HW9V Rechargeable Lithium Batteries with Charger, 4 Pack 1000 Cycles High Performance 9 Vlot Li-ion Rechargeable Batteries with 4-Bay Independent Channel Charger for Li-ion/Ni-MH/Ni-CD Batteries

This takes care of my battery needs perfectly. It's easy to use and I always have fresh batteries.

What more can I say. These batteries are super convenient. I don’t need to go out looking for 9V batteries again and I can just recharge these. They last pretty long and so far I haven’t had any issues.

This is a very convenient charger for me since I have 4 smoke detectors and the charger fits 4 9v batteries.I would like to see a meter to see how full the batteries are, and this only has red/green leds. It's not critical though.I can't yet speak to the longevity of the batteries, that will take a while.

This is one of those battery sets where the answer to the question "how good is it?" is going to depend on the specific device(s) where they will be used.Despite the box saying "9V Constant Voltage," these batteries are not true 9V batteries. (And yes, true 9.6V rechargeable batteries do exist, but those will usually always end up being NiMH batteries because of the properties of battery chemistry to voltage). The maximum voltage output on these is 8.4V, which would make perfect sense if these batteries are internally a 2S LiPo cell configuration. In my testing, the batteries came off the charger measuring 8.3V, which would be an average of 4.15V/cell.In the end, if the device you are putting these in is fine running off 8 volts, these will end up being quite impressive batteries. But, if your intended device is going to want the full 9 volts, you will likely be disappointed, and a single charge won't last very long.Assuming the use case of a device that's fine running off 8 volts, I put each of these batteries through a discharge test. The lowest drain I could specify on my test equipment is 100mA, which would actually be a fairly high drain for a 9V battery anyway, with the test running the batteries down to 6.6V (3.3V per cell). All four batteries showed a test capacity on their first discharge cycle between 455-473mAh, so given that most NiMH 9V rechargeable batteries will have a rated capacity between 200-250mAh, these would be roughly double the capacity of NiMH alternatives.All that said, though, there is still the potential safety issue with Lithium Ion-based rechargeable batteries. I would make the argument that the manufacturer should have much more prominent safety warnings on the batteries themselves about what charger can be used to recharge these batteries, because there would be significant safety risks if these were charged on a standard NiCd/NiMH battery charger. This is mentioned in the manual, but once the batteries are out in the field, there is nothing to do a good job warning someone else who may come across the battery in the future to make sure a Li-ion compatible charger is used.As long as that safety risk is acceptable to you, and you have devices that are fine running on 8 volts, these batteries will perform well at a nice price point.

These are not 9v batteries. They are in a 9v configuration, but they will only charge to 8.4v. Unfortunately I didn't figure that out until the 30 day return policy was expired. I purchased 4 sets of 4 to use in my smoke detectors. When I put them in, it didn't last long until the voltage dropped below the smoke detector minimum voltage and it started chirping. Because they start out at 8.4 volts. This is a deception from the seller. DON'T BUY!

I work in electronics field. So, I'm dealing with electronic devices that use 9 volt batteries every day. Charging them is simple. The blinking redl light signifies they're charging and the steady green light signifies they're fully charged. 8.24 volt detected when they're fully charged. That's totally acceptable for 9 volt batteries. Most devices will work without issues. If it's below 7 volt, it will be considered as low battries. Will continue to use them.

Due to owning a few rental houses we have several smoke alarms that periodically cheep at us for sustenance. In the stores they do not give the kind of batteries away that smoke alarms usually require so having several rechargeable ones on hand is a boon.Being rechargeable means we never have to buy them again.

The package arrived on time. This batteries and charger is just what I needed. It’s perfect for those smoke detectors cause baby they be going out like crazy. I love that they are chargeable. They charge fast and it let you know when they are ready