I’ve used rechargeable batteries for many years, mostly nickel-cadmium batteries, also known as nicads, which are ideal for infrequently used items such as radios or flashlights. They can be stored safely and they don’t lose their charge over time. Even though nickel-cadmium batteries can last far longer than most people think, they do eventually wear out and need to be replaced.

When I recently tried to buy some replacement nickel-cadmium batteries, I was surprised that I couldn’t find them anywhere. Nickel-cadmium batteries must have gone out of favor while I wasn’t paying attention. Environmental concerns may have played a role because cadmium is a heavy metal and difficult to dispose of safely.

Rechargeable Alkalines

Another option used to be rechargeable alkaline batteries. I’ve never used any rechargeable alkalines myself, but I have read some accounts suggesting that they weren’t very reliable. That might explain why they disappeared from stores not too long after their introduction.

I have had several people tell me that the best idea is to recharge ordinary alkaline batteries, despite the fact that every battery manufacturer warns you not to. But I’ve seen too many electronic items damaged or destroyed by leaking alkaline batteries to seriously consider that option. I don’t want to encourage batteries to burst.

Nickel-Metal Hydride Batteries

Now the stores are full of nickel-metal hydride and lithium-ion batteries. Consumer lithium-ion batteries seem to be quite new (some sources still say that they don’t exist). But I already use nickel-metal hydride batteries in a number of items. Many high-powered devices, such as digital cameras, require nickel-metal hydride batteries and won’t work properly with alkaline batteries.

But nickel-metal hydride batteries have two related disadvantages:

• they need to be charged before they can be used
• they discharge a good deal of their capacity in storage.

The need to charge the batteries before use doesn’t bother me. But the rapid loss of charge does make them unsuitable for the very applications for which nickel-cadmium batteries are best suited. Some of my nickel-metal hydride batteries lose half of their charge in just a matter of days.

Low Self Discharge Nickel-Metal Hydride Batteries

Fortunately, there seem to have been some advancements in nickel-metal hydride battery technology since I last purchased any. There is a new class of batteries called low self discharge (which has an unfortunate acronym). They address the two disadvantages of nickel-metal hydride batteries:

• they come precharged when you buy them
• they discharge much more slowly

Some of the low self discharge batteries appear to discharge even slower than nickel-cadmium batteries, and are advertised to keep nearly their full charge if stored for six months or a year.