The wattage on the box is a ceiling for one port. The mAh figure is counted at a voltage your phone never sees. Here is how I read both — anchored by one reviewed charger, three banks I own, and the testers who 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 honest spec is a table of every combination; one big number is marketing.
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 — 140, 180 and 240 W, the Extended Power Range — and 240 W cable rules (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), and 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: 100 Wh each without asking; 101–160 Wh with airline approval, two maximum; gate-check the bag and the bank comes out with you (FAA PackSafe). No accident that big banks stop at 27,000 mAh — 99.9 Wh, one decimal under the line.
"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 the range the bare cells weigh about a kilogram before case, board and 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 and couldn't fly at all.
"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 — 12 V at 10 A (Forester manual) — and a 15 A circuit allows 180 W at nominal voltage. Delivering 200 W means drawing more than 200 W after conversion losses: on 10 A 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.
Four items, all bought at retail. Every line is quoted from the listing or my review; nothing is measured yet, so the tag is text, not the seal.
Paid links: buying through the Amazon links below earns this site a commission at no cost to you.
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.
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 — 100 W into 37 Wh is about 20 minutes at full rate. Not linked: I could not verify the exact listing, and this site never links what it can't 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 AmazonEverything above is spec and arithmetic; the test that turns it into data has not run.
Notebookcheck does this against an FNB58-class meter; that is the bar. When my numbers exist they replace this section, and the seal stays off until then. How pages here are scored.
Picks that ChargerLAB's teardowns and Notebookcheck's meter tests rate well; I own none, and each card links what was measured. Baseus's 140 W bank, behind the efficiency numbers above, stays unlinked — no verifiable standalone listing.
Paid links: buying through the Amazon links below earns this site a commission at no cost to you.
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, emptied in "slightly more than half an hour" at that rate, hit 48°C worst-case with thermal shutdowns, and found the display 5–10% off its 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
Check price on AmazonPer-port table, ChargerLAB lineage, the failure-tail caveat, and the cable requirement.
USB-C lights are what these bricks feed; 1Lumen clocked the Wuben X4 charging at about 11.65 W.
Where a charger or a magnetic bank meets the gift box.
Paid links: buying through the Amazon links below earns this site a commission at no cost to you.
One email when a new guide or measured test lands. No spam, never sold, unsubscribe anytime.