USB Charger Tester: VoltLab

Slow charging? Compare your USB charger and cable using the battery measurements your phone can report. VoltLab brings an ampere meter, charger tester and charging journal together. See what changes when you swap a cable, check how steady a charging setup is, and keep the results for your next purchase or troubleshooting session. Understand your charging speed View battery-side power in watts, signed current in mA, voltage, temperature and battery percentage. Explore live graphs over 1, 5 or 10 minutes. Clear explanations help when the current sensor is unavailable, reports zero, or the battery is draining while plugged in. Compare chargers and USB-C cables Run a guided test for 1, 2, 3, 5 or 10 minutes after 10 seconds of stabilization. Review average and peak power, sample coverage, stability and temperature change. In a guided A/B comparison, keep one charger while changing cables, or one cable while changing chargers. Each of 2–3 stages starts when you are ready. Results explain differences in starting conditions instead of declaring an unreliable winner. Keep track of your equipment Create charger and cable profiles, add your own rated power and cable length, choose colors and save favorite setups. Reuse a setup and open its previous measurements. Historical labels remain attached to the original test. Record charging sessions Save recorded time, percentage change, Wh, mAh, average and peak power, maximum temperature and graphs. View summaries for 7 or 30 days. Without background monitoring, only the observed part is recorded. Tap Monitor to continue the current charge with an ongoing notification. Stop it in the app or notification; unplugging also ends monitoring. Keep useful tools close Use the resizable home screen widget, charge planner and V × A calculator. Share a PNG result card or detailed CSV. Save and restore a local JSON backup of equipment, tests, sessions, notes and comparisons. History is not automatically deleted. Private by design No ads, account, server, analytics or Internet permission. English, Ukrainian and Russian work offline. Light and dark themes and large text are supported. You choose when and where to export your records. What the numbers mean VoltLab measures the battery side, not guaranteed charger output. Results depend on your phone's sensors, battery level, temperature and phone activity. Some phones cannot report every measurement. Compare on the same phone under similar conditions, preferably below 80% charge. The app does not identify USB-PD profiles, e-marker data, certified cable wattage or battery wear, and it does not make charging faster. Use a hardware USB tester for those measurements. Support: [email protected]

A complete charging toolkit: equipment profiles, guided A/B comparisons, saved charging sessions, 7/30-day summaries, local backups and a home screen widget. Clearer diagnostics and a stable test layout make changing sensor readings easier to follow.