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[omega2018]

i've been checking my battery - when disconnected it was reading 12.5v or less - I just removed it after a reasonably long journey and it was 12.3v.  gave it a charge from an 8 amp charger and it went to float at 13.5v in a few minutes.  then when disconnected it dropped to 12.6V in a few minutes.  the at rest voltages seem quite low to me.  I have other 12V batts which happily sit at 12.8V hours long after the charge has been removed. 

also tested it with a basic drop tester, it showed 'weak' just under 'ok' (11V) for a 800a batt (it is 800a, i have the diesel batt fitted)

the batt is 3 years into a 5 year warranty, supplier says it should read 12.68v -12.73v at rest after charge.  even that seems low to me. 

what readings do others get?

i've now had it on float charge (actually 13.9V) from a 16 amp charger for a couple of days now.  will take it off charge tomorrow and report back if it stays above 12.75v which is what i would expect if it's still ok.

[Viral_Jim]

i've been checking my battery - when disconnected it was reading 12.5v or less - I just removed it after a reasonably long journey and it was 12.3v.  gave it a charge from an 8 amp charger and it went to float at 13.5v in a few minutes.  then when disconnected it dropped to 12.6V in a few minutes.  the at rest voltages seem quite low to me.  I have other 12V batts which happily sit at 12.8V hours long after the charge has been removed. 

also tested it with a basic drop tester, it showed 'weak' just under 'ok' (11V) for a 800a batt (it is 800a, i have the diesel batt fitted)

the batt is 3 years into a 5 year warranty, supplier says it should read 12.68v -12.73v at rest after charge.  even that seems low to me. 

what readings do others get?

Not got the multi-meter with me atm, will try and check later. Various webpages seem to point to 12.7v as the expected reading for a 100% OK 12v battery, so on that basis the supplier's suggestion seems correct. 

i've now had it on float charge (actually 13.9V) from a 16 amp charger for a couple of days now.  will take it off charge tomorrow and report back if it stays above 12.75v which is what i would expect if it's still ok.

[zirk]

Measuring Batt Volts after a Charge or being used in the car never really gives a true picture. ideally the battery should be charged and then left to rest, typically somewhere cool and for around 24 hours then measured. A good battery (almost New) will measure around 12.7 - 12.8, even after being drop tested it should still be close to those figures.

I always work on seeing around +12.6V for a rested, fully charged, well used good battery. 

[Kevin Wood]

The voltage is dependent on temperature too.

TBH, the only thing I'd be worried about is that it doesn't hold up under a "drop test".

[Diamond Black Geezer]

That's under load, lights, heaters, heated seats, etc yes?

[Kevin Wood]

That's under load, lights, heaters, heated seats, etc yes?

No. Open circuit battery voltage with no load when fully charged.

[Field Marshal Dr. Opti]

Mine shows about 12.4 volts an hour or so after stopping.

....and around 14.4 volts with the engine running.

[Field Marshal Dr. Opti]

....car last used 24 hours ago.

12.43 volts and 14.64 volts with the engine running but nothing switched on.

[Broomies Mate]

....car last used 24 hours ago.

12.43 volts and 14.64 volts with the engine running but nothing switched on.

That says to me, good Alternator, mediocre battery.  Or you have a parasitic drain, which is unlikely as you have not reported a non-start issue.

You have to remember though, that when you unlock the car, you don't just open locks, you start several systems which won't shut down for a while.

Unlock the car, open the bonnet and stick something heavy on the bonnet alarm switch.  Lock the car and wait for at least half hour (I think GM stuff is usually 15 minutes ish).

[omega2018]

currently showing 12.84v after resting 8 hours from its 3 day 13.8V float charge.

my little jump starter battery is showing 13.6V after the same rest.  a little used 900a bosch batt is still showing 12.82v and has been resting for 2 days.

my 800a seems to have benefited from its luxury treatment.  i'll drop test it again when the voltage has settled.

[Kevin Wood]

Nothing to worry about there.

[omega2018]

so after 3 days rest it is 12.73V so the battery (varta) is OK (after 3 days float charge before the rest).  however my 900a bosch has actually gone up .01v to 12.83 and that's after 5 days resting. so i don't think the varta is as good as new but can't complain after 3 years.  the bosch is well over 5 years old but has had a very easy life.

drop test went to 11V after 10 secs load, not great but ok. 

[TheBoy]

I just checked (by search the forum, as looking at receipts would mean getting out of the bath ) when the Silver Bullet last had a battery - January 2008, remembered as it was during the trip to the dealer I had an "incident" in the tractor causing all the oil to fall out 

Obviously, it was all Marks DTM Calib's fault, it usually is, as he's a wrong'un


So 8yrs, no grief, despite it frequently being left for extended periods without use, though less so now we don't have the Rover.