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Topic: Charging probably bad 12V sealed lead battery? (Read 772 times) previous topic - next topic

robitabu

Hallo experts :-)

Yesterday my motorbike didn't start at all. Bad battery, it was approximately 11V only. After a few simple inspections to the relais/starter/connectors I was shure the battery was the only culprit, so I bought a new one and temporarily stored the bad one.

Nonetheless, it still gives out 11V (which is of course way to low to be considered good) and I wonder if I could aim at some success trying to charge it somehow.

I quickly made up a small basic current controlling circuit based on the LM317 (with a big dissipator behind) in order to feed almost 1A. Well, I immediately noticed the voltage to build up. The volt meter shows now, after 15min charging, 13.5V.

Ok, here's the question. I really don't know what to expect from such a charging method, I've read it's a basic one (the sticker on the battery suggests 1.2A for 5-10hours as a method), but I don't know if this voltage raising is good/bad/unbiguous. Is it a good sign?

I'd like to know more from you all. I am pretty shure there's someone out there having tried something like this in the past. Hints?

Thanks,
  Roberto

Grumpy_Mike

When a battery goes bad it often looses capacity not voltage. So you need to do some charge and discharge cycles to see if the voltage holds up. Try putting a cycle bulb on the battery and measuring the voltage and see how long it holds up.

robitabu


Try putting a cycle bulb on the battery and measuring the voltage and see how long it holds up.

Do you mean a 12V light bulb? Would a 12V pc fan do the same?

I have to say, I already made a quick test. I stopped charging it and measured the voltage again while a 12v fan (the one I use to cool the heatsink on the lm317) was still attached to the battery and running.
Well, at first it immediately turns down to 12.5V, then slowly decreases even more, in a few minutes it's back at almost 11V again (I admit I interrupted the process before recheaching 11V and started charging again).
I don't know if that means something to you.

Grumpy_Mike

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Would a 12V pc fan do the same?

Yes, it takes even less current than a 12V bulb so it should hold up longer.

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I don't know if that means something to you.

It sounds like you have a bad battery on your hands that has very little capacity left in it.

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