JBD 100A BMS no longer connecting to Android after LVD

[Mr.Michael]

I build a 8S LifePo4 battery with a JBD 100A BMS for a cabin and used it for maybe 2 years but 3 months ago vacated the cabin, sold the solar setup to the new owner. The BMS was always working fine for 2 year with the initial firmware and either Xiaoxiang or Carplounge connected fine. I got a call from the new owner with a request for help - of course I went to the farm. He over-discharged the battery caused it to go apparent LVD. 2 cells had been below 3V, external battery terminal had 1.5V measured with my Fluke DVM.

The new owner said "I did not touch anything" so the firmware should be what used to work. I needed to download the apps as I removed them and also upgraded my main phone. However, none of the apps connect. Everything crashes except Lion-Tron which says it connects but remains blank. BT on, location on. I tested:

Samsung S20 with Android 12 Xiaoxiang 3.1.1026 via APK install
Moto 7 with Android 10 Xiaoxiang 3.1.1026 and a few older 3.1.x versions. Also tried Carplounge/Lion-Tron/PoliNovel2
Random old Android 6 phone Xiaoxiang 3.1.1026 and a few older versions down to 2.x

All versions do crash after it finds the battery or even before. Some stay connected for a bit with "get device info fail, please retry :-2" and crash. Only Lion-Tron does not crash but all remains 0.00 as if no data is transferred. The battery is shown as connected in Lion-Tron but no info seems to be transferred.

I disconnected the BMS a few times to do a power cycle reset in the hopes that does any good. Did not help.

I do not have a UART cable and a quick test with a home brew UART to USB adapter and the Overkill Solar app did not yield anything useful. The LED's show some RX/TX going on but the software remains in search mode and does not identify the BMS. I did charge the battery with maybe 1Ah since I do not have anything left here to properly charge a 24V battery. All cells went above 3.0V. Now the external terminal has 24V on it as expected, a small 24V light bulb works again.
Is it possible that the BMS died even so BT is on? I am reluctant to reconnect the battery to the 1KW solar panels and hope for the best.

Any hints would be appreciated.

 

[Banszi]

Did you try to depower the BMS, or restart it (I believe by connecting the B- to C- lead)?

 

[Mr.Michael]

Thank you for the suggestion. Yes, a few times in the process. BT comes back but same result.
I also like to mention since I obviously got a bunch of devices around that I turn off BT on any of the phones I do not use at the moment, only using a single phone at a time to avoid interference.

One more question: Does anyone know the commands available for Terminal to connect? I think it is 9600-8N1 and maybe I can tickle it via a console session.