added service "battery"

[hsteinhaus]

An open-source implementation for a MQTT-based interface to JKBMS on ESP32/ESPHome can be found here: https://github.com/hsteinhaus/esph-gadgets/blob/master/esphome/jkbms-mqtt.yaml

[freakent]

Hi, thanks for this. I'm not familiar with the battery settings but on first inspection it looks like the persist attributes don't look quite right. Can you provide a screen shot of how the setup screen for the battery from the GX device? I'd also like the descriptions to be the Victron ones. Do you have a test script to prove the settings work? Please see similar request here #110.

[hsteinhaus]

@freakent Thanks for the feedback and the pointer to a similar PR.

I will look into the persist issue as soon as I have physical access to the system again. Just found out in between that there are a few more data items available in the GUI now that represent the switches of the BMS, I will try to add them, as they might be very useful in the VRM log.