EBL LCD Battery Charger Smart Individual 907 AA AAA Rechargeable Battery Charger for Ni-MH Ni-CD Rechargeable Batteries

It's probably an old "dumb" charger that requires batteries to be of similar size, and in pairs. I would just buy something new. You can get something excellent for just $10-15: https://www.amazon.com/EBL-Battery-Individual-Rechargeable-Batteries/dp/B0GLZ49V7V