USB battery bank

As of 2025, most people have probably owned at least 5 of these things.

Most battery banks do not deliver on their promised capacity

When using or recharging your battery bank, they get hot. This heat causes them to throttle their speeds and even lose some capacity to heat. For example, the Nitecore NB10000 outputs 22.5W at first then throttles down to just 9W when it gets hot, and overall delivers 31Wh of actual charge which is around 75% efficiency. ^[1]

There exist a small number of battery banks with chemical structure and heat dissipation to maintain consistently high charging speed. One I would like to try is this one - one reviewer claims it can maintain 90W output charging speed from 100% battery all the way to 0, which seems almost impossible, but I'd like to see.