shot in the dark, but does anyone know of any compact USB battery banks (power banks) that broadcast their battery level via BLE for HA to pickup?
I need to find a way to bridge power to some esp32 sensors and cameras when mains is not available (prob 50% of the time,) and I need the battery data so I can get alerted if the battery level drops too low.
Cost is usually a factor in the power banks so you are unlikely to find any BLE smarts in them. Even a LED battery level display is a luxury.
Nothing stopping you from using an A to D converter to measure the voltage however. The ESP32 has them inbuilt, so you may be able to put your existing devices to broader use. You could even use the BLE functionality on the ESP32 to transmit the results, or WiFi via MQTT or JSON to HomeAssistant.
Just use an appropriate resistor voltage divider across your battery and configure the A/D port to report the voltage.
Be acutely aware that the ESP32 DOES NOT tolerate 5volts - it uses 3.3volts, so the divider resistors are essential.
By the time you do all this, a seperate mains rated battery backed UPS with a USB connector to HomeAssistant to monitor battery voltage may be a valid low cost option.