Twelve Volt: 12V Battery

Twelve Volt reads small Bluetooth battery monitors (BM2, BM6 and BM7, sold under many brand names) and keeps every reading on your phone. Nothing else.

PRIVATE BY DESIGN
• No internet access: the app doesn't have Android's Internet permission, so it can't reach any server. You can check it in the app's permission list.
• No location: sensors are added through Android's own device picker. The app can read your sensors without Location, but the performance improves if you enable it. Your position is never read, and never in the background.
• No ads, no account, no tracking. Your readings stay in a database on your phone and leave it only when you export or back them up.

WHAT IT DOES
• History that loads: the monitor logs the voltage every 2 minutes. Twelve Volt downloads it in seconds and keeps every reading for good, so your chart reaches back further with every sync.
• A charge reading you can trust: pick lead-acid, AGM, gel or LiFePO4. Charge comes from the resting voltage; while charging or under load the app says so instead of showing a made-up number. Tap it to see how it's worked out and why it is, or isn't, reliable right now.
• Alerts that fire: low voltage, low charge, a charging problem after an engine start, high temperature, and no readings for 3 days. Checked after every sync against the full history. One alert per problem, with a 24-hour mute.
• Short, reliable syncs: the app connects, catches up and lets go. It syncs in the background when the sensor comes into range and every few hours.
• Engine start and charging check: in Live mode it records the voltage dip at engine start and checks the charging voltage afterwards. The screen stays on while Live runs.
• Parked-drain forecast: how many days the battery can sit before it gets too low.
• Your data is yours: export to CSV or JSON, or back up everything to one file and restore it on a new phone.
• Read-only: Twelve Volt never changes your sensor's settings.

ALSO
• Morning summary: an optional, silent daily notification with every battery's voltage
• Fitting guide and signal meter: where to connect the leads, and where your phone still hears the sensor
• Several sensors, in your order
• Home-screen widgets: 1×1, 2×2 and a row of up to four sensors
• Light and dark themes
• Tablets and Android head units: two-pane layout
• 9 languages

MADE FOR BATTERIES THAT WAIT
Motorcycles, campers and vans, cars in storage, boats: batteries rarely die on the road, they die parked. Twelve Volt watches the ones you don't use every day.

Needs Android 10 or newer with Bluetooth Low Energy, and a BM2, BM6 or BM7 monitor on the battery. Twelve Volt is not affiliated with the sensor makers.

Questions: [email protected] · https://twelvevolt.app