Two numbers on the box, and neither means what it looks like. Here is how I read both, with the one charger I reviewed, the three banks I own, and the testers who actually put a meter on this stuff.
Per-port vs. total. "140W" on a multi-port brick means one port, alone. My AOHI Youth 140W is the clean example: C1 carries 140 W (28 V at 5 A), C2 stops at 100 W, and two laptops drop both ports to 65 W. Anker's 747 behaves the same — ChargerLAB's teardown lists each USB-C port at 100 W alone, 150 W total for two. The real spec is a table of every port combination. The one big number on the front of the box is the number for the day you own exactly one device.
PD 3.1. Until 2021, USB Power Delivery stopped at 100 W (20 V at 5 A over a 5 A-rated cable). PD 3.1 added 28, 36 and 48 V levels, which is 140, 180 and 240 W, and calls it the Extended Power Range. It also wrote the rules for 240 W cables (USB-IF). Above 100 W, charger, cable and device all have to speak EPR.
PPS. Programmable Power Supply lets a phone ask for 3.3–21 V in 20 mV steps and current in 50 mA steps (Hackaday). Samsung's and Google's fastest modes need it; without it those phones charge slower, whatever the box says.
GaN. Gallium nitride shrinks the brick, not the math. Teardowns show what's inside: the AOHI descends from the Magcube 140W, where ChargerLAB found the Power Integrations chip family Apple uses in its own 140 W charger.
mAh is at 3.7 V. Convert to watt-hours and the numbers stop lying: Wh = mAh × 3.7 ÷ 1,000 — 5,000 mAh is 18.5 Wh, 10,000 is 37, 20,000 is 74, 27,000 is 99.9. Some makers rate at 3.6 V (Anker lists its 27,650 mAh Prime at 99.54 Wh). Watts are speed. Wh is the tank. Input watts set the refill time.
Losses are real. Stepping cell voltage up to 5, 9 or 20 V burns energy as heat. ChargerLAB measured a Baseus 140 W bank at 79% efficiency at 5 V and about 90% at 28 V (review). The phone's own circuit loses more. Expect 10–30% of the rated Wh never to arrive — a 10,000 mAh bank fills a 4,000 mAh phone about twice, not two and a half times.
The FAA line. Spare lithium-ion batteries, power banks included, fly carry-on only. Up to 100 Wh each without asking the airline. From 101 to 160 Wh you need airline approval, two maximum. If the bag gets gate-checked, the bank comes out with you (FAA PackSafe). Big banks stop at 27,000 mAh for a reason: that is 99.9 Wh, which clears the FAA's 100 Wh line by the width of a decimal point.
"70,000 mAh" in a pocket. That is 259 Wh. Battery University puts the highest-energy consumer chemistry, NCA, at 200–260 Wh/kg and cobalt-oxide and NMC at 150–220 (BU-205). Even at the top of that range the bare cells weigh about a kilogram, before the case, the board and the cables. A 21700 cell is about 24 cm³ and tops out near 6,000 mAh (BU-301a), so the claim needs a dozen of them: roughly 300 cm³, a hardback book. At 259 Wh it would also sit above the FAA's 160 Wh ceiling. So: the box says 70,000 mAh, physics says a kilogram of cells the size of a hardback book, and the FAA says it stays home.
"200 W" from a cigarette-lighter socket. The socket is a fused 12 V circuit. Subaru's manual caps everything plugged into it at 120 W, which is 12 V at 10 A (Forester manual). A 15 A circuit allows 180 W at nominal voltage. Delivering 200 W means drawing more than 200 W, because conversion loses some. On a 10 A circuit the fuse goes or the number never happens. On 15 A with the engine running near 14 V it is marginal at best. "200 W" is usually every port's maximum added up, which nothing delivers at once. Each port is telling the truth. The box is just doing arithmetic.
Four items, all bought at retail. The numbers are the makers' numbers, plus what is in my AOHI review. I own all four and have put a meter on exactly none of them. The people who have put a meter on this stuff are linked where I use their numbers.
One true PD 3.1 port (140 W), a 100 W second USB-C, a 22.5 W USB-A. Both USB-C ports fall to 65 W when shared. Full review, including why it lights up my bedroom in the middle of the night.
For: one brick for a 16-inch laptop plus a phone
Skip if: two laptops at full speed, or a Dell — AOHI's listing says no full-rate charge
Check price on AmazonListed at 27,000 mAh / 99.9 Wh: 22.5 W USB-C port, four USB outputs, built-in USB-C and Lightning cables, three inputs, an SOS-mode LED, about 1.5 lb. "Power station" in the title. No AC outlet.
For: a weekend of phones off one pack
Skip if: charging a laptop — 22.5 W is a phone rate
Check price on AmazonListed as 10,000 mAh (37 Wh) with 100 W output, 40 W input, two USB ports, a TFT display and an SOS light. The box leads with the 100 W. The 37 Wh decides how long the 100 W lasts, which is about 20 minutes. No link: I could not pin down the exact listing, and I do not link what I cannot verify.
For: a fast top-up of a laptop or tablet
Skip if: a full laptop charge — 37 Wh is less than most laptop batteries hold
Listed at 5,000 mAh (18.5 Wh): 15 W magnetic wireless out, 20 W USB-C out, 18 W in, zinc-alloy shell about 0.6 in thick. Wireless charging adds its own losses.
For: stuck to an iPhone for a pocket top-up
Skip if: a full charge of a large phone — on paper it doesn't get there
Check price on AmazonThe watts and watt-hours here come from the makers' listings, the arithmetic above, or a bench test by ChargerLAB or Notebookcheck, linked where it is used. Notebookcheck runs an FNB58-class inline meter; that is the bar for a real charger test. I have not put a meter on my own four. How I decide.
Three I do not own, picked because ChargerLAB opened them up or Notebookcheck put a meter on them; each card links the test. The Baseus 140 W bank behind the efficiency numbers above has no verifiable standalone listing, so no link.
24,000 mAh, 140 W in and out. ChargerLAB's 2022 teardown called it the first PD 3.1 power bank and found four Lishen 21700 cells. Anker's listing is plain: 140 W needs a 5 A cable and a 140 W charger, and it weighs about 22 oz.
For: refilling a 16-inch laptop away from a wall
Skip if: you carry only a phone — 22 oz is a lot of pocket
Check price on Amazon72 Wh, 200 W total, 100 W per USB-C. Notebookcheck's hands-on held about 100 W into a laptop plus 15 W on USB-A and emptied it in "slightly more than half an hour" at that rate. It hit 48°C worst-case, with thermal shutdowns, and the display read 5–10% off their meter.
For: a smaller laptop bank with a readout you can mostly trust
Skip if: you'll run it flat-out — the heat finding is the whole review
Check price on Amazon160 W total; C1 and C2 do 140 W alone. Notebookcheck's review saw a laptop still getting 56–58 W with four other devices attached and the display 1–2 W off their meter. ChargerLAB's teardown found a Richtek power stage in a 360 g body. The two disagree on port C3 (30 W vs. 100 W), so read UGREEN's manual first.
For: replacing every brick on a desk
Skip if: it's going in a bag — 360 g against the AOHI's 306 g
Check price on AmazonThe per-port table, the Magcube it descends from, the cable it does not come with, and what I plug into each of its three ports.
USB-C lights are what these bricks feed. 1Lumen clocked the Wuben X4 charging at about 11.65 W.
The AOHI is on it, under the light-and-charger person.
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