lipo running in series

eschult · Mar 22, 2012, 04:12 PM

When running two 3 cell lipos together as a six cell how important is it to use the same exact c rating. Example. Running 2 3 cell 5000 mah together. Can one be a 20c rating and the other be a 30??????

everydayflyer · Mar 22, 2012, 04:23 PM

They need to be as exact as possible. Same capacity ,same C rate,same past useage history,same cell IRs.

Even with new LiPolys with cells of same batch it is common for a 4S to be harder to balance than a 2 or 3S. Each added cell makes the tast more difficult.

You could charge them in parallel tohelp with the balancing and may get by with discharging in series if you use only 60% or so of their capacity. Do a short flight and check eack battery seperately to see how close te cell voltage are and how many mAh it takes to recharge each one.

I would not do it my self,to much bother as inexpensive as LiPolys are these days.

Charles

abenn · Mar 23, 2012, 03:17 AM

Packs run in series are only as good as the weakest pack (or cell). The amps running through each pack will be identical when they're in series, so if you do run them that way, it's important to ensure that you're only running them at whatever amps the weakest pack is good for.

It's advisable to match them as close as possible though.

Mar 22, 2012, 04:12 PM	#1
eschult FLYINGJUNKY USA, FL, Jacksonville Joined Mar 2008 827 Posts	lipo running in series When running two 3 cell lipos together as a six cell how important is it to use the same exact c rating. Example. Running 2 3 cell 5000 mah together. Can one be a 20c rating and the other be a 30??????

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Mar 22, 2012, 04:23 PM	#2
everydayflyer Southern Pride Haralson County GA. USA Joined Oct 2004 34,187 Posts	They need to be as exact as possible. Same capacity ,same C rate,same past useage history,same cell IRs. Even with new LiPolys with cells of same batch it is common for a 4S to be harder to balance than a 2 or 3S. Each added cell makes the tast more difficult. You could charge them in parallel tohelp with the balancing and may get by with discharging in series if you use only 60% or so of their capacity. Do a short flight and check eack battery seperately to see how close te cell voltage are and how many mAh it takes to recharge each one. I would not do it my self,to much bother as inexpensive as LiPolys are these days. Charles

Mar 23, 2012, 03:17 AM	#3
abenn Registered User Letchworth, Great Britain (UK) Joined Jul 2004 10,273 Posts	Packs run in series are only as good as the weakest pack (or cell). The amps running through each pack will be identical when they're in series, so if you do run them that way, it's important to ensure that you're only running them at whatever amps the weakest pack is good for. It's advisable to match them as close as possible though.