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Old 11-02-2019, 09:22 AM   #1
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Equalizing with a Trickle Charger

I realize the title reads like an oxymoron: how can a 1 amp trickle charger equalize batteries? But I did an experiment and I think it works.

I had two Group 24 "dual purpose" batteries on a trickle charger hooked up in parallel for the last 6 months while we were in Connecticut. Before reinstalling them in my boat here in Florida I topped up the water level. A couple of cells used about twice as much water as the others, maybe they were low to start with 6 mo ago.

So I checked the SG with a hygrometer and sure enough those two cells were about 0.05 points lower than the others. Not surprising, the water diluted the electrolyte. So I fooled the charger into restarting its charging phase (I call it that because it is two steps) at about 13.8 volts by disconnecting it for a moment. It put out 0.8 amps to start with. It slowly dropped to 0.5 amps and then switched to float at 13.1 volts after about 18 hours. Then I did it again. Same thing but it started at 0.7 amps and took about 12 hours.

When I checked the SG on the low cells they were back up to 1.275 the same as all of the others. They had been "equalized".

I didn't think that small current could do the job, but the numbers said it did.

David
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Old 11-03-2019, 07:51 AM   #2
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I think the missing piece is how much spread there really was between cells to begin with. Charging stirs up the electrolyte, so those low cells might have actually had a higher SG than your initial reading after topping them up. So I'm thinking some amount of the recovered SG may have just been from mixing of the electrolyte.


Regardless, charging like you did will bring them towards balance, and yours clearly got there. We just don't really know how far off they were to begin with. I think the higher voltage associated with traditional equalizing is to combat tougher sulfation. In that case it can take a lot of time, and a lot of voltage to break it down.
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Old 11-03-2019, 08:04 AM   #3
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You are right, I wish I had measured the SG before watering. FWIW I tried agitating the cells by shaking the batteries after I added water and before I measured the SG to try to mix the added water.


And yes, traditional equalization with higher current does much more than bring all cells to the same SG. It causes agitation within the cell itself due to disassociation of electrolyte which puts any precipitated sulfate back into solution. I suspect I had little sulfation so the low charging current of the trickle charger was enough to bring all of the cells up to the same SG.


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Old 11-03-2019, 08:34 AM   #4
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Quote:
Originally Posted by djmarchand View Post
I suspect I had little sulfation so the low charging current of the trickle charger was enough to bring all of the cells up to the same SG.


David

That would be my take too.
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Old 11-03-2019, 09:58 AM   #5
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David
Was your trickle charger one of those that pulses and claims to reverse sulphation?
I have used them for many yrs and seen some situation where I was able to get to a higher V after some time on the trickle/ pulse maintainer.
Very anecdotal and I had little real before after data but it definitely seemed to improve fully charged V.
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Old 11-03-2019, 10:15 AM   #6
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I've also found that the resting voltage of a battery will tend to be higher after sitting on one of the desulfating trickle chargers for a while. Mind you, a while in this context is defined as something like 6 months (with intermittent use of the battery in between). Seems to work on AGMs too.
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Old 11-03-2019, 11:57 AM   #7
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David
Was your trickle charger one of those that pulses and claims to reverse sulphation?
I have used them for many yrs and seen some situation where I was able to get to a higher V after some time on the trickle/ pulse maintainer.
Very anecdotal and I had little real before after data but it definitely seemed to improve fully charged V.

I don't think it was a pulse trickle charger. It is a simple Black and Decker, $14 charger, like this one- https://www.amazon.com/BLACK-DECKER-...s%2C197&sr=8-4



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