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ContinuousWave: Small Boat Electrical
New OPTIMA Battery Has only 10.8-volts Open Terminal
|Author||Topic: New OPTIMA Battery Has only 10.8-volts Open Terminal|
posted 07-20-2009 06:47 PM ET (US)
I purchased a new Optima Blue Top battery today. Installed it on the boat today and my Xantrex Link 20 battery gauge says the battery has only 10.80 volts. Thought that was odd but I also was reading that something was drawing 1.8 amps. I have the battery on slow charge now but was wondering if the amp draw was a product of the low voltage. My other battery (also a blue top) is only drawing .3 amp when I switch to that circuit. There is nothing extra hooked to the first battery except the aforementioned Link 20 which normally draws next to nothing.
posted 07-20-2009 08:38 PM ET (US)
A lead-acid battery with a terminal voltage of only 10.8-volts is severely discharged.
posted 07-20-2009 09:37 PM ET (US)
A typical 12-volt battery consists of six lead-acid cells. Each lead-acid cell has a potential of about 2.15-volts when fully charged. Thus a battery with six cells will have a full-charge terminal voltage of 12.9-volts.
If a battery has a shorted cell, the terminal voltage will only be able to rise to
5 x 2.15-volts = 10.75 volts
The battery described above could be either a battery with six cells in a severely discharged state, or a battery with full charge and one shorted cell.
posted 07-21-2009 09:50 AM ET (US)
I realize that 10.80 is discharged and wondered if a battery can get in that state from sitting on a shelf waiting to be purchased. I put it on my charger last night and it seemed to charge up okay. I will install it tonight. Was still wondering if the 1.8 amp draw I was reading from the meter is a product of the discharge state.
posted 07-21-2009 09:08 PM ET (US)
You are probably right Jim. Battery was down to 11.82 in the garage overnite after I fully charged it. Likely a bad cell. I returned it this evening for a new one...this time I brought my VOM meter and got a battery reading 12.6 off the shelf. Will install tomorrow and see what I got.
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