Yamaha/Haibike battery won’t turn on. BMS dead?

robocam

10 kW
Joined
May 29, 2014
Messages
773
The 1st and 4th capacity lights flash rapidly when the button is pressed. According to an online manual, that means an unrecoverable error but I don’t see anything that matches the error code of just the 2nd and 4th LEDs being lit during the diagnostic.

This happened when I added a discharging plug in parallel with the power connector on my Haibike. I wanted a way to drain the battery down to 38V for storage to protect the battery but it looks like I bricked it. The problem was that I had the discharge load (two light bulbs) connected to the discharge connector when I put the battery back on the bike. This extremely light load must have caused something to happen in the BMS, and now the battery doesn’t work at all. The charger won’t charge it.

I was able to bring it down to 38V by opening up the battery and bypassing the BMS. Worst case, I’ll keep the cells for when the new battery needs new cells or maybe I could sell it for the cells. The diagnostic mode still shows 100% life with 101-200 cycles.

I have another Yamaha battery that I tested and the discharge connector works if I turn on the bike before I connect the load. Now that I see how easy it is to bypass the BMS, I’m going to discharge the battery itself with a plug I’ll add to it later.

Anyway, any idea what I can try to fix the battery? The BMS looks clean, with no burn marks or obvious signs of damage.
 
Based on various posts about such systems, the BMS is probably "smart" in a way that tries to detect any conditions other than those expected by it, and whenever one occurs it bricks itself so the user can't "tamper" with it and get around any limitations the system may have from the factory.

The good news is that there may be a way around this for your situation:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=114108
The linked page below says they're out of dongles but links the page the original hack came from so you may be able to build one yourself. I have not read that hack, or used the Yamaha system(s), so I don't know if this applies to your system or not.

avandalen said:
Yamaha PW series mid-drive motor hacking dongle to use 3rd party batteries

Please post your questions about the Yamaha dongle here.

See the full article: https://www.avdweb.nl/solar-bike/batteries/battery-hack
As with other brands, the Yamaha PW series motor doesn't allow to use any 3e party battery. But with the use of the dongle described here, the Yamaha ebike will be hacked so that you can use any battery instead of the original expensive Yamaha battery.

This are the most important characteristics of the Yamaha battery dongle:
  • You can use any battery on your Yamaha ebike instead of an expensive original Yamaha battery.
  • The battery capacity is measured very accurately with an LTC2944 fuel gauge IC, not just simple voltage measuring.
  • The battery capacity is stored in an EEPROM so that it is not lost when switched off.
 
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