BionX 36v 9.6AH pack teardown

This is the starting point.  This is a 36v, 9.6AH BionX battery pack.  It clearly has a battery in there somewhere - so, this being a dead pack (there’s a running theme in packs I deal with here - which is, “I don’t tear apart working packs”), it’s time to dive in and see what’s inside it!

This is a companion discussion topic for the original entry at

(Comments from Blogger)

2017-01-03 by Erik

Is there supposed to be voltage on the power bushings in the battery connector while the battery is not mounted?
Background: I just bought a Dahon folder with BionX PL350 with build date in 2008 (Pre CAN-bus)
It had been sitting for almost a year, but the seller had charged the battery for an hour, and the wheel would spin on throttle.
After a nights charging, the charger went green an d I took it for a spin in the dark. First off, nothing happenend, but suddently it started to pull. As soon a I hit the brakes, it went into regen and the display said “refuel”. Dead battery I guess.
Opening the battery, it had 41V, so I put it back together and put it back on the bike to test further.
But it wont turn on, and I’ve checked all the connectors.

I fear that I’ve ruined the BMS.


2017-01-03 by Russell Graves

Erik -

You won’t see voltage on the two large connectors unless you’ve turned the pack on (and then it will only have voltage briefly without seeing a wakeup command from the console). demonstrates how to short the proper pins to turn the pack on - you should get a few beeps if everything is good. 41V is definitely enough for the pack to turn on.

If you don’t get those beeps, it is likely that the BMS is dead. I’m working on a replacement for those, but I don’t have anything of the sort worked out yet.

You can check the voltage without opening the pack by checking across pins 2 & 4 on the charging connector. It’s possible you have a very, very weak battery that will hold a charge but not long enough to ride usefully. Check the voltage when it refuses to power on and see what’s happening.

2017-01-04 by Erik

It looks like I’ve bricked the BMS, because nothing happens when I short the pins as shown.
Voltage on the charging port is 41.2 Volts.
I will try to power my Bafang BBS01 crank motor with the pack to see if the cells have any life left.

2018-01-08 by Unknown

Hi Russ, I have been riding my 36V Bionx Bike for over 13 years, about 5000 mile per year. Due to the high cost of batteries, I have also rewired eight 18V Ryobi batteries to run in parallel with my Bionx batteries. This increases my daily travel distances to well over 100 miles. Now old Bionx batteries are relatively cheap and available on kijiji and eBay. I now have 5 working Bionx batteries with lots of spare parts. Over the years I have taken several apart to refurbish them. I have never seen the wiring arrangement that you show in your writeup, ie 6 parallel sets of 10 cells in series. The configurations that I have always seen are 10 sets in series of 6 cells in parallel. With this arrangement there are fewer wires. So my question is why do you wire the cells in this way with so many wires? By the way, I wish I stumbled across your blog years ago. Excellent work!
Thanks Al

2018-01-14 by Russell Graves

My blog didn’t exist years ago…

This arrangement is only on the very oldest BionX packs. They switch to the 3 wire system around the time they go to Canbus from I2C, though I think I’ve seen some three wire I2C packs.

2019-05-24 by Luis

I have a BionX 36v 9.6Ah Downtube Pack with the controller board shot. Does your rebuild include a new/refurbished board if needed? or can you get your hands on one.

2019-06-01 by Russell Graves

No, I do not have a source for old boards.

2020-08-19 by Unknown

I have a similar problem with dead battery pack on a BionX 36v 9.6AH.
Does anyone know a service shop can do battery replacement near San Francisco, California.
Thank you for any help.