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hello all, while away from my (other, smaller) boat for several months i attached a trickle solar charger to the start battery (century 600 cca, available on the internet). upon return, i tested its voltage and it had fallen to 6.6 volts... so i took it out and put it under a smart charger plugged into regular home outlet. now the puzzle:

the charger "fault" light showed up, meaning i had the connections +/- wrong, besides determining that it was a 6-volt battery, when it was actually a 12.

so i disconnected it from charger and tested it with a voltmeter. and yes, when i matched + to + and - to -, the voltmeter showed a negative 6.5 volt. when i reversed the contact pins of the voltmeter, then it shows a positive 6.5 volts. why has the much-drained battery changed polarity? (now, maybe the mfg got it mixed up and i never knew that - the website showed two kinds of +/- on left/right electrodes for each model it sells. could it be that they installed the polarity wrong or indicated it wrong on the case?)

upon reconnecting to the charger with the poles reversed, the charger still shows "6v" and "fault".

this craziness typical of a down/dead battery?

note: i nursed my car battery from 0 volts to functioning, using the same charger. 

thanks. yzlian
 

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YZ...

I can only suggest you charge it again with the correct polarity and at 12 V (the charger will probably operate at about 14 V to do it) and try to recover the initial function again.
Keep a close eye on it at first in case it mis-behaves or overheats or something horrible.
A very long time ago, I charged a near-new motorcycle battery with the wrong polarity and left it charging overnight.
When I realised my mistake, I switched it back and charged it the correct way and it worked again OK for years. It did not have to turn a starter motor though.

What size of battery was it you have? is it nearly new?

Remember to switch the charger off before you remove the charger leads. I have painful recollection of neglecting that advice. It is a mistake I have not made since.
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hi rockter, the battery is a normal sized car battery with 660 amp cold crank power, not real small or big.

will try to do it again as u suggested. thanks. yzlian
 
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