Technology buying guide

How to choose a power bank

A power bank's real usable capacity is lower than the number on the box because of conversion losses. Choose capacity for how many charges you need, a charging standard your devices support, and a model with proper safety certification, since lithium batteries can overheat if poorly made.

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Weighted criteria

What matters when choosing power banks

Weights add up to 100 and reflect how much each factor usually decides satisfaction. Change them to fit you in the scorecard.

  1. Safety & certification

    30%

    Protection against overcharge, short circuit and overheating, and a recognised safety mark.

    How to check: Look for required marks for your region (in India, a BIS registration number for power banks); check recall lists before buying.

  2. Real capacity

    20%

    Rated capacity in mAh and watt-hours (Wh); expect less usable energy at your device.

    How to check: Check the Wh figure on the label; compare it to your phone or laptop battery size.

  3. Charging speed & standards

    20%

    Output in watts and support for the fast-charging standard your devices use.

    How to check: Match the output wattage and protocol to your device's charging spec.

  4. Ports & recharge time

    10%

    Number and type of outputs, and how fast the bank itself recharges.

    How to check: Count the devices you charge at once and check input wattage.

  5. Size & airline rules

    10%

    Weight, size and whether it is allowed in cabin baggage.

    How to check: Check the Wh rating against your airline's limits; spare lithium batteries usually must go in carry-on.

  6. Warranty & seller

    10%

    Warranty term and a traceable seller.

    How to check: Buy from a seller with a real address and returns process.

Avoid

Red flags

  • Huge capacity claims at a very low price or very light weight.
  • No Wh rating or safety mark on the label.
  • Swelling, heat or a burning smell during use (stop using it).
  • Unbranded sellers with no returns or contact details.

Before you pay

Checklist

  1. Work out how many charges you need.
  2. Check Wh and the safety mark on the label.
  3. Match output wattage and protocol to your devices.
  4. Check airline rules if you fly.
  5. Search the recall list for the model.

Ask the seller

Questions to ask

  • What is the rated capacity in watt-hours?
  • Which safety standard and registration does it carry?
  • What fast-charging protocols does it support?

After you buy

Warranty & returns

Power banks commonly carry six months to a couple of years of warranty, often only against defects.

  • Stop using any power bank that swells, gets very hot or is damaged.
  • Recycle old batteries at a proper collection point, not in household waste.

Track the return window and warranty end date

Common mistakes

Myths vs facts

Myth A 10,000 mAh bank charges a 5,000 mAh phone twice.

Fact Conversion losses mean you usually get noticeably less than the label suggests.

Myth Leaving a phone on a power bank overnight ruins it.

Fact Phones manage their own charging; the bigger risk is a poorly made bank without protection circuits.

Where this comes from

Official sources

Criteria and weights are AltFTool's editorial judgement, not a statement by these bodies. This guide is general consumer information, not professional advice.

FAQ

Power Banks: common questions

How do I convert mAh to Wh?

Multiply mAh by the battery voltage and divide by 1000. Most power bank cells are rated around 3.6 to 3.7 volts, and many labels print the Wh figure directly.

Can I take a power bank on a plane?

Usually in carry-on only, with limits based on Wh. Check your airline and aviation authority rules before you fly.

Can a power bank charge a laptop?

Only if it supports a high enough wattage and the right protocol, usually USB-C Power Delivery.

Free tools

Use these with this guide

Weighted scorecard

Review pattern checker

Complaint letter writer

Warranty & returns tracker

True cost calculator

Also handy: battery health and lifespan predictor

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