21s bms to 17s?

[jumpman231923]

Hello every one !!! I am looking for some help as I have some self doubt just cause I've never used one of the cheap bms before, but I am building a 17s 4p pack for my 60v 1020 2000w motor plus controller set up by vevor. So I've only ever used jbd smart bms or active balancers and I know with the jbd bms I can take the 21s and place Leeds 15-19 onto parallel pack 15 and it will work as a 17s but this cheap bms is a 21s came off a old pack 20s pack and had a wire cut I'm assuming to make it a 20s so I'm wondering if I cut the rest the wires to make it a 17s or do I wire it same way as a smart bms but it is not a smart bms so I'm confused on what to do and cant find anything on the net that actually relates to what I'm looking for so if any one could help out that would be great

 

[amberwolf]

You'd have to check the diagram from the BMS manufacturer for that specific BMS for how to use it with less cells than it's made for, if it even can be used that way (some can, some can't, but they are not usually as simple as just leaving off the wires you're not using).

If the BMS manufacturer does not provide that info, then anything you do is a guess, and you would then need to test every function of your battery to be sure the BMS actually correctly detects each fault condition and properly reacts. That means at minimum simulating or testing actual HVC and LVC on each cell group you're using, one at a time, to be sure it properly disconnects for each group and each condition.

Otherwise you won't know that it's working and protecting you from overcharging or overdischarging the battery, either of which can lead to cell damage that can cause a fire.

(that's technically also true even if you have the documentaiton and wire it up per that, but at least if it's a documented wiring method then if it's a working BMS it should do what it is designed to....but when guessing at the wiring, testing isn't really optional).


It's even possible that the "wire cut" to 'make it a 20s" left the BMS nonfunctional and so not protecting that battery, or...any other possible fault or misfunctionality. Not knowing anything else about that battery, it's life or death, can't speculate much.

 

[A-DamW]

Remove the aluminum cover and take some pics of the main bms integrated circuit chip identification model number.
We can figure out how to connect 17s from the datasheet.

 

[jumpman231923]

The manufacturer was no help that's why I started this and thank you that does sounds like a lot of work lol

 

[jumpman231923]

Its almost like it has a Bluetooth module on it but I cant make out what it says

 

[jumpman231923]

HK W9700
D 75 C

That’s what that little module thing says

 

[jumpman231923]

Remove the aluminum cover and take some pics of the main bms integrated circuit chip identification model number.
We can figure out how to connect 17s from the datasheet.

I took off cover n posted pictures

 

[jumpman231923]

I guess no one knows lol crazy