Power Bank

A power bank is a portable rechargeable battery pack that stores electrical charge and delivers it via USB to charge smartphones, tablets, and other devices away from a mains outlet. Capacities range from 5,000mAh slim pocket models to 26,800mAh high-capacity travel units. Anker, Baseus, Xiaomi, and Mophie are leading brands. Power banks became an essential travel and commuting accessory as smartphone use expanded faster than battery technology could keep pace.

A power bank is a rectangular block or cylindrical tube typically 3.5 to 6 inches long, 2.5 to 3 inches wide, and 0.4 to 0.8 inches thick on slim models, thicker on high-capacity examples. Weight ranges from 150 grams on a 5,000mAh unit to over 500 grams on a 26,800mAh pack. The casing is aluminium or ABS plastic in silver, black, white, or brand colours.

One to four USB-A output ports and one or two USB-C ports appear on one end face. A micro-USB or USB-C input port for recharging the power bank itself sits on the same end or the opposite end. A small button on the side or face activates the battery level indicator — typically four LED dots or a digital percentage display — showing remaining charge. Some models have a single LED torch built into one end face.

Capacity in mAh is printed prominently on the casing or label — this is the primary specification driving purchase decisions. Wattage output — 5W standard, 18W fast charge, 65W laptop charging on high-end models — is also labelled. Brand name and model number appear on the casing.

Wireless charging power banks add a Qi charging coil beneath the top face — a device placed face-down on the top surface charges wirelessly. These are thicker and heavier than wired-only equivalents.

A power bank stores electrical energy in lithium-ion cells and delivers it on demand to charge USB-powered devices without requiring a wall outlet. A 10,000mAh power bank provides approximately two to three full charges for a modern smartphone. High-capacity 26,800mAh units can charge a laptop once or a smartphone six to seven times. They are used during travel, commuting, outdoor activities, festivals, power outages, and anywhere a mains socket is unavailable or inconvenient.

1. Lithium-ion or lithium-polymer cells inside the casing store electrical charge at 3.6 to 3.7 volts nominal cell voltage.
2. A boost converter circuit steps the cell voltage up to 5V for USB output, delivering the standardised voltage required by USB-powered devices.
3. A battery management system monitors cell voltage, temperature, and current, preventing overcharge, over-discharge, and short circuit — the primary safety systems that prevent lithium battery fires.
4. Fast charging protocols — Qualcomm Quick Charge, USB Power Delivery, Apple Fast Charge — negotiate higher voltages and currents between the power bank and the device being charged, reducing charge time from hours to under an hour for a full phone charge on compatible combinations.
5. When recharging the power bank itself, a buck converter steps the input voltage down to the cell charging voltage and the battery management system manages the charge cycle.

The first commercial power banks appeared in the early 2000s alongside the growth of portable electronics. Pisen, a Chinese accessory manufacturer, produced early lithium-ion based portable chargers from around 2001. The category grew modestly through the mid-2000s as mobile phones had relatively modest battery needs and charged primarily overnight.

The smartphone era transformed the power bank market. iPhone and Android smartphones with their large displays, continuous data connections, and power-hungry apps depleted batteries within a working day. By 2010—2012 the gap between smartphone battery life and user expectation was acute and power banks became mainstream accessories. Anker, founded in 2011 by ex-Google engineer Steven Yang, grew from a laptop battery startup to the world’s largest consumer charging brand within five years.

USB Power Delivery and Qualcomm Quick Charge standardised fast charging protocols from 2013 onward, enabling power banks to charge devices at 18W, 45W, and eventually 100W+. The introduction of 65W and 100W GaN (gallium nitride) power banks from 2019 meant a single compact unit could charge a laptop, tablet, and phone simultaneously — displacing the need for separate laptop charger and phone charger for travel.

Airline regulations under IATA restrict power banks to 100Wh (approximately 26,800mAh at 3.7V) in carry-on baggage, prohibiting them in checked luggage due to fire risk — a limitation that has shaped the maximum practical capacity of consumer power banks.

• Electronics retailers and phone accessory stores
• Online via Amazon — the dominant sales channel for the category
• Airport retail and travel accessory stores
• Petrol stations and convenience stores for emergency budget models
• Secondhand via eBay and marketplace apps — cell degradation is the key concern on used units

Laptop charger brick: A mains-connected AC adapter for charging a laptop. Distinguished by its mains plug and the absence of an internal battery — it requires a wall outlet and stores no charge itself.

UPS (Uninterruptible Power Supply): A large battery backup unit for desktop computers and network equipment. Shares the function of providing battery power but is distinguished by its large size, mains input and output, and design for stationary use rather than portability.

Wireless charging pad: A flat disc or mat that charges devices placed on its surface via Qi induction. Distinguished by its flat form, mains connection, and absence of a built-in battery — it does not store charge and cannot be used portably.

Power banks depreciate rapidly and cell degradation makes older units less desirable. Value is in current production.

• Budget 10,000mAh unbranded models: $10—$20 new
• Anker 10,000mAh PowerCore models: $25—$45 new
• High-capacity 26,800mAh Anker or Baseus models: $50—$80 new
• 65W GaN laptop-capable power banks: $60—$120 new
• Mophie and Apple MagSafe-compatible models: $80—$150 new
• Used power banks: 20—40% of new retail — cell degradation limits secondhand value

Actual capacity versus rated capacity is the key quality differentiator — budget unbranded power banks frequently deliver 60—70% of their rated mAh due to low-quality cells and conversion losses. Branded units from Anker, Baseus, and Mophie consistently deliver rated capacity.

Solar charging panels provide renewable charging away from the grid but at slow charge rates unsuitable for urgent device charging. Fuel cell chargers using hydrogen cartridges were briefly commercially available but found no consumer traction. Battery cases — phone cases with integrated batteries — merge the power bank into the phone itself but add bulk permanently. Improvements in smartphone battery technology and efficiency have reduced the urgency of power banks for single-day use in newer flagship phones, but travel and multi-day use cases ensure the category remains essential.

Looking for one? Where to buy a Power Bank →

Looking for one? Where to buy a Power Bank →

• Rectangular block or cylinder 3.5 to 6 inches long
• USB-A and/or USB-C output ports on one end face
• Input port for self-recharging on same or opposite end
• Battery level indicator button and LED dots or percentage display
• Capacity in mAh printed prominently on casing
• Aluminium or ABS plastic casing in silver, black, or white
• Brand: Anker, Baseus, Xiaomi, Mophie, or unbranded
• Weight 150 to 500+ grams proportional to capacity