In article ,
Steve Walker wrote:
I want to fit a battery backup to a small audio device.
Something that will charge a 7.2 volt Ni-Cad pack without damage
no matter how long left on and run the device at the same time -
and switch over automatically if power fails. Maximum
consumption of the device is about 250 mA.
There appear to be 'millions' of supervisory chips out there and
I was hoping someone could recommend one.

It sounds like a maintained emergency light would do what you want

Many cheap alarm clocks run on mains but with 9v PP3 backup...?

A PP3 wouldn't last long enough - but I want a re-chargeable anyway.

--
*Ah, I see the f**k-up fairy has visited us again

Dave Plowman London SW
To e-mail, change noise into sound.