EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ANTALIFE on March 23, 2018, 09:44:15 am
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M8's
I want to charge x3 NiMH's in series with a solarcell-DCDC converter (ST SPV1040). It has a programmable current limit but that's about it, so no temperature or -deltaV monitoring for charge termination.
My question is which is the better topology for charging the NiMH's, is it even worth trying to use 1Meg resistors to try and balance the cells?
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There's no gain in using these 1M resistors
1. they're way too large to do anything but slowly discharge the cells
2. NiMH is equalized by slightly overcharging the "faster charged" cells. That's well within their specs, and common practice.
The only alternative to series charging (identical) NiMH cells is to charge them seperately, each one with its own charge termination circuit. That's what the better chargers do.
NiMH cells don't like continous charging (or trickle charging) for longer periods, this will kill them. So you definitively want some kind of charge termination circuit here.
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There's no gain in using these 1M resistors
1. they're way too large to do anything but slowly discharge the cells
2. NiMH is equalized by slightly overcharging the "faster charged" cells. That's well within their specs, and common practice.
The only alternative to series charging (identical) NiMH cells is to charge them seperately, each one with its own charge termination circuit. That's what the better chargers do.
NiMH cells don't like continous charging (or trickle charging) for longer periods, this will kill them. So you definitively want some kind of charge termination circuit here.
Righto thanks for that. Will leave the 1Meg resistors out and just go with a series combination. Guess my charge termination for now will be the sun not shining :-/O
EDIT: Also if I was to leave the 1Meg resistors in there then they won't do much discharging, we talking ~1.2uA