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[Entwood]

My personal take on the PS problem is that the batteries fail, possibly due to the "memory factor" of rechargeables, which all the stuff I've read says you should fully discharge a rechargeable every so often .. never happens to a PS battery (and I know that "rule" only applies to older rechargeables .. but thats whats in the PS) !!

Just my thoughts .. nowt else .... 

Battery readings would suggest to me that all is well with your car.

I understand where you are coming from with the memory effect, and I know that powersounders are never run down

However,

There are millions of rechargeable batteries in circulation, and if they kept spontaneously combusting, then someone would have noticed by now - and they would all have been withdrawn - and yet a fairly small group of people are experiencing an exceptionaly high percentage of failures - that does not seem to me like the battery failing, more like the circumstances under which its failing.

My thoughts ... probably rubbish ... I don't think the actual batteries would kick out enough power to ignite, especially if they are failing and not holding a charge - even though a directly shorted battery can put out a large current for a short time - I'm thinking that, because the batteries monitor the car battery - thats what sets the alarm off after all - it is the very large reserve of power from the CAR battery that actually causes the fires ... the PS batteries fail and shortcircuit .. so causing a very large drain/heat source inside the PS, which eventually ignites.

Now Mark DTM knows a lot more about electronics than I .. so perhaps he's right, and the short is not actually in the battery .. but the componenets trying "feed" a high current to a failed battery ??

[Dave DND]

I don't think the actual batteries would kick out enough power to ignite, especially if they are failing and not holding a charge

totally agree, but I don`t think its the power that is causing the ignition, I think its the temperature.

A very hot battery, albeit very small encased inside plastic - surely thats more than enough for combustion?

and that would also add credability to those that have combusted once removed from the car and stuck in the garage. Damage has already been done and they are now leaking and now "self contained"

[Entwood]

I don't think the actual batteries would kick out enough power to ignite, especially if they are failing and not holding a charge

totally agree, but I don`t think its the power that is causing the ignition, I think its the temperature.

A very hot battery, albeit very small encased inside plastic - surely thats more than enough for combustion?

and that would also add credability to those that have combusted once removed from the car and stuck in the garage. Damage has already been done and they are now leaking and now "self contained"

AH .. didn't realise some had gone up "on the shelf" .. I thought they were all "in car" and so drawing power from the car battery in attempting to charge ... blows my theory right out the window then ..

[Dave DND]

The ones that I am aware of going up on the shelf were all within a week of being removed as faulty. So its conceievable that these have already started to leak, been removed and they have been stored under ideal conditions for them to continue to burn.

 

but what caused the failure in the first place?

Thinking more on this diode - my thoughts are that although the batteries / sounder chassis have a few variations, I bet that the smaller components, diodes etc come from a  single source, and its certainly not uncommon for a diode to break down.

 :-/

Marks DTM, i`m presuming that its a dead sounder that you are disecting, and I would be very interested in any such diode type / readings if you could oblige

 

[feeutfo]

If it helps, mine only ever false alarmed on first start up on Monday morning after the car stood unused over the weekend.

After disection, the one in the guide, the board was fine and only slight leak on the battery showed. Kevin checked the voltages with a meter which showed a tired car battery, possibly original.

New car battery and the problems stopped. New PS  batterys where soldered in shortly after iirc. Although i was tempted to leave them to prove the car battery voltage dropping was the cause in my case.

Obviuosly with the ps monitoring car battery voltage it would be under highest load at start up on a cold morning. Then straining the tired car battery beyond the ps limit and the alarm goes off thinking the battery is being disconnected and the car stolen.

[Dave DND]

If it helps, mine only ever false alarmed on first start up on Monday morning after the car stood unused over the weekend.

After disection, the one in the guide, the board was fine and only slight leak on the battery showed. Kevin checked the voltages with a meter which showed a tired car battery, possibly original.

New car battery and the problems stopped. New PS  batterys where soldered in shortly after iirc. Although i was tempted to leave them to prove the car battery voltage dropping was the cause in my case.

Interesting - kind of works with my theory.

Obviuosly with the ps monitoring car battery voltage it would be under highest load at start up on a cold morning. Then straining the tired car battery beyond the ps limit and the alarm goes off thinking the battery is being disconnected and the car stolen.

Now this is where I think there is an issue -
If there is a sudden and rapid change in state of the voltage being monitored, disconnection, cranking etc etc, then the sounder will sound - but I`m wondering if there is a slight drain that causes the voltages to drop by such a small amount at a time, that the sounder would never actually sound, and depending on which battery was draining what, you would either end up with a flat main battery or a red hot powersounder battery.

I think this charging circuit really may be the key to this.

 :-/

[Kevin Wood]

I also find it hard to believe that the batteries are spontaneously combusting without being abused. I have seen the same type of battery in many applications. I have seen them leak and muller the PCB before but, as you say, they would be withdrawn if the problem were widespread.

I have a power sounder PCB on the bench and I believe I did trace the circuit to a certain extent a while back.

I reckon either the charging circuit is bad or, what I had observed on one of them, is that the battery had leaked conductive goo over the MOSFET (iirc) that drives the output transformer. It had started to conduct due to a partial gate-to-VCC short and had harmlessly flattened the battery in this case. Had that failure happened quicker, it might have sent enough current through the primary of the transformer (low DC resistance) to have ignited it, perhaps?

Anyway, I'll have a little play next time I'm bored and see what I can find out.

Batteries are 2 3.6v NiCd  packs in series IIRC.

Kevin

[JohnM]

My 2p - could be way off here.

First omega.  Sad main battery, car had been used daily on long, motorway runs.  Soon after that stopped main battery gave up.  When battery changed the sounder was allowed to go off (didn't do the ign - 15s procedure) - sounded nice and loud.  No alarm issues I can remember of. 

Second omega.  Had been standing for unknown time.  Battery charged okay (and is still running) sounder gave 3? beeps straight away.  Told just because main battery had been low/stood.  Did improved, warning beeps less became frequent - thought all was well.  Later, alarm problems - random alarms (alarm horn) couldn't find the cause (not helped by someone elses nearby going off) when one day arrived & parked up and the sounder was going off after a few mins.  Couldn't do a thing with it, ign on/off, even started up the sounder was squawking (parked somewhere out of the way).  All well (well flat?) on my return.  Seem to think it isn't fitted now - might have given a dying breath noise as it departed.

Now that one may have been murdered.  As whilst chasing the alarm problem I had that sparky moment and those reds? from one of the big blade fuses were seen on the pas pully.  The fuse was intact so I thought if that was the charging/monitor feed that was causing the alarm triggers, or lowering the main battery charge at least (I assume the 12v is monitored too).  In reality it may have part-shorted the charge feed - they were a good shower of sparks - and killed the nicads prematurely.

[TheBoy]

My PS is right in front of me. Sadly, its has been waterproofed with a potting compound by look of it.  I can see 6 batteries, presumably cheap, nasty nicads, so thats 7.2v

I know there are various types of PS that all do the same thing, so its possible some use other voltages - it's probably provided a simple 12v, 0v and some signalling to alarm ECU, with the internals being entirely up to the specific manufacturer of the PS.


I suspect the fire reports are probably where, over time, the batteries have leaks or vented, causing PCB damage?


Mine lasted about 10yrs before I removed it. It wasn't the usual failure, mine just used to occasionally go off whilst driving!

[Dave DND]

I suspect the fire reports are probably where, over time, the batteries have leaks or vented, causing PCB damage?

But I fear that is a very easily reached conclusion as to what has happened, without looking a bit more in depth as to the cause, and every time another one goes up, we (myself included) are all too quick to blame the powersounder and add this to the growing list of torched cars instead of looking into it further.

Old rechargeables simply do not leak or vent on such a scale as we see here on the forum, and even if they did, as the gooey acidic mess comes out, there would be little or no current left inside to cause a spark. Find a leaking nicad that still holds a good charge and prove me wrong !!

But you are right that there are various types of Powersounder that all do the same thing, and as they are all having the same fault, the problem MUST lie with something else on the car that is causing this to happen.

[doog]

When mine went it was....

What time of year was it?   winter
What time of day was it? 8.50am
What was the weather / temperature?  cold (frost)
Is the car used for long / short journeys? both
When was the Battery last replaced? 2 2 years previously
Have you heard any "beeps" from the sounder? no

note frosty roofs in picture  so it was cold at the time



Doug

[Dave DND]

When mine went it was....

What time of year was it?   winter
What time of day was it? 8.50am
What was the weather / temperature?  cold (frost)
Is the car used for long / short journeys? both
When was the Battery last replaced? 2 2 years previously
Have you heard any "beeps" from the sounder? no

note frosty roofs in picture  so it was cold at the time



Doug

Interesting -
From that I would suspect that your battery would certainly be below its normal voltage due to the very cold weather - still enough to start, but definately a volt or so down would be expected.

I think I may be on to something here then.

 :-/

Has anyone had one of these go up on a hot sunny day after a reasonable run and a good main battery?

 :-?

[Marks DTM Calib]

Well if the sounder batteries are 7.2V (6 off nicads) then its fair to assume that they are not driivng out into the main vehicle load.

I have a spare hour this evening, will crack mine open and pop a few pics up.

[Dave DND]

Well if the sounder batteries are 7.2V (6 off nicads) then its fair to assume that they are not driivng out into the main vehicle load.

Disagree - surely the transformer there could still theoretically allow it to happen ?

[TheBoy]

This is inside of mine...