These are LiPO batteries so incompatible as far as I know with all the usual NiCd/NiMH/LiIon battery chargers you have for your other devices. They do provide a warning card with the item, to 1. not charge the batteries in another charger type and 2. not use the charger to charge other battery types. The 6 pack is enough to cover all the typical number of smoke alarms in all but the biggest houses. Appreciate not having to increase the waste stream of discarded batteries as much. Given all the warnings on the card, more obvious notes on the charger and batteries themselves might be helpful, someday someone in my house I bet will forget, and since the card doesn't travel with every individual battery, the potential to forget it won't work in regular chargers is out there. Seem to work well enough in my smoke alarms, time will tell if they last as long/longer per charge than the typical NiMH I've been sticking in my alarms these past year.