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Charge currents

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Douglas Wheelhouse 124/03/2019 11:58:40
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140 forum posts
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Hi to all,

Can someone tell me the safe charge currents for,

9.6 nihm tranny battery (eneloop)

4.8 2000mAh eneloop battery

12v pb battery

just need clarification, Thank you

Douglas

Gordon Tarling24/03/2019 12:11:05
229 forum posts
4 photos

Charge the two Eneloop batteries at 1 Amp or less. They CAN be charged at up to 2 Amps, but they tend to get warm at that level, so best not to. As for your lead acid battery - we need to know what type and capacity before making a recommendation.

Douglas Wheelhouse 124/03/2019 12:14:56
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140 forum posts
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Thanks Gordon for being so prompt, I appreciate it

Douglas

Don Fry24/03/2019 12:23:43
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3491 forum posts
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What sort of charger are you using. Does it try to detect if the battery is fully charged, or is it a dumb charger. Makes a big difference to how you charge batteries.

Edited By Don Fry on 24/03/2019 12:24:21

Douglas Wheelhouse 124/03/2019 12:31:07
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140 forum posts
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Hi Gordon,

Its a 12v 7AH lead acid battery

Douglas

Douglas Wheelhouse 124/03/2019 12:34:20
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140 forum posts
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Hi Don

Ita a Sigma touch 2 80w balance charger

Don Fry24/03/2019 13:04:55
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3491 forum posts
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The lead acid. A tenth of capacity, on the PB program. So that's 700mAh. That's conservative, and the charger gets to 2.4 v per cell and starts to slow the charge.

the enloops are a bit more complex. Your charger will try to detect a full battery, it's a very small rise in cell voltages, detected amoung rising voltages as the cell charges.

Bottom line is, the charger misses the peak if the charge current is too low. Most folk reckon to do it at about 1/2c, to c. So that's 1 amp to 2 amps for the 4.8 v pack. The transmitter pack, same maths, look on the side for its capacity.

C is the capacity of the battery as written on the pack, i.e. 2000 mAh on your 4.8v pack.

That sort of cell is not fussy, and if you were in a hurry, with your charger, you could double the charge current.

Edited By Don Fry on 24/03/2019 13:05:48

Allan Bennett24/03/2019 21:04:55
1507 forum posts
38 photos

As has been pointed out, a peak-detection Ni charger can miss the peak if the charge current is too low. But with too high a charge current the cells can heat up to their detriment. So for Rx and Tx Ni batteries, be they Eneloop or any other brand, I still prefer to charge at about 1/10C overnight. The charge rate is so low that it won't harm the cells if they become fully charged before the charge is stopped, and the long duration ensures that any cell that is lagging behind will have time for its voltage to reach that of the others in the pack.

Martin McIntosh24/03/2019 22:10:34
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2796 forum posts
1045 photos

I have found that to get maximum capacity into Eneloops, 600 mA is ideal. If I suspect a false peak I use an additional charge of 1A. Some quite elderly ones I have will still take 1850 mA/hr by treating them this gently. 2A will certainly not charge them to full capacity from flat. Fine for a torch maybe but not for my models!

Jon - Laser Engines24/03/2019 23:01:30
4612 forum posts
172 photos

I agree with martin and do my nimh's at .5 or .6amps. My bigger packs will take more but i am rarely in that much of a rush so why abuse them?

robert chamberlain19/05/2019 00:51:49
110 forum posts

My son ran into a situation lately that puzzled me. he has 2 twelve volt batts in series for 24 volts. I believe they are LiFE .

This was for a power drill. Not A/C related but I figured it is the same chemistry. Taking it off the charger, he separated the two 12 volt batts , and the one measured 35 volts! How can this be? What is going on here? Any thoughts out there?----------------Bob in Kansas

Percy Verance19/05/2019 06:49:08
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7935 forum posts
152 photos

Same technique as Martin and Jon here. Usually 600ma into my transmitter packs (12yr old 35mhz Mpx Royal Evo) - 6 cell nimh. Never had an issue. First pack replaced after 7 or 8 years, now on replacement pack. Onboard battery management indicated when the first pack was past it, with displayed remaining operating time showing far less than normal. Showing less than 6 hours after a charge. It's usually about 24 hours. Pretty much the same with newer Royal Pro, although this still has 6 AA nimh cells, they're higher capacity than the old Evo. They can show 30+ hours operating time after a charge- again at 600mh.

 

 

 

 

Edited By Percy Verance on 19/05/2019 07:14:01

Martin McIntosh19/05/2019 16:47:58
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2796 forum posts
1045 photos

Got me stumped there. Are you sure that the meter read 35V and not 0.35V or 3.5V?

They cannot be LiFe because the two together would be 26.4V, not 24V. Only NiMh, NiCad or lead acid can give 24V in total unless the stated 24V is just nominal. Li-on cells could also be somewhere near and much more likely to be found in a drill these days.

Is it the charger which came with the drill or something else?

Pete B - Moderator19/05/2019 17:29:21
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Moderator
7544 forum posts
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Posted by robert chamberlain on 19/05/2019 00:51:49:

My son ran into a situation lately that puzzled me. he has 2 twelve volt batts in series for 24 volts. I believe they are LiFE .

This was for a power drill. Not A/C related but I figured it is the same chemistry. Taking it off the charger, he separated the two 12 volt batts , and the one measured 35 volts! How can this be? What is going on here? Any thoughts out there?----------------Bob in Kansas

Hi Bob,

Just a thought but might it be worth starting a new thread to deal with this? It's a long way from Eneloops...smile

Pete

Geoff Sleath19/05/2019 19:43:57
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3243 forum posts
247 photos

I've had a 7 cell 3.3AH NiMH battery powering our bathroom radio for about 10 years. It get used every day for about an hour, I suppose, sometimes more if my wife uses it elsewhere. I charge it at 2 amps on my Graupner Ultramat 16 and it certainly gets hot (or very warm, perhaps 35/40 degrees) and still takes it full capacity each time.

Obviously the current draw is quite low in use but the charge regime doesn't seem to be a problem and a lesser current means the charger timer kicks in before the charge is complete.

Geoff

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