BMS Replacement

nmp85

New member
Local time
4:30 PM
Joined
May 30, 2023
Messages
2
Location
Florida
So I consider myself pretty good with electrics but for some reason what I thought was going to be an easy swap has got me stumped. Unless there's different types of bms's cause this part is pretty new to me. Anyways I have a Jetson bolt battery that I smoked the Bms on. It's a 36v 10s 6AH battery with 30 cells. I labeled the wires before I took off the old Bms. Iordered a cheap Bms off Amazon. When I got it hooked it up my charger stayed green when I plugged it in (not charging) I ordered a second Bms slightly better and that has the same problem so I decided I should probably do a little more research and this is what I have come up with.

I have taken pictures of both sides of the battery, both new BMS's, and the old BMS. I think I figured out what my problem is but don't know enough to figure out how to fix this issue. Besides the fact I'm pretty sure I need to disassemble the battery and charge all the cells to the same voltage before I move forward.

No what I think the problem is...
When I use my meter and test each numbers where the old BMS wires (scene wires?) were going to this is what I get

1. 9v 6. 23.2v
2. 8v. 7. 18.1
3.12.1v. 8. 30.5
4.18.2. 9. 39.6
5. 28.6v. 10. 38.7 (Bats + and -)

Everything I have read and watched says these spots should be 3.5v. like I said these are where the old wires went to I just assumed that's where the new ones would go. Can someone please explain this better what the problem may be and what I need to do to correct this.
20230530_092612.jpg
20230530_092658.jpg
20230530_093033.jpg
Screenshot_20230530_093304_Amazon Shopping.jpg
Screenshot_20230530_093145_Amazon Shopping.jpg
 
each reading in sequence should between 4.2 and 3.0, they are additive, you must subtract the previous reading from the next, each time, to get a reading for each parallel group, 4.2, 8.4, 12.0 would mean first group at 4.2, second group at 4.2, third group way low at 3.6.

Something is very wrong with your wiring.
 
Yeah but the crazy thing is this is the battery that came with this Jetson bike. I haven't done anything to it besides remove the old BMS because it's clearly fried and wrote the numbers on the battery from what the wires said they were coming from the old BMS. The battery was designed this way and somehow worked before I fried the thing.
 
Has it occurred to you that the pins on the new BMS are not in the same order as the old one?

Also, you have no pin 1 reading, lowest is 8V. Next is 9V. Big problems, already. Should be in order low to high, first pin, or pin 0, should be negative, 0 to 1 is first group, 0 to 2 second group, etc. Neg to pos, each time. No single jump greater than 4.2, or smaller than 3.0 (ideally). Over 4.2 is theoretically not possible and less than 3 is dangerous and damaged, you got one of 8V, one at 1V, one at 0.1 volt. Not to mention up and down all over the lot.

The cells and their connections did not re-arrange themselves. The BMS you connect to and read from, where the pins are located, is DIFFERENT from original. That is where the changes are happening.
 
Hey man. I just stumbled upon your post while trying to understand my jetson bolt battery. Something clicked for me when the person replying to you explained the 4.2v voltage drop between groups. After labeling mine like yours, I realized you had your labeling wrong according to what mine showed. Your 5 and 7 groups are reversed compared to mine. I double checked the top of your old BMS and it's the same. Obviously I can't see where your old sense wires went because you chopped them, but I think its safe to assume yours were the same as mine before they got chopped. Take a look at my pics. Hopefully this might help you in some small way.

 
Hey man. I just stumbled upon your post while trying to understand my jetson bolt battery. Something clicked for me when the person replying to you explained the 4.2v voltage drop between groups. After labeling mine like yours, I realized you had your labeling wrong according to what mine showed. Your 5 and 7 groups are reversed compared to mine. I double checked the top of your old BMS and it's the same. Obviously I can't see where your old sense wires went because you chopped them, but I think its safe to assume yours were the same as mine before they got chopped. Take a look at my pics. Hopefully this might help you in some small way.

HTML:
<a href="https://ibb.co/N1gSrR4"><img src="https://i.ibb.co/N1gSrR4/20230602-190736.jpg" alt="20230602-190736" border="0"></a> <a href="https://ibb.co/g95FBx0"><img src="https://i.ibb.co/g95FBx0/20230602-190828.jpg" alt="20230602-190828" border="0"></a> <a href="https://ibb.co/prFLfPS"><img src="https://i.ibb.co/prFLfPS/20230602-190843.jpg" alt="20230602-190843" border="0"></a>

 
Back
Top