Connecting a BMS Quick Guide [How-to]

Fail…

What is this??

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Trying to wire up the bms. Was trying to switch the connection from the 4s battery to the 8s BMS. I was having a hard time getting the 3rd wire in so I used tweezers to pull it back out and accidentally touched 2 together and now I hope I didn’t destroy the battery.

It shouldn’t have damaged the battery. Thats tough luck though.

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Hey oriol,

Is it necessary to solder one ground Lead from one pack to the negative terminal of the bms? What will happen if this is not done, and both ground leads are cut?

Hi man Your diagram look right, but the charger don’t cross over the bms, so i don’t understand this point. Can you help me to understand please ? The black wire of the charger will be on the P- of the BMS ? If i have a B1- on my bms (7pin for 6s), Do i have to take also the same wire (balance cable) to connect to the B- of the BMS ? Does the last pin served to something ?

Thanks a lot!

Sorry for the beginner question, but can someone show a pic on the exact way to connenct the BMS to the Charge port. and do you know if this port is good enough:

Thanks!

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I’ll just hijack this since I don’t want to make a new thread for every question I have.

I just wired up my BMS and when I tried to connect my charger to the setup I got a big spark that scared the shit out of me.

I’m just wondering if I got something wrong

This is how I have everything wired up. I excluded further connections since they were not connected to anything at the moment. Just tried to check that my setup can charge.

Oh and I used a charger from a hooverboard that I have. Input: 100-240VAC, 50/60Hz 2A Output: DC 42V 2A

This should be ok, no?

Make sure that your charger port wire on the tabs are correct. I had one that had black wire onto positive tab and the red wire into the negative tab.

Yeah i actually had to change the tip on my adapter for a regular dc-style plug and everything should be correct on both ends. Plus on the inside and so on. The female part has three connectors though, where one of the pins seems to be a contact switch. Atleast there’s connection between two of the outer pins until a plug is inserted.

I’ll have to double check the positives and negatives before next try, but i’m curious if there’s more possibilities as to why there’s a spark. I should be able to connect the charger with no anti spark-connectors in that loop, am I right?

EDIT: Ok, upon further investigation, it seems that the female plug I have has this contact-switch inside and I have wired my negative lead to it. The burn marks on my male connector lead me to the conclusion that the switch-contact was pressed so tightly in that it’s not in contact with the positive of the female plug but it will be in contact with the positive of the male plug when trying to plug in. So it seems that my problem was a short circuit after all.

my lithium ion batterys have stopped charging is there any reason that could have happend

Great post! Thank you. Do you think that this bms works the same way, except that it is labeled -C where you have -N?

Why does my bms (12s) have 13wires and not 12

Depending on the bms you have it can be that you need to connect on of the leads to the battery minus. Which bms you have? There where no schematics delivered with your bms?

image image image

You can see, first pin is b- If you have a multimeter you can check if the b- pin is connected to the B- terminal on the pcb. Sometimes it’s like this and than you don’t need to connect the first balance wire to your battery

So the b- is going to the first neg then all the rest are pos

Hope this is correct

The drawings you got a bit confusing me. Looks like the drawing is upside down to the pcb. You wire it up for charge only? My d140 is wired up like this image

In my case the b- and the B- are on the pcb connected. So no need for the first lead to be connected to the first pack minus. If that’s not the case with your bms than you need to connect the first lead to the first pack minus. From lead b1 the leads gonna be connected between cell 1 and 2. If you connect the balance lead on the plus of pack one or minus of pack 2 doesn’t matter.

If you have a time @b264 please have a look too that I don’t tell something totally wrong.

It depends totally on the specific BMS but in most cases if you aren’t discharging through the BMS, you can leave B- unhooked if it’s connected to B0 in the balance leads. But if you have the load connected through the BMS, you’d need to do it the other way like your image above.

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