Please help with my esc substitute

I bought these motors from dickyho And I bought this esc substitute And I already had 2 10s 2p batteries that I wired in parallel. It worked for about a month and it could go 27mph, but then it started beaping and turning off when I would accelerate up to 27mph. I checked the voltage of the battery before, and it read 42v and then I checked the voltage after it shut off and it read 9v. When I unplugged the battery it jumped up to 42v again. Now I can’t go even 20mph before it’s shuts off. Please help me figure out why.

it is either your 18650 or BMS couldn’t supply the current thats why it shut off. The easiest & quickest way to check 18650 is to hook up a 0.1 ohm 5 watt resistor parallel to your multimeter & measure each cell, the voltage shouldn’t sag to below 3 volt, the one that does is the faulty cell. You must do this quick or the resistor will get real hot or you can also dunk it into a glass of water to keep it cool. If its the BMS then you can bypass it, further info then use the search function, there are plenty of discussion here.


I have an extra 10s 40a bms, can I wire that to one of my batteries and have 2 bms’s on one battery?

Yes you can but that will be a lot of work. You’ll need to split your existing 2P battery into 1P & install each a BMS to it but doing so won’t identify the fault. Since you can access to the battery, when it shut off, measure each cell & you’ll know which one is the culprit.

Can you test individual cells even of they have been spot-welded together? I just put my longboard together and I took for a test ride and I couldn’t even go 15mph, I think it’s been getting progressively worse over time. And thank you so much for your help, this is my first time trying to build an electric longboard, Much appreciated.

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sounds more like a battery problem then a esc problem to me. also do you have a heatsink on it because these esc’s beep and shut off when they overheat.

No, but I was going to use some little fans to cool it though-It just stopped working after a couple of weeks, so I never got around to it.

10S2P in your case it means two cell, refer to the above pic, after it shut off, measure cell 1 to 10, one of them should be way less than 3 volts, thats the one. Normally its just one cell faulty. Split them up to identify it.

You can also measure directly at the BMS at each of the connector. Do not remove the BMS connector while doing this, it will just restore back to the normal voltage as you have experience it.

Pic taken from JLabs

Thank you so much, that makes total sense

I think it’s my BMS, I measured the voltage before the BMS and it read 36v, and after the BMS it read 9, so should I replace the BMS?

could be a few things

one: your bms is bad (you can bypass it for charge only to fix this or replaced it )

two: you have a bad connection (a spot weld disconnected)

three: your cells are out of balance( measure each parallel pack with a multi meter to find out which one it is)

How off do the packs have to be, one says 36.4v and the other days 36.5v

If one of your batteries is discnected, wouldn’t it still make a circuit?

it would still make a circuit but it the parallel pack with the loose will lose its voltage must faster then the others so the bms would pick realize that and cut off power.

not talking about the entire packs voltage im talking about the individual parallel packs voltage like @yuweng said .

Every battery cells voltage was very close to being the same

Is it dangerous to bypass the BMS for discharge?

most people say its fine there is tons of info on bypassing just use the search button. I personally use my bms for discharge only. what cells is your battery using?

I’m not sure, I stole both my batteries off of prieviouse longboards, the cells are BFN ICR 18650 170320. I looked them up online and I couldn’t find anything though.

Should I replace my BMS, or should I just keep the ones I have and assume i was just drawing to much?