21700 battery won't fit

If you get into this hobby, you’re going to need it.

Do you know if that manufacturer makes that charger as a 2 battery charger?

Unless someone is really pressed for space, I prefer 4 cell chargers.

If it's a universal charger, you can charge AA or AAA Eneloops at the same time as your lithium cells.

Although most of the time I only charge 1 or 2 cells at a time, sometimes I use all 4 battery slots.

Of course, it's your choice.

You have chosen wisely grasshopper. :wink: