9v Battery,POOVER 680mAh Rechargeable 9volt Lithium Li-ion Battery with 9v Connector Smoke Alarm(4 Pack USB battery & 4-1 cable)

This is not the same size as a standard 9V battery, and does not fit where a standard 9V battery would be used.

This appears to be a pair of Lithium rechargable cells in series with a protection circuit - it measures 8.4V at full charge and 7.0-7.4V thru most of it's discharge under load. (which might be an issue for some more fussy things). From my tests, I would estimate the capacity between 500-510 mAH capacity at the point the safety circuitry shuts the voltage off just below 6.0V.They do seem to be the same physical size as my Duracell 9V batteries, so I wonder if the product was redesigned to correct another reviewer's complaint (that would also explain the slightly lower capacity if it's slightly smaller to be the proper physical size now). I only had minimal difficulty getting it in/out of one product because of the "shrink wrap" label snagging on a contact, but it did fit and work as expected.I don't think I'd trust this in anything life-critical like smoke alarms but it's probably excellent for toys and other gadgets that eat expensive 9V batteries. I plan to use it in a TPMS test tool and a model train DCC controller both of which take a 9V battery and go thru them fairly quickly but aren't that big of a deal if the voltage gets low.I've attached charts of a discharge around 1C (~680mA) and around 0.2C (~100-130mA) using a resistor as a load to show how the voltage drops over time. On one hand, it would be nice if this had a boost-converter so it was 9V but on the other hand, the way it drops off should let low-battery alerts work (though they may signal prematurely).

Item is good size and fits into my Ibanez TMB100 Bass just as snug as the original 9v, and other "standard" 9v batteries. I gave them a charge for about an hour and the led on the bottom turned green. I grabbed my multi-meter, and the battery only read 8.35 volts. I assumed that the charging cube i was using probably wasn't putting out above 5-7volts. So i grabbed a 12 watt charging cube and let them charge longer. It charge again for another 10 minutes and the led turned green again. I checked the voltage again and it again stated 8.35 volts. A standard 9v read about 9.6-9.7 volts on the same multi-meter.I don't believe that the slightly lower than 9v on the battery will cause any issues. I did not purchase these to operate anything that has a high drain. So i am not too worried about that. I decided to use the rechargeable lithium battery in my Bass as i did not want to have an alkaline battery that is sealed (2 screws) inside a Bass and plugged in and have it go bad and leak and damage the Bass. And these are about the same cost as a 10 year lithium 9v, and i have also seen a handful of lithium 9v that were a good chunk larger than a standard 9v, and the standard 9v was a tight fit already. I have only used it for about a day or so, and so far no issues.I did some reading on rechargeable 9v's and they are most commonly around 7.6 to 8.4 volts. If this is common information and design, I'm kinda surprised it is not listed in the specs on this, or many other rechargeable 9v listings.Item came well packaged, and the multi-plug cord that it comes with is a nice addition and aside from being short, works well. I will update this review if any issues arise. So far I'm happy and would purchase again.

A great idea finally! I've AA and AAA rechargeable batteries that you plug into their USB ports. Having a 9V rechargeable battery is great. Most people including me, when I go on business trips, I occasionally fail to bring a charger for my rechargeable batteries. So I've converted to those types of rechargeables that have micro USB ports built into them. I always carry a variety of charging cables, so it's a no brainer. Plan to purchase more. Typical 9V LiPo construction and design. RECOMMEND: Buy a few it's worth it (I'm ordering more).

I bought this one because I thought it’ll be handy for my guitar pickup. Easy charging with a cable, instead of a big charging case. But the battery is a little longer that the regular 9V battery. Because of that it won’t fit in my battery compartment of my Ovation applause guitar. Which is a bummer. It probably fit in other guitars with an open compartment where you can just slide it in the guitar, but it won’t fit on guitars with a battery case where you put the battery in a bracket and then in your guitar. Batteries are not a waste. I have other purposes for it now.

Batteries charge very well, takes maybe an hour for a full charge. Comes with a USB cable that has many leads running off for charging the batteries. Be advised, if you are trying to charge all the batteries at once, have a brick that can handle it

Bought these for my smoke & CO detectors, and follow the rule of thumb to change them when daylight savings time changes. They seem to have plenty left when I do. Thinking I might see if they'll last a year. I have no doubt that they will unless I burn the meatloaf a few times.

I love this product. The recharging is so simple. I love that the micro-USB charger fits directly into the battery and no additional piece of equipment, like a holder, is necessary. They come in pairs, so you'll never be out if you're using it for a single purpose.