Charge NiMH (Nickel-Metal Hydride) AA and AAA batteries from the sun in as little as 1.5 hours when the Guide 10 is connected to a Nomad 7 solar panel. It can also charge batteries from any USB power source. This charger is about the size of a cell phone, and includes 4 rechargeable AA batteries. Leave the batteries in the Guide 10 Plus to power devices on the go through the built-in USB outlet. Also includes a built in flashlight that runs for 20+ hours on a full charge. These batteries have a Low Self Discharge, which means they can sit on your shelf for 6 months before they start to lose effectiveness.