I've recently bought some of the sacred mercury px625 batteries and I was wondering if anyone has any advice on keeping them fresh. I heard putting them in the fridge helps?
I'd say fridge but don't freeze. All chemical activity (including battery drain) slows down at lower temperatures, but you don't want to get them so cold that you damage the electrolyte.
I was warned once by a camera repairman that storing mercury bateries in the fridge is not a good idea since there may be some emission from the batteries and some mercury may get in the food. After that I took my px640's out of the fridge and I have been storing them in room temperature. I do not know for sure whether there actually is emission but I would look into that if I were you before putting the batteries in the fridge.