Just bought some. They each run off a single AA rechargeable battery. Instructions say to position in full sun for three days before switching on to enable a charge to build. Being somewhat impatient, I wonder, could I just charge the batteries in a battery charger and then replace them into the units or would this damage the solar cell?
I was lucky with mine, the bettery's had a pretty good charge in them to start with and gave a good glow on the first night.
My brainy brother however waited a bit longer for them to come on, apparently a friend said, "have you turned the switch on" ? End of problem ;-]