Wiring Charge only BMS

Build, Repair & Mod
1

Hi everyone,

today i’ve built my first battery and now my brain feels somewhat fried when it comes to wiring the charge only BMS. So I thought, why not embarrass myself a little bit :slight_smile:

I have this BMS here Charge only bms

  • B- is going straight to the negative of the battery pack.
  • C- is going to the XT90 (load connector)
  • Positive port of the pack is going to the XT90 (load connector)
  • Balance wires to every cell coming from the BMS (Voltage is adding up 1-8s, 28.xV on the connector)

Looks something like this:

Dischrge BMS
Dischrge BMS1920×2560 307 KB

But here it comes? Discharge port? I only have a few volt on the XT90.

What am I missing?

Sorry and thanks in advance for your help!

Cheers,
P

2

IMG_0995
IMG_09951900×920 130 KB

I drew this up ages ago to help someone out. This is how Foildrive does it with the XT90i connector so you can charge and direct discharge via one plug. Quite clever. Means you need to rely on the vesc low battery shut off and there is no protection for over discharge (if you leave the battery connected) which can brick a battery unless you charge through the discharge pins.

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3

Thanks heaps for your response @Strongarm
This is indeed for mate’s Gen1 8s3p.

I checked his Gen1 battery and it seems to be connected this way(only connected to one centre pin). But I also have one of his charger here. Standard XT90 connector without centre pins on the charger.

What would be the situation/risk charging the batteries this way?

Thanks,
P

4

Charging via the larger outer pins will bypass the BMS so it won’t stop charging if one cell goes over 4.2V which is very dangerous.

Was the charger an unmodified Foildrive one? For a while they were charging via a seperate xt30 i think

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