High Power 10s Lipo Battery Pack with BMS

so you just balance them with a charger then soldered them up and charged via bms?

Yes, I balanced each pack with my hobby charger before putting them together. Then the bms keeps them in balance. I attach them to the bottom of my deck with servo tape and then solder them together.

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If itā€™s still available and not sold to twan Iā€™ll take it. Iā€™m in Atlanta.

Unfortunately it has already been sold. Though something tells me you will seem them being sold on this forum more often, they have an impeccable reputation here.

Hey @Namasaki, love your battery pack design! I also was thinking several times about such a way to make a pack but thereā€™s always 2 questions i have.

Isnā€™t it a problem with one short and one long battery lead (in your case the positive lead is long)? Read often all leads must be the same length and even the distance from one side to the other of your pack is about 23cm, so the positive lead to the controller incl. BMS is min. 30cm, maybe moreā€¦ (In my case the positive lead would be 40cm and the negative 15cm). Thatā€™s why i never did it.

About the BMS, your bestec has over-discharge protection at 2.9V which is quite high but still 2,9V would damage the Lipo cells i think. Most BMS have even lower over-discharge (i have one with 2,5V) because they are maninly made for Li-ion so i donā€™t know why to use a BMS when e.g. one cell is drifting and the BMS starts working when the weak cell reached 2,5-2,9V when itā€™s too late.

Are there any advantages to use a BMS compared to fuse only and cheap BMS for charging? I would like to use a BMS for dischgarge in the future, too but iā€™m not sure if it can really save the liposā€¦

Iā€™m currently using the same bms with the over discharge detection set at 3.0V which is the highest option. If one cell drifts down to 3.0v the bms shuts everything down. Some Lipos may handle 3.0v without damage others might not. Normally I try not to run my battery lower than 36v and much of the time I donā€™t go below 38v. The other advantages of discharging through the bms are short circuit protection.( if a short anywhere in the system occurs, the bms will instantly shut down the entire system.) This happened to me once when I accidentally shorted the charge port. The bms shut power down so fast that nothing was damaged not even the battery. People have complained about having problems with Regen braking downhill on a full battery with their vesc shutting down because of over voltage and then being suddenly without any brakes. I have tested braking down steep hills with a full battery whiled monitoring my battery voltage. The bms would not let the voltage climb higher than 42.8v on my 10s battery and as soon as I stopped braking, the bms quickly pulled the voltage back down to 42v while I was just coasting. So it seems safe to say that the bms protects against overcharging though regen braking.

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DC current moves in one direction from negative to positive. Therefore I canā€™t see why the positive wire being longer than the negative wire would make any difference at all except that the longer your power wires are, the more resistance you have. But itā€™s not a matter of balancing the positive and negative wires.

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Hallo @Namasaki i have the same BMS on the way for my Trampa 10S build. Nice to hear that the bms is working perfectly fine for you :slight_smile: Do the bms needs to be turned on via E-switch, when charging or ?

And oh, what charger are you using ?

Sorry for this stupid question (iā€™m no electician) but shouldnā€™t a fuse with the same amount of ampere as BMS max doing the same job (beside the fact that the fuse has to be changed afterwards)? But maybe the BMS is much fasterā€¦

I donā€™t have bestec, i have other brand 10s 60A cont./120A max. But this is charging/discharging on different ports where iā€™m afraid to use it because of regenerative braking. Thatā€™s why i ordered the same BMS with charging/discharging at the same port which iā€™ll use for my Li-ion pack (build not finished).

I have a second build just finished (MTB with 10s 10Ah Lipo) and you make me wanna use BMS now :wink:

well thatā€™s a good point

Right now i have a cheap bypassed BMS for charging only. Iā€™m afraid to use my ā€œproperā€ BMS and send energy back to the discharge portā€¦

I try it too but when i ride i always forget to watch the voltage. Some days ago i was riding my MTB in the middle of nowhere in the night when my vescs let me know that iā€™ve reached 0% (32V) :joy: It was a long way backā€¦

Yes, the bms E-switch has to be on during charging. I have a Battery Supports 5a brick charger for mobile charging and at home I use a CC/CV Lab Power supply to charge.

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The Bestech bms also has a separate C- (charge only) pad. Still it handles Regen charging coming in through the P-(output) pad.

I recommend locating your voltage meter on top of your board or through the deck so you can monitor your battery while riding. The BMS over discharge protection should be used as a protection against extreme cell drift and not as a first line defense or as a fuel gauge. I also recommend using a voltage readout instead of a percentage readout since that can be deceiving and the voltage is what really matters.

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So the escā€™s / vesc is on when charging ?

And how kan you se on your lap power supply , when the charge is ready ? The Amp draw in the display shows 0 ? Or

The vescā€™s are on while charging. I donā€™t have a problem with that although a loop key would solve it. The power supply starts out giving 5a with a voltage a little higher than the batteryā€™s current voltage and slowly raises the voltage as the battery charges. This is CC mode and it prevents heating of the cells during charge. Once the voltage reaches the finish voltage that is set, say 42v the power supply automatically switches to CV mode and the current starts reducing as the battery fills. Theoretically, the current will drop to zero when the battery is full. I usually stop charging when it gets down around 50ma but since the bms trims the high cells at the rate of 126ma, it seems feasible to let the power supply trickle charge at 50ma and continue to fill low cells while the bms trims the higher cells.

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True thatā€™s important! Thatā€™s why i have voltage meter and percentage with backlight top mounted, i just have to look down. But my MTB build is brand new iā€™m too excited to watch the battery level :joy:. But after my experience i have to change my behaviour.

That makes me hope, i think iā€™ll give it a try. But in this case i gonna use the BMS with different ports for Li-ion pack (10s4p charging max. 16A) and the BMS with same ports and charging max. of 60A for my Lipo pack (10s charging max 50A) where i need stronger brakes anyway (MTB).

Do you think an additional fuse is needed when using BMS for discharge as safety?

Many thanks for your help! :grinning:

How many cycles do you think you have put on the pack so far? Iā€™m building one similar but 12s and wondering if its worth getting the more expensive packs like nanotech or graphene? They advertise higher charge rates upto 15c and I like to run high regen battery amps. Currently I am running 25 amps on regen but I dont have a logger to know how many amps the system is actually generating during braking. But I wonder if it really matters as its only for a few seconds, its not like your charging the pack from empty at 5c which you would expect it to get warm if you did that?

On Power Hungry racing quads (mines pull over 100amp on full throttle) Graphene batteries are one of the best batteries to take the abuse. But they are also heavier and bigger. And in a board with less apm pulls, i dont know if graphene is overrated.

@Namasaki What button are you using and battery meter on your board? it looks nice!

You donā€™t need a fuse when discharging through the bms because:

  1. The bms acts like a circuit breaker that is easily reset by the e-switch in the event of a short.
  2. The Vesc controls current.
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How does the switch work @Namasaki? My two white wires arenā€™t connected together but when I measure the voltage on the P- terminal thereā€™s still a voltage . Isnā€™t it suppose to be nothing ?