Android battery health, explained
Straight answers to the questions people ask about Android batteries — and exactly what Power Battery can and can't measure.
How do I check battery health on Android?
Most Android phones have no battery health screen, and Android gives apps no public “state of health” value. Power Battery estimates it instead: it watches your phone's charge counter as the battery level changes to estimate the full-charge capacity in mAh, then compares that with the design capacity your phone declares. The result is an estimate and is labelled as one; on phones that declare no design capacity, the app shows “—” rather than a made-up percentage. A few recent phones also show battery health in their own Settings.
What do mAh and design capacity mean?
mAh (milliamp-hours) measures how much charge a battery holds. Design capacity is what the battery held when new — for example 5,000 mAh. As lithium-ion cells age they hold less, so a battery that now holds about 4,300 mAh is at roughly 86% health. Health is about the size of the “tank”, not the charge percentage in your status bar.
Why doesn't Android show battery health, and what does Power Battery do instead?
Android exposes a charge counter, current, voltage, temperature and, on Android 14+, a cycle count on many phones — but no public battery-health value, and the system battery files are closed to apps. Power Battery works only with what Android allows: it derives capacity from the change in the charge counter across a change in battery level, and uses the design capacity your phone reports. It never claims more precision than the phone provides.
How can I see my battery's charge cycles?
On Android 14 and later, many phones report their charge-cycle count; Power Battery reads it directly and marks it as reported by your device. On older phones, or phones that don't report it, the app estimates cycles from your charging history and labels the number as an estimate. One cycle is 100% of charge in total — two charges from 50% to 100% make one cycle.
How do I see my phone's charging speed in watts?
Charging power is voltage × current. Power Battery shows the live current in mA and the power in watts while you charge, and a speed test rates charging as fast, moderate or slow so you can compare cables and chargers. A charger rated at 30 W won't always deliver 30 W — a worn cable, a weak adapter, or a nearly full or hot battery all lower the real number. Readings are what your phone's hardware reports.
Should I stop charging at 80–85%?
Lithium-ion batteries age faster when they sit at a high charge, especially when warm, so many people unplug at around 80–85% for everyday use. Some phones have a built-in charging limit in Settings. Power Battery's charge-limit alarm (Pro) alerts you — with a full-screen lock-screen alert — when you reach your chosen level, so you can unplug. It is an alarm: the app does not control your charger.
Is Power Battery safe, and what data is sent to the AI?
Battery readings are stored on your phone. Only when you ask Volt a question, or turn on the weekly AI report (Pro), is a summary of your battery numbers — no contacts, accounts or personal identifiers — sent with your question to Google's Gemini API to write the answer. It is not sold. Volt is in beta and can be imprecise, so each answer carries a notice and a one-tap report option. The app asks for Bluetooth (to read connected devices' battery level) and notifications (for alarms and alerts), and never force-closes other apps.
Is Power Battery free?
Yes. The core app is free on Google Play: live battery stats, the health and capacity estimate, charge cycles, charging speed in watts, the speed test, wear prediction, connected-device battery levels, widgets and a limited number of Volt chats. An optional Pro subscription adds unlimited Volt chats, care insights, the charge-limit alarm, history & graphs, the weekly AI report, Light/Dark/Material You themes, CSV/JSON export and priority support.
What should I look for in a battery health app?
Look for an app that shows where each number comes from, labels estimates as estimates and explains its limits. Be cautious of apps that promise to “boost”, “repair” or “save” your battery by closing other apps: Android manages background apps itself, and force-closing them does not restore battery capacity. Power Battery is built on that principle — it measures and explains, and helps you build charging habits that slow long-term wear.
More detail: the complete battery health guide.