Cobra specifies Cobra “GA-BN” NiMH rechargeables AA’s in these radios. There’s a sensor contact in the radio battery bay that senses rechargable or conventional battery by contacting the lower ~ 1/4 inch of the lower case (-) this prevents the charging base unit from attempting to recharge a conventional battery which would not be a good thing. I had some Sanyo eneloop (a claimed 1,000 charging cycles) NiMHs avail for use but they wouldn’t recharge in the Cobra charging base w/o modification (see below).
You can use other brand (e.g. non-Cobra OEM) NiMH batteries in the radio/charger if you remove the plastic label wrapping on the lower 1/4 inch of the battery case with a utility knife so the battery bay sensor contact makes contact with the lower 1/4 inch (-) portion of the lower case.
Often the label is shrink wrapped and comes off easily with a light scoring, other times there is a bit of residual adhesive you can remove with a solvent to present clean case for contact. Check to see the red charging indicator light(s) come on when radio is inserted in the charger (correct orientation).
To save time/trouble, you only need to remove the bottom ~1.4 inch of the label on ONE of the four batteries in each radio - it’s the one that is adjacent to/makes contact w/sensor (viewing the radio from the rear, in a upright position - it’s the lower right battery).
Or you can buy the Cobra OEMs at a higher price… :rolleyes:
Hope this tip helps! 