Ok so I know of batteries don't self balance in series but do in parallel but what is they are 2s1p? Basically I have 6 lithium batteries rigged to make 11.1v. Maybe the whole S and P thing is not correct description so like I said 3 batteries are rigged to make 11.1v and so is the second then tied together for parallel. So will this self balance the voltage on all batteries? I thanks.
Self balancing 26650 lithium batteries question
- Thread starter Lukasz
- Start date
Drunkskunk
100 GW
Nope. What you have is a 3s2p battery to make 6 cells into 11.1 volts. The batteries in parallel will self balance. The batteries in series won't. So at 11.1 volts, you could have the first two cells at 3.7 volts, the next two at 2.5 volts (very bad/destroyed) and the last two at 4.9 volts (very bad/soon to be on fire)
TheBeastie
1 MW
Nothing without BMS or balance charging stays balanced forever, eventually even well paralleled cells will have an inconsistent level with the next set in series..Lukasz said:
If your are drawing high amps then adding more cells in parallel significantly helps it stay balanced in general. If you find your pack extremely unbalanced at the end of each usage it means the cells are being hit much harder than what their are rated for.
Maybe you need a pure parallel balance charger? You can use one of these below for just 2-4 cells..
http://www.banggood.com/Charsoon-DC-4S-2-4S-Li-polyLi-ion-Battery-Balance-Charger-Voltage-Detector-with-Power-Adapter-p-1081892.html
http://www.banggood.com/New-B3-20W-Balance-Charger-2S-3S-Lipo-Battery-Charger-for-RC-Helicopter-Model-p-1022724.html
Or a big one..
http://www.radiolink.com.cn/doce/product-detail-102.html
Might help if we knew the application of the battery setup/whats it for?
Hi, thanks for quick answer. So here is what I have 26650 batteries each with built in protection. I was assuming that once each battery hits 4.20v then the battery circuit kicks in and it becomes passive letting the others get charged as well. I use it on a ice fishing flasher which pulls about .450mah and the batteries are digital energy 26650 from radio shack.
Drunkskunk
100 GW
Generally, when an individual cell says it has "built in protection", that means it has a fuse. try to pull too much current, or short circuit it, and the fuse blows, preventing a fire but ruining the cell.
No, the cell won't shut off at 4.2v to let others charge. you need a BMS for that.
No, the cell won't shut off at 4.2v to let others charge. you need a BMS for that.
Drunkskunk
100 GW
With that kind of set up, none will at all. No batteries are wired in parallel individually.
You would need to wire 2 cells together in parallel, then two more, and then 2 more. then treat each pair like a single battery and wire them together in series.
You would need to wire 2 cells together in parallel, then two more, and then 2 more. then treat each pair like a single battery and wire them together in series.
Adverse Effects
10 W
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nothing there will "self balance"Lukasz said:
that is the most unsafe setup that can be done
dogman dan
1 PW
The only thing that arrangement will do,, is one string of cells in series will be the same voltage as the other string.
So no cells balance, but connect two strings in parallel, and then if one string is higher voltage than the other, it will charge the low voltage string till both are at the same voltage.
Always be sure when making parallel connections, that both packs are the same voltage, that is,,have them both full charged when you connect.
So no cells balance, but connect two strings in parallel, and then if one string is higher voltage than the other, it will charge the low voltage string till both are at the same voltage.
Always be sure when making parallel connections, that both packs are the same voltage, that is,,have them both full charged when you connect.
dogman dan
1 PW
I never said it was unsafe. But if you want the cells to behave as if the two are one cell, parallel first, then series. The resulting pack won't balance itself, but you will have in effect, cells twice the size. parallel first, then series, is how bms equipped packs are built.
But there are still valid reasons for series first, then parallel.
But there are still valid reasons for series first, then parallel.
Thanks, I did it only in series because I wanted the voltage was most important to me also I thought that the pcm on individual batteries would self balance the pack.... I was wrong. I took the packs apart and there certainly was voltage difference in all my packs. This all started because one of my "series" packs mysteriously lost ah. I guess the pcm shut down one cell which in turn shut down one string of series. The dangerous part is this... If one battery has a very bad failure the voltage still has to travel thru it causing heat possibly smoke or fire.
