charging
05-09-2009 | 04:37 PM
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From: lake peekskill,
NY
charging
I am charging 2900mAh, nimh AA batteries and they are getting fairly hot after about 5 hours is this normal? I never hade nimh batteries before and concerned about leaving them charging overnight.
05-09-2009 | 05:38 PM
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RE: charging
Normal charge rate is .1 ( 1/10) C meaning if it is 2900 ma (2.9 amps) then the probably charge rate is 290 ma .290 Amps per hour for 10 hours. .290 X 10 = 2.900 Amps or 2900 milli-amps.
For those of you that do not understand ..this is, after all, a beginners forum, milli - .001 or 1/1000. In this case, 1 milliamp = .001 amp. 1000 miliamps = 1 ampere. Some more scientifically inclined might start with the coulomb thing, but that's much more detail than needed for this explanation. Fair enough?
Now you can charge it faster than that, the end result is a warmer battery, lower life expectancy, and, most likely not an absolutely fully charged battery.
A fairly accepted rule of thumb is that you should add about 10%, sometimes more, due to overhead (heat, internal resistance (ok.. I apoligize) and other factors) to that charge time to come up with a full charge. But, as mentioned, this is not the best situation, but most likely, the best charge rate, and what many may use for charging that type of battery.
With that said, there are chargers that will produce a faster charge at the cost of the life span of that battery. I have a Sirius field charger that will charge some smaller battery packs in an hour. My packs are not 2900 mah, but 1200 mah, and I do charge them at the fast rate using the field charger.
Is that safe? Well, it charges them, but, knowing that I am being a tad bit reduncant, maybe at a cost of the life span of that battery pack.
When dealing with battery packs, you fast charge them at your peril. Slow is best. But, as always, that's not convenient.
Your choice, I guess. I do fast charge and accept the risk.
By the way, I use AND always recommend Voltwatch. Look it up. (no, I don't work for them, but recognise that they are a valuable addition to your model investment).
CGr.
For those of you that do not understand ..this is, after all, a beginners forum, milli - .001 or 1/1000. In this case, 1 milliamp = .001 amp. 1000 miliamps = 1 ampere. Some more scientifically inclined might start with the coulomb thing, but that's much more detail than needed for this explanation. Fair enough?
Now you can charge it faster than that, the end result is a warmer battery, lower life expectancy, and, most likely not an absolutely fully charged battery.
A fairly accepted rule of thumb is that you should add about 10%, sometimes more, due to overhead (heat, internal resistance (ok.. I apoligize) and other factors) to that charge time to come up with a full charge. But, as mentioned, this is not the best situation, but most likely, the best charge rate, and what many may use for charging that type of battery.
With that said, there are chargers that will produce a faster charge at the cost of the life span of that battery. I have a Sirius field charger that will charge some smaller battery packs in an hour. My packs are not 2900 mah, but 1200 mah, and I do charge them at the fast rate using the field charger.
Is that safe? Well, it charges them, but, knowing that I am being a tad bit reduncant, maybe at a cost of the life span of that battery pack.
When dealing with battery packs, you fast charge them at your peril. Slow is best. But, as always, that's not convenient.
Your choice, I guess. I do fast charge and accept the risk.
By the way, I use AND always recommend Voltwatch. Look it up. (no, I don't work for them, but recognise that they are a valuable addition to your model investment).
CGr.
