Re: charging a fully discharged car lead acid battery

Jim Adney wrote:

There is one thing that you should check occasionally, and that is to
verify that you don't have a shorted cell in there, which would make
this a 10V (or 8V) battery. To test for this, just leave it off the
charger overnight and check the open circuit voltage in the morning.
It should be above 12V.


I always disconnect it for overnight. It has been reading 12.0 volts the last two mornings.

I know you did this earlier, and at that time it was still only up to
11 volts. At that time it looked like this was reasonable, but by now,
I think you should be back up to "normal." Haven't you put ~50 Amp-hrs
into this thing so far?


Well, it's more like 32 amp hours. The built in hygrometer is starting to show green, so it is progressing. I can wait it out, no problem ;)

If the voltage drops to ~10V, then you have a shorted cell, and I
really don't think that is ever repairable.

I'm surprised that you're not higher in voltage by now, so maybe some
caution is worthwhile. Your 1 A charging is still fine; that won't
hurt anything.

But wait! Isn't your charger a 12V CC/CV lab supply? In that case, I
think you just need to switch to something higher in voltage. Just
keep the voltage under 14.1 V.


I was wrong about the supply. It is 12 volts nominal, but you can dial it up higher. To push 1 amp into it, the open circuit voltage is 14. But when loaded onto the battery, it is rock solid at 12.0 volts.
.

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