10s BMS died? Outputs 28v only

How-Tos & Esk8 mechanics Esk8 Mechanics
#1

Hi Team,
Need some help please.
I think my 10s BMS died due to water damage?
It no longer powers on my VESC not does it charge.

I take my multimeter and the 10s5p 30Q battery itself outputs a healthy 38.2v. By the time it goes through the BMS, it shows only 28.7v… my Focbox Unity is fine as it works when plugged into another battery. Pics below.

Any ideas? If the reco is to replace the BMS, what should I get? Or just buy the same model (I think it’s a Bestech) so that I don’t have to mess with the balance leads?

Thanks in advance!

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#2

Alot of bms won’t display the full voltage of the battery unless there is a load being drawn from it.

If you have something you can use as a small load (i use a hair dryer) you can determine if the bms is working as intended.

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#3

Did you also unplug your balance port and check the voltages of each cell group? It’s pretty common for BMS’s to output below minimum voltage when a fault is triggered. Also does the BMS output voltage match the charge port/plug output voltage.

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#4

Hi! Thanks for looking!
Yep. P groups are balanced:
Voltage Readings from bottom of PCB: 3.8 7.6 11.5 15.3 19.1 22.9 26.7 30.5 35.3 38.2
Charge port voltage says 28.4v vs BMS output voltage of 28.7v.

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#5

Hmm… I don’t have anything to test with atm. I need my hairdryer. LoL can I just use the phase wires of my actual motors? Or would that not work? Thanks!

#6

PS. I don’t have a solder atm.

#7

Wow, hold up, unless you mistyped those numbers this is not healthy.

#8

Sorry was typo. Meant to put 34.3v instead of 35.3v

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#9

Then it does certainly seem like the BMS has just died on you. Any burns or anything on the PCB?

#10

@A13XR3 nothing burnt. I definitely see some dried up water deposits though between the two layer of PCB. I am guessing it’s salt… RIP.

Should I get the same BMS for simplicity’s sake?

#11

Woho. Fixed! I took a toothbrush to brush away the salt water deposit on the PCB a few times and then all the sudden it’s back to 38.2v output!

Thanks all!

Here’s a picture of the MVP tonight:

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#12

Haha better clean that bad boy up really well! Sweet that you were able to fix it tho