I cannot say enough good about these batteries. They continue to preform at peak power and efficiency even after 3 years of steady use. I first bought two batteries just to try out and because I was so impressed, that in two weeks time, I bought two more. These batteries have served one purpose only and that is to power my Headroom Portable Headphone Amp.. The reason I use this amp. even at home, is because I am driving a AKG K701 headphone and it requires a little more Oomph! then my iPod and iPhone can give to produce the quality of music that I enjoy. When I first started using these batteries, I compared them to a couple of different top of the drawer Alkaline batteries. No, I am not going to tell you that these batteries lasted longer than the Alkaline batteries but they were not too far behind the Alkaline batteries in longevity. I do not remember the exact figures because this was three years ago but rather than lie, I will just say there was not enough of a difference to be concerned about. These batteries and charger have more than paid for themselves. I would also say that probably now, I am using these batteries for free, its like icing on a cake. Sure I can also plug my amp into a wall outlet and save wear and tear on these batteries but it is much more convenient to be able to just pick up my amp and charger combo and go where ever I please without missing a beat.

We use these at our church in our wireless mic setups. These batteries save us a bunch over the years as we keep a few fully charged and if something goes wrong, we can swap and recharge as needed. The batteries recharge relatively fast, so a few batteries could support a small presentation team fairly easily. Our first set lasted 4 years of light use (got left in a wireless pack and swelled due to discharge) and we rarely bought alkaline batteries during that time. The only reason I have to give them 4 stars is that they are typical rechargeable batteries. These are not 9V; they are "9V" batteries. The fully charged voltage is around 8.5 volts. Now these have a normal discharge curve for lithium batteries, but they start lower than alkaline batteries. This causes our wireless mics to register them as used batteries, so it is hard to gauge how much remains. A few spares ready to go can stave off disaster, but the wireless mics will have little warning before dropping below the "empty" voltage range.

I like to use rechargeable batteries as much as possible. When I bought some new battery water timers, they required a 9V battery. I had an old 9V rechargeable, but the timer wouldn't work. So, I bought these, as they had a higher output. They worked like a charm. So, now after the season ends, I can take them out for the winter and charge them again for another season. Less waste is good.

I had two of these batteries. I am the lead singer in a very busy band, and I use 9 volts in my headphone monitor. Well, when one of our members left the band, he gave me one of these 9 volts. We do over 100 shows per year, and about 3 1/2 hours per night. I left one battery at a show accidentally, and the other one finally stopped working after almost 7 years of constant use! One battery lasts the full night. Very reliable and quick to charge! Also, my best buddy is a doctor in Phoenix AZ, and his clinic swears by these rechargeables that I told him to try.

This is the second set of these batteries I got for the sound system at church. The first batch lasted several years. The 520 Mah capacity is perfect. I'm seeing some others on the market with 700+ which I might consider for tougher requirements.

I was instructed to pick a few of these and a charger up for our local theatre and was really impressed. We have tried normal rechargeables before and those always run the risk of dying during a performance, but these last so long on a single charge that is not an issue. Great battery!

After one year, very high self-discharge. YMMV, I suppose. For my uses, not worth the cost premium or risk. I\'d rather get mass-produced, industry tested/standard NiMH\'s.

Purchased these to use in Shure wireless microphones for my church. We have been using them since the beginning of the year and they are still working great. We do productions for Easter and Christmas and I have never had a battery run dead even for our day-long Saturday Rehearsals. The only problem I\'ve encountered is I need to tighten the negative terminals about once every three or four months so they plug tightly into the mics and the charger.

I reviewed these batteries in March 2010. They are stilll going strong. I am using them more now too but they still last me at least 5 days even with the heavier usage. I\'ll give another review next year but I\'m pretty sure it\'ll still be good

Purchased in Dec, 2009, I\'ve used these batteries for 2 theatrical shows now in Shure wireless mics (LX and ULX series). When I did a first test, I let a mic run nonstop (I set it up near our boom box while we were working on the set). It did a full 8 hours and was still going. For two-show days we do recharge between shows (15 minute recharge), and we\'ve noticed the battery indicators on the newer Shure mics read even newly charged batteries as \"1 or 2 bars\" of power, but they work the whole show, no problem. Definitely a good investment. In two shows I\'ve already recovered what I would have spent in regular batteries.

I\'ve been using these batteries since 12/09 and have been very satisfied. I use them in medical equipment called an Abbott I-Stat. It uses 2 batteries at a time to power it. When fully charged the batteries last at least 5 days usually 7 to 9. By the way my machine stops working when voltage drops below 7.25 volts. These batties also seem to recharge themselves to an extent when they arent being used cause they voltage gauge changes and goes up after they sit awhile bewteen uses. I would definitely recommened these to others. Dont know about how 1 to 2 life of them but I will let you know.