Power bank capacity numbers are on every product listing, but most people have no idea whether 10,000mAh is enough for them or overkill. This guide explains what mAh actually means, how to calculate exactly how many charges you get, and why the number on the box is never the number you actually get.
What mAh Stands For
mAh stands for milliampere-hour. It is a unit of electric charge — specifically, how much charge the battery can store and deliver. One milliampere-hour represents a current of one milliampere flowing for one hour.
In practical terms: a higher mAh number means more energy storage, which means more charges for your device before the power bank needs to be recharged itself. It is the battery capacity equivalent of saying a fuel tank holds more gallons.
How to Calculate Real-World Charges
The formula seems simple: power bank capacity divided by phone battery capacity equals number of charges. But two adjustments make the real number different:
Step 1: Account for voltage conversion. Power banks store energy at battery voltage (~3.7V) but deliver it at USB voltage (5V). This conversion loses approximately 20% of the stored energy to heat.
Step 2: Account for cable and connector losses. Another 5 to 10% is lost in the cable and connectors during transfer.
Net efficiency: approximately 70 to 80% of stated capacity reaches your device.
Real-world formula: Usable capacity = stated mAh × 0.75 (approximate)
| Power Bank | Stated Capacity | Real Usable Capacity | Charges for iPhone (3,279mAh) |
|---|---|---|---|
| Small | 5,000mAh | ~3,750mAh | ~1.1 full charges |
| Medium | 10,000mAh | ~7,500mAh | ~2.3 full charges |
| Large | 20,000mAh | ~15,000mAh | ~4.6 full charges |
| XL | 30,000mAh | ~22,500mAh | ~6.9 full charges |
The PowerGo 10,000mAh delivers approximately 2 to 2.5 full charges to a modern iPhone in real-world use — enough for a full day of heavy use or two days of light use without finding an outlet.
Shop PowerGo 10,000mAh Magnetic 4-in-1 Power Bank →
mAh vs Wh: Why Airlines Care About Wh
Airlines do not care about mAh. They regulate power banks by Wh (watt-hours) — actual energy stored. The conversion:
Wh = (mAh × V) / 1000 — where V is typically 3.7V for lithium batteries
- 5,000mAh = ~18.5Wh
- 10,000mAh = ~37Wh
- 20,000mAh = ~74Wh
- 27,000mAh = ~99.9Wh (just under the 100Wh no-approval limit)
All power banks up to 26,800mAh are comfortably under the 100Wh airline carry-on limit with no special approval required.
What is a Magnetic Power Bank?
A magnetic power bank uses the same MagSafe or Qi2 magnet system in modern iPhones and Samsung phones to snap directly to the back of your phone and charge it wirelessly while you carry it. No cable required between the power bank and your phone.
The PowerGo snaps to the back of any MagSafe iPhone (iPhone 12+) or Qi2 Samsung (Galaxy S24+) and charges wirelessly at Qi speeds while you carry it. For travel, commuting, or any situation where you are moving and need your phone charged, this hands-free approach is significantly more convenient than holding a power bank in your other hand or sharing a pocket with a cable.
The PowerGo is a 4-in-1 device: Qi magnetic wireless charging pad + USB-C PD output + USB-A output + built-in Lightning cable. One unit covers every charging scenario for iPhone users.
Charging Speed: Why Wattage Matters Alongside mAh
mAh tells you capacity. Wattage tells you speed. A 20,000mAh power bank with only 5W USB-A output has enormous capacity but charges your phone agonizingly slowly.
For meaningful charging speed:
- USB-C PD output of at least 18W for fast charging phones
- USB-C PD output of 45W+ for charging tablets
- USB-C PD output of 65W+ for charging laptops (and the power bank must be large enough to handle the laptop's draw)
The PowerGo's USB-C output delivers 18W PD — enough for fast charging any modern smartphone from the power bank.
The Right Size Power Bank for Your Situation
- Daily commute backup: 5,000mAh — enough for a top-up, ultra compact
- Full-day travel / day trips: 10,000mAh — 2+ full charges, travel-friendly weight
- Weekend trips without reliable outlet access: 20,000mAh — 4+ full charges, heavier but worth it
- Multi-day adventure travel: 26,000mAh+ — maximum capacity within airline limits
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Frequently Asked Questions
Why does my 10,000mAh power bank not charge my phone 2.5 times as the label suggests?
Power banks lose approximately 20 to 30% of their stated capacity to heat and voltage conversion during charging. A 10,000mAh bank delivers approximately 7,000 to 7,500mAh of usable charge to your device. This translates to about 2 to 2.3 full charges for a 3,000 to 3,500mAh phone battery.
Is 10,000mAh enough for a day of travel?
For most travelers with one phone, yes. 10,000mAh delivers 2 to 2.5 full charges — more than enough for a full day of heavy use. If you need to also charge a tablet or have a very large phone battery, step up to 20,000mAh.
Can a power bank charge my laptop?
Only if the power bank has USB-C PD output at sufficient wattage for your laptop — typically 45W to 100W. The PowerGo's 18W USB-C output is designed for phones and tablets. For laptop charging, you need a higher-output power bank specifically rated for laptops.
Does leaving a power bank fully charged damage it?
Not significantly. Modern lithium battery management in quality power banks includes protection against sustained overcharge. For long-term storage (months), storing at 50 to 70% charge is better for battery longevity than 100%, but for daily or weekly use this is not a concern.
What is the difference between a power bank and a portable charger?
They are the same thing. “Portable charger” and “power bank” both describe the same device category: a battery pack with USB output ports that you carry to charge other devices. Some people use “portable charger” to refer to the entire category and “power bank” to refer specifically to larger-capacity units, but the distinction is not standardized.
