Deleepow USB 9V Lithium ion Rechargeable Battery, High Capacity 650mAh Rechargeable 9V Battery, 1.5 H Fast Charge, 800 Cycle with Micro USB Cable, 1-Pack

Here is the deal, nice and short. - it maintains enough power output to keep a fire alarm from beeping. Cool. - it charges via usb. take it out and charge it for an hour to get 4ish more months of battery life in the alarm. - doesn't last anywhere near 6 months, but who cares because you don't have to buy another battery for your alarm when it dies. - over priced for one battery, but will pay for itself within a couple of months if you use this type of battery a lot. - keep a couple in stock so you don't have to wait for the dead battery to charge. - had it for over a year and it still charges up and works nicely.

Amazing product! Very happy so far and have been using it daily for about 2.5 months! Nifty product and saves me a ton on batteries. It’s a medical device that I use daily and I was going through one battery a day. This has already saved me $75 in batteries! Worth every penny x750! Literally! Now, I had purchased a 9v battery replacer, a 120v wall plug converter with the funny battery connections 9v batteries have. It was a waste of money. At the end of this here, I’ll add the review for that product. That’s why I’m so happy with THIS rechargeable USB 9v battery. THE REVIEW FOR THE SUBPAR PRODUCT: Worked great for about 8 months then I unplugged it and one of the prongs broke off on the power outlet plug. Then I tried to issue a return and nothing happened. Would have given 2 stars, but the lack of customer service made me drop it another star. Too bad. Could have been a fluke. Cheap enough to replace though. I replaced it with a USB rechargeable 9v battery and I’m extremely hoppy with that product!

I bought these because I absolutely love the idea of USB-rechargeable batteries. However, I have noticed that these will not charge up past 8.4 volts at the maximum. The power runs down much more quickly than a regular alkaline battery, too. I'm sure they're just fine for things like remote control, or another low drain device. I use them in guitar pedals. You can get some pretty fun results with fuzz pedals, but they would drain too quickly for any other type of effect.

Works great for replacing the 9V battery in my TENS unit, no more tossing a battery after every few uses and this has already been well worth the cost in terms of how many 9V batteries I would have blown through by now. Amazon asked about a star rating for "remote control" which makes no sense...

These are great batteries holds charge quite well and is a lot easier to charge than the ones that need a base to charge. Simple charging with a android power cord which they include but is very short. But I have several 10 foot long cords hooked up so I just use one of them and it charges fine.

It may be asking for too much to get a 9V USB rechargeable battery, and in this case, it is. This battery charged for 4 hours til the green light came on, and my test meter reading showed 8.4 volts. When placed in my 9v light, the light did not come on. I then tested the battery immediately, and it read 7.7V . So keep that in mind -- your experience and needs may vary.

I use active pick-ups in most my guitars and finding a 9volt battery isn't always easy and they are expensive. This battery charges quickly and the longevity is just what I needed. Actually I need a few more 😂

I wanted to convert a lamp to cordless but didn't want to burn through lots of disposable 9Vs, so I bought this. It's great. In fact, I liked it so much, I bought another and am converting another lamp. It runs a 12v candelabra bulb for about 2 nights before it starts to dim. The light given off by that set-up isn't enough for a task light or reading light, but I just wanted it to brighten up a dark corner, and it does that well.