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Hot LiPo balancer?

Old 06-10-2012, 05:44 PM
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RC Fan chris
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Default Hot LiPo balancer?

I have a balancer for my LiPo's and it gets hot when I use it. Is this normal? I honestly couldn't find anything about this.
Old 06-10-2012, 06:34 PM
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t9dragon
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Default RE: Hot LiPo balancer?

What balancer are you using?
Old 06-10-2012, 07:18 PM
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chuckk2
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Default RE: Hot LiPo balancer?

It can be normal. If the cells are really out of balance, and the balancer tries to bring the high cell down by charging the low cell at a controlled current, or just absorbing the "extra" charge from the higher cell. There is a difference between really warm and hot!
Old 06-12-2012, 07:27 PM
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RC Fan chris
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Default RE: Hot LiPo balancer?

It's a Common Sense RC balancer from the LHS for $30. That was the first time I balanced the LiPo's, so they could have been way out of balance. One of the batts had a couple cycles on it, the other had about 9-10. I got the batteries just last year.
Old 06-14-2012, 06:26 AM
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bgosselin
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Default RE: Hot LiPo balancer?

Yeah, like chuckk2 said, the balancer is discharging the high cell(s) and that is creating heat. IIRC, that balancer (I have one) balances at 150mA, which equates to around 0.6w of heat dissipation per cell. If one cell is being actively balanced (discharged), then it should be a little warm, but if multiple cells need balancing, heat can climb quick.

Keep in mind that the balancer, since it isn't connected to the charger, doesn't "talk" to the charger to tell it to lower the charge rate, and so isn't truly 100% effective. If you are charging at 5A, any cell that is being balanced is effectively being charged at around 4.85A (5A charger rate minus 150mA balancer bleed current). At that high of a charge current, the balancer might not be able "keep up" with the charger to prevent an individual cell from exceeding the 4.2v limit. If the balancer is quite hot, it means it is working hard, so I would lower the charger's charge rate to allow the balancer to have an easier time to do its job; something like 1A.

I have an older version of their balancer and I modded it a little to help with excessive heat by adding a heatsink to the bottom. Ideally, the sink should be attached directly to the heat-producing devices, but that wasn't feasible. So I found a spot on the back that had no exposed components, traces, or solder tabs and attached it there:


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