Varta 9V Rechargeable Battery

can hold charge for a very long time – Normally rechargable batteries aren't recommended for fire alarms, however in my case, I found that my domestic fire alarms could run for 18 months without needing to recharge the batteries. Batteries didn't leak, get memory or go bad like some other rechargable batteries. I've used Dick smith, tandy, energiser and other rechargable batteries. This one is the best I've used. It holds charge for a long time, don't need to recharge often, don't need to buy new batteries, just need to recharge with a suitable NiMH charger.