Personally, I’ve more or less given up on rechargeables. For starters, they only put out around 1.2 volts whereas a dry cell will put out 1.5. Digital equipment seems to have some sort of sensor which shuts the thing down unless a certain voltage is available and this will happen far sooner with a rechargeable battery than a normal one.

By way of example, we had a digital radio in the bathroom which was used regularly but not for that long and I was recharging the batteries every week. We bought an anologue one a couple of years ago and that uses the same set of batteries. I last charged them at Xmas!

If you must go for rechargeables, check out the milliamp-hour rating printed on the side. The higher the better. If you want normal alkaline ones, chesk out 7dayShop. I buy them in boxes of 40 and they’re on offer quite regularly.