mAh to Wh, for power stations

A milliamp-hour is an amount of charge — how many electrons moved, not how much work they did. Work needs pressure behind it, and in a battery that pressure is voltage.

The plumbing analogy holds better here than most: mAh is how many litres flowed, voltage is the pressure they flowed at, and watt-hours is the useful work that came out the other end. Litres alone will not tell you whether you can run a shower. This is why two batteries with identical mAh figures can hold very different amounts of energy, and why the industry settled on Wh for anything larger than a phone.

Comparing a power bank’s mAh against a power station’s Wh, and concluding the bank is the bigger battery.

It is an easy trap, because the bank’s number is often five digits and the station’s is four. A 26,800mAh travel bank at 3.7V holds about

The second trap is subtler: assuming the advertised mAh is what reaches your device. It is not. The figure is measured at cell voltage, and your phone charges at a higher one, so the delivered mAh is lower before a single percentage point of conversion loss is counted.

Every row below is roughly a kilowatt-hour. The mAh column is the one that moves.

1,024Wh is the rated capacity of several kilowatt-hour-class stations in our catalogue, including the Anker SOLIX C1000 Gen 2 and the EcoFlow DELTA 3 Plus. The mAh figures are arithmetic from that rating, not manufacturer claims.

Every lithium-battery flight rule in the world is written in watt-hours. An mAh figure has to be converted before it means anything at a boarding gate.

The FAA’s rules for spare lithium-ion batteries set two thresholds, and both are expressed in watt-hours: up to 100Wh travels in carry-on baggage without asking anyone, 100–160Wh needs airline approval, and above 160Wh is not permitted in passenger baggage at all. This is where the conversion stops being trivia. A power bank advertised at 27,000mAh sounds far below any limit until you convert it —

Thresholds per the FAA’s PackSafe guidance for portable electronic devices and spare batteries. Confirm with your carrier before flying — airline policies vary within the rules, and we are not an authority on carriage.

This is also why almost no portable power station flies. A 500Wh unit is five times the unrestricted limit and three times the approval ceiling, which is a hard constraint no amount of packing cleverness solves. If you need power at a destination, the realistic plan is a sub-100Wh bank in the cabin and a station waiting at the other end.

The useful question is not how big the battery is. It is how many times it refills the thing you care about.

Once both sides are in watt-hours the arithmetic is a single division, and the answer is usually smaller than the marketing implies. A modern phone battery holds roughly 15–20Wh, a tablet 30–40Wh, and a thin-and-light laptop 50–75Wh. Divide the bank or station’s watt-hours by that figure and then take off roughly 15% for conversion loss, because every transfer between a battery and another battery pays a tax in heat.

Device battery sizes here are typical ranges for planning, not measurements of your hardware — check your own device’s rating, which manufacturers publish in Wh precisely because it is the comparable unit. For appliance loads rather than device charging, the calculation changes shape entirely: see Wh vs W for why a big battery still cannot start a microwave, and the sizing tool to work from a load list instead.

Because mAh is the only spec on a battery that gets larger when you describe it less precisely.

A manufacturer quoting at single-cell voltage produces a number roughly three times larger than one quoting at a three-cell pack voltage, and about seven times larger than one quoting at 25.6V — for the identical battery. Nobody is lying; they are choosing the convention that flatters. Watt-hours cannot be gamed this way because the voltage is already inside the number, which is exactly why the specification most useful to a buyer is the one used least often in advertising.

The practical defence is simple. If a listing gives you mAh without a voltage, treat the figure as unusable rather than impressive, and look for the Wh rating — reputable power stations publish it, and where a product only advertises mAh, that choice is itself information. Every capacity figure on this site is the rated watt-hours, shown with its source and date on the model pages, and compared directly on the capacity-class pages.

Whether the mAh figure on the carton is true in the first place.

The conversion above is arithmetic, and it is exactly as reliable as the number you put into it. Where a manufacturer publishes both mAh and Wh and the two disagree, trust neither and treat the discrepancy as the finding — it usually means the mAh is quoted at cell level while the Wh is quoted at pack level. Every capacity figure on this site is the rated Wh, sourced and dated on the model page.