# Power banks

Choose a power bank by three numbers: the watts one port can push into your device, the watt-hours it stores, and whether it snaps onto your phone magnetically. The mAh in every title is the cells' capacity at a voltage the brand chooses, before conversion losses, so compare in watt-hours and expect 80 to 90 percent to reach a laptop.

## How it works

A power bank is a stack of lithium-ion cells, each at a nominal 3.6 to 3.91 V, plus a circuit that steps that voltage up to what USB asks for (5, 9, 12, 15, 20 or 28 V) and agrees the figure with the device over USB Power Delivery (PD). Capacity: mAh is the cells' capacity at the cells' voltage; multiplying by that voltage gives watt-hours, the number regulators require on the case and the only one comparable across brands. Loss: the step-up circuit turns about 10 to 21 percent of the energy into heat, most at 5 V and least at 28 V. Output: 20 to 45 W fills a phone, 60 to 100 W a laptop, and above 100 W on one port needs PD 3.1 at 28 V and a 5 A e-marked cable. Magnetic banks add a Qi2 coil at 15 or 25 W. [15] [16] [1] [2] [19] [6] [40] [23] [48] [22] [21] [20]

| Family | What it is | Suits |
|---|---|---|
| Magnetic wireless packs | One or two flat soft-pack cells, 5,000 to 10,000 mAh in total (19 to 39 Wh), behind a magnet ring and coil, 15 W wireless on most certified units plus a USB-C port, about 120 to 240 g. | iPhone 12 or later and Qi2 Android phones, for a cable-free top-up in a pocket. |
| Pocket cylindrical packs | Two cylindrical 21700 cells, about 36 to 37 Wh, 20 to 45 W from one USB-C port, about 200 g. | One to two full phone charges a day, in a jacket pocket. |
| Laptop-class bricks | Four or more 21700 cells, 72 to 100 Wh, one or two ports at 100 to 140 W using PD 3.1 at 28 V, 500 to 600 g, kept just under the 100 Wh airline line. | Charging a laptop or several devices on a travel day. |
| Over-100 Wh packs | Eight or more cells, 140 Wh and up, close to a kilogram, and carried on aircraft only with airline approval, a route that closes under the 2027 international rules. | Field work and camping where flying is not involved. |

## How an expert narrows the choice

```mermaid
timeline
  section 1 · Maximum output from one port
    laptop : ask Built-in cable, Total output across ports, Recharge input : skip Magnetic wireless charging
    phone : ask PPS support
  section 2 · Stored energy
    laptop-sized reserve : ask Airline band : skip Magnetic wireless charging
    pocket top-up / a day or two for your phone : skip Airline band
  section 3 · Magnetic wireless charging
    magnetic but uncertified / Qi2 15 W / Qi2 25 W : ask Safety certification : skip Cell format
```

1. **Maximum output from one port.** Charging a phone, a tablet or handheld, or a laptop?
   It maps onto the watts one port must deliver: 20 to 45 W for a phone, 100 to 140 W for a laptop, tablets and handhelds between. A phone answer removes every laptop brick, a laptop answer every pocket pack.
   If laptop: ask Built-in cable, Total output across ports, Recharge input; skip Magnetic wireless charging.
   If phone: ask PPS support.
   Skip if already known: devices the user owns, laptop model, phone model.

2. **Stored energy.** Pocket top-up, a day or two for your phone, or laptop-sized reserve?
   Capacity and weight move together at about 13 to 19 Wh per 100 g, so this asks how heavy a bank the buyer tolerates. It leaves one band: under 25 Wh, 35 to 40 Wh, or 70 to 100 Wh.
   If laptop-sized reserve: ask Airline band; skip Magnetic wireless charging.
   If pocket top-up or a day or two for your phone: skip Airline band.
   Skip if already known: travel habit (flies often), an earlier capacity answer in this session.

3. **Magnetic wireless charging.** Snaps onto your phone with no cable, or wired?
   A yes removes everything but magnetic packs and makes the certified tier (Qi2 15 W or Qi2 25 W) the next thing to show. A no leaves the wired packs, the larger part of the catalog.
   If magnetic but uncertified or Qi2 15 W or Qi2 25 W: ask Safety certification; skip Cell format.
   Skip if already known: phone model (iPhone 12 or later, or a Qi2 Android phone), a stated preference for cables.

## What to surface

### Maximum output from one port

The most power, in watts, that a single port can deliver to one device. This number decides whether your device charges at full speed, and it is not the number in the title. A phone fast-charges at 20 to 45 W and cannot use more, a laptop wants 60 to 140 W, and above 100 W on one port means PD 3.1 at 28 V plus the 5 A e-marked cable that usually comes in the box. Brands advertise the sum across ports (300 W); one device sees the per-port maximum (140 W). [30] [45] [46] [32] [6] [7] [8] [35]

Range: 10 to 140 W. Pocket packs give 20 to 45 W. Laptop bricks give 100 or 140 W on their best port and 22 to 33 W on USB-A.
Question to ask: Charging a phone, a tablet or handheld, or a laptop?

Used as: top-level split, filter, sortable. Data: needs research, backfill cost low. Look for it as: Marketplace titles carry only the total. The per-port figure is a line such as '28V/5A 140W Max' in the brand page's spec table.
One brand-page lookup per product. When only a total is available, assume the best port equals the total for single-port banks and 140 W for anything advertised above 200 W total, and flag it as inferred.
Chart: Port power-split table.

### Stored energy

How much energy the bank stores, in watt-hours, which is the cells' capacity in amp-hours times their nominal voltage. Watt-hours are the only capacity figure comparable across brands, because mAh depends on which nominal voltage (3.6 to 3.91 V) the brand multiplies by. Regulators require Wh on the case, and the 100 Wh line decides whether the bank boards a plane without approval, which is why so many flagship banks are 26,000 to 27,000 mAh and 90 to 99.75 Wh. Expect 80 to 90 percent of stored Wh to reach a laptop. [1] [4] [44] [30] [34] [22]

Range: 10 to 160 Wh. Magnetic packs 19 to 39 Wh, pocket packs 36 to 39 Wh, laptop bricks 72 to 100 Wh. Above 100 Wh is rare and travel-hostile.
Question to ask: Pocket top-up, a day or two for your phone, or laptop-sized reserve?

Used as: top-level split, filter, sortable. Data: on the listing, backfill cost low. Look for it as: Often in the title or bullets as '90Wh', otherwise in the spec table next to mAh. Printed on the unit's label by law.
When missing, compute mAh times the stated nominal voltage; if no voltage is stated, use 3.7 V and mark the value as estimated. A label photo settles it exactly.
Chart: Watt-hours against weight.

### Magnetic wireless charging

Whether the bank charges a phone through a magnet-aligned coil, and if so which certified tier it meets. Qi2 is the Wireless Power Consortium's magnetic standard, borrowed from MagSafe alignment: 15 W in the original tier, 25 W in the tier certified from mid-2025. MagSafe compatible without a Qi2 mark means magnets but no certification. Teardowns show one or two 5,000 mAh soft-pack cells, so these packs hold 19 to 39 Wh and the convenience costs capacity and speed. The aviation regulator flags wireless banks: easy to counterfeit, often no UN 38.3 evidence, passenger reports of thermal runaway. [40] [41] [42] [43] [23] [48] [49] [2]

Values: none, magnetic but uncertified, Qi2 15 W, Qi2 25 W.
Question to ask: Snaps onto your phone with no cable, or wired?

Used as: top-level split, filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Title words 'MagSafe', 'magnetic', 'Qi2', 'Qi2.2' or '25W wireless'. Certification status is on the brand page, sometimes only as a Qi2 logo.
Map 'Qi2' to the 15 W tier unless 25 W or Qi2.2 is stated. Treat 'MagSafe compatible' alone as magnetic but uncertified.

### PPS support

Whether the bank supports Programmable Power Supply, the USB PD option that lets a phone ask for a precise voltage and current. Samsung's Super Fast Charging only engages over PPS: 25 W needs 3.3 to 11 V at 2.25 A, and 45 W needs 3.3 to 11 V at 5 A plus a 5 A e-marked cable. Without PPS a Galaxy charges slowly even from a 100 W port. iPhones do not need it. On a spec sheet PPS shows up as a line such as '3.3-11V 3A' in the output list, which is easy to miss. [37] [38] [39] [31]

Question to ask: Is your phone a Samsung Galaxy?

Used as: filter, shown on the card. Data: needs research, backfill cost low. Look for it as: Not in titles. On brand spec pages as 'PPS' in the protocol list or as an output line with a voltage range such as '3.3-11V 3A'.
One brand-page lookup per product settles it. If the brand page lists protocols and PPS is absent, record false rather than unknown.

### Built-in cable

Whether a charging cable is permanently attached to the bank, and whether it retracts. A built-in cable means there is no separate cable to forget, and on laptop bricks it is rated for the bank's own wattage, which a random cable above 60 W may not be. The cost is that the cable is now a wear part you cannot replace, and a fixed cable sets the connector type for the life of the bank. [21] [31]

Values: none, built-in fixed, built-in retractable, loose cable included.
Question to ask: Built-in cable, or bring your own?

Used as: filter, shown on the card. Data: on the listing, backfill cost none. Look for it as: Title words 'built-in cable', 'retractable', 'with USB-C cable'. Brand pages state the cable's wattage rating.
Absent from the title means none; the product photo confirms it.

### Airline band

Which of the three aviation capacity bands the bank falls in, derived from its stored energy. Up to 100 Wh flies in carry-on with no approval; 100 to 160 Wh needs airline approval, two at most, a route the ICAO addendum of 27 March 2026 closes in the 2027 rules; above 160 Wh is forbidden. Since 2025 and 2026 most Asian carriers and Japan ban in-flight use or recharging, passengers are limited to two banks, and mainland China flights require the 3C mark, so a traveller wants one bank under 100 Wh, charged before boarding. [3] [1] [2] [5] [13] [14] [11]

Values: under 100 Wh (no approval), 100 to 160 Wh (airline approval), over 160 Wh (not allowed).
Question to ask: Will you fly with it?

Used as: filter, shown on the card. Data: derived from listing fields, backfill cost none. Look for it as: Titles say 'TSA-approved' or 'airline approved' for banks under 100 Wh, which is marketing for the same fact.
Derived from energy_wh. Ignore the 'TSA-approved' claim when the Wh figure is known.
Chart: Watt-hours against weight.

### Low-current mode

A setting that keeps the output on for devices that draw very little current, such as earbuds, watches and rings. A bank's output circuit switches off when it sees almost no load, and an earbud case or a watch draws so little that many banks treat it as nothing connected and switch off. Low-current mode, often toggled by double-pressing the button, holds the port on. The threshold is product-specific; Anker states 30 to 90 mA for its banks. [28] [29]

Question to ask: Charging earbuds, a watch or other small gadgets from it?

Used as: filter, shown on the card. Data: needs research, backfill cost low. Look for it as: Not in titles. Sometimes in Amazon bullets as 'trickle-charging mode' or 'low current mode'; reliably only in the user manual.
The manual always says. Backfill from the manual for the top N and leave the rest unknown rather than false.

### Advertised capacity

The capacity of the cells in milliamp-hours at their own nominal voltage, which is the number in every title. It is the number people compare on and the least comparable one. The nominal voltage a brand multiplies by ranges from 3.6 V (UGREEN, Baseus) to 3.8 V (Anker Prime) to 3.87 and 3.91 V (Xiaomi and Anker magnetic packs), and Battery University notes that marking cells at 3.7 V rather than 3.6 V is a marketing choice that boosts watt-hours on paper. Keep it for recognition, rank on watt-hours. [15] [16] [23] [48] [30] [34]

Range: 3000 to 50000 mAh. 5,000 for magnetic packs, 10,000 for pocket packs, 20,000 to 27,000 for laptop bricks.
Question to ask: Any mAh size already in mind?

Used as: shown on the card. Data: on the listing, backfill cost none. Look for it as: Always in the title, formatted '10000mAh' or '26,250mAh'.

### Pass-through charging

Whether the bank can charge a device while it is itself being charged from the wall. With one outlet at a hotel desk, pass-through means the phone and the bank both fill overnight. The device on the output side gets priority and the cells take the surplus. The cost is heat, and heat is what ages lithium cells, so banks that run everything through the cells rather than past them wear faster. Brands call it two-way charging in titles. [25] [24] [17] [33]

Question to ask: Need bank and phone both charged overnight from one outlet?

Used as: filter, shown on the card. Data: on the listing, backfill cost low. Look for it as: Title or bullets: 'pass-through', 'two-way charging', 'charge while charging'.
The user manual states it when the listing does not. Absent from both usually means unsupported.

### Recharge input

The most power, in watts, the bank accepts when it is being refilled from a charger. Input sets how long the bank takes to refill: a 90 Wh bank is stated at about 2 hours at 100 W input, and an 86 Wh bank refilled at 140 W took 66 minutes in a measured test. Input is often far below output (65 W in on a 200 W bank), and it only helps if you own a charger that supplies it. The bricks that accept 140 W or more need a laptop-class charger to do so. [31] [32] [19] [30]

Range: 10 to 250 W. Pocket packs accept less than they put out. Laptop bricks accept 65 to 140 W, with one at 250 W across two ports.

Used as: shown on the card, sortable. Data: needs research, backfill cost low. Look for it as: Not in marketplace titles. On the brand page as 'Input: 65W Max' or a per-port input table.
One brand-page lookup per product. Record the single-port maximum, not the dual-port total.
Chart: a second bar beside output on the same watt scale.

### Total output across ports

The sum of power the bank can deliver when several devices are connected at once. This is the headline number in titles (165 W, 200 W, 300 W) and it tells you about multi-device use, not single-device speed. When two devices connect, the power splits by a fixed table: a 140 W bank measured at 90 W plus 27 W with two devices and 90, 9 and 7 W with three. Read it with the per-port maximum and the split table, never alone. [19] [31] [45] [32]

Range: 10 to 300 W. Pocket packs 20 to 45 W. Laptop bricks 140 to 300 W.

Used as: shown on the card, sortable. Data: on the listing, backfill cost none. Look for it as: The wattage in the title. The split table is on the brand page.
Always present. The split table is worth backfilling for the top N laptop bricks.
Chart: Port power-split table.

### Rated capacity at 5 V

The capacity the bank can actually deliver at 5 V output, printed on the unit's label as rated capacity. This is the honest mAh. On measured units it is 58 to 61 percent of the advertised figure: 11,600 of 20,000 (UGREEN), 5,900 of 10,000 and 3,000 of 5,000 (Xiaomi), and 6,068 of 10,000 in Anker's own worked example at 82 percent conversion efficiency. The gap is the voltage step from 3.6 V to 5 V plus the converter loss, not fraud, but it is what a phone at 5 V sees. [21] [23] [49] [26] [47] [27]

Range: 2000 to 30000 mAh. About 60 percent of the advertised mAh.

Used as: shown on the card, sortable. Data: needs research, backfill cost medium. Look for it as: Rarely on the listing. On the unit's printed label and in teardowns as 'Rated capacity: 11600mAh (TYP 5V 7A)'.
Read it from a label photo or a teardown for the top N products. Where absent, show the 60 percent estimate labelled as an estimate.
Chart: a shorter bar inside the advertised-capacity bar.

### Safety certification

Which safety tests the bank is stated to have passed: UN 38.3 for transport, UL 2056 for the product, 3C for China. UN 38.3 is the transport test every lithium battery must pass to be shipped at all, so its absence from a listing means little. UL 2056 covers overcharge, short circuit, drop and thermal abuse, is voluntary in law but required by Amazon and other marketplaces. The 3C mark matters to anyone flying within mainland China, where banks without a clear mark have been barred from flights since 28 June 2025 after a run of in-flight fire and smoke incidents. [9] [10] [11] [12] [1]

Values: none stated, UN 38.3, UL 2056, 3C (CCC).

Used as: shown on the card, filter. Data: needs research, backfill cost medium. Look for it as: Seldom on Western marketplace listings. UL and UN marks sit in the brand page's compliance section; the 3C mark is printed on the unit.
Brand compliance pages for UL 2056 and UN 38.3; a label photo for 3C. Under the Zamana schema this is markdown material, not a column.

### Measured conversion efficiency

The share of stored watt-hours that reaches the port in a bench discharge test, at a stated output level. Efficiency is lowest at 5 V and highest at 28 V, though not in strict order between: one 140 W bank measured 79 percent at 5 V, 84 at 9 V, 82 at 12 V, 86 at 15 and 20 V and 90 at 28 V. Higher efficiency means more charges per bank and less heat in the hand. Only testers with a USB power meter produce this number, so it exists only for bench-reviewed products. [19] [20] [27]

Range: 79 to 90 percent. The three measured units span 79 to 90 percent, lowest at 5 V output and highest at 28 V. Nothing outside that span has been measured here.

Used as: shown on the card, sortable. Data: needs research, backfill cost high. Look for it as: Never on a listing. In ChargerLAB reviews as efficiency per output level.
Pull from ChargerLAB and similar bench reviews for the top N and lazy-load the rest. Record the output level the figure was measured at.
Chart: Efficiency by output level.

### Cell format

What kind of cells are inside: cylindrical 21700 or 18650 cells, a flat pouch cell, or lithium iron phosphate. Teardowns show laptop bricks built from branded 21700 cylinders and magnetic packs from one or two ATL soft-pack cells. Cylinders from named makers come with cycle claims (over 70 percent after 1,000 cycles) against a generic 300 to 500 for lithium-ion charged to 4.2 V. Lithium iron phosphate lasts 2,500 cycles or more and resists heat but stores about half the energy per kilogram, so it is rare in banks and common in power stations. [21] [22] [48] [49] [17] [16] [18]

Values: 21700 or 18650 cylindrical, pouch (lithium polymer), lithium iron phosphate, not stated.

Used as: shown on the card. Data: needs research, backfill cost high. Look for it as: Amazon's 'battery cell composition' row says lithium ion or lithium polymer and is not reliable. Teardowns name the cell model.
Backfill from teardowns for the top N. Infer soft-pack for magnetic packs, since both teardowns that name the format found ATL soft-pack cells, and leave the rest not stated.

## Numbers worth computing

| Metric | Formula | Why |
|---|---|---|
| Watt-hours from mAh (Wh) | `cell_capacity_mah * nominal_voltage / 1000, with nominal_voltage = 3.7 when the listing states none` | Fills energy_wh when the listing omits it. The regulators define Wh exactly this way. 27,000 mAh at 3.7 V is 99.9 Wh, which is why flagship banks stop there. [1] [44] |
| Watt-hours at the port (Wh) | `energy_wh * conversion_efficiency_pct / 100, or energy_wh * 0.8 when no measurement exists` | What a device can actually take. Measured efficiency runs 79 to 90 percent on laptop bricks, so 0.8 is a fair default and errs low. [19] [20] [27] |
| Full phone charges (charges) | `deliverable_wh / phone_battery_wh, with phone_battery_wh = 14 for a standard flagship and 18 for a large one when the user's phone is unknown` | The number a buyer is really asking for. A 37 Wh pocket pack gives about two charges of a 14 Wh phone; a 90 Wh brick gives about five. [36] |
| Watt-hours per 100 g (Wh per 100 g) | `energy_wh / sizing.weight_g * 100` | Separates a dense bank from a padded one. Reviewed banks sit between 13.5 and 18.6; below 13 the buyer is carrying casing, and above 19 the Wh claim is outside anything measured here and should be checked. [30] [21] [22] [23] |
| Estimated refill time (hours) | `2 * energy_wh / recharge_input_w` | Charging slows as cells fill, so the naive Wh over watts figure undershoots. On the two sourced points the real time was 1.8 and 2.2 times the naive figure (66 minutes at 140 W, about 2 hours at 100 W), so treat this as plus or minus 15 percent and as our fit from two points. [19] [31] |
| Price per watt-hour (currency per Wh) | `price / energy_wh` | Capacity is the main thing the price buys. Dividing by Wh rather than mAh stops a 3.87 V brand looking cheaper than a 3.6 V one.  |

## What you give up

- Every reviewed bank stores 13 to 19 Wh per 100 g, so a 90 Wh brick is a 600 g object and a 37 Wh pack is 200 g. There is no light high-capacity bank; the chemistry does not allow it. [30] [22] [20] [16] Board branch: "See more pocket-sized banks".
- A phone fast-charges at 20 to 45 W and cannot draw more, so a 140 W port charges it no faster than a 45 W one. Pay for 100 W or more only if a laptop is on the list, and expect a 600 g brick with it. [35] [39] [6] [30] Board branch: "See more laptop-class banks".
- Magnetic packs carry one or two soft-pack cells, 19 to 39 Wh, at 15 W wireless on most certified units. You trade a day of capacity and most of the speed for never plugging in. [23] [48] [49] [40] Board branch: "See more magnetic banks".
- Over 100 Wh means airline approval and, from 2027, no approval route at all under the international rules. A 146 Wh bank also weighs over 900 g. Buy above the line only for ground use. [2] [3] [20] Board branch: "See more flight-legal banks".
- The total only exists when several devices share the bank, and each gets a fixed slice: 90 W plus 27 W from a 140 W bank with two devices. One device sees only the per-port maximum. [19] [31]
- Charging in and out at once pushes more current through the same small box, and heat is what ages lithium cells. Use it on the road and not as the nightly routine. [25] [17]
- Lithium iron phosphate lasts 2,500 cycles or more and tolerates heat, but stores roughly half the energy per kilogram of standard lithium-ion, which is why it lives in power stations rather than pocket banks. [18] [16]

## How to draw it

**Port power-split table** (other, shows Maximum output from one port, Total output across ports). A small table with one row per combination of ports in use and the watts each port gets, so a buyer sees at once that a 300 W bank gives one laptop 140 W and two devices 90 W and 27 W, which a single wattage number hides. Used today by brand spec pages (Anker, UGREEN, Baseus) and ChargerLAB reviews. [31] [32] [19]

**Efficiency by output level** (bar, shows Measured conversion efficiency). One bar per output voltage (5, 9, 12, 15, 20, 28 V) with the measured share of stored energy that reached the port, which shows that the same bank is a worse deal for a phone at 5 V than for a laptop at 20 V. Used today by ChargerLAB bench reviews. [19]

**Watt-hours against weight** (two axis map, shows Stored energy, Airline band). Stored watt-hours on the horizontal axis against grams on the vertical, with the 100 Wh airline line drawn. Banks fall on a narrow diagonal, so a point below the band is unusually dense and a point above it is carrying casing, and the buyer sees the weight they are signing up for at each capacity. This is a proposal, nobody draws it this way yet. [30] [21] [20]

## Words you will meet

- **mAh**. Milliamp-hours, the cells' charge capacity at their own voltage, which is the number in the title and the one least comparable across brands.
- **Watt-hour (Wh)**. Energy stored, equal to amp-hours times nominal voltage, printed on the case by law and the figure airlines use.
- **Nominal voltage**. The average voltage of a lithium-ion cell over a discharge, which brands set between 3.6 and 3.87 V when they convert between mAh and Wh.
- **Rated capacity**. The mAh a bank can deliver at 5 V output after conversion losses, printed on the label and about 60 percent of the advertised figure.
- **USB Power Delivery (PD)**. The USB-C protocol by which a device and a charger agree on a voltage and current, up to 100 W in PD 3.0 and 240 W in PD 3.1.
- **PPS**. Programmable Power Supply, a PD option that lets a phone request voltage in fine steps, which Samsung's fast charging requires.
- **EPR**. Extended Power Range, the PD 3.1 mode that adds 28, 36 and 48 V so one port can carry more than 100 W.
- **E-marked cable**. A USB-C cable with a chip that declares it can carry 5 A, needed for anything above 60 W and required in an EPR version above 100 W.
- **Qi2**. The Wireless Power Consortium's magnetic charging standard, at 15 W in its first tier and 25 W in the tier certified from mid-2025.
- **MagSafe**. Apple's magnet ring and wireless charging on iPhone 12 and later, whose alignment Qi2 adopted; 'MagSafe compatible' on a bank promises magnets, not certification.
- **Pass-through (two-way) charging**. Charging a device from the bank while the bank itself charges from the wall.
- **Low-current (trickle) mode**. A setting that stops the bank switching off when a tiny load such as an earbud case is connected.
- **21700 cell**. A cylindrical lithium-ion cell 21 mm wide and 70 mm long, about 18 Wh each, used in fours in laptop bricks.
- **Pouch cell**. A flat lithium-ion cell in a foil envelope, often called lithium polymer, used singly in slim magnetic packs.
- **Lithium iron phosphate (LiFePO4)**. A lithium-ion chemistry at 3.2 V per cell that lasts thousands of cycles and resists heat but stores about half the energy per kilogram.
- **UN 38.3**. The transport safety test every lithium battery must pass before it can be shipped, so it is a floor rather than a quality mark.
- **UL 2056**. The North American safety standard for power banks covering overcharge, short circuit, drop and thermal abuse, voluntary in law but demanded by marketplaces.
- **3C (CCC) mark**. China's compulsory product certification, which a power bank must show to be carried on flights within mainland China since 28 June 2025.
- **Total output**. The sum of watts across all ports when several devices are connected, which is the number in the title and not what one device gets.

## Where we made a call

- Watt-hours, not mAh, is the capacity figure to rank and filter on. (confidence high). Regulators define Wh and require it on the case; teardowns show brands multiplying by anything from 3.6 to 3.87 V, which makes mAh incomparable. Ours, built on those sources. [1] [15] [23] [21]
- A bank delivers about 80 to 90 percent of stored Wh and about 60 percent of advertised mAh at 5 V; both gaps are physics. (confidence high). Sources disagree. Bench tests and brand worked examples agree on the ranges. One primer cites a study with gaps up to 40 percent, which we read as the 5 V mAh view of the same loss plus poor units. We side with the measured tests. [19] [20] [26] [47] [27]
- The title wattage is the total across ports; one device sees the per-port maximum, and two devices get a fixed split below the sum. (confidence high). Every brand spec sheet we read publishes a split table, and ChargerLAB measured 90 W plus 27 W on a 140 W bank. [31] [32] [19] [45]
- Phones cannot use more than 20 to 45 W, so a laptop-class port buys a phone owner nothing. (confidence high). Apple specifies 20 W for 50 percent in 30 minutes and 40 W for 20 minutes; Samsung tops out at 25 or 45 W. [35] [39]
- The current threshold below which a bank switches off is product-specific, and Anker's 30 to 90 mA should not be read as a category constant. (confidence medium). Sources disagree. Anker states a number for its own banks; a second source says there is no universal figure. We cite Anker's as Anker's. [28] [29]
- The 100 Wh line now adds a two-bank cap and no in-flight recharging; the 100 to 160 Wh approval route closes under the 2027 rules. (confidence high). From the ICAO addendum of 27 March 2026 as described in IATA's operator and passenger guidance. Airlines may be stricter, and several Asian carriers and Japan already ban in-flight use. [2] [1] [13] [14]
- Laptop bricks use branded 21700 cylinders and magnetic packs use one or two soft-pack cells; lithium iron phosphate is rare in this category. (confidence medium). Based on five teardowns (three cylindrical, two soft-pack), which is enough for the pattern and not for the long tail. Lithium iron phosphate's energy density explains its absence. [21] [22] [48] [49] [18]
- Qi2 25 W banks exist since August 2025, but most magnetic banks on sale are 15 W Qi2 or uncertified MagSafe-compatible packs. (confidence medium). The 25 W tier and the first certified banks (Baseus from August 2025, UGREEN MagFlow in Q3 2025) are documented; the share of uncertified packs is our reading of listings, not a count. [42] [40] [43]
- Refill time is roughly twice the naive watt-hours over input watts, give or take 15 percent. (confidence low). Our fit to two stated times, one from a brand page and one from a bench test, which miss the 2x rule by 10 and 12 percent. A third point from a Trusted Reviews summary was dropped because the page could not be read. [19] [31]
- UL 2056 is the only product-safety mark worth showing on a US listing; UN 38.3 is a transport floor, 3C only for flights within China. (confidence medium). Marketplaces require UL 2056 while the law does not, so its presence says the seller cleared that bar. Under Zamana's schema rules this stays in the markdown line. [9] [10] [11] [12]

## References

1. [IATA Guidance Document for Passengers Travelling with Lithium Batteries, 2026](https://www.iata.org/contentassets/6fea26dd84d24b26a7a1fd5788561d6e/passengers_travelling_with_lithium_batteries.pdf) (regulator). Supports: Wh equals Ah times nominal voltage; Wh must be marked on the case; two power banks of at most 100 Wh per passenger; no recharging from aircraft power; UN 38.3 applies to all carried batteries.
2. [IATA Guidance for Operators: Changes Regarding Power Banks, 31 March 2026](https://www.iata.org/contentassets/90f8038b0eea42069554b2f4530f49ea/guidance-to-operators---power-banks.pdf) (regulator). Supports: ICAO addendum of 27 March 2026 limits passengers to two power banks and bans recharging in flight; the 100 to 160 Wh approval provision will not enter the 68th edition; wireless power banks flagged as an emerging concern: counterfeiting, missing UN 38.3 evidence, passenger reports of thermal runaway.
3. [49 CFR 175.10(a)(18), passenger exceptions for lithium batteries](https://www.law.cornell.edu/cfr/text/49/175.10) (regulator). Supports: 100 Wh limit without approval; two spares of 101 to 160 Wh with operator approval; spare lithium batteries in carry-on only.
4. [49 CFR 173.185, lithium cells and batteries](https://www.law.cornell.edu/cfr/text/49/173.185) (regulator). Supports: lithium ion batteries must be marked with the Wh rating on the outside case from 10 May 2024.
5. [TSA, What Can I Bring: Power banks](https://www.tsa.gov/travel/security-screening/whatcanibring/items/power-banks) (regulator). Supports: power banks must be packed in carry-on bags.
6. [USB Promoter Group announces USB Power Delivery Revision 3.1 (26 May 2021)](https://www.usb.org/sites/default/files/2021-05/USB%20PG%20USB%20PD%203.1%20DevUpdate%20Announcement_FINAL.pdf) (standards body). Supports: PD was limited to 100 W at 20 V with 5 A cables before 3.1; 28 V serves above 100 W, 36 V above 140 W, 48 V above 180 W; 240 W maximum.
7. [Granite River Labs, Introduction to PD 3.1](https://www.graniteriverlabs.com/en-us/technical-blog/usb-power-delivery-specification-3-1) (primer). Supports: EPR cables must contain an e-marker declaring EPR mode, 50 V and 5 A.
8. [Wikipedia, USB-C (Power Delivery section)](https://en.wikipedia.org/wiki/USB-C) (primer). Supports: every USB-C cable carries 3 A up to 60 W; cables beyond 3 A need an e-marker chip; EPR allows 240 W at 48 V 5 A.
9. [UL Solutions, Enhance the safety of power banks with UL 2056 testing](https://www.ul.com/insights/enhance-safety-power-banks-ul-2056-testing) (standards body). Supports: UL 2056 covers overcharge, short circuit, overload, drop and thermal safety.
10. [Compliance Gate, Guide to US power bank regulations and standards](https://www.compliancegate.com/power-banks-regulations-united-states/) (primer). Supports: power bank standards are voluntary in law; Amazon requires UL 2056 and UN 38.3 reports; UN 38.3 is required for shipping.
11. [ChargerLAB, China's Civil Aviation Authority bans certain power banks on domestic flights](https://www.chargerlab.com/chinas-civil-aviation-authority-bans-certain-power-banks-on-domestic-flights/) (specialist review). Supports: from 28 June 2025 banks without a clear 3C mark or from recalled batches are barred from flights; the ban followed in-flight fire and smoke incidents.
12. [People's Daily Online, Power banks without a 3C certification are banned on flights in China](https://en.people.cn/n3/2025/0711/c98389-20339109.html) (other). Supports: effective 28 June 2025; banned: no CCC label, unclear 3C label, or subject to recall.
13. [Time Out, Japan to ban in-flight power bank usage from April 2026](https://www.timeout.com/asia/news/japan-to-ban-in-flight-power-bank-usage-from-april-2026-heres-all-you-need-to-know-022526) (other). Supports: Japan's MLIT bans in-flight use or charging from April 2026; over 160 Wh banned, two units per traveller.
14. [AeroTime, Inflight fire risk: which airlines are banning power banks?](https://www.aerotime.aero/articles/airlines-banning-power-banks) (other). Supports: South Korean airlines stopped overhead-bin storage from 1 March 2025; Hong Kong, Taiwanese, Thai and Singaporean carriers banned in-flight use during March and April 2025.
15. [Battery University BU-303, Confusion with voltages](https://www.batteryuniversity.com/article/bu-303-confusion-with-voltages/) (primer). Supports: nominal lithium-ion voltage is 3.60 V per cell; marking cells at 3.70 V boosts watt-hours on paper.
16. [Wikipedia, Lithium-ion battery (infobox)](https://en.wikipedia.org/wiki/Lithium-ion_battery) (primer). Supports: specific energy 160 to 300 Wh per kg; 400 to 1,200 cycles; nominal voltages of 3.6, 3.7, 3.8 or 3.85 V.
17. [Battery University BU-808, How to prolong lithium-based batteries](https://www.batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries) (primer). Supports: 300 to 500 cycles when charged to 4.20 V per cell; heat and a full state of charge age cells fastest.
18. [Wikipedia, Lithium iron phosphate battery (infobox)](https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery) (primer). Supports: 95 to 172 Wh per kg; 2,500 to 9,000 cycles; 3.2 V nominal; higher decomposition temperature than other lithium-ion chemistries.
19. [ChargerLAB, Review of Baseus 140W PD3.1 power bank (2C1A)](https://www.chargerlab.com/review-of-baseus-140w-power-bank) (specialist review). Supports: 24,000 mAh equals 86.4 Wh at this brand's 3.6 V; efficiency 79 percent at 5 V rising to 90 percent at 28 V; two devices get 90 W and 27 W, three get 90, 9 and 7 W; full recharge in 66 minutes at 140 W.
20. [ChargerLAB, Review of AOHi Starship 40000mAh 140W power bank](https://www.chargerlab.com/review-of-aohi-starship-40000mah-140w-power-bank-2) (specialist review). Supports: 146 Wh banks exist and weigh about 916 g; peak efficiency 82.9 percent at 100 W.
21. [ChargerLAB, Teardown of UGREEN Nexode 20000mAh 165W power bank with retractable cable (PB726)](https://www.chargerlab.com/teardown-of-ugreen-nexode-20000mah-165w-power-bank-with-retractable-usb-c-cable-pb726) (specialist review). Supports: rated capacity 11,600 mAh at 5 V against 20,000 mAh advertised; 72 Wh from four SunPower 21700 cells at 3.6 V; 534 g; cell maker claims over 70 percent capacity after 1,000 cycles; retractable built-in cable.
22. [ChargerLAB, Teardown of CUKTECH 10000mAh 30W power bank (PB100)](https://www.chargerlab.com/teardown-of-cuktech-10000mah-30w-power-bank-pb100) (specialist review). Supports: 10,000 mAh is about 36.5 Wh; two EVE 21700 cells; about 196 g.
23. [ChargerLAB, Teardown of Xiaomi 22.5W 5000mAh magnetic wireless power bank (WPB0507S)](https://www.chargerlab.com/teardown-of-xiaomi-22-5w-5000mah-magnetic-wireless-power-bank-wpb0507s) (specialist review). Supports: 19.35 Wh at 3.87 V nominal; rated capacity 3,000 mAh at 5 V; a single LS cell, format not stated; 15 W wireless; 122 g and 8.87 mm thick.
24. [ChargerLAB, POWER-Z KM003C tests power bank pass-through charging performance](https://www.chargerlab.com/chargerlab-power-z-km003c-tests-power-bank-pass-through-charging-performance-with-tutorial) (specialist review). Supports: pass-through is common on multi-port banks; high temperature during pass-through can throttle output.
25. [Anker, Pass-through charging: one outlet, two devices](https://www.anker.com/blogs/power-banks/pass-through-charging-power-bank) (primer). Supports: definition of pass-through; the output device gets priority; pass-through adds heat and heat ages lithium cells.
26. [Anker support, Why is the rated capacity marked on a power bank lower than expected](https://service.anker.com/article-description/Why-Is-the-Rated-Capacity-Marked-on-a-Power-Bank-Lower-Than-Expected) (spec sheet). Supports: 10 Ah times 3.7 V is 37 Wh, which is 7,400 mAh at 5 V; conversion efficiency typically around 82 percent; rated capacity 7,400 mAh times 0.82 is 6,068 mAh.
27. [Power Bank Expert, The difference between real and rated battery capacity](https://www.powerbankexpert.com/real-battery-capacity/) (primer). Supports: 5 V capacity equals 3.7 V times advertised mAh over 5 V, about 69 percent; converter efficiency 80 to 90 percent; one study found gaps up to 40 percent.
28. [Anker support, What is Trickle Charging Mode](https://service.anker.com/article-description/What-is-Trickle-Charging-Mode) (spec sheet). Supports: mode for earbuds, earphones and smart rings; Anker banks need 30 to 90 mA of draw to stay on; double-press toggles it and it ends after 2 hours.
29. [ChargeKeku, Power bank turns off with earbuds? Check low-current mode](https://www.chargekeku.com/blog/power-bank-turns-off-charging-earbuds/) (primer). Supports: banks shut down when the load is below a model-specific threshold; there is no universal shutdown-current number.
30. [Macworld, Anker Prime 26K Power Bank (300W) review](https://www.macworld.com/article/2958027/anker-prime-26k-power-bank-300w-review-slim-macbook-power-bank.html) (specialist review). Supports: 26,250 mAh equals 99.75 Wh, so a 3.8 V nominal; two USB-C at 140 W and USB-A at 22.5 W, 300 W total; 250 W input; 599 g; under the 100 Wh carry-on limit; charged a 14-inch MacBook Pro fully with a third left.
31. [Anker Laptop Power Bank (25K, 165W, built-in and retractable cables) product page](https://www.anker.com/products/a1695-anker-power-bank-25000mah-165w) (spec sheet). Supports: input 100 W max; PPS shown as a 3-11V 3A output line; 165 W across two USB-C, 133 W for USB-C plus USB-A; about 2 hours to recharge with a 100 W charger; 595 g; two built-in retractable cables.
32. [UGREEN Nexode Power Bank 25000mAh 200W spec table (GigaParts)](https://www.gigaparts.com/ugreen-nexode-power-bank-25000mah-200w-with-smart-digital-display.html) (spec sheet). Supports: 25,000 mAh equals 90 Wh; USB-C1 140 W at 28 V 5 A, USB-C2 100 W, USB-A about 22 W; input 65 W max per port; 592 g.
33. [Amazon listing, Anker Prime Power Bank 26,250mAh 300W (B0F66LNB8D)](https://www.amazon.com/dp/B0F66LNB8D) (retail listing). Supports: titles carry mAh, total W, port count, 'Two-Way Charging' and 'TSA-Approved'; the product-information table did not render.
34. [Amazon listing, UGREEN Nexode 25000mAh 200W (B0CXHM5RY2)](https://www.amazon.com/dp/B0CXHM5RY2) (retail listing). Supports: titles carry mAh and often Wh ('90Wh'), total W, PD version and port count.
35. [Apple support, Fast charge your iPhone](https://support.apple.com/en-us/102574) (spec sheet). Supports: a 20 W adapter or higher reaches 50 percent in about 30 minutes; a 40 W adapter reaches 50 percent in about 20 minutes on iPhone 17 models.
36. [Wikipedia, iPhone 16 Pro (infobox)](https://en.wikipedia.org/wiki/IPhone_16_Pro) (other). Supports: 13.94 Wh battery on the 16 Pro and 18.17 Wh on the 16 Pro Max.
37. [usb-guide.com, Samsung PPS charging guide](https://usb-guide.com/samsung-pps-charging-guide/) (primer). Supports: 25 W needs PPS at 3.3 to 11 V and 2.25 A; 45 W needs 3.3 to 11 V and 5 A; a 3 A cable caps a 45 W charge at 25 W.
38. [Samsung UK support, How to use Super fast charging](https://www.samsung.com/uk/support/mobile-devices/how-to-use-super-fast-charging/) (spec sheet). Supports: 45 W super fast charging needs a 45 W adapter plus a 5 A e-marked cable; standard chargers do not trigger super fast charging.
39. [Wikipedia, Samsung Galaxy S25 (infobox)](https://en.wikipedia.org/wiki/Samsung_Galaxy_S25) (other). Supports: S25 charges at 25 W, S25+ and Ultra at 45 W; S25 Ultra has a 5,000 mAh battery.
40. [Wikipedia, Wireless Power Consortium](https://en.wikipedia.org/wiki/Wireless_Power_Consortium) (primer). Supports: Qi2 Magnetic Power Profile delivers up to 15 W with magnetic attachment; Qi2 25W delivers up to 25 W.
41. [Anker, Qi2 wireless charging explained](https://www.anker.com/qi2-wireless-charging) (primer). Supports: Qi2 is a Wireless Power Consortium standard at up to 15 W; its Magnetic Power Profile borrows MagSafe alignment.
42. [audioXpress, Industry begins Qi 2.2 wireless charging deployment](https://audioxpress.com/news/industry-begins-qi-2-2-wireless-charging-deployment) (other). Supports: Qi 2.2 supports up to 25 W, with the specification allowing up to 50 W device-dependent; available to WPC members since April 2025; Baseus shipped Qi2.2-certified power banks globally from August 2025 and UGREEN's MagFlow was announced for Q3 2025.
43. [Powerbanks.fyi glossary, Qi2](https://powerbanks.fyi/glossary/qi2) (enthusiast community). Supports: original Qi2 is 15 W; for a power bank it means a certified magnetic phone pack.
44. [Anker, Can you bring portable chargers on a plane](https://www.anker.com/blogs/power-banks/electronics-on-the-go-can-you-bring-a-portable-charger-on-a-plane) (primer). Supports: Wh equals volts times mAh over 1,000; about 27,000 mAh at 3.7 V is 100 Wh.
45. [Basic Tutorials, Anker Prime Powerbank (26K, 300W) review](https://basic-tutorials.com/reviews/gadget-reviews/anker-prime-powerbank-26k-300w-review/) (specialist review). Supports: USB-C 140 W per port, USB-A 22.5 W, 300 W total; 26,250 mAh and 99.75 Wh; 250 W input across both USB-C ports; about 600 g.
46. [WattBench, Anker Prime Power Bank (26K, 300W) review and specs](https://wattbench.eu/reviews/anker-prime-powerbank-26k-300w.html) (specialist review). Supports: 140 W single-port output; 300 W total output and 250 W total input; 600 g, lithium-ion.
47. [Anker UK, How to check capacity of a power bank: rated vs real output](https://www.anker.com/uk/blogs/power-banks/how-to-check-capacity-of-power-bank) (primer). Supports: 10,000 mAh stores about 37 Wh, delivers about 30 to 35 Wh, roughly 6,000 to 7,000 mAh at 5 V; usable output is roughly 60 to 75 percent of the rated mAh.
48. [ChargerLAB, Teardown of Anker Nano 10000mAh magnetic wireless charger power bank (A110Z)](https://www.chargerlab.com/teardown-of-anker-nano-10000mah-magnetic-wireless-charger-power-bank-a110z/) (specialist review). Supports: two ATL soft-pack cells of 5,000 mAh at 3.91 V nominal, 39.1 Wh in total; supports Qi2 15 W; 238.7 g and about 21.9 mm thick.
49. [ChargerLAB, Teardown of Xiaomi 10000mAh magnetic power bank (WPB1007ZX)](https://www.chargerlab.com/teardown-of-xiaomi-10000mah-magnetic-power-bank-wpb1007zx) (specialist review). Supports: rated energy 39.1 Wh from two ATL 5,000 mAh cells at 3.91 V; rated capacity 5,900 mAh at 5 V 3 A against 10,000 mAh advertised; 15 W wireless; 225.6 g and about 20.3 mm thick.