Nickel-Cadmium (nicad) batteries have the strange tendency to stop working unless they are completely drained then completely recharged. If the batteries are fully charged, drained maybe 20% then charged again, and this is repeated several times, the batteries simply don't work any more. If the batteries are fully charged, then drained down completely before being recharged, they virtually last forever. Why is this? Do Lithium batteries act the same way? I've heard that lithium batteries act completely different and that they should be kept as close to fully charged as possible at all times (charge em as often as possible).