Battery rapid Voltage drop

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Battery rapid Voltage drop

Postby turx » Wed Oct 21, 2015 8:53 pm

so..i purchased a new 115Ah battery 5 months ago. Everything was great guns until over the last 2 weekends i note the battery monitor is showing rapid voltage drops.
I have had the van on mains to fully charge the battery , however day 4 and its not getting past 12.60 volts. This previously reached 12.71 volts.
I note also when i disconnect the mains and with no Amp /current draw..the voltage drops rapidly from 12.60 volts down to 12.54 volts in a matter of 2 minutes!!!

I am suspecting a dropped cell - your thoughts???

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Re: Battery rapid Voltage drop

Postby mattn » Thu Oct 22, 2015 7:13 am

Does sound suspiciously like a cell has failed.

Best option is a discharge test with logging of current - failing that, discharge at around 5 amps and watch what the voltage does over a day (5 amps, 10 hours should be 50% discharged - around 12.2V. If its a cell failure, it will much lower much quicker. If you have access to another battery (the starter or borrow one from your car ), swap the house battery out and check the charger is getting to over 13.5V.
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Re: Battery rapid Voltage drop

Postby RaymonD » Thu Oct 22, 2015 1:27 pm

You have checked your charger output voltage with no battery connected ?? it has to be higher than the battery other wise it will not charge.
Quite normal for battery voltage to drop when disconnecting charger which indicates that it was getting some charge, but maybe not enough due to charger output voltage not being high enough... what is charger rating ?

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