Deleepow 9V Lithium ion USB Rechargeable Battery, High Capacity 650mAh Rechargeable 9V Battery, 1.5 H Fast Charge, 800 Cycle with Micro USB Cable,4-Pack

good value, don't buy throw away batteries again

Work on my fire alarm without any problem.

1 of the 4 batteries "puffed up" similar to how some cell phone batteries will when defective. It may have been that the power source was inadequate (I had it on a USB hub in a pinch as opposed to a charging brick). Overall the batteries are good, but I was surprised when I saw the bloated battery on my desk. As for the charge, they are almost on par with standard 9V batteries you would buy in a retail store. They don't last as long as industrial batteries, but work well. If you are looking to use these in a tens unit they won't last too long as far as charge life or overall. I can use these in other things, but the tens seems to have shortened their overall life by quite a bit. Regardless, it was a pretty short ROI given the price of disposable 9V batteries.

These rechargeable batteries were supposed to be useful for smoke detectors and were advertised to be long lasting. No such chance - of the 4 that I received - all of them were first fully charged (led on them showed green) - Of the 4 one simply did not meet the threshold for the smoke detectors low battery threshold within 30min of being put inserted. The remaining 3 lasted on a full charge for about a month and then the smoke detectors started chirping a low battery alarm... TOTAL WASTE OF MONEY - DO NOT BUY!

I received 2 x 4 packs of these Delipow rechargeable 9v batteries on 6/5/20 and, after fully charging, replaced all of the batteries in my smoke detectors 1-2 weeks later. On each of the past 4 days a smoke detector has begun to beep indicating low battery. I used to replace the alkaline 9v batteries annually as regular maintenance and it's not going to work having to drag a ladder into the house every 3-4 months to remove, charge and replace these batteries. I have 7 smoke detectors so that meant buying 2 x 4 packs at a cost of a little over $60.00. Now I'm to be out more $$$ as I need to buy Energizer or Duracell batteries.

They work well and charge great over several hours, but two of the four have a defect and on the same charger and cable stop at 7.7v, hopefully seller can correct. At 8.4v they appear to be equivalent to 70% full alkaline, the defective ones are basically less than a quarter, or dead.

Unfortunately we had to send these back because even on a full charge they would not work in a smoke detector. :-(

2/4 of these that i ordered delivered a voltage that was too low after being fully charged; thus, the smoke alarm kept saying that my batteries were low and had to be replaced. i purchased the significantly more expensive Blackube USB rechargeable batteries. they worked and have an advertised 100 mAh larger capacity (750 vs. 650), though i didn't independently confirm the capacities myself.