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Capacity is listed in milliamp-hours, but conversion losses mean the usable output is lower than the number on the box. Choose enough capacity for your real day rather than automatically buying the largest battery.
Check these details
- Output wattage: Phones need less power than many tablets and laptops. Match USB Power Delivery output to the device.
- Ports: Decide whether you need USB-C input and output, older USB-A ports, or simultaneous charging.
- Safety documentation: Prefer an established brand with clear electrical specifications, warranty, and recognized testing information.
- Travel rules: Airlines generally require spare lithium batteries and power banks in carry-on baggage, with capacity restrictions.
Stop using a battery if it swells, becomes unusually hot, leaks, smells strange, or has a damaged case.
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