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 Zach Spangler

I received this on Nov. 14, 2020. I put it in a smoke detector that day. It is now April 17, 2021. The smoke detector just started doing its low-power beeping yesterday. I just recharged it for the 1st time yesterday! So it lasted 5 months on 1 charge, which is pretty darn good. It recharged using the micro-USB port in about 3 hours.The micro-USB recharging port is AWESOME! It is SO EASY to recharge them. The bottom glows red when charging, and turns green when it's done. EASY! No need to find a special charger. Just plug it in and you're good-to-go in about 3 hours. Probably close to the best $5 I've ever spent. Not completely sure if/when I will break-even compared to buying 5 cheap 9v batteries from Dollar Tree. But it's nice to have a rechargeable battery that charges so fast and easily.It is also VERY NICE that you only have to buy 1 battery. You don't have to spend $20 on 4 of them. Unless you use a lot of 9v, it's hard to justify spending $20 on 4 of them. Also, a 4-pack of Duracell 9v disposable alkaline batteries costs $14 on revain ($3.50/ea). So if this battery lasts longer than 2 of them, then you're ahead. You can buy generic alkaline 9v's for as little as $1 that last nearly as long as a Duracell. However, it is nice not to have to search for a new disposable one in a box you put somewhere. Just find a USB to micro-USB cable (which you should already have, or can buy for as little as $1), plug it into any USB port, and you should be ready to go in 3 hours.