Converting the chemical energy in your power bank to electricity and back to chemical storage will dump some of it as waste heat. In the end, you can roughly estimated the “actual” battery capacity of a power bank for charging devices at about two thirds of the capacity stated at a 3.7V nominal voltage.
Let’s explore the battery further: Lithium-Ion (Li-ion) Battery: Li-ion batteries are widely used in power banks due to their excellent energy density, long cycle life, and low self-discharge rate. They consist of multiple cells connected in series or parallel to achieve the desired voltage and capacity.
Watching your phone or tablet steadily run out of power when you're nowhere near an outlet is stressful. But there's an easy solution: a portable battery or power bank. These are available in many sizes and capacities, and can include lots of handy features like fast charging and multiple ports.
Nearly every rechargeable power bank you can buy (and most portable devices) contain a lithium-ion battery. These beat other current battery types in terms of size-to-charge capacity, and have even increased in energy density by eight fold in the past 14 years.
A power bank ensures their devices don’t run out of battery before they reach their destination. Check the battery capacity of your device, usually measured in milliamp-hours (mAh). Choose a power bank with a capacity at least equal to or greater than your device’s battery. For multiple charges or multiple devices, opt for higher capacity.
For now, we’ll have to make do with battery technology that’s not quite magic, but definitely usable. Thanks to power banks, we can enjoy slim, attractive devices while also having some way to top them up when away from mains power or a car’s charging socket. No more FOMO or battery anxiety.