21700 3.7 Volt Rechargeable Battery, 21700 Battery 5000mAh Flat Top 21700 Li-ion Batteries for Flashlight, Headlamps, etc 2 Pack

These are great. Have bought 4 of them so far. The battery life (functionality) seems to be good they last about a week or so. They are used in the controllers of my grandson's gaming systems and my husbands. They are great priced. They fit great.

This is a standard 21700 battery，I used this as a replacement for the battery that came with flashlight. I’ve had the battery in the flashlight for over awhile, using it briefly at least once or twice daily and there is no reduction in strength. High performance with a low cost, high value to get.

I got 2 and one had 5,039mAh, and the other had 5,105mAh after the first charge. That's pretty good. So this battery is a good buy.

I was hoping these rechargeable batteries would be great but no luck. I'm not sure if i received a bad batch but the batteries i received don't hold a charge. I changed the batteries in outdoor cameras and i got a message the batteries were low after just 3 hours. I tried a different set and even recharged again but they still died, after a few hours! I purchased non-chargeable batteries and my cameras worked fine.

I used these to replace a couple of dead cells in a 20v dewalt battery pack. They work well.

These batteries do last longer for the first generation Arlo camera.

Internal resistance (Ri) of a battery represents the inherent impedance of current flow due to various factors such as the quality of materials used and the chemical reactions that occur with repeated charge/discharge.The tested batteries had been previously charged and discharged about four times. I measured the Ri on fully charged batteries using two methods: 1. Direct measurement of current with a known external resistor and 2. solving for Ri from measurements of a voltage bridge and an external load. Both measurements agreed closely.A resistance above 500 mOhms per cell is considered a fail. The measurements for this battery exceeded 1800 mOhms. The voltage measured was nominal but there is probable low recharging lifetime. I have not measured the lifetime directly.

great batteries for my jumper T14 radio