Power Bank Capacity Explained: mAh vs Wh & Real Charges

mAh numbers are misleading. Here is how to tell how many times a power bank will actually charge your phone today.

mAh vs Watt-Hours (Wh)

mAh only makes sense with voltage. Wh = mAh × V ÷ 1000. Airlines limit batteries to 100Wh (≈27,000mAh at 3.7V). Wh is the honest number.

Real-World Charges

Expect ~65–70% usable capacity after conversion losses. A 10,000mAh bank gives roughly 1.5–2 phone charges; 20,000mAh about 3–4. Always round down.

• 5,000mAh — a top-up in your pocket.
• 10,000mAh — the everyday sweet spot.
• 20,000mAh+ — trips, laptops, camping.

Speed & Ports

Check PD output (e.g., 20W, 30W, 65W). For phones, 20W is plenty; for USB-C laptops, look for 45W+.

What Else to Check

• Pass-through — charge the bank and your phone together.
• Cycling accuracy (1% display) — better for travel.
• Airline-safe — under 100Wh and clearly labeled.

How to Compare Models: Key Specs Side-by-Side

Not all 20,000mAh power banks deliver equal performance. Output wattage, port count, battery chemistry, and thermal management vary widely. Below is a comparison of three AEMAI models commonly ordered by B2B partners for retail bundling or corporate gifting:

Before You Buy: 5 Critical Checks for B2B Buyers

As a distributor or reseller, avoid stock mismatches and returns by verifying these before placing bulk orders:

• Voltage labeling compliance — Confirm Wh is printed on packaging and spec sheet (not just mAh). Required for EU CE and US DOT shipping docs.
• PD version support — AEMAI PD-61 uses PD 3.1; older models may lack PPS (Programmable Power Supply), limiting fast charge compatibility with newer Samsung or OnePlus devices.
• Cell grade — All AEMAI power banks use Grade A lithium-polymer cells (not recycled or refurbished). Ask for cell datasheet upon request.
• UL 2056 certification status — Verified on PD-61 and PD4; not yet on CD167 (still compliant with IEC 62133-2).
• Firmware upgradability — PD-61 supports over-the-air firmware updates via AEMAI Power Suite app (Windows/macOS) — critical for future USB-C standard shifts.

Maintenance & Long-Term Usability Tips

Power banks degrade faster than expected if misused. Maximize cycle life (500+ cycles at ≥80% retention) with these practices:

• Store at 40–60% charge — Never ship or warehouse fully charged or fully depleted units.
• Avoid ambient temps >35°C — Do not leave in parked cars or direct sun during summer logistics.
• Use OEM or E-Mark certified cables — Non-compliant cables cause throttling, heat buildup, and false low-battery warnings.
• Re-calibrate every 3 months — Fully discharge then fully recharge once to reset fuel gauge accuracy.

Top 4 Mistakes B2B Resellers Make

Assuming “20,000mAh” means 20,000mAh output?

No — that’s nominal cell capacity. Real output is ~13,000–14,000mAh due to 3.7V→5V/9V conversion loss, PCB draw, and temperature derating.

Ignoring port configuration when bundling?

CD167’s built-in cables simplify retail kiosks but limit flexibility for users with USB-C-only devices. PD-61’s dual USB-C ports suit tech-forward retailers.

Overlooking input speed for rental or loaner programs?

Slow recharging (e.g., 10W input) creates bottlenecks. PD-61’s 45W input cuts turnaround time by 60% vs. entry-tier models.

Using mAh alone to compare across brands?

One brand’s “20,000mAh” may be rated at 3.6V; another at 3.85V — a 6.9% Wh difference. Always convert to Wh first.

Frequently Asked Questions

Why do airlines restrict power banks to 100Wh — not mAh?

Wh measures total energy storage, which directly correlates with fire risk and thermal runaway potential. mAh without voltage is meaningless for safety regulation.

Can I carry two 99Wh power banks on the same flight?

Yes — TSA and IATA allow multiple units under 100Wh, as long as each is individually labeled and carried in cabin baggage (not checked).

Does pass-through charging reduce battery lifespan?

Only if sustained for >2 hours continuously. AEMAI’s thermal-regulated pass-through (on PD-61/PD4) limits temp rise to <4°C above ambient — within safe cycling range.

Do magnetic power banks interfere with pacemakers or credit cards?

AEMAI PD5’s magnets are <15 Gauss at 2cm distance — well below FDA-recommended 50 Gauss threshold. Still, advise end users to keep >2cm from medical implants.

Is PD 3.1 backward compatible with older phones?

Yes — all AEMAI PD models negotiate downward automatically. A PD 3.1 bank delivers 5V/2A to legacy Androids and 9V/2A to QC-enabled devices without manual switching.

Understanding Wh, real-world efficiency, and model-specific capabilities ensures you stock what your customers actually need — not just what looks impressive on the box. For high-turnover retail, prioritize accuracy and airline compliance (like the PD-61 or CD167). For premium bundles or corporate gifting, add firmware upgradability and thermal intelligence into your pitch.

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