Power banks are no longer high-tech gadgets—they’re everyday essentials for home, travel, and life.
But every time you upgrade your phone or add more devices, choosing the right power bank can leave you totally confused.
On e-commerce homepages, you’ll find dozens of power bank brands with thousands of models—all looking almost identical, yet prices vary wildly.
For the average shopper who doesn’t understand technical specs, vague marketing claims like “Works with Android & iPhone,’ ‘Massive Capacity,’ or ‘PD Fast Charging’ mean little. So, they just buy the top-rated or best-selling brand—only to end up with a fast-charging power bank that either trickle-charges their phone or dies halfway through.
1.Buying a power bank? Battery capacity isn’t everything!
Before buying a power bank, understand this key concept.
Think of a power bank’s stored energy like water in a teapot, and your phone as a drinking cup. Pouring 1L from the teapot into two 500ml cups doesn’t change the total water volume. Similarly, how many times a power bank can charge your phone depends on its total energy storage, measured in watt-hours (Wh).
The “10000mAh” capacity marked on power banks is like the water level in the teapot. You can’t simply divide this by your phone’s battery capacity (e.g., 4000mAh) to get charge cycles.
This is because we haven’t considered the “spout size” – the teapot’s output flow rate. In power banks, this equals the battery cell’s nominal voltage (typically 3.7V).
The actual energy stored = Capacity (mAh) × Voltage (V). Example: A 10000mAh ZMI power bank at 3.7V stores 37Wh.
Now, to know how many “cups” this can fill, we need your phone’s battery energy (usually hidden unless you disassemble it).
We’ve tested popular smartphones in the market and will show exactly how many charges you can expect from different power bank capacities.
Please note these are conservative estimates. The stated charging cycles don’t account for energy loss during cable transfer, phone heat dissipation, and other factors. For example, Baseus power banks only have about 75% energy conversion efficiency.
Generally, we don’t recommend 5000mAh power banks. Most Android phones released in recent two years have batteries over 4000mAh, meaning a 5000mAh power bank can’t even fully charge your phone once after accounting for efficiency loss.
For daily use:
Light users: A 10000mAh power bank can provide at least 1 full charge
Moderate users: Consider 20000mAh models that can deliver 3-4 full charges
Bigger capacity isn’t always better. Unless you have special needs like outdoor camping, you can rule out oversized power banks over 30000mAh.
This is because power banks’ size, weight and price increase significantly with capacity. For example, a popular Romoss 20000mAh power bank weighs about as much as 3 iPhone 12 units, making it very inconvenient to carry.
For frequent flyers, pay special attention to your power bank’s capacity when traveling by air.
For frequent flyers, pay special attention to your power bank’s capacity when traveling by air.
Civil Aviation Regulations:
≤100Wh (≈27,000mAh): No airline approval required
100-160Wh (≈27,000-43,000mAh): Requires airline pre-approval
>160Wh: Strictly prohibited on all flights
2. Always choose a fast-charging power bank
While battery capacity determines a power bank’s endurance, fast charging capability decides how quickly your phone charges—directly impacting user experience.
Fast-charging power banks cost just slightly more than regular ones but deliver vastly superior performance. With fast charging now standard in modern smartphones, trust me—always opt for a fast-charging power bank!
However, don’t blindly buy any “fast-charging” power bank. You must check its fast-charging protocol compatibility.
Here’s the golden rule: Fast charging only works when both the phone and power bank support the same protocol. No matter how powerful the power bank claims to be (e.g., 125W ultra-fast charging), the final charging speed depends entirely on what the phone accepts.
Without protocol compatibility, even a 125W super-fast power bank might charge at a sluggish 5V/0.5A speed.
The sheer variety of fast-charging protocols can overwhelm any buyer. The market includes:
- Universal standards (USB-IF’s USB PD, Qualcomm’s Quick Charge)
- Brand-specific proprietary tech (Huawei SCP, Samsung AFC, Oppo VOOC)
These protocols create serious decision fatigue for average consumers who lack technical knowledge.
But don’t worry – here’s exactly how to buy the right one.
1️⃣ Android users: Always prioritize your phone brand’s official fast-charging power bank.
Why is this important?
First, for average users, identifying protocol compatibility is full of pitfalls.
Take Qualcomm’s Quick Charge (QC) protocol as an example. Most Chinese Android phones (except Huawei) use Qualcomm Snapdragon processors, so while they support their own proprietary protocols, many are also compatible with QC.
But this doesn’t mean a QC-compatible power bank will fast-charge all OPPO or Xiaomi phones.
Why? Because QC itself has version compatibility issues!
QC 3.0 is backward compatible with QC 2.0 and 1.0
QC 4.0 supports USB PD but not QC 2.0 or 3.0
QC 4.0+ supports QC 2.0, 3.0, and USB PD
This isn’t just wordplay—without knowing your phone’s fast-charging compatibility, you might end up with a painfully slow power bank.
For example:
A QC 4.0 power bank can fast-charge a Redmi Note 7
But it won’t fast-charge an OPPO Reno 4 (QC 2.0-only)
Second, most phone brands only support low-wattage USB PD charging.
While newer protocols are becoming more compatible (e.g., USB PD 3.0 now works with QC, MediaTek PE, Huawei, and OPPO’s proprietary tech), there’s a catch:
Phones only support up to 18W via USB PD—technically “fast charging,” but far slower than their native speeds.
Example:
A Huawei 66W SuperCharge power bank charges the Mate 40 at 66W
A generic USB PD power bank maxes out at 18W for the same phone
No comparison, no disappointment. 18W charging can’t even match OPPO’s fast-charging technology from seven years ago.
To put it simply: Unless you need universal compatibility (for devices like the Nintendo Switch or laptops), consider a high-power USB PD power bank.
Otherwise, your phone’s original fast-charging power bank will deliver faster and better performance.
2️⃣ For Apple Users: Choose PD-Compatible Power Banks
iPhones keep things simple—they only support two fast-charging protocols:
Apple’s own Apple 2.4A (12W, slower)
USB-PD (18W/20W, much faster)
For iPhone 8 and newer models, just grab any USB-PD power bank—no second-guessing needed.
3.Fast charging requires both a compatible power bank AND cable – neither can be overlooked.
Many overlook that fast charging requires three components working together: the power bank, cable, and phone. All three are essential for true fast charging.
Every fast-charging cable contains a certification chip that stores specifications like power delivery capacity and data transfer rates. When charging begins, the three devices “communicate”:
Power Bank: “I offer 5 charging profiles. Which do you need?”
Phone: “I require 9V/2A.”
Cable: “I can support 9V/2A.”
Once matched, they “handshake” to enable 18W fast charging.
Cable Selection Guide:
1️⃣ Android Users: Always use your phone brand’s original cable.
Proprietary protocols (Huawei SCP, Oppo VOOC, etc.) require matching cables with specific connectors (USB-A to USB-C, USB-A to Micro-USB, etc.).
For universal PD charging (laptops/tablets/Switch), USB-C to USB-C is mandatory (per USB-IF standards).
2️⃣ iPhone Users (iPhone 8+): Must use MFi-certified USB-C to Lightning cables for 18W/20W PD fast charging.
Avoid scams: USB-A port power banks claiming “PD fast charging” for iPhones only deliver 12W (Apple 2.4A).
3️⃣Cable Length:
1m cables are standard, but 10cm–30cm short cables are ideal for portability with power banks.
4️⃣Avoid Wireless Power Banks:
Wired fast charging guarantees ≥18W, while most wireless models max out at 10W.
Source：鸣玉
