HW 9 Volt Batteries 4 Pack, 1400mAh Rechargeable Lithium Battery 9V with USB C Fast Charging Cable, 1000 Cycles Square Baterias for Smoke Detectors, Fire Alarms, Remote Controls, Clocks and More

A year ago I purchased a small practice amp for my guitar that runs on either a single 9V battery or on a 9V power supply. Because this amp rapidly used up the energy of a new Maxell 9V battery I bought for it, I purchased a four-pack of Amazon alkaline batteries so that I would have a fresh battery to replace the existing battery when it became drained. This was only a short-term solution because I knew I would use up the power of all four batteries in the space of one week. I decided to find a power supply to run the amp without batteries. While I have several power supplies that produced 9 V, none of them worked because the connection on the amp is the reverse of the plugs that go into the amplifier. I got back on Amazon and look for a power supply with the connections reversed and found that electronic keyboards use power supplies like the one I need. I ordered that power supply and it worked great. However, if I wanted to play my guitar on the beach, at tailgating parties or anywhere else where 110 V outlets are unavailable, I would need longer lasting 9 V batteries. I wondered if I should be using rechargeable 9 V batteries instead of single use batteries that would be costly to keep replacing both to my wallet and to the environment. While looking for a traditional battery charger, I came across this self-contained battery/charger for the price that was slightly more than what I paid to buy the four alkaline batteries. I was still skeptical that this would work, but to my surprise it charged up quickly and lasted as long as the standard batteries did (which is to say not very long). Of course the difference now is that I no longer have to send useless batteries to the landfill. The battery comes with a short connecting cable where you take its large, male USB-A plug and insert it into your smartphone charger's large female USB-A port. The small, male USB-A plug on the other end of the cable is inserted into the small, female USB-A port located on the bottom of the battery. Note that cables with USB-C connectors - the ones that have no top side or bottom side - will not work with this battery). When the charger is inserted into a standard 110v wall outlet, a small light on top of the battery will glow red when it's charging and turn blue when it's fully charged. I can't tell you how long this battery stays charged because I always connect the charger after I am done using the battery and since it is lithium-ion, there is no need to worry about memory effects of charging a partially filled battery. I highly recommend this battery.

Very well made, and excellent for musicians, especially those who have preamps built into their Guitars. I was going through 3-4 batteries a week and now all I have to do is recharge them. Big money saver

Well made and work just fine... they can be charge with a USB cable, there's a port right on the upper side of the battery, or like me in a lithium charger...

These batteries arrived on time and intact. All 4 accepted charging. How long these will hold the charge remains to be seen. Since these are lithium batteries my prior experience with rechargeable batteries isn't relevant.

These seem to work OK, but I did not check actual capacity. They do have a small LED that indicates when charging is complete.

As described

Good deal for the price rechargeable is a plus

So they are easily rechargeable and seem well-made. Unfortunately, I needed them to provide 18V of power when combined and I couldn't find a combination of any 2 the 4 that made that happen.