BMS heating after pluging the balancing cable

Hey there. I am new to the topic and I couldn’t find an answer on other topics related to BMS.

So, I bought brand new Samsung batteries and created a 8s2p pack. All batteries have same voltage individually and also when connected in parallel. Currently the pack has 28.1 volts since it hasnt been charged yet.

I wired a BMS on it starting with B- and P-. I connected also the balance wires to all the positive ends of the battery cells. When I check the voltage from negative wire to all the individual balance leads it is in line with the battery, total 28.1 volts.

However when I plug the balance flat cable into the BMS, it starts to heat up. When I measure the voltage on the P- lead it is showing 26.0 volts so it seams this is heating up the BMS.

Anybody struggled with a similar problem before?

Thanks Anze

Can you show us some photos of the batteries, leads and bms? Do you have a link or any documentation for the bms you can share with us and where you bought it?

Hi. Thanks for replying. Attached a BMS spec!imageimage|281x499

Batteries are Samsung bought from this page https://eu.nkon.nl/samsung-18650-inr18650-25r.html

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image

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Sorry I meant pics of your built battery. Maybe one of the members here can spot something. I hope this works out.

My only thought it the balance leads aren’t in the proper order or the bms is defective. I know you said you checked… Does it get really hot or just warm? I’m wondering if it’s bleeding of power to balance.

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Put pictures of your wiring up. Also I am not seeing the manufacturer wiring diagram.

I have a similar BMS I am using for charge only.

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Here the picture of the wiring with voltage measured between battery negative and battery positive (28.1 volts). image

And here the picture with voltagr measured between battery positive and P- string which is supposed to go into the ESC.

image

cant tell about the wiring with that picture, but the first couple times I wired a bms I got the balance wires all back wards from 10 - 1 instead of 1 -10 and when i plugged in the pigtail the bms got hot quick which i quickly unplugged and it was still fine…just had to re wire in the proper sequence… id double check all balance lead are in perfect order…

standard reply i know…

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I feel kind od stupid but at the end despite double checking the cables were not wired correctly. I reversed the order and no heating occurs. What is interesting though is that now also to voltage on P- plug is equal to the battery voltage. Thank you guys for quck response. image

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Hell yeah! Glad it’s sorted

like i said…i did the same dumb ass mistake twice…on 2 diff batteries… now i wont F it up again =P

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I always get my wife to double check. Another set of eyes. She doesn’t know batteries, but she’s not dumb like me, lol.

I’ve done the same thing as well even after thinking I had double checked. It’s because sometimes the wires will overlap each other when they come out of the connector and are easy to mix up. Luckily the bms was fine.

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I did the same thing when I installed my first bms.

Don’t feel stupid. We all done it.