Charging Question

[piper]

Hello everyone,

I use a couple of AAA eneloop batteries to run my LOP SE. I was wondering about charging them in my Maha MH-204f.

Specifically is it ok to charge a pair of batteries (any nimh really) when one of the pair may be discharged to a different state: say one has about 25% left and the other 90%.

Does this do any damage to either of the cells?

 

[Anders]

Hello Piper.

Charging two cells with different state of charge is not adviced with a charger who charges in parallel.

I found it remarkable that this information doesn't exist in Thomas Distributions website.
http://www.thomas-distributing.com/mh-c204f-manual.htm
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Silverfox earlier wrote:
"[font=&quot]The battery manufacturers do not recommend charging NiMh cells in parallel. Some of the early battery chargers would charge a pair of cells in parallel, but this is not the best way to charge. If both cells are at the same state of charge, are of the same capacity, are charged at a slow rate, and are left on the charger to trickle charge for a period of time after the charge is complete, they will charge up fine in pairs.

The problem with parallel charging NiMh cells is that they signal the end of the charge with a slight dip in voltage. If one cell dips before the other one, the charger will not see then end of charge signal and will end up either timing out the charge or cooking one of the cells. Of course, if both cells peak at the same time, there is no problems.

[/font][font=&quot]."
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[/font]Edit: didn't realize first that you wrote "when one of the pair may be discharged to a different state"
In that case it would be just fine because the charger has two independent banks.

Anders

 

[piper]

No, if I'm understanding correctly you may have misunderstood, I have 2 AAA Eneloop batteries.

Is it OK to charge them as a pair when 1 may be at a different state of discharge in relation to the other: let's say one is at 35% and the other 65%.

I'm using a Maha MH-204f.

Thanks,

Piper

 

[WildChild]

It is better if both are at the same state of discharge... You'll end up overcharging one of the cells with this charger if they are at different states of discharge.

 

[eluminator]

I have to disagree that parallel charging is a bad idea. My experience shows otherwise. I think that terminating the fast charge with a simple zero delta volts is a bad idea, and apparently that is what this Maha charger does.

Also connecting two cells in parallel when their voltage differs significantly seems like a bad idea.

I was somehow under the impression that this charger charged two is series, but I was probably wrong.