is it safe to charge small SLA @ 10A +

[needWheels]

I have a fancy car battery charger that also handles SLA (specifically, has a AGM/GEL mode).

There is an independent rate mode, I can choose "small battery" which is a 2A charge
and a regular battery rate which will auto-vary from 10A to 20A

I've been using the "small battery" mode, which takes awhile obviously when battery is very low.
Any chance I can safely use the 10A-20A mode? Or is there some danger?

BTW these are all RBC2 7AH batteries, not 12A.

 

[dogman dan]

For a short time, it would be not only safe but would make a good desulphinator. But don't do it without monitoring it very closely. And don't do it all the time. Get a charger for the voltage you are using. I've done charging of 12 ah sla with my generators 10 amp dc output, but I was doing that in a way that never left a battery on it for more than 20 minuites or less, and then I would rotate it to a normal 2 amp charger to find out if it was charged. That kept em cool. That kind of charge rate does affect how many cycles you will get though. I wouldn't do it unless you need to, like on the weekend and you don't want to wait 48 hours to charge the whole pack. If the charger was slow to shut off, it would cook the battery quick.

 

[Randomly]

Most SLA don't like charge rates higher than about 0.4C (4 amps for a 10AH battery).
If you charge them at high currents it rapidly degrades the cycle life and you will soon be buying a new battery.

 

[dogman dan]

That's right, I only did it a few times when I first got my e bike, and the charger died on the second use. It was the weekend and charging with the 12 v 2 amp charger I bought was going to take a day and a half. By rotating the batteries I was able to keep em from getting hot. As I understand it, a short period of high amperage at the start of the charge cycle is supposed to knock the sulphite back into solution. Mine were 12 ah batteries, smaller ones would need to be at the high amps even shorter time. I would think that the damage would be worst if the battery gets hot, so I made sure they didn't. Do not try this without watching em pretty much continuously. At the time, I just wanted to ride so I took the chance of some battery damage. I'm at about 50 cycles now and no problems so I didn't do too much damage doing it 3 times.

 

[Eric G]

The spec sheet that came with my sla recomend the initial current for charging be no more than .25c.

 

[Ypedal]

Like above, all lead acid batteries are not created equal.

I have some Hawker Genesis SLA's that can be charged up at high-rate ( 25ah PC925's ) spec sheet says they can handle up to 20 amps all the way to full.. more on short bursts , without harm !!

However, most others canot handle this much current and will boil ( litterally you will hear the acid boil in the battery .. ) and dry them up, making them paper weights. :wink:

http://www.enersysreservepower.com/documents/US-ODY-AM-001_0406.pdf

 

[safe]

Very high charge rates are best used on really old batteries for a short time. When new the high charge rate will NOT desulfate because there's nothing there yet, but it will eat away at the opposite side and cause excessive oxidation. Oxidation means irreversible damage.

Save the high charge rates for reviving old batteries...

 

[dogman dan]

Good advice Safe. I knew I could count on you to know this subject. I did say don't do it all the time. Sometimes when that bike is new, we just can't resist something that we know is bad, but I get to ride today!