A Rant About Repairability and Proprietary Systems: Why Electric Bikes Need Rebuildable Batteries

It’s the end of February, 2016.  The anti-Trump fortress of “Well, yeah, he’s got some support now, but there’s no way he can win the primaries” has been thoroughly overrun, and it’s occupants are beating a hasty retreat to the stronghold of “Well, yeah, he’s winning primaries, but there’s no way he can win the general!”  Additional fallback positions may include “Well, he won the general, but he probably won’t live to be inaugurated” and the rather dismal cave of, “Well, shit.”

This is a companion discussion topic for the original entry at https://www.sevarg.net/2016/02/21/a-rant-about-repairability-and/

(Comments from Blogger)

2016-02-21 by Mike Halcrow

Great article. I completely agree that vendors should support maintainability in their products.

I’ve got some thoughts about this statement you made:

"I understand that the manufacturers are worried about liability, or lawsuits, or something. Knock it off. If it fails in warranty, it’s your problem. If it fails after that, it’s someone else’s problem, and if you think your product is any good at all, it’s likely that they’ll want to keep using it. Don’t get in their way."

The CPSC recently dropped the ban-hammer on today’s crop of hoverboards:


Suppose a manufacturer constructs a pack where batteries can be trivially swapped out by any Tom, Dick, or Harry. Dick decides he’s going to drop in some lithium cobalt oxide cells. After a brief re-enactment of Ghost Rider on his way to work, Dick has a bad time.


The CPSC takes interest at that point and issues a recall for all “user-serviceable” battery packs.

Then when it comes time for Dick’s medical insurance company to recover its costs, who does it go after? Naturally, the manufacturer who wantonly encouraged Dick to stick crazy in his pack.

2016-02-21 by Russell Graves

I don’t see a need for “individual cell replacement” level rebuildability. Unless you’re building a pack out of junk cells, it’s unlikely for individual cells to fail.

If the pack has a competent BMS, putting in LiCoO2 cells won’t have any bad effects - charge to 4.2v, discharge to 3.0v, and don’t overheat. If your pack is designed for 4.2v cells and can’t handle lithium cobalt oxide, something is seriously wrong.

But I don’t think “swapping cells” is the path likely to be taken - I’m happy with just “not gluing stuff together,” or preferably “Just take volts & amps, and don’t ask where they come from.” There’s no point in rebuilding any of the standard packs out there, as you can just buy a replacement with newer cells. It’s only the proprietary stuff that requires a cell replacement rebuild.

2016-02-22 by LosingMyConnection

I have some hopes that I read your article correctly and there is indeed a way to rebuild BionX batteries?

2016-02-22 by Russell Graves

It depends on the battery, but, yes, I have successfully rebuilt a number of BionX batteries. Mostly the older ones, but I believe newer ones can be rebuilt as well.

There’s a contact form in the right column. If you want to contact me with details, that would be the preferred method.

2017-06-22 by Philou

For your information, I rebuilt a Tranz-X BL-07 battery pack for a relative :slight_smile:
Pretty hard but it can be completed with the skills you own.
I need to write the tutorial…
Cyclurba, le vélo utile

I made it also for my own e-scooter Matra e-Mo (E-Ton EV3) :
Cyclurba, le vélo utile
Translations may come one day…

2017-08-04 by Unknown

Another great article, thanks for starting this discussion. I am investigating resistance soldering, both as a way to build a new pack, and to repair older packs.
Resistance Soldering Bus Strips to 18650 Cells - Endless Sphere

I’d also like to state, I have come to believe that charging to only 4.1V per cell can double the life of a lithium battery pack.

2017-10-17 by Unknown

“I have come to believe that charging to only 4.1V per cell can double the life of a lithium battery pack” TRUE more so storing a pack at 4 volts or under even 3.8 will make it last much longer as volts over time not over recharge cycles is what kills batteries. I have watched several talks on this. For each .1 volt you drop about 1/2 life so if you store for 3 months at 3.8 you gain years of life!!

you can do this with a dedicated charger capped at 3.6-3.8 volts, would have to hack one in but that’s life.

2019-06-01 by chrisj

Thanks for this great article. I fully agree that the right to repair is vitally important.

I have a Bionx 350 HT RR L battery pack which has suffered a couple of years idle time and has dropped to about 15% of its original capacity. I’m not sure if I have the stones to attempt a rebuild, but it may be my only option. I live in South Australia, so access to technical services and components is limited.

One alternative I might consider is to keep the electronics from the battery pack, but connect them to a completely new source of “volts and amps.” Making up a 37volt battery from ten prismatic lithium cells, with suitable battery management and charging, may actually cost less and give a better range than trying to rebuild a 10S6P pack from 18650 cells. The potential for shorts and fires in a 60 cell assembly is daunting to say the least.

2019-06-05 by Russell Graves

Yes, your approach will work, and is better than trying to rebuild the rear rack pack.