Lipo Balancing Question
04-28-2010 | 05:14 AM
#1
Lipo Balancing Question
In the past I have only run 1/10 scale and used no more then 2S lipos. I had several different brands from no name packs to nice max amps packs.
I recently got into 1/8 electric. I have a 4S 25C Flight Max battery. With my 2S packs after running there was at most a 0.08v difference between the 2 cells. On my 4 cell the few times I have run it the difference between the cells seems larger with the high and low being as much as 0.4V difference. Does this large difference mean there is a problem with the pack or is it just a function of having 4 cells instead of 2?
Also, I have used two chargers an IMAX B5 and AC6. Both seem to take a long time to balance the pack. It gets close quickly with cells at 4.19, 4.19, 4.19, and 4.2 but bringing all 4 cells to 4.2 seems to take forever, sometimes the charger times out before it is completed. Again is this just a function of balancing 4 cells?
Is this type of behavior normal for the larger 4S packs?
I do know that both chargers I used were 50watt chargers so were limited on charging capacity.
Thanks
I recently got into 1/8 electric. I have a 4S 25C Flight Max battery. With my 2S packs after running there was at most a 0.08v difference between the 2 cells. On my 4 cell the few times I have run it the difference between the cells seems larger with the high and low being as much as 0.4V difference. Does this large difference mean there is a problem with the pack or is it just a function of having 4 cells instead of 2?
Also, I have used two chargers an IMAX B5 and AC6. Both seem to take a long time to balance the pack. It gets close quickly with cells at 4.19, 4.19, 4.19, and 4.2 but bringing all 4 cells to 4.2 seems to take forever, sometimes the charger times out before it is completed. Again is this just a function of balancing 4 cells?
Is this type of behavior normal for the larger 4S packs?
I do know that both chargers I used were 50watt chargers so were limited on charging capacity.
Thanks
04-28-2010 | 10:07 AM
#3
Joined: Jul 2008
Posts: 11,530
From: Houston, TX
You've got a cell with a much higher IR (internal resisitance ) than the others - thats what is driving the voltage to be diff with that cell. Pretty sure HobbyCity lipos use unmatched cells so occassionally you can get lipo thats pretty diff than the others.
No, this is not just due to being a 4S pac. The cells should behave the same whether its a 2S or a 6S. My Neuenergy 3S pacs don't do this and the cells stay a lot closer - usually around 5mv (.005v) but these are made with matched cells so thats what I'd expect. My HC lipos show a lot more diff like yours.
One thing you can do is to raise your lvc - cell imbalance gets bigger the deeper you discharge them. Balancer just takes time to get them evened out, just set your safety time long enough that it isn't turning it off or just pull the lipo off when cells are close enough. 3 at 4.19 and 1 at 4.2 is plenty close enough.
No, this is not just due to being a 4S pac. The cells should behave the same whether its a 2S or a 6S. My Neuenergy 3S pacs don't do this and the cells stay a lot closer - usually around 5mv (.005v) but these are made with matched cells so thats what I'd expect. My HC lipos show a lot more diff like yours.
One thing you can do is to raise your lvc - cell imbalance gets bigger the deeper you discharge them. Balancer just takes time to get them evened out, just set your safety time long enough that it isn't turning it off or just pull the lipo off when cells are close enough. 3 at 4.19 and 1 at 4.2 is plenty close enough.
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