WAVYPO 1300mAh 4-Pack Rechargeable 9V Batteries,9 Volt Lithium-ion Batteries Long Lasting with 2-in-1 USB-C Fast Charging Cable, for Smoke Detector Alarms, Microphone, Toys, Walkie-Talkies

This is a great product. Everyone needs 2.

Since 1999 25 years I have been working in technology industry IT support. Seems every device in my tool-bag uses 9volt batteries.. inevitably I go to use device in my tool-bag, and the battery be dead. Then I have to leave job site wasting labor cost and my time trying to find store that sells 9 volt batteries.This was an Easy decision…Stop throwing away money and creating wasteIt’s hard to tell how many 9volts I have thrown away over the years. Conservative numbers here let’s do the math.2 fluke multimeters, Harris Telephone butt set, Dymo label maker, 3M label maker, Data cable wire map, Digital Tone generator, matching magic wand, Analog Tone generator, matching magic wand, just to name a few.1. 10 devices total.2. All devices replace batteries twice a year:• 10 devices × 2 replacements/year = 20 replacements per year3. Half of those devices (5 devices) replace batteries three times a year instead of two:• 5 devices × 3 replacements/year = 15 replacements per year for those• The other 5 devices remain at 2 replacements/year = 10 replacements per year4. Total replacements per year:• 15 (for the half that gets 3x) + 10 (for the other half at 2x) = 25 replacements per year5. Over 25 years:• 25 replacements per year × 25 years = 625 total batteries thrown in trash!The cost of a 9-volt battery can vary so• Budget bulk price: around $1 per battery• Mid-range (Duracell/Energizer multipacks): around $2–$2.50 per battery• Premium/lithium brands: around $3–$41x625:6252x 625:12503x 625:18754x 624: 2500Easy to see why the value money saved is substantial. for buying 3 of these sold as 4 pack for $60+Should mention these charge super fast connected to any USB port and batteries connector using standard C type charging cable.

I use to go through a battery every 3 40 minute uses of my NexWave ifc stimulator on IFC MODE for my neck and back. it’s kinda like a tens unit but uses a lot more power. The 4 instead of 5 stars is because the always work when charged and have to be plugged back in for a sec to turn them on from time to time which isn’t convenient if I need them and don’t have a C charger around.

Good product

Great batteries. They last long. And don’t have to buy batteries for a long time. Thanks

I bought a four-pack of these about six months ago and used two of them immediately. When those two went dead I attempted to charge them, and... nothing. No LED light, no charging, no charge. I tried several different USB power sources and multiple cables, and also made sure to push the cable end firmly into the battery. I tested the third, also dead. The fourth still had a charge from purchasing, but I'm not expecting that one to be any better than the first three when I attempt to charge it.Update 07-10-24: the last one, which was showing full charge when I put it into a garage remote a week ago, is now fully dead and will not charge, just like the rest. These are garbage.

I did a review on a set of "AAA" batteries and I mentioned that I also have the "AA" and these 9 volts, plus how easy it is to recharge. I mentioned that if you can charge your phone, you can do the same with these.

The product description says the batteries are useful for pro audio and guitars, but when I installed two of them in my 18V active bass guitar (in a battery compartment separate from the preamp), they caused audible hiss in the output signal. This is likely due to the circuitry inside each battery (charger, overload protection, etc.). The hiss disappeared when I swapped in regular alkaline batteries. Other than the problem in my particular use case (and the description leading me to believe they would work well for it), they seemed great--it was cool to be able to charge them with a USB-C cable. I tested them with a multimeter and they output 9.1V (not under load) compared to my nonrechargeable alkaline Duracells that output 9.5-ishV. Also, like many rechargeable batteries, they were just a hair thicker than Duracells so they may be a tight squeeze in some applications. I was hoping to avoid the expense and waste of nonrechargeable batteries in my guitars but I need to stick to them for that use, and I didn't have another use such as a smoke detector where I think they would work fine. So I returned them for a refund, which went smoothly.