a car which is sold in both markets...
I doubt a US bar would be type-approved for use in the EU; so pre-2001 would be fine but not post-2001 (I think that was the date, anyway).
Always wondered what the towing capacity of an old 1950s half-ton would be, fitted with suitable V8..
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Is there any reason why an US spec towbar cannot be used here? Obviously if fitted to a car which is sold in both markets...
I doubt a US bar would be type-approved for use in the EU; so pre-2001 would be fine but not post-2001 (I think that was the date, anyway).
Always wondered what the towing capacity of an old 1950s half-ton would be, fitted with suitable V8..
Whatever she'll haul partner ;D ;D
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(I'll stop short of suggesting a TB-like cull ;D)
Bloody namby pamby liberal type ;D
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
When I start the car and put my foot on the brake, the eco systems will be cancelled, and the car will operate normally, controlling the fridge relay and charging of the leisure battery.
If it doesn't, then I'm to go back to them as the car will not have been re-programmed correctly.
Thank goodness I used one of their approved fitters.
So apart from turning up at the destination with warm beer, how will you know if the eco systems have been disabled when you hook up the caravan? :-\
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
When I start the car and put my foot on the brake, the eco systems will be cancelled, and the car will operate normally, controlling the fridge relay and charging of the leisure battery.
If it doesn't, then I'm to go back to them as the car will not have been re-programmed correctly.
Thank goodness I used one of their approved fitters.
So apart from turning up at the destination with warm beer, how will you know if the eco systems have been disabled when you hook up the caravan? :-\
:-\
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So apart from turning up at the destination with warm beer, how will you know if the eco systems have been disabled when you hook up the caravan? :-\
if both batteries are charged, why would you care? After all, fiddling with the alternatorcharging rates 'to improve emissions' will give such small improvements that don't justify the cleverness required to implement them.
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
When I start the car and put my foot on the brake, the eco systems will be cancelled, and the car will operate normally, controlling the fridge relay and charging of the leisure battery.
If it doesn't, then I'm to go back to them as the car will not have been re-programmed correctly.
Thank goodness I used one of their approved fitters.
So apart from turning up at the destination with warm beer, how will you know if the eco systems have been disabled when you hook up the caravan? :-\
:-\
I suppose I could buy one of these :-
https://www.amazon.co.uk/DEOK-Digital-Voltmeter-Generator-Cigarette/dp/B00GX5VMTY/ref=sr_1_16/258-6395587-9795351?ie=UTF8&qid=1502266152&sr=8-16&keywords=lighter+voltmeter
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How long is the drive from home to campsite AA?
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How long is the drive from home to campsite AA?
Normally go distances between 2/4 hours drive, depending how long we've booked to stay.
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
When I start the car and put my foot on the brake, the eco systems will be cancelled, and the car will operate normally, controlling the fridge relay and charging of the leisure battery.
If it doesn't, then I'm to go back to them as the car will not have been re-programmed correctly.
Thank goodness I used one of their approved fitters.
So apart from turning up at the destination with warm beer, how will you know if the eco systems have been disabled when you hook up the caravan? :-\
Thinking about what Witter said, the stop/start eco system should be disabled :)
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
When I start the car and put my foot on the brake, the eco systems will be cancelled, and the car will operate normally, controlling the fridge relay and charging of the leisure battery.
If it doesn't, then I'm to go back to them as the car will not have been re-programmed correctly.
Thank goodness I used one of their approved fitters.
So apart from turning up at the destination with warm beer, how will you know if the eco systems have been disabled when you hook up the caravan? :-\
:-\
I suppose I could buy one of these :-
https://www.amazon.co.uk/DEOK-Digital-Voltmeter-Generator-Cigarette/dp/B00GX5VMTY/ref=sr_1_16/258-6395587-9795351?ie=UTF8&qid=1502266152&sr=8-16&keywords=lighter+voltmeter
I'm afraid that those plug-in voltmeters are not very accurate; I have had a few of them and not one agrees with another!
Ron.
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
When I start the car and put my foot on the brake, the eco systems will be cancelled, and the car will operate normally, controlling the fridge relay and charging of the leisure battery.
If it doesn't, then I'm to go back to them as the car will not have been re-programmed correctly.
Thank goodness I used one of their approved fitters.
So apart from turning up at the destination with warm beer, how will you know if the eco systems have been disabled when you hook up the caravan? :-\
Thinking about what Witter said, the stop/start eco system should be disabled :)
That's true :y
There might even be a little light on the dash that shows up :-\ .....Ive seen a green light of a towbar before on some cars.
Have a butchers in the handbook :)
About 15-20 years when my Dad had a caravan I can remember there was a buzzer fitted in the boot that you could hear in cabin that went off when he used the indicators...to let him know the indicator lights on the caravan were working....im sure things have progressed since then :)
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Just had an informative conversation with Witter Towbars.
The tech guy said the car should have been re-programmed to know that it is towing a caravan.
When I start the car and put my foot on the brake, the eco systems will be cancelled, and the car will operate normally, controlling the fridge relay and charging of the leisure battery.
If it doesn't, then I'm to go back to them as the car will not have been re-programmed correctly.
Thank goodness I used one of their approved fitters.
So apart from turning up at the destination with warm beer, how will you know if the eco systems have been disabled when you hook up the caravan? :-\
Thinking about what Witter said, the stop/start eco system should be disabled :)
That's true :y
There might even be a little light on the dash that shows up :-\ .....Ive seen a green light of a towbar before on some cars.
Have a butchers in the handbook :)
About 15-20 years when my Dad had a caravan I can remember there was a buzzer fitted in the boot that you could hear in cabin that went off when he used the indicators...to let him know the indicator lights on the caravan were working....im sure things have progressed since then :)
No such thing on the Merc Dave :(
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No such thing on the Merc Dave :(
Thank Christ ...... buzzers are only fitted by tow bar fitters for ease. My Merc flashes rapidly when a trailer/caravan indicator fails ..... just like when one fails on any other car. Try it ;)
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Did a rough test last night, after it stopped raining.
Plugged the 'van into the car, started the engine and ran it for about 20mins., stationery.
Car, 'van & fridge all getting a full charge output from the alternator.
Not a proper test I know, proof will be in towing it for an hour or two.
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Seems Witter are correct, first tow with the Merc, fridge still cold and leisure battery fully charged after a 4 hour journey, with a couple of 15 min stops :y