I have been off the forum for a little while and not sure if this has been covered yet but… If anyone is interested in seeing whats inside a Gen 2 Max battery…
This is… well was… a 11s3p 40v v2 Max power battery.
A friend brought it by after having issues charging to see it was salvageable. Turns out the very end series cell group was dead (like 0v dead). These are totally potted in epoxy so not serviceable obviously. I used a flap wheel on a grinder to carefully expose cell ends so I could get voltages across all the series groups. While this won’t be running his gen 2 anymore sadly, I should be able to salvage the remaining cells to make a 36v pack for my homemade foildrive, ebike or something…
Yes I understand this is a grenade. Don’t worry, it’s being treated as such and will be stored outside in an ammo box. I’ve built several diy lithium ion packs in the past.
Hopefully someone finds this useful for building their own pack or possibly saving their FD battery. I do think it would be possible to bump a series group back to life if it fell slightly below BMS cutoff voltage. Just need to have a steady hand with a grinder to expose the bus bar and then recoat with epoxy after defibrillation.
However, the owner can estimate how many times he used the device. At least approximately. For example, I ride two seasons, 40-50 times per season. The number of charging cycles is from 80 to 100.
I would also be interested to hear versions of the reason for the battery failure and whether it is typical for FD batteries.
No telliing but he did buy the system used and used it very frequently. So i imagine it had lots of cycles. FD warrantied the battery for him so I assume it wasnt so old that it was no longer covered.
You could get a bms from the onewheel universe.
See here: VESC BMS (Smart and Dumb) List - Battery Guides - pev.dev
They are all small and some have can and/or bt to connect and check the cell values. The smart ones are not cheap though. Ennoid xlite v4 is really good and very small but expensive.
Thanks for posting those pics. Any chance you can show how they made the connection to the XT90 connector? Looking at the exposed connections, I’m not understanding how the pack is wired. Also curious what thickness nickel strip they used.
