dilemma: JK-B2A24S15P and inverter deadlocked waiting for eachother to start

Hi! Is there some way to reliably and automatically start a JK-B2A24S15P? When the external inverter-charger itself requires battery power before it will start up?

Working on the setup, I had initially assumed it is enough to have the thin lead "B+ BMS Power" (and 16S lead) hooked to the +48V terminal of the LFP. Alas, the entire setup stayed dead. After triple-checking the manuals, JK mentions "The protection board does not have a power-on control switch, and it is designed as a charging activation mode, that is, after the battery is assembled, a charger needs to be connected to make the protection board work."

Alas number 2, to my surprise, my hybrid inverter (Steca Solarix PLI 5000-48) appears to be designed to start up *only* from battery, regardless of PV and/or grid input presence. Once the Solarix inverter actually runs, it is able to charge from PV and/or grid, and can thereby "sustain" itself.

Ergo: the hybrid inverter and BMS are both designed to wait for the other to start first :-( I messed up device selection...

One test I did was to bypass the JK-BMS protection board by tying its B- and P- leads together. The hybrid inverter started fine. The BMS remained off, of course.

The Solarix draws about 20W from battery in quiescent mode. This is quit a lot. Another test to start the JK-BMS, still todo, is to get a high-wattage 50 Ohm(?) resistor and permanently wire it across the B- and P- leads.

That *might* pass the ~20W needed by the inverter to power up and operate, and then in presence of PV input, the inverter should begin "charging", thus raising the voltage by >2V higher than the LFP voltage as required for the JK-BMS to start. After that there *should* be proper LFP via the then operational BMS protection board.

Otoh this potential 50 Ohm high-wattage resistor setup seems a bit stupid -- semi-bypassing the battery protection...

Is there some other, more elegant way to get this mess working?

Somehow use the PV input (~82V OC) to bootstrap the JK-BMS? Maybe 10k resistors to the JK-BMS B- and P-, and some protective 68V Zener diode or such acorss?

Or some other...?

Has anyone run into this same issue?

I'm not sure I'm following. Once the JK BMS is on it stays on. You do that either with a push button switch that can be included with the BMS or apply 5V to it as indicated in instructions. But once that is up it should always be on unless something goes seriously wrong. When you quoted "a charger needs to be connected to make the protection board work" that is not the correct terms.. as I've indicated above.. It doesn't need a constant source of special voltage from anywhere except the battery once it is initially turned on.

i.e. you can have the JK BMS running with nothing other than it connected to your battery bank (once you initially turn the BMS on).

Thanks! Unfortunately, no push button included, and no obvious connector for one.
The English instructions say 5V higher than battery voltage to start, chinese ones talked about >2V iirc.
With 5V higher, I'd need to find a >57.5V supply. At the moment there's about 49.5V across the BMS B- P- rather than the full 52.5V of the LFP, because there is a ~3V drop across the Solarix inverter +/- battery input connectors. Hmm, well. If the BMS will stay running once turned on, I can try tomorrow to detach P- leads from the Solarix inverter and connect these P- via a series 9V battery to the 52.5V LFP for a minute, then move the P- back to the Solarix inverter.

The bluetooth interface started up after providing 5V across the B- P- with the inverter disconnected. Partial success. The BMS is running. But with the P- lead attached back to the inverter again, the BMS remains “open circuit”.

I see about 52V accross B- P- (yesterday with BMS completely off it was ~49V), and the inverter does not start up ?

Is there some setting to tell the JK BMS to start conducting…?

Ah, never mind, I should have chosen “discharge” as well rather than only “charge” on this screen.
Now the BMS works, the inverter gets powered up via the BMS, and has finally started charging from PV.