BMS identification and replacement

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Mar 11, 2018
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Hello knowledgeable peers

I’d be very grateful for your assistance

I’m quite stuck with repair of an e-bike battery and have tried everything I can think of to get it sorted.
My first post on a forum so if it’s the wrong question or in the wrong place please feel free to delete and point me in the right direction.

The basics...

Battery is a 36v lithium battery with BMS, over temperature protection, balanced charge, 70A output and 10s charge plug/cables.

It’s powering a 250W fun8 front hub motor.

Bike usually has plenty of grunt on the climbs and is only about 15months old with quite limited use. No signs of the batter degrading over time...was working, then it wasn’t.

Checked paired cells separately and all looked quite well balanced, even and increased equally as I tested all 10 from 1 -10.

Bypassing the BMS, the bike throttle controller works flawlessly and powers the hub with no issues.

My thoughts are that the BMS has packed in.

I’d love to get a direct replacement (e-Bike is a WOOSH Bikes big bear) but can’t get electrical parts from seller as they don’t deal with that level of electrical spares.
I’ve tried looking on Google, Google images and Ali-express, etc. with no luck.

BMS is 45mm x 67mm, has a temp cutout, and apparently 70A limited output (which seems very high) Most of the e-bike BMS’s I seem to find online are 40/45A output. Maybe a smaller one will be fine and help reduce strain on the battery in future??

Space for replacement BMS is relatively tight at approx 85mm x 50mm.
The 10s plug and cables have very little ‘slack’ so really need to go into the top/narrow side of any BMS

Photos attached...

Really looking forward to hearing back from someone who might recognise the BMS or has a solution for this. My hopes were to fit heavy push m/f connectors to install the new BMS so that if ever happens again I can do a ‘road side’ repair without too much difficulty.
05CC3532-29C2-4574-A784-909A3FCCA8F6.jpeg
1F59716D-ECF8-4ED7-ABB0-12CACE0919E5.jpeg
767DEA4D-749C-40F6-9C2F-DB5DA3441AB4.jpeg
 
Gravity’s Child said:
Battery is a 36v lithium battery with BMS, over temperature protection, balanced charge, 70A output and 10s charge plug/cables.
It’s powering a 250W fun8 front hub motor.

Is this a typo ? Should be 250/36=6.94A output for such a tiny motor. I don't know if you will be able to find an exact replacement for your battery pack, but maybe it's not advisable anyway, since the last one died rather quickly. Just get any cheap chinese 10s - 15A bms: https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20180318065748&SearchText=10s+bms

Some even come with temps sensors like your's, if you want to stay fancy. Check the size in the product description et get the one that fits. With a bit luck, your old jst connector will fit the new bms; otherwise you will have to rewire the balancing cables.

Good luck-

PS: maybe not the right sub-forum to post this ?
 
I agree that 70A sounds like waaaay to much for a 250w motor, although your output to the motor comes from the controller. I doubt your controller delivers 70a. I also doubt you have a battery charger for that battery pack that can charge at 70a.

Double check with the manufacture as to what the battery pack can do. If you can find out what cells are in your pack, research their C rating so you know what you need to buy. Unless you have some really strange batteries your 10s pack isn't delivering 70a.

A few of the folks around here made a couple of group buys from this company in the past. They might want you to purchase two at a time, but it is another option to look at.
http://bestechpower.com/pcmbmspcbforli-ionli-polymerbatterypacks/

:D
 
This from the WOOSH website....
WOOSH Bikes big bear
Motor Bafang with torque arm
Controller Lishui Sine Wave Controller
Battery 36V 15AH Samsung cells

Spare battery
36 Volts 15 Amp Hours Samsung cells
New set of 2 keys
Internal configuration: Samsung cells

http://wooshbikes.co.uk/?bigbear

:D
 
Guys, thanks very much for taking the time to look into this for me.

Qwerkus, e-Beach, I think you are both correct that the 70A is not the BMS controlled output. Even though it is printed on the casing of the BMS itself, I may be misinterpreting the numbers.

If the manufacturers state the battery is a 36v 15A, then it makes sense that I go looking to replace the old BMS with a 15A. Thanks for the links too. Quite like the idea of Bestec so I’ll look into that a bit further.

The 15A BMS’s are much better priced too than the 60 - 80a ones I was previously looking to buy :) Going yo purchase two so that I have a spare if it does the same in future.

The bike is my mother’s and I was very keen to get it sorted for her, so once again thanks for your help

Ps. From reading all the posts and threads on ES, I’m pretty excited about tackling one of my own e-bike build projects soon ;)

All the best
 
Thanks.

However, the AH of you battery pack is the total capacity not the discharge or charge capacity. Your batteries may be able to take more or less then 15a depending on the cells.

Can you post pictures of an individual cell so we can see the actual manufacture number. That will give us a better understanding of what the cell is capable of. Make sure the pictures are in focus and with good light. To upload them they should be no bigger then 640x480.

Also, how many parallels are in there? If you arn't sure, count the total number of cells and we can figure it out from there.

But try to get the numbers on a cell and post a picture.

:D :D
 
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