You can buy 8 packs of rechargeable NiMH AA batteries now for less than £3 so experimenting needn't be expensive. I've bought similar from £ shops with reasonable success. The old Nicad batteries suffered from a 'memory effect' but that could be sorted by draining the batteries. More modern batteries don't suffer the same problems.

If I were using the recorder at home Id be tempted to sort out a mains power supply, if that is an option. With batteries you will have to get a charger. Smart chargers come for mains or USB. I've seen 6 slot mains chargers but not 6 slot USB chargers. There's a variety of prices but I would expect to pay less than £30 for batteries and charger.