odd battery behaviour??

[Birdseye]

my boat has three batteries - one engine and two domestics, both the latter are identical but one a year older than the other.

using my sterling battery charger (excellent) all three float at slightly more than 13.4 volts. but after disconnecting the charger, one of the domestics drops to 12.62 within 36 hours whilst the other 2 drop to 12.72. At this point most people would say "internal leakeage" in the odd one out. but from thereon, the voltage drops slowly and in line with both the others. so it cant be a problem of charge leaking away through the sludge at the bottom of the battery.

even when fully charged, the SG of the odd battery isnt as high as the others. so could it simply be that this battery was fed a weaker acid / less acid when new?

over to the pbo experts?

<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[Talbot]

more likely that a cell is going.

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[pandroid]

Its either that the service battery is a little 'older', or it maybe that you have some small load (i.e. The stereo 'memory' or a clock or something) that is on the battery even when 'disconnected'.

Either way, 12.6v is OK. The batteries are probably of different types anyway (service batteries are usually semi-'traction' types) so differences might happen anyway. I wouldnt worry about it too much, but if you are worried you can get the battery capacity tested.

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[jerryat]

Hi Birdseye,

I agree with Pandroid, your batteries are close enough following the charging regime not to cause concern. 12.6V is effectively a fully charged battery, so the slight difference in the time taken to regularise to this level is understandable as no two batteries will be exactly the same whether of the same make or not.

The fact that both seem to steady when this point is reached is proof of this IMHO. I doubt very much that you have any problem with faulty cells, as the SG difference would be readily indentifable once the batteries had 'rested' though you don't say whether this is the case. They sound pretty good to me so I should stop worrying!

Cheers

jerry

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