Repair water damaged battery pack.

[LudvigF]

Hi, I am a new user on this forum. If I break any rules with this post pleas let me know.

I have a battery pack that is a few years old, unfortunately it got some water damage and I am looking for a replacement bms.
The model is joycube JCEB360-14.5 if that means anything?

It is a 14.5 Ah 36v pack. It has 45 cells that goes with 9 wires to the main circuit board. I would like to replace this board, hopefully without too much soldering.

What would you say is a good BMS to choose and how do I figure out how it is wired up?

Best Regards

Ludvig Friberg

 

[Sparfuchs]

I'm not an expert at these thinks at all but i'd at first check the cells its self with a multimeter to find out if they got damaged as well. They don't look that good on the pics and you'd waste your money on the BMS if the cells are broke.
Are you sure that it is made of 45 cells and not 50 ? Because for 36v you need 10 serial connected batteries and for 14.5 Ah you need 5 parallel connected batteries (in your case samsung 29E) So it should be 10s x 5p = 50 cells. Maybe i've a mistake in thinking, but i'd not know how to get to 45 cells ? So i'll calculate with 50 cells. The 29E cells have a continuous discharge rate of 2750 mAh and peak 8250 mAh. So if you take that x 5 paralell you'll get continuous 13.75 A and peak 41.25 A. So that's what your BMS should be able to do. You find them as "BMS 10s". I guess you already checked if there is the original BMS somewhere to buy ? I think it depends on the BMS how you'll have to wire that thing. I wish you good luck but won't be to optimistic about a "a few years old water damaged" rusted battery back.
If anyone found a mistake at my calculation, please let me know.

 

[LudvigF]

Thank you for your reply!

Yes I guess you are right but a new battery like this cost many hundred euros though and a new cheap bms is only 10 euros so I guess its worth a try! I will inspect the batteries again and count them. It is a bit strange to me that its only 9 wires to the current circuit board.

 

[flippy]

repair will not work. the cells are toast and the bms is also starting to corrode. you need to replace everything including the wires exept for the case itself.

 

[LudvigF]

When I measure the whole pack I get 32volts and most cells I tested so far is 3.6, are you sure they are gone? How can I know?

Thanks a lot for your help. When I buy a new bms for this size battery do you have any recommendation? I guess it would be best to copy the same layout with batteries so it fits nicely in the box. Can I use the same charger? Its a black box with a five pin round cable. It has a led that goes from red to green when its finished charging.

Thanks for all your help!

 

[flippy]

the rust means the cell has been damaged. the emergency overpressure protection valve is located underneath the positive terminal where water collects. rust will cause it to leak and let oxigen in wich causes the cell to commit seppuku by bursting into flames internally and melt your battery or if the cells are fully charged it will shoot out flames if you are really unlucky.

fun fact: leaking cells are highly dangerous. dont keep this thing indoors.


that you read voltages is about this logic: the tire still holds pressiure so it must still be a good car.

you battery is the whole car, not just the tire pressiure. :wink:

dont underestimate the dangers of damaged cells. there are people here that lost their house because of crap like this.


rip everything out. mesure the bms size and try to find a replacement. but check first if the bms and bike are not linked. most bikes have interlocks that prevent the bike from operating if it does not see a original bms.

 

[LudvigF]

Very good points!

I will look for a new battery pack, it seems to me like my bike dont have any smart functions that connects to the battery so any bms probably work. Do you have any thing to say about what vendor/brand that makes good bms?

 

[flippy]

Do you have any thing to say about what vendor/brand that makes good bms?

for applications like this: aliexpress. and put the biggest in that you can fit, not one with the specs you need. go oversize because the amp ratings on aliexpress bms are 50% or actual ratings at best.