for clock, use cheap carbon zinc battery, dont even need alkaline..

Rechargable at full charge only dish out 13.4v and not close to 1.5v, so clock might run slower. After a while with it will only put out like 1.2v then you will lose few minutes every month.

Also rechargable not suitable for slow drain battery, more for fast drain like Alkaline replacement.

I have heaps of AA/AAA batteries as well. No leaks are the bonus. but clocks and remotes, I still use alkaline/zinc batteries, the rest are all rechargables.

Camera and Flashes are recommended not to use Nimh batteries though.