I take a couple of batteries with me when I go camping to use for the CPAP machine and a DC to AC box, so I don't stop breathing too often.
I have charged up one of them and must do the other - although power cuts are not usual here, it is as well to be prepared for interesting times.

Oddly enough the same two batteries are getting harder to move around - they must be putting on weight. The larger one in particular seems almost impossible to lift these days. Maybe I'll get a bit of rope and drag it to the charger, or find it some wheels.