For some products, such things are already available. For example, want to mains-power your Panasonic digital camera? [1] provides mains power in a battery for

For some products, such things are already available. For example, want to mains-power your Panasonic digital camera? [1] provides mains power in a battery form-factor. Just what you need for long term time-lapse photography. [1] https://www.amazon.co.uk/dp/B01HGLXHVE/ https://www.amazon.co.uk/dp/B01HGLXHVE/