10S4p six Lipo packs 36V 11Ah with BMS convert to 72V

[monette999]

Dear Forum, for my E Kart I am now working on the batterie pack.

So I have purchased LIPO BIKE PACKS. Six of them with integrated BMS. I opened one pack and saw a separate port to charge the 36V pack. Ground is switched

So two packs in Series. Times three.

Here my thoughts, I want to bypass the Mosfets and connect the B- and P - together. BRIGDE THEM.

I am not sure if the safety circuit is activate if I desolder B Minus from the pcb.

I want to use the balancer and charging function. The 72V is going to a big contacter !
.

This contacter 12V is controlled by an Batterie protection circuit to disconnect it when the cells are below 55V.

Is this a way to go. Let me know what you think?

I have the cells, the contacter and all kind of extras already.

Good day Bob

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[BlueSeas]

Breaking into and modifying the BMS in the 36V packs probably isn't a good idea. Not without more knowledge of how those protection circuits work.

The objective of any BMS is to monitor cell voltage and limit the pack on the most restrictive cell. If you disable that, and monitor at pack level, dropping the contactor at 55V, you don't have cell level protection. This is pretty important for safety with LIPO. Even more important is limiting charging so a high cell isn't pushed beyond limits.

 

[999zip999]

Is easiest and best to make one big pack for one BMS. What cells do you have name and model number as all cells have pros and cons. Thats important part. Plus what controller and amp limit ?

 

[monette999]

Hi 999Zip999

The cells are Samsung INR18650E. 29IAA. Cells.

I think these are warranty returns. It needed repairs. One cell block dead.

The max current tested 7A at 42V. and the Powerline is fused with 40A.

That's all I know.

Greetings Bob

 

[monette999]

Hi the BMS has a full bridge with 35A 60V Mosfets.
Let's assume that 30A is feasible per pack.

I wonder if I can use the BMS for charging and balanceing if I bypass the ground.
BRIGDE B- to P-.
Does anyone know if this works.

I have concern that the safety function gets active when the Mosfet Source Drain Voltage is OV.

Greetings Bob

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[999zip999]

Can we see a pic of the battery pack are all the same configuration ? I thinking best to build one big pack 20s 12p. With a beef up POS and neg buss. What controller at what amps.

 

[monette999]

I have 10Packs of 10S4P 29E.

So I have 400 cells.
The are all configured in blocks 3S4P
3S4P and 2S4P 2S4P.

My controller is still in the mail.
A 24Mosfet 80A 3000W.
72V.

Greetings
Bob

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[mannydantyla]

I think the right thing to do is to recover the cells, find which ones are good and which are bad, and toss everything but the good ones and start over with a fresh BMS large enough for the whole pack that you are building. Ideally you would be able to keep them in the 3s2p and 2s2p blocks and if the solder taps are salvageable then you wouldn't need to re-weld the cells. And leave the BMS wires to the cells and reuse those as well.

And I do not believe they are LIPO cells, they look similar but not the same as these Li-ion cells: https://www.alibaba.com/product-detail/Rechargeable-Lithium-ion-Battery-INR18650S-2500mAh_62348208534.html

What are the markings on the plastic case? I wonder if they are these sort of ebike battery packs found on ebay and amazon. If so then this thread raises doubts about their quality.

I am still very new to this hobby so hopefully somebody else can give you a second opinion.

 

[monette999]

Any recommendations how to build the pack using the modules and not braking all cells apart.

Do recommend to use a SANYAAN 20S 200A BMS.

Thanks for the support

Greetings Bob

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[999zip999]

First the bad cells must go. Yes keep in large as you can keep in parallel groups. And may be able to use series connections also. Be careful a lot of stored energy there.

 

[monette999]

Dear all it took me a while to sort out the bad cells. Charge discharge wow what a time consuming process

This unit is a 8S 8p.
//My ISDT charger can do 8s.

What insolation do I have to use before I place it into shrink tubing.

Any proposal?

Thank you for the support.
Bob

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