Review on Long-Lasting EBL 9V Lithium Rechargeable Batteries With USB 5400MWh Capacity (Pack Of 2) by David West

Six months ago I started using these in one of my smoke alarms. Since then, I have suffered the dreaded "chirping smoke alarm in the middle of the night while I am trying to sleep" issue THREE times. I.e., I have had to replace/recharge the batteries once every two months!I believe I know the reason now. After charging the batteries, they only get up to 8.29-8.34V. After two months, the battery voltage drops to 8.0V. It's a reasonable rate of discharge, but since it starts at a low voltage to begin with, even a small amount of discharge results in chirping smoke alarms.Too bad because I really wanted these to work. My plan was to use these in all my smoke alarms, recharging all of them at once on, say, the spring and autumn equinoxes, to avoid ever having the chirping issues. But that would require them to go 6 months between charges, not 2!Edit 2021-04-27: Customer service from EBL contact me soon after I posted this review. They agreed about the max voltages, I wrote about here and offered to send me EBL 9V NiMH rechargeable batteries instead to evaluate in my smoke detectors. I accepted their offer and received the NiMH batteries promptly. Encouragingly, the EBL NiMH batteries are reading 9.01-9.04V. Their capacity is about half that of the rechargeable 9V Li-ion batteries, but about the same as 9V alkaline batteries. Therefore, I believe the NiMH batteries are suitable for smoke alarms and would last long enough between my bi-annual battery changes. I will post a review for those many months from now after I confirm their longevity in said smoke alarms.Because of EBL's excellent customer service, I almost added an additional star, from 2 stars to 3. However, EBL hasn't changed their listing for the rechargeable 9V Li-ion batteries, which continues to claim they "support stable power and longer working time for high frequently used devices, such as smoke/fire alarms." I believe that is misleading at best and for typical smoke alarms such as mine, simply wrong. Therefore, I am keeping the rating at 2 stars in hopes that people thinking about buying these batteries for smoke alarms do not buy these. They should consider rechargeable 9V NiMH (such as EBL's) instead.