WattBench
Live power meter for FNB58
Only for iPhone
$2.99 · Designed for iPhone. Not verified for macOS.
iPhone
The bench instrument for your FNIRSI FNB58: live V, A and W, charger detection, guided battery and cable tests, reports, and your Lock Screen and Apple Watch.
WattBench turns your iPhone into a wireless display, data logger and test bench for the FNIRSI FNB58 USB power meter.
Connect over Bluetooth and watch voltage, current and power live. See what your charger is doing on the USB data lines. Record a whole charge cycle with the phone locked. Then run guided tests that answer real questions: how much a power bank actually holds, how fast a phone really charges, and whether a cable is wasting power.
LIVE
• Big, glanceable voltage, current and power with peak hold
• USB data lines: D+ and D− voltages and the meter's temperature
• Charger detection: Quick Charge, USB PD, Apple, Samsung and BC 1.2 patterns named automatically
• Full-screen chart with V, A, W or all three, up to the last 60 minutes, in portrait or landscape, with pinch to zoom
• Trip counter for energy (Wh) and capacity (mAh) without starting a recording
TESTS
• Power Bank Capacity: compares what a bank really delivers with the mAh on its label
• Device Charge: shows the fast, tapering and trickle phases of a charge, with a battery estimate
• Cable & Charger Check: guides you through load steps with a USB electronic load and grades the resistance of the cable and charger
RECORDINGS AND REPORTS
• Recordings keep running with the screen locked and survive a crash or a Bluetooth drop; dropouts are shown honestly as gaps
• Lock Screen, Dynamic Island and Apple Watch Smart Stack show live readings while you record
• Automatic markers when the charger changes mode or voltage
• Session reports with zoomable charts, range statistics, a power histogram, a voltage-versus-current plot, cumulative energy, temperature and D+/D− over time
• Compare up to four sessions on one chart
• Export PDF reports and CSV files
ALERTS
• Over- and under-voltage, over-current, over-power, current below, voltage drop, disconnect, over-temperature and "fast charge lost", with presets
• Banners in the app, notifications in the background, with Stop & save during a recording
PRIVATE BY DESIGN
No account, no ads, no analytics, no network access. Your recordings stay on your iPhone.
REQUIREMENTS
The FNIRSI FNB58 USB power meter with Bluetooth. Turn Bluetooth on in the meter's settings menu, then tap Connect. A USB electronic load is recommended for the power bank and cable tests. No meter yet? Tap Try Demo Data to explore every screen.
User guide and test recipes: https://redthoroughbred.github.io/wattbench/guide.html
WattBench is an independent project and is not affiliated with or endorsed by FNIRSI.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
The developer, Seth Egger, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Seth Egger
- Size
- 5.7 MB
- Category
- Utilities
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Seth Egger
