I bought this as a back-up battery for the E340 Video Doorbell so I could keep using the doorbell while one battery is charging. I found that if you use the motion detection settings on high along with the other settings maxed out the batteries only last a week or so. I ended up hardwiring my doorbell because I wanted the highest video resolution and motion detection possible without having to change a battery every week.
If you have the doorbell settings set to minimum and don't have a lot of traffic in front of your door, using only battery power would probably work great. But because of how I wanted the doorbell settings, it drained too fast. The battery itself is a nice lithium-ion battery that I never had an issue with. I still kept it because the doorbell doesn't work without a battery installed, and I like having a backup just in case.