Bosch Athlet battery pack rebuild

[justaguy]

I'm fighting with the battery pack of a Bosch Athlet BCH 6ATH18 vacuum cleaner.
Device did not take charge. Upon inspection, one of the 5 Li-Ion cells was showing only about 0.5V. I have bought new cells and rebuilt the pack, however it still refuses to charge. There are a BQ77PL900 battery manager and an atmega328 running the show. The charge mosfet appears to be ok and if I connect the pack keeping the uP under reset (which should let the BQ77 run in stand-alone mode) the batteries get charged. Therefore I assume that the uP has stored the battery failure in eeprom and got in some lockdown/brick mode.
My only hope seems to be to reflash the uP, does anybody have the right firmware?

[SilverSolder]

Have you seen this thread?

https://www.eevblog.com/forum/reviews/dyson-v7-trigger-cordless-vacuum-teardown-of-battery-pack/?all

It looks like manufacturers really don't want you to repair their battery packs, since they essentially self destruct if you are not careful - like a time bomb! 

It may be possible to buy a replacement battery module on AliExpress that works on this model?

[abdulbadii]

pass BMS by ?

try put its schematic/picture on

[amyk]

RE the communication protocol between the battery and device which uses it, write your own firmware or emulate it... might be easier to always report 100% than an actual battery gauge.

[justaguy]

I'm under time pressure from my wife  I think I will just buy a new vacuum cleaner.
It's just a shame that those things are not meant to be repaired; I can understand the manufacturer's concerns about safety when dealing with Li-Ion, but sometimes it smells of planned obsolescence...