TENAVOLTS1.5V AA Lithium Rechargeable Battery, 1.8h Fast Charge, USB Charger, Constant Output at 1.5V, 2775 mWh, 4 Count with Charger

I use it for my led flashlights. Before this I had to use disposable lithium batteries to get good brightness and wasted money. This battery last longer between charging too. I wished I had found this product earlier.

These have really held up well over the last 3+ years compared to many other brands I've tried. They still have a shelf life of more than 6 months which isn't bad after 3 years. They have also never given me any problems after the manufacturer quickly replaced 2 AAs that had issues when I first got them. Sometimes these lithium rechargeables can have problems charging if the power drops too low for too long. The chargers just don't detect them and won't charge. Some brands will overheat while charging and take forever to charge. But I have never had these problems with Tenavolts. They also thought of simple things like having the LED light on the battery go OFF when they are fully charged rather than stay on once they are charged which begins depleting the battery power as soon as they are charged. That may sound like a "no brainer," but a LOT of lithium's have a light that stays ON, full blast, when they are charged. Those are always the bad ones that don't last.If you're going to try rechargeable lithium AAs and/or AAAs, the Tenavolts charger is a "must-have." It is a super simple charger. No fancy lights or electronics. Because of that, it will charge ANY brand of lithium AA or AAA if the battery is salvageable. I've had countless other brands of rechargeable lithium AAs & AAAs that won't charge on their own brands charger, but the Tenavolts charger will charge them. I would have had to toss out many of them if it weren't for this charger. Sometimes other brands get "stuck" and their own manufacturer's charger won't detect them. But because this charger is so simple, it will "jump start" them so the other charger can finally detect them. Then they work fine after that. And yes, it will even charge lithium's that have a USB charging port built-in, often better than the USB port.

I purchased these for use in wireless microphone transmitters. I can get about 8 hours from 2 batteries per charge. That's plenty for any show I do. Disadvantages is, the battery indicator on the microphones is always 3 out of 3 bars. The indicator does not indicate capacity remaining, only voltage. I wish they made an 8 bay charger, or something more than the 4 bay and less than the 20 bay.8/11/20Follow up.I now have 2 of these chargers and 16 AA batteries. I use them for karaoke mics. Unfortunately, I haven't been able to use them every day since Covid to really test their durability/cycling tolerance.I'm using them in VocoPro 5800 mics. I can leave the mics on for a 4 hour show with no issues. I've left them on for a 7 hour show with no issues.They charge pretty quickly. I've never had to wait more than about 90 minutes for 4 batteries to charge. I have both chargers plugged into a 7 port powered USB hub. The chargers draw about 1.25 amps per charger. The hub is capable of 30 watts which is 6 amps at 5 volts, but I'm guessing that the charger is only capable of drawing the 1.25 amps, which is half of 2.4 amps, which is what a normal phone charger delivers to a phone. It's probably because it's charging at a lower voltage. Perhaps 1.5 volts x 1.25 amps which is just a little less than 2 watts (1.875 watts).One thing I've found is that if the batteries sit for any length of time (say, over 2 weeks) and you try to use them, they don't hold their charge. I used 2 week old batteries in a couple mics recently and they squealed out and died less than an hour into the event.When fully charged, though, with these mics, they last a good long time. At least 7 hours as stated above.2 minuses:1. Using with mics with battery indicators is, the battery indicators work off voltage. When the voltage decreases, the battery indicator is supposed to glow. With these batteries maintaining a constant 1.5 volts, there is no indication that the batteries are dying. They just quit. Once they dip below 1.5 volts, they just shut off.2. They're expensive.