btVolt
BLE battery voltage sensor + Android widgets
A device + app for mobile terminals: a battery voltage sensor transmitting over Bluetooth to multiple Android terminals at once, automatically and without pairing, shown as background widgets.
Task
Develop a device that transmits the battery voltage over bluetooth to several Android terminals in range, simultaneously, automatically without pairing setup. The app must work in the background as widgets, color-code battery status, and allow sharing a module via the internet.
Hardware
ESP32-C3 based modular build, DC-DC converter for 12V/24V systems (up to 30V), hermetic compound-filled 3D-printed enclosure, redesigned antenna, external fuse. Tested in engine bays and a solar power monitoring system.
Software
Kotlin, Jetpack Compose, compose-charts, glance widgets, QR-code sharing with a FastAPI backend, multilingual UI.
Features
- Simultaneous broadcast to many Android terminals
- No pairing setup needed
- Background Android widgets
- Voltage history chart
- Hermetic 3D-printed enclosure