If you have a device which uses
AA or even
AAA cells, you can purchase
Nickel Metal Hydride (
NiMh) rechargable batteries. They were one of the first kinds of rechargable cell to be hailed as having "no
memory effect" (although in reality, this means "less vulnerable to
memory effect"). While not as
spiffy as
Lithium Ion cells, they do hold considerably more charge than
Nickel Cadmium (
NiCad) rechargables. They can be charged in most existing
NiCad chargers, only the charge times will differ (longer).
PS. Follow the NiMh link for information on where you can buy them.