[jxf]

The idea with really cheap batteries is that they don't need good energy density. You just swap them every so often and put the one you aren't using in the charging rack. You could even carry your own reserve energy with you!

[TrainedMonkey]

We used to have swappable batteries in virtually all of portable electronics. You could even get them in a rechargeable accumulator format. Virtually all of portable electronics has integrated batteries.

[pjc50]

Chinese devices have standardized on taking 18650 "3.7V" cells for this purpose.

We might eventually get back there; maybe the EU will do for e.g. hand tool batteries what they have done for phone chargers and mandate an interchangeable standard.

[Gigachad]

Yeah but AAs suck, and the newer more advanced batteries all have different voltages and require different charge circuitries so it’s hard to create a new standard for them.