We have had these since they came out. Very poor battery life. Even firmware update did not fix. Expect to replace cr2025 battery every month. Taking it out for a while and putting it back in will help but not cure the problem.
If it shows low battery on the Zip, try this. Then in a day or so! the low battery sign usually disappears from the Zip.
Otherwise, this is a great product. Perhaps they have fixed this problem, but nothing we have tried has helped. We buy CR2025 batteries in bulk from MEC. ( name brand)
Fitbit Zip is no misnomer: the device setups in under five minutes, syncs with your phone or USB dongle quickly when in range, and entering data in the app, such as activities or food consumed, is simple and quick to do. As the lower price may suggest, the Zip doesn't have all the features of the One, such as sleep tracking and stairs climbed, but it is fairly priced for what it does. The zip is essentially a smarter pedometer that records and syncs your data usually without you needing to manually do anything to it. Set it up, clip it on, and go.