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on March 5, 2014
I mainly use these in a wireless guitar setup twice a week, every week.

The higher power that these batteries provide allow me to make it through the night using only one battery, whereas I had to switch mid-way through the gig with the other rechargeable batteries.

500 mAh -although twice as strong they are quite strangely very light in weight. Maybe one-third the weight of conventional rechargeables. Very odd. Who knows WHAT types of elements they are putting inside these things these days, but they work wonderfully.

I have used the Tenergy "blue" or regular type batteries for over two years without fail.
I have saved hundreds of dollars and have rewarded myself thusly! -lol.

They do tend to discharge a little when stored, so if you want them fresh and full, make sure to charge them right before you use them.
The guide says it can take up to ten hours to charge these, but since I don't completely drain them I find that in about 3-5 hours they are fully charged, or at least the green light comes on the charger indicating full charge.
If you are only charging one battery, then it may take much shorter time to fully charge.

I try to remove them as soon as I see the green light come on, because I feel that the charger automatically shuts off and does not keep them trickle charged fully, but I could be wrong.

As others have mentioned, there is only one light on the charger and the "other" one is a "dummy" without a light or LED. This is no big deal at all.

Since I have used Tenergy batteries with great success I feel confident that after just a couple months using these, I see no reason to believe that they are any less in quality and much more in performance.

Hope this helps!
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on November 24, 2013
Near double the run time of Alkaline batteries and almost the same voltage. Actual voltage is 8.4V, same as NICd but much better charge retention and capacity. I use them in my guitar effects pedals and wireless gizmos and not having to change batteries during a gig is a huge benefit. Being able to recharge them is saves landfill space and money - reduces the "starving artist" effect. They will have paid for themselves in a few weeks. They are also very light which is an advantage in wireless handheld microphones.

The charger design is better than some others and securely holds the batteries in place and stores flat. Overnight charge time is adequate.

A neat little hard plastic carrying case for a few batteries and the charger would be a great product...Tenergy?
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on June 17, 2014
I purchased this to use in my TENS unit. Unfortunately the battery strength when it is fully charged does not appear to be as strong as a regular 9-volt battery. I was also disappointed that the charge does not last very long and I'm constantly needing to change the battery and recharge the other two. I use the batteries within a day of fully charging them, but they still don't seem to hold their charge. It takes a long time (many hours) to charge the two batteries. I'm very disappointed with this product.
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on December 6, 2012
I bought these for my 18v CMOY pocket amplifier. I charged two of these, threw them in the amp, and started listening. I then bought a few sets of headphones over the course of a couple weeks. I proceeded to burn-in both headphones with the amp attached. With hours of listening every day and the 40+ hours of burn-in, I have yet to recharge them. I'm starting to wonder if my amp is being powered by some sort of nuclear fission not yet released to the general public.

In short, buy them. There is a 1200 mAh version of the battery too, it's recharge cycle must be measured in millennia.
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on January 18, 2014
Another quality Tenergy product. Bought 4 of these rechargeable 9 volt batteries and the plug in wall charger. Two batteries can be charged at a time, but there is only one indicator light. The doucumentation states that each cell monitors delta V, and it will fully charge each cell then trickle charge to keep the batteries at full.
Each battery can be recharged hundreds if times, this the small price for this could potentially have a great ROI over time.
Using a multimeter each betters fully charges to just shy of 9 volts at full charge. These are comparable to the charge on a new alkaline battery.
The mAhour rating is 550, which falls short of an alkaline battery (listed at 600 or 650) but is far better than most rechargeable 9V batteries (listed at 250 or worse)
I would recommend this to anyone looking for rechargeable 9V batteries.
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on March 30, 2013
I would give the batteries 5 Stars, but the Charger with only One light for Two batteries is worthless. No instructions on what the light tells you. If one battery had 1 Hr of use & the other battery 6 Hrs, I assume you don't know when the lightly used battery is done charging. The picture makes it look like there are 2 lights. I would call that FALSE ADVERTISING - Chinese marketing.
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on November 7, 2014
The battery life on these is incredible, thanks to lithium-ion. (My Ni-Cad 9V on a fresh charge lasts maybe a fourth as long, or less.) But there's only one functioning light on the charger (one hole is a dummy), and no directions on how to use it.

I *think* the batteries themselves should have overcharge protection, but I'm still a bit reluctant to leave them in the charger, as it doesn't shut off after X hours.
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on January 26, 2016
I haven't used them at this time. Have bought other size Tenergy batteries. Very pleased with product.
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on December 19, 2013
Doesn't matter if one or two batteries are plugged in, only one light shows if they are charging. Which works just fine. Seems to charge pretty quickly. Quality of both the battery and charger are very nice.
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on May 23, 2014
These are supposed to hold a charge a longtime so should be a better option over nimh for things like smoke alarms,so far they work like they are supposed to but I have only had them a short while so haven't had to recharge yet, but for the cost and what you get I believe these are well worth it definitely a better choice than disposables which can cost almost as much per battery at the store as these
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