How to choose a power bank in India: capacity, speed and flight rules

1. Choose capacity for the job

Start with how long you will be away from a socket. A compact 5,000mAh bank is an emergency top-up, not an all-day solution for every modern phone. Around 10,000mAh is the practical everyday tier for most people: it is usually easy to carry and can provide meaningful backup without turning a pocket or sling bag into a brick. A 20,000mAh model makes more sense for long journeys, tablets, multiple devices or two people sharing one bank. Laptop users may need 20,000–27,000mAh, but should judge the pack in watt-hours and watts rather than mAh alone.

Do not estimate the number of phone charges by dividing the advertised power-bank mAh by the phone-battery mAh. The cells inside most banks are rated around their nominal cell voltage, while the output is converted to the voltage requested by your device. Conversion, cable resistance, heat and the charging process all consume energy. Recent independent testing by Tom's Hardware found that usable capacity varied materially with output voltage and load, which is why two products with the same printed capacity can perform very differently.

2. Translate mAh into watt-hours

Watt-hours are the cleaner way to compare stored energy and are also the number airlines care about. A useful approximation for a lithium-ion bank is: watt-hours ≈ mAh × 3.7 ÷ 1,000. That makes a 10,000mAh pack roughly 37Wh, a 20,000mAh pack roughly 74Wh and a 27,000mAh pack roughly 100Wh. Use the Wh value printed by the manufacturer when available because the exact nominal voltage can differ.

A missing watt-hour label is a warning sign, especially for travel. So is an implausibly huge mAh claim in a very small or light enclosure. Battery cells have physical mass; a pocket-sized listing claiming hundreds of thousands of mAh should not be treated as credible without verified test data.

3. Match charging watts to your device

Capacity tells you how much energy is stored; wattage tells you how quickly it can be delivered. Check the highest charging power your phone, tablet or laptop accepts and the protocol it needs. A phone that charges at about 20–30W gains little from a massive 100W output unless you also plan to charge a laptop. A USB-C laptop may need 45W, 65W, 100W or more just to charge reliably while in use. The device, power bank and cable must all support the required mode.

USB Power Delivery is the most broadly useful standard to look for on USB-C devices. USB-IF says the current USB PD specification can support up to 240W, but that is a protocol ceiling—not a promise that every USB-C port, cable or power bank can supply it. Read the output table printed on the bank and confirm the specific USB-C port can deliver your required voltage and wattage.

• For one phone, prioritize a reliable USB-C port and the phone's supported fast-charge protocol.
• For tablets and small laptops, confirm the single-port USB-C output, not just the large total wattage on the box.
• For proprietary fast charging, verify compatibility with your exact device model; USB-C shape alone does not guarantee the fastest mode.

4. Check what happens when several ports are used

Multi-port banks often advertise a total maximum output that is available only under certain port combinations. A bank labelled 100W may provide 100W from one USB-C port when used alone, then divide power sharply when a second device is connected. Look for a port-allocation table showing each combination. If the seller does not publish one, assume the headline wattage does not describe every real-world setup.

Also check input power: a large bank that recharges slowly can be frustrating on a short overnight stop. Output wattage and input wattage are separate specifications. A 20,000mAh bank with fast USB-C input and a compatible wall charger may be far more useful than a larger pack that takes most of a day to refill.

5. Verify BIS registration and basic safety

Power banks for portable applications are listed in India's compulsory registration framework under IS 13252 (Part 1): 2010. Look for clear BIS registration information on the product or packaging and verify that the model and manufacturer details are consistent. Registration is an important baseline, but it is not a substitute for buying from a traceable seller with a real warranty and service path.

Avoid a unit with a swollen case, cracked enclosure, damaged port, chemical smell or unusual heat. Stop using it if those symptoms appear. Prefer models that clearly state protection against over-charge, over-current, short circuit and temperature problems, and then look for independent testing or credible long-term owner reports that support those claims. Do not leave a bank charging under a pillow, inside a hot car or in another place that traps heat.

6. Know the current flight rules before buying

If you fly, keep the power bank in cabin baggage—not checked baggage—and protect it from accidental activation or short circuits. IATA's current passenger guidance says power banks up to 100Wh are generally allowed in carry-on baggage, while larger batteries require airline approval and anything over 160Wh is usually not permitted. Its 2026 power-bank guidance also advises a maximum of two lithium-ion power banks not exceeding 100Wh, says they should not be kept in overhead lockers, and restricts charging or using them during parts of the flight.

Airlines can impose stricter rules, so check your carrier before departure rather than treating a marketplace listing as permission to fly. If your cabin bag is moved to the hold at the gate, remove the power bank first. A clearly printed Wh rating makes security checks much easier.

7. Ignore features that do not fit your routine

A percentage display is convenient, but it does not improve the underlying cells. Built-in cables reduce clutter, but a damaged non-replaceable cable may shorten the useful life of the product. Wireless charging is handy on a desk but usually adds heat and conversion loss compared with a cable. Pass-through charging can simplify travel, though supported wattage may fall while the bank itself is charging. Choose these features only when they solve a recurring problem for you.

Weight and shape matter more than buyers expect. A high-capacity bank left at home because it is too bulky has zero practical capacity. Compare dimensions and measured weight, then decide whether the product belongs in a pocket, handbag, backpack or laptop sleeve.

8. Use a five-minute buying checklist

Before paying, match the power bank against this checklist. If a listing hides several of these details, move on rather than assuming the best.

• Capacity and watt-hours are clearly printed and physically plausible.
• BIS registration details, manufacturer identity, warranty and seller are traceable.
• The exact USB-C port supports your device's required wattage and charging protocol.
• Input speed, included cable rating and multi-port power sharing are documented.
• Independent tests discuss usable capacity, sustained output, heat and recharge time—not only design.
• For travel, the Wh rating and your airline's latest cabin-baggage rules are compatible.

The simple recommendation

For most phone users, begin your comparison at 10,000mAh with USB-C input and output, adequate USB PD wattage, verifiable BIS details and a useful warranty. Move to 20,000mAh only when you regularly need multiple charges, share the bank or power a tablet. For laptops, start with the laptop's wattage requirement and then choose enough watt-hours for your travel pattern. Use Gaandfaad search with your device, budget and use case—for example, ‘power bank for a 65W laptop under ₹4,000’—instead of searching for one universal best model.