# NIMH Battery charging question

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etec3
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Last seen: 15 years 1 month ago
Joined: Tuesday, March 20, 2007 - 23:04
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NIMH Battery charging question

Hi, i have a NIMH battery pack thats 28.8 volts and im charging it with a 25.2 volt charger. will this damage the batteries?

HCT
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Last seen: 4 years 4 months ago
Joined: Wednesday, February 7, 2007 - 08:16
Points: 137
Re: NIMH Battery charging question

:) Your 28.8 pack has 24 cells in series , when charging each cell should have at least 1.5 volts available ( current limited of course ) just doing the math 24 X 1.5 = 36 volts .You should use a 36 volts charger with enough current capabality to recharge the pack in a couple hours at most , have found that charging NIMH at anything slower that C/2 make it very difficult to determine the the end of charge .
Charging at less than C/10 is possible if the state of charge is now .NIMH are not easy cells to recharge without some overcharging .

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andrew
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Joined: Tuesday, November 28, 2006 - 17:21
Points: 1361
Re: NIMH Battery charging question

etec,
unplug the charger from the batteries, and measure its open circuit voltage. If the existing charger comes up high enough in voltage, than you may not need a new charger. But because the charger current will taper off when the voltage comes up, then it may take a very long time to charge the pack to 100%. You might want to measure the charging current throughout the charge cycle.

Good resource:
http://www.powerstream.com "Technical resources" - "How to Charge NiMH Batteries"

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