Review on TalentCell 9V Lithium Ion Battery: High Capacity 500MAh Rechargeable Li-Ion Polymer Battery With Micro USB Charging Port - 1-Pack For Ultimate Convenience by Ellington Gardner

I have a gas detector that runs on power and uses a 9v for batter backup. Unfortunately, where we have the unit can be bumped and will fall off the wall once a blue moon. It won't announce it's on battery until the batter is low, and it doesn't take more than half a day to kill the battery. I bought this rechargeable battery so that if it happens to drain, I'm not out a battery. It's already paid for itself.