Over-discharging
- Thread starter FNinjaP90
- Start date
mattheww50
Flashlight Enthusiast
The usual problem when this happens is the charging current initially is more than the charger can handle, so it crowbars thinks it has been shorted out. The fix is to insert a resistor between the charger and battery pack such that the the current through the dead battery will be equal to less than the normal charing current, and let it charge that way for a while.
So for example a 16 cell pack would normally charge to about 24 volts, If you put a 500 ohm resistor in series, that will limit the charging current to about 50ma initially, (and is unlikely to seriously overheat the resistor). Within a few minutes, the batteries will no longer be completely discharged, and you can take the resistor out of the circuit.
So for example a 16 cell pack would normally charge to about 24 volts, If you put a 500 ohm resistor in series, that will limit the charging current to about 50ma initially, (and is unlikely to seriously overheat the resistor). Within a few minutes, the batteries will no longer be completely discharged, and you can take the resistor out of the circuit.
Also, your charger would have detected the pack voltage as being too low, and would have refused to charge it.
You probably caused some irreversable cell damage. Showing only 2 volts, you may have reversed several of the cells in the pack. They will likely have less capacity now than they did before, and will probably expire before the rest of the pack. I'm not sure what percentage of capacity you typically lose when reversing the cell, but repeated cell reversals can severly reduce the cell's capacity.
You probably caused some irreversable cell damage. Showing only 2 volts, you may have reversed several of the cells in the pack. They will likely have less capacity now than they did before, and will probably expire before the rest of the pack. I'm not sure what percentage of capacity you typically lose when reversing the cell, but repeated cell reversals can severly reduce the cell's capacity.
Hallis
Flashlight Enthusiast
Might not be too bad an idea to disassemble the pack and check each cell individually. Then replace the effected cells.
Hallis
Flashlight Enthusiast
well, /ubbthreads/images/graemlins/icon3.gif sounded like a good idea. lol
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Hallis said:
well, /ubbthreads/images/graemlins/icon3.gif sounded like a good idea. lol
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It's a great idea, you just need to test the cells under load and when the pack is at "discharged" voltage (~1-1.1V/cell) to see if any cells are significantly weaker.
Hallis said:
well, /ubbthreads/images/graemlins/icon3.gif sounded like a good idea. lol
[/ QUOTE ]
It's a great idea, you just need to test the cells under load and when the pack is at "discharged" voltage (~1-1.1V/cell) to see if any cells are significantly weaker.
Hallis
Flashlight Enthusiast
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FNinjaP90 said:
I think it's time I get myself a Triton. The pack is charging fine now at 0.35A.
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Tritons are NICE. if i ever get into lights with multi-cell packs i'll definately be picking one up.
Evan: Thanks for the reassurence /ubbthreads/images/graemlins/smile.gif
FNinjaP90 said:
I think it's time I get myself a Triton. The pack is charging fine now at 0.35A.
[/ QUOTE ]
Tritons are NICE. if i ever get into lights with multi-cell packs i'll definately be picking one up.
Evan: Thanks for the reassurence /ubbthreads/images/graemlins/smile.gif
Got a cell phone pack with bad cells in it once, it charged up fine tested good with voltmeter on each cell but when you used it to power a light after about 5 minutes the light went dim and measuring the cells I found one was -.02v, reversed. I could recharge it and it would test fine. Only when it was disharged some would it reverse itself. Best test is probably to use it and see if it works normally. If it has bad cells you may find it going weak a lot sooner than normal.
