We purchased these batteries for microphones in our church. They were used each week, usually twice, for a minimum of 3 1/2 hours; Left on the charger station when we were not using them. We are very happy with how they held up. I'm needing to replace most of them now, 4 years later.

I have five 520mAh and 700mAh 9vdc rechargable IPower batteries. The battery itself provides good power and longevity, BUT, BUT, the negative bud contact that is supposed to grip the negative terminal of the item it powers is loose. It will cause drop outs, interruptions, and because of loose holding or contact creates loud surging static is wireless microphones. Putting something in the battery compartment to force more against the terminal does not always work. It is loose and does not grip. Comparing its physical structure or design to other manufactures of 9vdc batteries it has more gripping prongs (6) but that makes it have weaker gripping strength. Squeazing some of the prongs closer togsethor does not consistenly work. Other manufactures of non-rechargable 9v use a 4 prong negative connector which always holds the negative terminal without a problem. Though iPower company has told me they already had modified it in the past, as you will find, it still needs further refinement. If you are producing a professional venue instead of using the battery for typical home entertainment or ???, this is a critical issue to have drop outs by this. Please refine the connectors design. Your battery has been through tests by independant 3rd party electronic technicians and was demonstrated to be the best tested at the time for duration, time to power decay, and rate of power decay. Please change the design of your 9v rechargable negative connector.

They work well in our wireless mic for a while but they only seem to last for about 8 to 10 months then it's another $16 for another battery.

I\'m a lead singer in a band and the 9 volt rechargeables I was using in my wireless mic would last about 3 hours before I needed to change them. I found this battery online, read some of the reviews and thought I\'d give it a try. When I received the battery, I made sure it was fully charged then put it in my wireless mic and turned it on. Ten hours later it was still on!! Wow! Everyone in my band uses the I-Power 520mah batteries now. If you need a battery that will last, it will definitely do the job!

We use these in Lectrosonic wireless mics in a TV studio. The mics are used about 3 hours and then we recharge with the iPower Fast Smart charger, so the batteries see a minimum of 2 cycles per day, EVERY day. We start to see problems after 8 weeks of this type of use. That\'s over 100 charge cycles. Even though these batteries cost significantly more than alkalines, we are saving literally thousands of dollars per year.