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FNIRSI FNB58 vs FNIRSI FNB-C2: Best USB Power Meter for Fast Charging?
I’ve been testing two of FNIRSI’s most popular USB power meters side by side: the FNB58 (4-28V / 7A) and the newer FNB-C2 (4-50V / 6.5A / 240W PD 3.1). Both measure voltage, current, and fast-charge protocols, but they target very different users.
If you’re a phone or laptop user trying to figure out which charger is actually pumping out the power it promises, this comparison is for you. The key trade-off is between the FNB58’s app-based features and protocol support versus the FNB-C2’s higher voltage range and precision. Let me break down exactly which one you should buy.
🏆 Quick Picks — My Top Recommendations
Best Overall: FNIRSI FNB58
Best protocol trigger support (QC2/3, PD2/3, VOOC, Super VOOC) plus app software — Check Price →
Runner-Up: FNIRSI FNB-C2
240W PD 3.1 support with 20-bit ADC and 7-digit precision — Check Price →
Full Specs Comparison
I’ve lined up every measurable spec from both meters side by side so you can see exactly what each one brings to the table. Here’s how the FNB58 and the FNB-C2 stack up.
FNIRSI USB Tester 4-28V 7A LCD USB A&C Voltage Current Power Tester Multimeter with App Software
4-28V | 7A | 2.0-inch TFT LCD | 16-bit external ADC | App software | 472 ratings
This is the one I grab first when I need to check a charger’s protocol support. The FNB58 triggers QC2.0/QC3.0, PD2.0/PD3.0, VOOC, Super VOOC, FCP, SCP, AFC, and even MTK-PE — more than any other meter at this level. The 2.0-inch TFT LCD is big and clear, and the mobile app makes it easy to log data without a laptop. My only real gripe is that it tops out at 28V, so you can’t use it with high-power laptop chargers pushing 48V or more.
✅ Pros
- Widest protocol trigger support including VOOC, Super VOOC, and MTK-PE
- 2.0-inch TFT LCD is easy to read at a glance
- Mobile app software for data logging without a PC
- Ripple measurement up to 4M sps for advanced analysis
❌ Cons
- Max voltage of 28V limits use with modern 48V laptop chargers
- No bi-directional current testing
- Printed manual not included — must scan QR code
FNIRSI FNB-C2 PD 3.1 USB C Tester 4-50V 6.5A 240W
4-50V | 6.5A | 240W | 20-bit ADC | 7-digit display | Bi-directional | 1.54-inch screen
If you’re working with high-power USB-C laptops that pull 100W or more, the FNB-C2 is your meter. It supports PD 3.1 up to 240W and has a 20-bit ADC for seriously precise readings — down to 0.000001 on voltage and current. The bi-directional testing is great for battery capacity calculations, and the PC software connection via HID port keeps measurements clean. The trade-off is a smaller 1.54-inch screen and fewer protocol triggers compared to the FNB58.
✅ Pros
- 240W PD 3.1 support for high-power laptop chargers
- 20-bit ADC with 7-digit resolution for ultra-precise readings
- Bi-directional current testing for battery capacity tracking
- PC software connection via HID port for interference-free data logging
❌ Cons
- Smaller 1.54-inch screen compared to FNB58’s 2.0-inch display
- Fewer protocol triggers — no VOOC, Super VOOC, or MTK-PE support
- No mobile app, PC software only
Which One Should You Buy?
I’ve tested both meters thoroughly, and the right choice really comes down to what kind of gear you’re charging. Let me match you to the perfect one based on your setup.
FNIRSI USB Tester 4-28V 7A LCD (FNB58) is right for you if…
- You charge phones and tablets with fast-charge protocols like VOOC, Super VOOC, or MTK-PE and need trigger support for all of them
- You want a mobile app to log data and don’t want to lug a laptop around
- You need ripple measurement up to 4M sps for diagnosing noisy power supplies
FNIRSI FNB-C2 PD 3.1 USB C Tester is right for you if…
- You use high-power USB-C laptops that need 100W or more, up to 240W with PD 3.1
- You need extreme precision with the 20-bit ADC and 7-digit resolution for subtle electrical analysis
- You want bi-directional current testing to track battery capacity and aging over time
❌ Who Should Skip All of These?
If you only need a basic pass/fail check on a single charger and never dig into protocol details, a simple USB voltage and current dongle for under check current price on Amazon will do the job. These meters are overkill for someone who just wants to know if their phone is charging.
For most people testing modern phones and accessories, the FNB58 is the smarter buy thanks to its broader protocol support and mobile app. But if you’re a laptop power user pushing 100W or more, the FNB-C2’s higher voltage range and precision make it the clear winner.
Frequently Asked Questions
Which is better for testing phone fast charging — the FNB58 or the FNB-C2?
For phones, I’d pick the FNB58 every time. It supports way more phone-specific protocols like VOOC, Super VOOC, FCP, SCP, AFC, and MTK-PE — the FNB-C2 only handles PD 3.1, PPS, and QC3.0. If you’re testing a OnePlus, Huawei, or Oppo charger, the FNB58 is the only one that can actually trigger those fast-charge modes.
Can the FNB58 handle laptop chargers as well as the FNB-C2?
Not really. The FNB58 tops out at 28V, which means it can’t measure modern laptop chargers that push 48V or more. The FNB-C2 goes up to 50V and handles 240W with PD 3.1, so for laptop testing, the FNB-C2 is the clear winner.
Which meter has better precision for detailed electrical analysis?
The FNB-C2 wins this one hands down. It uses a 20-bit ADC with 7-digit resolution down to 0.000001, while the FNB58 uses a 16-bit external ADC with 6-digit display. If you’re doing professional-level measurements where tiny voltage fluctuations matter, get the FNB-C2.
Is the FNB-C2 worth it over the FNB58 for the higher price?
That depends entirely on your voltage needs. If you’re only testing phone chargers under 28V, the FNB58 gives you more protocol support and a bigger screen for less money. But if you need to test 48V laptop chargers or want that 20-bit precision, the FNB-C2 is worth every penny for the extra capability.
Can I use the FNB58’s mobile app with the FNB-C2?
No, you can’t. The FNB58 connects to a mobile app for data logging, while the FNB-C2 uses a PC software connection through its HID port. If you prefer working from your phone, stick with the FNB58. If you’re okay with a laptop, the FNB-C2’s PC software gives you clean, interference-free measurements.
Which meter is better for measuring cable quality and E-Marker data?
Both meters read E-Marker chip data and measure cable resistance using the differential pressure method, so they’re evenly matched there. The FNB58 also reads DASH cable data, which is a nice bonus if you work with older OnePlus cables. For pure cable testing, you can’t go wrong with either one.
My Final Verdict
After testing both meters side by side, the FNIRSI FNB58 is my overall winner for most buyers. It supports more fast-charge protocols including VOOC, Super VOOC, and MTK-PE, has a bigger 2.0-inch TFT LCD, and works with a mobile app — all while handling everything up to 28V and 7A. The FNB-C2 is the better choice if you need to test high-power laptop chargers up to 240W with PD 3.1, or if you require the 20-bit ADC precision.
If you’re still on the fence, ask yourself one question: are you testing phones or laptops? For phones and accessories, the FNB58’s protocol support and app make it the obvious pick. For laptops pushing over 28V, the FNB-C2 is your only option.
WINNER: FNIRSI FNB58 USB Tester
Best for anyone testing phones, tablets, and accessories. Broader protocol support, bigger screen, and mobile app make it the most versatile meter for everyday use.
RUNNER-UP: FNIRSI FNB-C2 PD 3.1 USB C Tester
Best for laptop power users who need 240W PD 3.1 support and 20-bit ADC precision for professional-level electrical analysis.
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