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High Power 10s Lipo Battery Pack with BMS


Sorry, how do you define which is cell #1 using a multi-meter on yellow and red wire?
One should give you a reading and the other does not?


Rule of thumb for 2s Lipo balance wires.
Black wire on edge of connector is ground
Red wire on opposite edge is cell 2
Wire in middle of connector is cell 1
On Lipos that are 3s to 6s, the balance wires are always in succession and cell 1 is always next to the black ground wire.
The red wire on the edge is always the last cell in the pack.
The black wire on the edge is always ground.


Got it, thanks.


Normally, I just buy batteries pre-packed, or pre-made. Cause I’m one of those guys you call lazy, sadly.
This is my 1st attempt to make my own. Starting the the least expensive ones, the LiPo’s.

Learned from some articles and videos that LiPo’s are some scary sh!t. One of the most dangerous batteries around.
No wonder hard packs are nice, for extra battery protection. With BMS (assuming in good working condition), will, somehow, eliminate over charging and make it safer. But still, it does not mean you will let your battery charging unattended.

Anyway, I just got my 4 pack of 10 (2s/5000mah/7.4v 60c LiPo) from hobbyking and will start solder them in series.
So I used my multi-meter to test the balance wires (for curiosity sake).
The cell #1 reads 3.7v, while cell # 2 reads 7.5v.
So the conclusion is, the lowest voltage reading is the cell #1, and adds up till you reach 37v, which is cell #10.
Since I’m doing the parallel, I’ll just match-up the balance wire with the same voltage reading.
Thanks to @mmaner 's crystal clear diagram, I know now where to connect the volt meter, and charger.
Thank you too @Namasaki.


It’s a really good idea to balance charge each pack before soldering them together. Especially if your connecting them in parallel.
anytime you connect multiple cells or packs in parallel, they will auto balance themselves quickly with high current transfer that can damage the cells involved.

I have been using Lipos for years, first in helicopters and now in Eboards. I have never had a problem with them catching fire or exploding.
Just use quality Lipos and balance charge them either with a good hobby charger designed for Lipos or a bms and brick charger with the correct voltage output.
Since I’ve been into Eboarding, I have not seen anyones lipo build catch fire but I have seen 2 builds with Li-ion batteries burn to the ground.
When you stop and think about it, the Lipo build is somewhat flexible.
The welded Li-ion pack is more rigid and consequently, more susceptible to vibration and road shock.
The pics below are both Li-ion builds that just caught fire. The top one for no apparent reason. The bottom one ignited after riding over a very rough road.


Battery min at -20 for a 5ah battery?
Thought one shouldn’t go beyond 2c, meaning -10 in this case.


The Lipo packs that are featured in this thread are rated for 5C charge or 25a
I bench charge them at 5a
They have been doing fine with regen brakes batt min at -20a total


Mine are rated 3C charging. Best to leave it at 10 instead of 15?



Currently hooking up the 10s battery to the 10s BMS… Before I did so, I measured all cells, and later the total for the pack which was 41.6v (I actually screwed up the batteries a little bit from charging carelessly, and now 41.6v is the maximum it charges) at any rate… All cells are balanced…

When I check the voltage THROUGH the BMS it reads 40.8v, that’s 0.8 less volts.

Is it normal for the BMS to “eat” up some voltage?


I’ve never known the bms to eat any voltage.
Where are you measuring the voltage?
Try waiting about 5 seconds after turning it on before measuring.
If your batteries are balanced but not charging to full 42v then the problem most likely is with the charger your using.
That is, if your using the BMS and settings featured in this thread


Hey, I was measuring the voltage without turning the BMS on.

Once I turned it on it gave the proper reading.

Side note, I installed the charge port to the -C on the BMS and the positive to the positive that comes out of my battery. As it was charging I turned on the BMS and the charger blew up.

Smoke… Fear… Fun.

So, I advise not to do that to future builders.


Your charger did not blow up because you turned the bms on.
The bms is supposed to be on while charging per the manufacture’s instructions.
I usually turn my charger on first and then turn the bms on immediately and nothing has ever blown up.


Oh crap…

I remember I plugged in the charger to the charging port, and the charger seemed to be making some sort of sound (which I can’t recall) then I turned on BMS and just smoke everywhere. I nearly soiled myself.

Anybody know what it can be due to? I’m not sure I should plug another charger in…

BTW used the same batteries, same BMS, a 24 euro 42v 2a charger, and I think even the same charging port for segways, and the connections I’m 99.9% sure they are right.


Double check the polarity of the charger and your charge socket on the board.
It sounds like you got the polarity wrong.


It was indeed a polarity problem. Everything seems to be connected properly now, except…

This is the charger connected only to the plug in my house

As you can see the light on the charger turns green.

And this is what happens when I connect the other end to the board

You can bearly tell, but it powers up my focbox, and the light on the charger goes from green to red, and that’s with the bms off.

I’m afraid to turn it on, and there aren’t any instructions that come with these chargers. Should I just switch on the bms?

Sorry for the shit pictures.


Quick update, I left the charger on without turning on the BMS and saw that the voltage was going up… Meaning the battery was being charged, so I manned up and turned on the BMS.

Battery is fully charged. The joy is unexplainable… It only charges to 41.6v, but still… I’m happy as hell.

Thanks for enduring my constant noobness @Namasaki.

Will open up a thread with my build and pictures when I get the chance!

Thanks again!!


Your Bestech BMS should automatically turn on when you plug in the charger. If this is not the case than I think something is wrong with your wiring.
I can confirm this since I have a battery indicator connected between the pos and neg ports coming out of the BMS

As to the 41.6v of charge: just because your charger says 42v on the enclosure doesn’t mean it will actually charge to 42.0v
A charger or higher quality might, but a 24 bucks charger almost certainly won’t.



None of my BesTech BMS’s automatically turn on when I connect the charger, I have to turn them on to charge. That’s one of the characteristics of the BEsTech BMS that it does not allow any traversal unless the ON/OFF circuit is completed. I haven’t bought one in about 3 months, so it might be different now, but of the 4 that I own none auto turn on.


Hmmm interesting.
Mine also turns automatically off as soon as the charging has completed, or so it seems.
Probably the charger that stopped charging resulting in the BMS turning off


Ahhhh you meant the charger, I thought you meant the board electronics. I was trying to say that to charge I have to have the BMS switch on, when its off it doesnt charge.