I bought this to charge both AA batteries, so far I've only used it for AA batteries. You must charge in pairs. My flashlight holds 3 batteries, so I had to charge a fourth battery that wasn't going to get used. I put all four in the charger and checked the time, one pair was done in about three hours, the other pair took an additional hour and a half. I suppose the one pair was getting more current than the other, IDK. They got quite warm, I kept coming back and checking their temperature to make sure there wasn't a danger of fire, but they didn't get that hot. I had checked all the batteries with a multimeter before they went in the charger and all were close to the same voltage.
This charger is easy to use, plug it in and insert the batteries negative end first, all oriented the same direction. A red light comes on and will stay on during the charging process, when it goes out that pair is done. There is also a USB port, but the instructions tell you that when it is being used to charge a device, no other batteries will get charged. I don't see this feature as very useful, but maybe some households don't have USB chargers around. I also wasn't aware of this, but rechargeable batteries of the size that would normally be 1.5V. Our klarus AAs charged to about 1.34v and the charge light went out, telling me it was fully charged. This is normal. will only charge
