List of battery powered appliances etc.?

[Paul]

One thing to consider though is rechargable batteries have a "life" i.e. a maximum number of times you can recharge them.
An average life of 500 to 800 cycles (even up to 1000 for NiMh) is often quoted but if you are hitting your cells hard i.e. loads of power quickly and deeply discharging them everytime, it does impact on the longevity of the cell.

Incidently, batteries do self discharge. NiMh are the worst. Some more expensive chargers can deliver a maintenance charge (typically 1/300 of the batteries capacity) but IMHO it's best to just use them and recharge at the correct 10 hour rate.

How they are charged is another factor. Usually the best approach is a timed charge. So much current over so much time. The problem is not every charger cuts off at the end of a charging cycle so if you haven't set your alarm clock, you can again shorten it's life.

This is nothing to do with what type of cell i.e. Nicad, NiMh, Lithium or even lead acid.
It's just the chemicals within the battery only last so long and unlike lead acids, you can't replace the "gunk" easily.

To give you an example. I've just changed the batteries in a wind up / solar powered radio.
THey were just 5 years old, light usage, stored in a bright room.
When I changed them (soldered in nicads) they showed signs of gassing (white fur) which is indicitive of too much charge for too long or too fast. I also had to replace the connection wires as the positive lead had turned black. This is a sign of corrosive gasses venting out due to overcharging.

Anyway, just a couple of thoughts for you.