E-switch on BMS

It is clear from the picture that on your bms one of the 2 holes connects to nothing. To make it work you should add 2 resistors I guess (too complicated).

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Those two medium size holes by Q13 and Q15 do they complete the alarm circuit? Or the large hole by the 205 and Q13

My wild guess is this:

But ,again, it seems risky and complicated.

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Not so wild IMHO. The ones by Q13 and Q15 looks like large vias, and my guess is you add Q13 (a transistor that looks to be missing here) and 2 resistors above it (from the orientation of this picture) and then the two holes (which look to be actual holes, not vias) to the left of the resistors would be your switch wires

Basically, the switch would control Q13 directly, which would control Q15 and the rest of the circuit. Not sure how, but that’s my guess given that configuration.

Does anyone have one with the switch attached? We could pretty easily determine it the layout, and the transistor and resistors needed.


I imagine that actual resistors used are determined by which temperature probe and the desired temperature number.

@raphaelchang @JTAG Do you guys know where the switch would go?

You guys with an E-switch on BMS! Wired everything up today and gave it a go, measured everything, and all good so far. But. If E-switch is off, I still have 2,5V on the BMS output. Seems like something is wrong. Does some of you have one and could measure output current. I´m using the same 77A 10S BMS that @ajaynagra and @fedestanco bought in group buys.

I had the same thing, I think its just when you put a load on it that you get the reading. Multi-meter counts as a load. Regardless I didn’t like the BMS so I pulled it off and replaced it with a BesTech 10s BMS.

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Why don’t you like it? For its bulkiness or something else?

Also battery won’t charge if the switch is off! I don’t wanna have my board on the whole time while loading! So wtf e-switch! ?

I don’t like that it would bleed voltage for any reason when off and that it was freekin massive :grinning:

Don’t all BMS bleed voltage? If you were going to leave for a long time, ideally you’d just disconnect the BMS

They might but I just didn’t understand why this one would supply power under any load even when the switch was off. As I was gonna have to jump through hoops to house it’s size I just decided to do away with it.

My guess is there

I tested 4 different bmss from china. They all bled voltage, but when I used a 5amp fuse to test current, voltage dropped and the fuse remained intact. Yes @TarzanHBK ,bms-on while charging sucks very much. For this and a lot of other reasons I would love to see some badass bmss (like jtag’s) get funds to reach the market… @smurf If I had that board on my bench, I probably would have tried shorting 90% of the f**ing holes to get the holy switch function :smile:.

Hmm that sucks… I think I’ll add a second switch to disconnect the vescs, so they won’t fry over time due to constant low current

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Has anyone figured out the definitive way to add an e-switch to the supower (battery supports) BMS? I am going to use the e-switch and unplug the vescs while charging. Not going to have room for a separate anti-spark switch and would prefer something more elegant than the XT-90S

IMO this mod it’s not worth it at all, If you guys find the way to add the e-switch you will requiere to power on your battery while it takes a charge, if you are willing to do that and leave your board turned on all night (if you forget to turn it off) or stay standed up besides the board until it reaches 100% SoC, then yeah go ahead and add the e-swtich, otherwise just get an antispark switch and forget about it.

I really wonder where Enertion got their Space cell BMS, it’s literally like 3x7cm and has a built in e-switch that doesnt require the board to be on to charge.

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There are many things Enertion or Evolve won’t ever tell us, but if you know the right people you could get your hands on whatever electronic device you could think of.

Nevertheless, we need to look further in China, there must be something for us there

I’ve looked at a ton of places, but even the smallest 10s BMS’s I find are quite a bit larger than the SCP BMS. The search continues…

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