Last Updated: January 2026
At ChargeGrade, we do not simply trust the specifications printed on the box. Marketing teams lie; physics does not.
To ensure every power bank is graded fairly, we subject every unit to a standardized, multi-stage testing process in our Singapore-based lab. We use industrial-grade DC electronic loads and protocol analyzers to measure the actual performance against the manufacturer’s claims.
Here is exactly how we test.
Table of Contents
1. The Lab Equipment
We do not use cheap USB multimeters found in hobby kits. Our data is derived from calibrated validation instruments.
- Programmable DC Electronic Loads (180W): We use these to perform full discharge cycles at constant current (CC). This allows us to drain a battery from 100% to 0% at a precise rate to measure the true energy capacity.
- Precision Protocol Analyzers: Connected via USB-C, these analyzers handshake with the power bank to verify supported standards (PD 3.1, QC 5, PPS) and monitor voltage stability at the microsecond level.
- Oscilloscopes: Used to detect “Ripple & Noise”—fluctuations in the DC power delivery that can damage sensitive electronics over time.
- Thermal Probes: Contact probes are attached to the chassis during stress testing to monitor heat dissipation and detect thermal throttling.
All tests are conducted in a climate-controlled environment at 25°C ±1°C to ensure consistency.
2. The Standardized “Wattage Ladder”
Unlike other reviewers who test at random speeds, ChargeGrade follows a strict Completionist Protocol.
We test every power bank against a standardized matrix of wattages that correspond to the most common real-world devices. This allows you to answer the specific question: “Is this efficient for MY device?”
Phase 1: Output Discharge Matrix (Efficiency)
We verify efficiency by draining the power bank at specific Voltage/Amperage profiles defined by the PD 3.0 standard. We only run tests that fall within the power bank’s rated limits.
| Test Point | Target Device Simulation | Voltage / Amperage | Why We Test This |
| 10W | Standard Phone | 5V / 2.0A | The universal baseline. Allows fair comparison between a $15 slim bank and a $150 pro bank. |
| 20W | iPhone / Pixel | 9V / 2.22A | Simulates the standard “Fast Charge” for base iPhones and Google Pixels. |
| 45W | Samsung Ultra / Steam Deck | 15V / 3.0A | The sweet spot for Samsung S24/S25 Ultra, Valve Steam Deck, and Nintendo Switch (Docked). |
| 65W | Standard Laptop | 20V / 3.25A | The industry standard for Ultrabooks, MacBook Air, and Dell XPS. |
| 100W | Pro Laptop | 20V / 5.0A | The maximum limit of standard USB-C cables. Used to test thermal endurance. |
| 140W | MacBook Pro 16″ | 28V / 5.0A | The PD 3.1 limit. Only “Grade A” engineering survives this stress test without overheating. |
You might wonder: “If I’m buying a 140W power bank for my MacBook Pro, why does ChargeGrade test it at a slow 10W?”
We test 10W (5V/2A) on every single unit because it represents the “Silent Majority” of your electronics. While 140W is for your laptop, the 10W test reveals three critical things about the power bank’s engineering:
1. The “Wearable & Creator” Ecosystem
Most of the gadgets in your bag do not use Power Delivery. They rely on the standard 5V USB profile. If a power bank is inefficient at 10W, it will waste massive amounts of energy when charging devices like:
- Audio: Wireless Earbuds (AirPods/Galaxy Buds) and Noise-Canceling Headphones.
- Wearables: Smartwatches and Fitness Trackers.
- Cameras: GoPro/Action Cams, Drone batteries, and Mirrorless Cameras (idle charging).
- accessories: Portable lights, microphones, and e-readers (Kindle).
2. The “Bad Cable” Fallback
If you (or a friend) plug a modern phone into a high-tech power bank using an old or damaged cable, the digital handshake often fails. The system defaults to the safe USB-BC 1.2 standard, which is capped at roughly 10W-12W. We test how the bank performs when high-speed tech fails.
3. The “Ferrari in Traffic” Efficiency Check
High-power banks (100W+) have heavy-duty internal circuitry designed to handle massive energy flows. However, these circuits often consume a lot of power just to stay “awake.”
Testing at 10W reveals the Static Power Overhead. It separates the well-tuned engineering (which scales down efficiently) from the brute-force engineering (which wastes energy at low speeds).
The Math:
We compare the Measured Watt-Hours (Wh) against the Claimed Watt-Hours.
- Efficiency % = (Real Wh / Claimed Wh) * 100
The Grading Standard:
We hold manufacturers to a strict standard. Most generic power banks fail to hit Grade B.
- Grade A+: 85% & above Efficiency (The Gold Standard – Rare)
- Grade A: 80% – 84% Efficiency (Great / Recommended)
- Grade B: 75% – 79% Efficiency (Above Average)
- Grade C: 70% – 74% Efficiency (Acceptable Industry Average)
- Grade D: 65% – 69% Efficiency (Below Average / High Heat Loss)
- Grade E: 60% – 64% Efficiency (Poor Quality)
- Grade F: < 60% Efficiency (Fail / degraded cells)
Phase 2: Input Recharge Matrix (Speed)
A power bank’s usefulness depends on how fast you can refill it. We test recharge times using different “Bottleneck Chargers” to simulate what you might have in your travel bag.
| Wall Charger Used | Device Simulation | Why We Test This |
| 20W Charger | Phone Block | The “Emergency” Scenario. How long does it take if you forgot your laptop charger and only have an iPhone brick? |
| 30W Charger | MacBook Air / Tablet | The “Slim” Standard. Crucial for MacBook Air (M1/M2) and iPad Pro users. Distinct from 20W and 45W. |
| 45W Charger | Samsung / Deck | The “Mid-Range” Standard. Common among Android enthusiasts and gamers. |
| 65W Charger | Laptop Brick | The “Common” Standard. The charger most people have in their backpack. |
| 100W+ Charger | Unrestricted | The “Max Speed” Run. We use a 140W GaN Prime charger to remove all bottlenecks and find the power bank’s absolute limit. |
Note: For the Input Matrix, we measure the 0% to 100% total time. For high-capacity units, we also log the 0% to 80% time, as charging speeds often throttle significantly for the final 20%.
3. Test Phase B: The Stress Test (Power Output)
If a power bank claims “65W Output,” it should sustain that output without overheating.
The Test:
We force the bank to output its maximum rated wattage (e.g., 65W, 100W, or 140W) continuously.
What We Look For:
- Thermal Throttling: Does the power bank drop from 65W to 45W after 10 minutes to save itself? (This results in a grade penalty).
- Sudden Shutdowns: Does the Over-Current Protection (OCP) trip too early?
- Max Temperature: If the external casing exceeds 60°C, it is flagged as a safety hazard.
4. Test Phase C: Power Quality (Ripple & Noise)
“Dirty” power can cause touchscreen lag, audio buzzing, and battery degradation in your phone.
The Test:
Using the oscilloscope function of our analyzer, we measure the Vpp (Voltage Peak-to-Peak) during high-load charging.
The Grading Standard:
- Excellent: < 50mV (Clean, safe power)
- Acceptable: 50mV – 100mV
- Poor: > 150mV (Not recommended for sensitive devices)
5. Test Phase D: User Experience Features
We verify the features that matter in the real world:
- Recharge Speed: How long does it take to refill the bank from 0% to 100% using a high-power GaN charger?
- Pass-Through Charging: Can it charge a device while being recharged itself?
- Low-Current Mode: Does it stay on when charging low-power devices like earbuds or smartwatches? (We test this with a simulated 50mA load).
6. Physical Analysis: Energy Density
A power bank’s utility is defined by how much power it holds relative to its size and weight. To measure this, we calculate Gravimetric Density (Wh/kg) and Volumetric Density (Wh/L).
However, calculating density is not as simple as dividing the battery size by its weight. High-performance power banks often appear less efficient at low speeds due to the “BMS Overhead” phenomenon.
The “High-Power Paradox”
High-wattage units (100W+) require complex internal circuitry, heavy heat sinks, and advanced Battery Management Systems (BMS) to operate safely. These components consume a static amount of power just to stay “awake.”
- At Low Loads (10W): This static consumption eats a significant percentage of the total energy, making the power bank appear chemically inefficient.
- At High Loads (Max Rated): The static consumption is negligible compared to the total output, revealing the true potential of the cells.
To account for this, ChargeGrade records two distinct density metrics for every unit:
Metric A: Base Density (at 10W)
- The Formula: Measured Wh (10W) / Weight (kg)
- What it tells you: How efficient is this unit at charging low-power peripherals like earbuds, smartwatches, or a base iPhone?
- Why it matters: Buying a massive 140W brick just to charge an Apple Watch is physically inefficient. This metric exposes that “dead weight.”
Metric B: Peak Density (at Max Rated Wattage)
- The Formula: Measured Wh (Max Output) / Weight (kg)
- What it tells you: The absolute maximum amount of usable energy the manufacturer managed to engineer into the chassis.
- Why it matters: This is the “True” density. It gives high-end power banks credit for their advanced cells (like 21700s) which perform best under high load.
Think of a 140W Power Bank like a Supercar. It has a massive engine that burns fuel even when idling in traffic (10W).
A standard 20W Power Bank is like an Economy Car. Highly efficient at low speeds but cannot reach high speeds at all.
We test both scenarios to help you choose the right vehicle for your journey.
How We Grade:
For our Laptop Class Tier Lists, we prioritize Peak Density (since you buy them for power). For Slim & EDC lists, we prioritize Base Density (since you buy them for efficiency).
QoL Features Category Weighting
💻 Laptop Class — Workflow continuity
| Feature | Weight |
|---|---|
| Charging channels | 2.5 |
| Display screen | 2.0 |
| Pass-through charging | 2.0 |
| Silent operation | 1.5 |
| Port labelling | 1.0 |
| Attached cable | 0.5 |
| Flashlight | 0.25 |
| Magnetic strength | 0.25 |
| Total | 10 |
Why:
Coil whine in a quiet room is unacceptable here. Port clarity saves real time.
📱 Slim & Lightweight — Frictionless carry
| Feature | Weight |
|---|---|
| Attached cable | 2.5 |
| Charging channels | 2.0 |
| Silent operation | 1.5 |
| Display screen | 1.5 |
| Port labelling | 1.0 |
| Pass-through charging | 0.75 |
| Magnetic strength | 0.75 |
| Flashlight | 0.0 |
| Total | 10 |
Why:
Pocket devices live close to your body — noise and fumbling matter more than raw features.
✈️ Travel Ready — Chaos tolerance
| Feature | Weight |
|---|---|
| Pass-through charging | 2.5 |
| Charging channels | 2.0 |
| Display screen | 1.75 |
| Port labelling | 1.25 |
| Silent operation | 1.0 |
| Attached cable | 1.0 |
| Flashlight | 0.25 |
| Magnetic strength | 0.25 |
| Total | 10 |
Why:
You’re tired, it’s dark, outlets are weird — labels and silence reduce mental load.
🔋 High Capacity — Confidence & control
| Feature | Weight |
|---|---|
| Display screen | 2.5 |
| Charging channels | 2.0 |
| Pass-through charging | 1.75 |
| Silent operation | 1.25 |
| Port labelling | 1.0 |
| Flashlight | 0.75 |
| Attached cable | 0.5 |
| Magnetic strength | 0.25 |
| Total | 10 |
Why:
Big banks should communicate clearly and not sound stressed doing their job.
🧲 Wireless — Trust & alignment
| Feature | Weight |
|---|---|
| Magnetic strength | 2.5 |
| Silent operation | 1.75 |
| Attached cable | 1.75 |
| Display screen | 1.5 |
| Port labelling | 1.0 |
| Charging channels | 0.75 |
| Pass-through charging | 0.5 |
| Flashlight | 0.25 |
| Total | 10 |
Why:
Wireless noise and weak magnets are instant QoL killers.
☀️ Solar / Rugged — Utility under stress
| Feature | Weight |
|---|---|
| Flashlight | 2.5 |
| Display screen | 2.0 |
| Silent operation | 1.5 |
| Charging channels | 1.5 |
| Port labelling | 1.25 |
| Pass-through charging | 0.75 |
| Attached cable | 0.25 |
| Magnetic strength | 0.25 |
| Total | 10 |
Why:
Noise can signal instability outdoors; clear labels matter when conditions are bad.