E-switch on BMS

Hi guys, as many of you may know, there’s a group buy going on right now for some batteries in Europe, which is quite a rare thing. Since the manufacturer lets us take a design, and I noticed that many people are asking for a good battery with a bms in a compact form factory, I was wondering if any of you has a diagram (or can make a quick one) for one like this from @denton I would do this by myself but I know nothing about batteries :smile: Thank you very much :slight_smile:


Here is the website I picked up my BMS from http://www.batterysupports.com/lion-lipo-nbsp-36v-nbsp-10s-c-32_41.html They have this wiring Diagram that I followed for this battery. I would recommend one of the BMS that have a built in power switch.


Just FYI batterysupports can actually add an e-switch for you on their BMS’s

Are you sure? @fedestanco has a group buy with e-switchs on the bms

Yes, but you have to reach out to Lilian directly to have her add the e-switch to the BMS.

I don’t think the bms in the group buy is from batterysupports, so at the moment that’s not a priority, I think. E-switches are cool though, hope it will be possible to have one :wink:

DANGIT! If I would have known that I would have had it done… Well… You live and learn I guess. That would have saved me a lot of trouble.

The bms itself is an e-switch: it can turn off the battery for several reasons: voltage errors/ amp errors/ temperature threshold… When it comes to add a physical button the options are 2:

  1. there is a spot on the bms board designated to add one on-off switch (like the bms on my thread)

2)You make the bms think something is going wrong: for example you can short the temperature switch/ fake a failure in one of the balancing wires/…

All the options mentioned work in the same way since the reaction in the board is simply the activation of the mosfets.

So you’re the one who adds the switch in your GB?

Yes, I asked the manufacturer to leave the soldering spots (for the switch) free, so that I can solder an on off switch with a better design (the original was red and rectangular).

Is there a place where I can actually do that on the board I already have?

woah, really? I traied earlier this year and she just kept sending me to a different product.

Can i get my usual 12S 60Amp favorite with an integrated eswitch?

oh Lillian…

the 2 spots in the circle should be designated for e-switch/temperature switch. If you could provide me with hi-res pictures I could confirm what I am saying.


I will later, thank you!


So If I short that the BMS will power down?

So Lilian told me you connect the switch like this,

However, she said the BMS would have to be modified first before you can do this.

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Here’s some of the email thread


I will try to explain: When it comes to print a circut, although the bms company has several models of the same bms (the standard, the fancy one with an e-switch…), they manufacture just 1 type of printed board; all the fancy add ons will be added later.

These 2 spots (see pic) could have served 2 functions: 1)temperature switch 2) e switch ACCORDING TO THE ONE (function) THEY PICKED, YOU HAVE TO OPERATE IN 2 DIFFERENT WAYS TO ADD YOUR E SWITCH

1)spots designated for temperature switch: IN THE NORMAL CONDITION, current DOES flow through the temperature switch. TO GET THE BMS IN “ALARM MODE” (to turn off the battery) you will need to OPEN THE CIRCUIT: remove the resistance next to the spots (see pic).

2)If the spots are meant to be for an e-switch, it couldn’t be easier: just short them to turn off the battery.

I hope this will help you build better packs.


Could this be tested with a BMS that is not 100% functional. Because someone should with extra BMS’s from prior builds or with a burnt out component should give this a try and let us know because this is a game changer.

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When this change is made, does the BMS switch have to be on to charge the battery?