1.3.6.1.4.1.61513@xssfox@cloudisland.nz
after starting from 0, I worked my way up. 1, 2, 3,... 9998, 9999. Jackpot.
I kid, I just used apk2gold to decompile the app and searched for "password".
Two passwords exist. 9999 and 736263.
1.3.6.1.4.1.61513@xssfox@cloudisland.nz
The 736263 passcode seems to allow setting the device name.
9999 is more scary and seems to set a lot of the BMS parameters. I'm not sure if these are sanity checked by the BMS but I don't think it would be hard to put the BMS into an unsafe state with this control.