I use those batteries on electronic keypad deadbolt and they works really good.

I keep them in the case they came in when I'm not using them. I would hate to lose them.Everything was perfect. Thank You :)

These are novel and strange batteries. It's super convenient to recharge via USB chargers (which are ubiquitous these days). It'd be nice if they came with a 4-way cable to permit charging all cells off one suitable USB charger. These are excellent when you have a device that's really meant for cells like alkaline or lithium primary cells that put out a full 1.5V. Sometimes such a device won't work as well from 1.2V rechargables like NiMH or NiCad. These cells will work better, but you'll need to be aware of key downsides:1) Because they output a full 1.5V steadily until fully discharged, there's no voltage dip for electronic gadgets to use to gauge battery charge remaining. So your device will appear fully-charged on these batteries 100% till cutout, which will be sudden and unexpected. Have a backup set ready!2) Because of (1), these cells are a little risky when used to power devices like digital recorders and cameras. They'll work, but because of the sudden cut-out when discharged, if you fail to stop your recording in the normal way beforehand, you may lose the /entire/ recording due to failure to write-out and close the recording file to the flash memory normally. For a still camera, this'll be just the last picture at cut-out, but for an audio or video recording, you might lose the whole recording. The risk can be minimized by timing the runtime in the device you get from the cells in a test-run first, then being careful to stop using the device in the field in sufficient time to save and close your recording before that time (being sure to adjust for extreme temperatures, which reduce capacity).3) These batteries work by using a micro-mini voltage convertor to step the cell's native 3.6V (4.2V - 3.0V) down to a fixed 1.5V output. A side effect of the convertor's operation is stray radio-frequency emission, some of which is conducted thru into the device being powered. If that device is a radio receiver, like a handheld scanner or FRS/GMRS handy-talkie, or similar, you can expect reduced receive performance.In testing with a handheld scanner I use to monitor operations at my local airport, I experienced a 50% reduction of sensitivity, and some low frequencies (e.g. the AM broadcast band) were lost in the RF noise from these cells entirely. This isn't a defect, it's just a side-effect of how the cells work. A battery-powered GPS device may also be affected, I tried them in a Garmin GPSmap 60CS 2-AA handheld GPS unit. They worked flawlessly for me here, with no reduction in satellite signal strength, but your device may vary and you could try it out first before going into the field. And again, there will be no warning prior to end-of-discharge cut-off, the GPS will appear "fully charged" the entire time.So what do I use them for? I have an LED flashlight that's super bright, but was designed for alkaline cells and would not get to full brightness on normal NiMH rechargeables. These cells work _perfectly_ there. The only remaining downside is limited cell capacity. From 2400 mAh NiMH cells, I'd get two hours continuous runtime, but these cells can only provide one hour (1200 mAh capacity). Again, that's simply a side effect of the design and isn't a defect.I also have a couple of fancy electronic flash units for my SLR camera, and these cells work extremely well in that device too!So, know your device and your application to decide if these cells are right for you. Most modern electronic gadgets like radio equipment or digital recording devices will be designed to operate just fine from 1.2V NiMH cells, and these won't harm the receive performance of a radio like these USB cells. Plus, you'll get proper charge-state indications from NiMH cells. Just remember to select and pack a quality NiMH charger in that case.

The fact these even exist in the first place is a godsend. They charge via any USB port in about an 90 minutes and will work in your every day electronics. Is perfect for game controllers that still use AA batteries, TV remotes, wireless mouse and keyboards (which is what I got them for) and many other devices.If there is one thing I will say is a small concern is the cap on top that covers the USB port. It's held on by a small elastic cord to prevent it from being misplaced. I would be very careful when removing and replacing, as it feels it can snap off if moved too fast, so just be careful.Other than that, my only other complaint is........why did I not get these sooner? They are 100% worth the money. I plan to get some more of these and some AAA versions soon.Edit 11/5/2020 - OK one minor complaint, but this might not be the battery's fault, but in devices that tell you the battery is running low and to replace them soon (Ex. keyboard, mouse, Wii remotes) it doesn't give that warning from the device, so devices will all of sudden stop working when the battery is depleted, but I have other batteries charged and on standby to replace. So not a deal breaker, especially if you have more ready to use.

I had purchased a large pack of regular lithium batteries for my Blink cameras and Kwikset Smart Locks, so I would have extras on hand. The batteries last so much longer than standard batteries, so I decided to look into rechargeable lithium batteries.I bought this 4-pack a a test. I like that you just pop the cap off and stick them in a USB to charge. It takes about 90 minutes to fully charge the batteries. The red light is on during charge and off when done. No looking around for the charging equipment either, which is incredibly convenient.I put these batteries into a new Kwikset Smart Lock I had just installed. I replaced the batteries in another Kwikset Smart Lock elsewhere in the house, so I could compare the rechargeable vs standard lithium. The other lock is used much more often and the batteries in it are still going strong after I just had to charge these batteries. Time was about 3.5 months. Considering I could recharge them and replace them at no additional cost, AND that they still lasted 3.5 months in the lock was impressive enough that I plan to buy more.Next, I would like to test them in my Blink cameras to see how they fare. I will update this review once I have done so.