AmpMeter — Battery Health

AmpMeter shows what your battery is actually doing. One large gauge tells you
the situation at a glance; everything else sits below it in the order you
actually look at it.

NOW
See charge level, charging status, time to full or empty, current, power,
voltage, temperature, charging speed and a live current curve. Every reading has
its own mini chart, so you see the trend and not just a number. The whole view
fits on one screen — no scrolling.

HEALTH
How much of the rated capacity is left, the rated and measured capacity, charge
cycle count and battery technology.

Most apps divide one single reading and call it capacity. That number is
inaccurate: the charge level is rounded to whole percent and many devices have a
constant offset in the counter. AmpMeter instead collects measurement points
across different charge levels and fits a line through them — the slope is the
full capacity, and the constant term absorbs the meter's zero offset.

The fit uses the Theil–Sen median slope rather than least squares, because the
counter occasionally returns a completely wrong reading and a single one of
those shifts a least-squares fit by more than 20%. The median does not move.

The estimate is only shown as a gauge once there are at least 8 points spanning
25 percentage points of charge. Until then you see a progress bar and the figure
is marked preliminary. In normal use the measurement completes in a couple of
days.

HISTORY
Charging sessions are recorded automatically from plug-in to unplug: duration,
charge gained, average current and maximum temperature. Recording keeps working
while the app is closed, and each session is written to storage as it goes — a
night of charging is not lost if the system closes the app.

CHARGE ALERT
Get a notification when the battery reaches the level you choose, 80% by
default. Keeping a lithium battery off a full charge is one of the few things
that measurably extends its life.

SETTINGS
Theme (system, light, dark) and temperature unit (°C/°F).

PRIVACY
Everything stays on your device. No account, no ads, no analytics, no network
access. AmpMeter does not collect or share any data.

GOOD TO KNOW
Current, voltage and temperature come from the device's own battery sensors, and
not every manufacturer reports every value. A reading the device does not report
is shown as a dash rather than a guess. Cycle count requires Android 14 or
newer. Rated capacity is read from the system power profile; on the rare device
where that fails, the health estimate is not shown at all.

Languages: English, Finnish, Swedish.