BMS common port help

What are the disadvantages of bypassing discharge on a common port bms? I rushed ahead of myself and purchased a daly 20a common port now realising all diagrams ive seen are seperate. What should I do?

B- to battery, P- to Load - . Then for bypassed discharge simply run wires from the battery terminals to your load. Main disadvantage on bypassing any BMS is if anything happens to your battery, the connection doesn’t get cut.


alright cheers, whats the difference between bypassing a common vs seperate port?

Common port used charge and discharge on same connections

Separate port used two connections one for charge and one for discharge.

Bypassing just makes makes the proctction functions redundant so if there is a fault it won’t switch off the supply to vesc, but it will balance charge and balance each cell in the pack.

20 amp BMS is useless really, but there is a way to protect everything by just using a 20a, Depending on your vesc but it’s complicated, also as Lee mentioned you loose your brakes.

if you want to protect the battery or eac, as it won’t be able to supply enough current to your esc I would bypass it and use it as a balance charger and balance each cell. Just bypass it you’ll be fine


If you bypass a common port you use the P- in place of your C- and run directly from battery to the ESC. This way you can still use a charge port.

In this configuration you don’t have any discharge protection from the BMS buuuut as I always say I’d rather ride a fireball of death with brakes to a stop than lose my brakes as the BMS shuts off to protect everything.

In general, if you have been sensible with wiring most issues would come from an internal battery fault anyways. It is possible for something to short post battery but I’d rather take that risk and run bypassed personally.


Very good point Lee didn’t think about that, if the battery is well made with new cells should be fine.

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What is p+ for


P+ sounds like positive have you got a wiring diagram?

Or do you mean b+ in the diagram it’s battery positive.

I think p- and p+ are for the charge port but not sure. 4s1p for spotwelder

There is a wiring diagram there, looks like you have you got magic smoke from it?

There is a video of how to wire it up as well :slight_smile:

Talking rubbish seperate port connection :slight_smile: looks good to me.

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I hooked it up correctly. B1 b2 & b3 always confuse me.

Hey guys, just want to triple check.
I have a common port bms.
I want to bypass discharge,
B- to - battery / P- to - vesc.

P- goes to charge port negative
I believe

@muf my charge port + and power wire are the same wire.

Hey @all,
I do have some Samsung 30Q, which I used with N.E.S.E. modules before.
Now I would like to make my own Battery Pack by spot welding to save some space.

Also I would like to use a bypassed Common Port BMS instead of Seperate Port.
Is the shown diagram correct?

Best regards