Timothy Murphy wrote:
Ian Stirling wrote:

I know this theory about the limits of rechargeable batteries,
but I use them all the time, in everything (except smoke alarms).
I find they work perfectly well in devices that claim otherwise,
eg TV remote controls and wireless computer mice.

NiMH cells are especially poor for this service.
They will often be essentially dead at 6 months.
NiCd is significantly better, usually having power at 12 months. (IME)

What exactly does "essentially dead" mean?
Do you mean that the battery is no longer rechargeable?

Sorry, no.
I mean that it will have essentially no power left, due to self-discharge.

If you mean that a single charge lasts for 6 months
then I would be more than happy with that.

Not quite - a freshly charged NiMH battery, left for 6 months will have
essentially no usable power left, if it's been stored at room temperature.