I've got a bird feeder that dishes out peanuts to the local birds - tit's,
finches, sparrows etc.
It's made of metal and is supposed to keep off the squirrels (grey squirrels
in my case).

It doesn't work - the squirrels still feed on it.
So I'm looking for a way of stopping the squirrels feeding on it.

I've got the metal bird feeder suspended from a piece of copper wire (I
thought the squirrels would not be able to climb down the copper wire).
This also did not help.

Is there any way I can attach a battery to the copper wire to give the
squirrels a polite shock to persuade them not to feed there?