Two questions on BMS wiring

I think it must be a different one that Ernesto uses… I was just double checking the diagram he sent after the question and all the connection points are (while between + and -) they are made on the negative side of the (is it “parallels”?) He’s built a number of function boards, so I can only imagine this is the correct way to do it for this BMS, I just don’t know the “why.”

I’ll certainly take the advice on the checking and double checking after I get it all hooked up… and will solder first and connect after. Thanks!

no, they’re not. They’re on the positive side. The diagram is ambiguous because its a 1P. But look at #12, and notice there is no balance on the negative side of #1

? so then are all these spots opened and waiting for me to solder in the incorrect location? @kaly can you chime in here? I think I’ve read some posts from @Eboosted who’s done a Kaly build? Also… I can simply solder this together as indicated in my photograph, where the current solder points were provided for me (not hook it to the BMS) and see if I’m getting the correct Voltage readings via the voltmeter… ya… I think I’ll do that.

Hi there the spots are marked correctly, you are going to start connecting the balance leads by the positive side of the negative main wire, that is the one marked #1 on the picture above and them follow the diagram. notice that the balance lead has to be connected on the bridge part of the cell connection it can be on the positive side or negative side but on that join connection.

As you can see on the picture i choose to put the tap on the negative side of the connection because in the event that the shrink wrap on the cell get scratch the metal tab will only touch the negative side of the cell on which is already connected minimizing any possible complication.

for more info check

Thanks for the clarification Kaly! I gathered you had it done right, but with the new question there was some hesitation on my part. Uncertainty, I can do without when dealing with this much battery. :slight_smile: Huge help here, thanks!

kaly, how do I get info and pricing on a build? Thanks.

Practical question: how do you check the balance wires with the voltmeter?

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attach your negative probe to the negative side of the pack using a clip or something, then place your positive probe on each one of the connector contacts starting at pin 1. They should get progressively higher in voltage on each pin and the differences between each pin should be very very close in measurement, in fact they should all be the same as the measurement of one cell because the cells should have arrived with all the same voltages, which should be somewhere close to nominal (about half charge). So pin 1 should be around 3.6v while pin 12 should be around 43.2 for example. if they’re at 3.2 or something like that its ok, i’ve seen cells arrive at 20% charge before and they turned out fine once the pack was built, charged, and balanced.


Perfect! Thank you, I will give it a try tonight.