Bypass BMS wiring diagram

I am very new to esk8 but I just made a silly wiring diagram for bypassing my BMS for discharging. Could someone please tell me if this is right?


Yes it is. Ditch the anti-spark for a loop key.

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When making battery diagrams, I usually keep the balance wires off since balance leads makes it messy. So two diagrams. Anyway.

Looks good, I think you got it.

Loop key


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First of all thank you very much. I don’t understand how your P- goes to CHG-. Is’t the P- useless if i am bypassing the BMS for discharging? Isn’t the CHG- going to the CH- on the BMS?

Oh, why do you prefer a loop key?

Simple, cheap, and utterly reliable.

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But not as nice as the FS enhanced AS.

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Labeling on bms can vary. This one has P- and C- on the same connection. But yes, generally if there’s a pad on the bms labeled C-, that’s where charge- would go.

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Looks good. Consider adding a fuse to the charge port as well.

Could you provide me with a good example of a fuse I could use? And since I’m a noob, does it go in serie (if yes between positive of negative or it doesn’t matter?) or in paralel with the charging port? Thank you

In series. I’m not sure if there’s a rule of thumb for positive or negative. Either should work.

Thank you, what kind of fuze can i use?

There are many options. Just make sure the fuse is rated for the your battery pack voltage and slightly above your intended charge current. This is what I use – a small 10A axial fuse: 🖼️ Pictures and nothing else!_Legacy

I’ve made a 10S4P battery (42V, 6Ah). The charger I’m planning on using outputs 42V, 2.0A. Is the 10A fuse you used to much for me? Also, could you maybe explain what it does?

You may want to read up a bit. A fuse will blow in case of overcurrent / short circuit and will open the closed circuit. Anything rated between 5A and 10A would be fine for your setup.


So a little general electrical theory here.

In your home there is a breaker panel. It is fed by large wires and will likely have a 200A circuit breaker feeding it. Then breaker panel then will have smaller circuit breakers for all of the circuits in the house.

The size of these breakers is based on the wire size eg 15 A for 14 awg 20 A for 12 awg etc. The idea behind these is to open the circuit if something attempts to draw more current than the wires can safely carry. If the breaker were undersized the wires could over heat and cause a fire.

In the case of the battery charge port the fuse protects you from shorts in the charger or at any point up to the fuse. Without an inline fuse this failure would cause the battery to push a bunch of power through small wires potentially causing a fire.