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380 of 388 people found the following review helpful
The product description of PowerGenix Nickel-Zinc Rechargeable AA cell promises many advantages over other rechargeable batteries: higher voltage, higher energy density, lighter weight, longer cycle life, and so on. But how does it stack up against the current gold-standard of low-self-discharge NiMH cell, the Sanyo Eneloop? Let's examine the following aspects:

[Operating Voltage]
The NiZn cell has a nominal voltage of 1.65V, which is 30% higher than that of a NiMH cell (1.25V nominal). When freshly charged, its terminal voltage is even higher at 1.85V!

[Power Density]
Since 'Power' is defined as 'Voltage * Current', most people may assume that "30% higher Voltage" translates to "30% higher Power". But it depends on the application:

- Most electronic gadgets (digital camera, MP3 player, etc) contain internal DC/DC regulators which operate in constant-power mode. If the battery voltage is higher, then input current will drop to maintain the same output power. That's why higher voltage alone does not make your digital camera shoot any faster.
(One exception is photo flash unit, which operates in constant-current mode. So in this case, 30% higher voltage does translate to 30% higher power and shorter cycle time)

- For an unregulated appliance such as a flashlight or power tool, its current increases with voltage (although not linearly). A typical 2-AA flashlight bulb is rated for 2.3V * 0.5A = 1.15W. When you apply 3.6V to it, the current may increase to 0.65A, so the power consumption is now 3.6V * 0.65A = 2.3W. Twice the power means twice the heat. That's why the bulb may burn out in seconds.

[Energy Density]
The PowerGenix AA cells are marketed as "2500 milli-WATT-hour" (energy capacity). Most people may confuse this with "2500 milli-Ampere-hour" (charge capacity). But the data sheet for NiZn AA cell shows that its current capacity is only 1500mAh (this is verified by my own testing). It turns out that an 1500mAh NiZn cell actually contains the same amount of energy as a 2000mAh SANYO eneloop AA cell:

- Energy in eneloop AA cell: 1.25V * 2000mAh = 2500mWh
- Energy in PowerGenix AA cell: 1.65V * 1500mAh = 2475mWh

[Weight]
The weight of each NiZn AA cell (25g) is essentially the same as that for eneloop AA cell (27g). For certain applications, it is possible to use three NiZn cells (3*1.65=5V) to replace four NiMH cells (4*1.25V=5V). Doing so reduces battery weight by 25%, but it also shortens run time by 25%.

[Cycle Life]
Technical data found on PowerGenix web site says NiZn cells are rated for 200 cycles (at 100% deep-discharge). This is much shorter than the 1000 cycles cited for eneloop cells.

I have tested a set of 4 PowerGenix AA cells. After subjecting them through 12-16 deep discharge cycles, the average charge capacity already dropped 5% from original value. In comparison, I have a set of 4 eneloop AAA cells that have went through about 100 cycles in the past 2.5 years, and they still exhibit over 95% of original capacity.

[Self-Discharge Rate]
In my long-term storage test after two months, a set of four NiZn cells retained 74% original charge capacity on average. This translates to about 13% loss per month, which is much better than that of ordinary high-capacity NiMH batteries (with capacity > 2500mAh). But it cannot compare to low-self-discharge NiMH cells.

Previously, I have conducted storage test for several brands of LSD cells, including Sanyo eneloop, Rayovac Hybrid, and Kodak Pre-Charged. All those cells can retain 85-90% of original capacity after FIVE months in storage.

[Recharging Time]
The PowerGenix NiZn cells must be recharged using a specially designed PowerGenix NiZn Charger. The charger is called '1-hour', but it actually takes 2.5 hours to fully recharge a set of four 1500mAh cells.

Eneloop (and all other brands of LSD cells) can be recharged using any good quality 'smart' NiMH charger. Depending on which charger you use, the charge time can be as short as 15 minutes, or as long as 8 hours.

[BOTTOM LINE]
The only verifiable benefit for PowerGenix NiZn cell is its higher operation voltage. However, even this may turn out to be a curse rather than a blessing, as higher voltage can cause unregulated appliances to burn out.

If you have a digital camera that works well with eneloop, stay with it. Switching to NiZn will not offer more power, nor longer run time. Only if your camera does not work well with eneloop, then it is worthwhile to try NiZn cells as a last resort. But you better contact PowerGenix, and ask whether they will assume warranty liability for the use in your camera. Otherwise, try it at your own risk!

[Update on Nov 21, 2010]
My first set of four NiZn cells was used for capacity testing and long-term self-discharge testing. They have gone though maybe 20-30 deep discharge/recharge cycles (discharged down to 0.9V only, not 0V) over the past year. As of right now, two out of four cells have already failed, suffering from voltage depression and rapid self-discharge problems. The other two suffered from reduced capacity (~1200mAh, down from the original 1500mAh). The PowerGenix '1-hour' charger needs to detect 1.9V during charging, before it can change from constant-current mode to constant-voltage mode. When voltage-depression hits a cell, its voltage cannot reach 1.9V during charging, so the NiZn charger will simply fry the cell!
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22 of 22 people found the following review helpful
on February 10, 2010
When I was still using Nimh batteries in my Pentax k100d camera, I was constantly switching out the batteries. The camera would shut off as the voltage dropped slightly, even though there was still plenty power available. Plus I was constantly buying new sets, as the problem gets worse as the set is used- even though there were very few recharge cycles used. That was because the camera needs minimum 1.2 volts to function. Well, Nimh is only rated at 1.2 volts. Unless new AND fully recharged, your not going to get that full 1.2 volts that are needed.It was the main thing pushing me to upgrade to a new camera that would use the more expensive lithiums.

However,thanks to the high 1.6 voltage on these Nizn batteries, I've been going on seemingly forever with one set. Plus my flash gun recycles way quicker (note: due to the quicker recycle time the flash can overheat if repeatedly cycled on full power without a break - do a web search). It's even been measured when fully charged to reach over 1.8 volts.

Note that the amount of recharges you can get will probably be less then with Nimh. Maybe more in line with Ni-cad. However, I don't see myself using that up for quite some time. Also note that you can't use a non-Nizn battery charger, so you'll need to buy a new PowerGenix charger as well.

A fantastic buy!
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11 of 11 people found the following review helpful
on December 30, 2010
Out of the 32 cells I purchased, 12 refused to charge right out of the package (the charger's LED flashed rapidly indicating at least one cell was bad. Rotating different cells through the charger showed all were bad). Perhaps these cells sat on the shelf at the store too long and they self discharged to the point of no return? Nevertheless, I was able to resurrect these bad cells by briefly charging them in a "dumb" solar charger (that pushed 6v through 4 cells at a time) for just a few minutes in bright sunlight, then I moved the AA's to the NiZn charger and it finally accepted them and brought them to full charge (took a couple hours for the LED indicator to go green).

But even with that, none of the cells (even those that did charge right out of the box) were good for more than a few charge/discharge cycles before turning completely dead. The manufacturer's claims of 200 cycles (as opposed to most other NiMH and NiCd optimistic claims of 500 to 1,000 cycles) would appear to be a tacit admission to the Nickel Zinc chemistry's lack of longevity.

I can offer one peice of advice to squeeze out the most from these NiZn AA's - Don't drain them to exhaustion. Run them as you need to but then charge them when you're done. Draining them all the way almost always guarantees the NiZn charger will refuse to recharge them (the rapid flashing error).

So what are they good for? NiZn AA's cycle my camera strobes faster than almost any other AA (except maybe energizer lithiums).
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15 of 16 people found the following review helpful
on September 17, 2010
Great product when working. Great concept dating back to 1903?
Use in AA Maglite, walkway lights, remotes, PC mouse, Wx stations, etc.

I have had to send back 24 of the batteries. Failed to charge any more.
I have both slow and fast PowerGenix chargers.

Too many have died.

Amazon was kind enough to replace many of them.
Will not send them back for exchange any more, just take the loss and throw them away
as they fail.
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15 of 17 people found the following review helpful
on February 26, 2010
So this is a preliminary test of the flash recycle times capable with these batteries.

I purchased 3 sets and compared them out of the package uncharged to Duracell and Energizer alkaline straight from package. Here are the results!

Recharge time 1/1 power, 5 shot average. 3 new sets of 4 batteries of each type were used to obtain average.

Flash: Nikon SB-24 Nikon SB-25 Vivitar 285 (non-HV)

Duracell 10.2 secs 10.9 secs 11.5 secs
Energizer 10.1 secs 11.0 secs 11.9 secs

POWERGENIX 2.2 secs 2.3 secs 3.3 secs

Obviously flash recharge times are far faster, I will be further testing the batteries tomorrow shooting the state swim championships. Check back for another review then.
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6 of 6 people found the following review helpful
on September 15, 2010
I bought 3 sets of Powergenix AA's back in January of 2010 and now (September 2010) the sets were doing the blinking red light of death on the charger. The sets were always grouped together. I'm sending the dead batteries back to Powergenix to get them to replace them. They carry a 1 year warranty on them. I was using them in Nikon SB-24 Speedlights which would work great with fast recycle times in the 2 second range until now. The charger doesn't tell which battery is dead, it just blinks red OR has solid red light on and a blinking green light. I chose Powergenix to get away from the pitfalls of batteries not holding charges. Now I'm running into the same issue with poor battery performance after 6 months of heavy use.
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5 of 5 people found the following review helpful
VINE VOICEon June 7, 2010
For my Metz shoe mount flash this is wonderful! The recycle time between flashes is incredibly quick. I would highly recommend this for for flash units.

For everything else I recommend to proceed with caution.

It does not work with my Zeikos ZE-CBG7D Battery Power Grip for Canon 7D Camera. I kept getting error messages about the battery when I attempted to snap a picture. For general use I highly recommend Sanyo Eneloop 8 Pack AA NiMH Pre-Charged Rechargeable Batteries. I have used this brand for years. Even with repeated use it still holds a full charge.

Also note these PowerGenix batteries need their own charger they do not charge in typical NiMH chargers.
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5 of 5 people found the following review helpful
on July 29, 2012
Liked the batteries at first. I have some devices like the my programmable thermostat and my weather station that don't like the lower voltage in most rechargeable. Thought I would try these. Bought them in December 2010 and now 1 1/2 years later 4 of 8 are dead. Always used in low drain environments, never subjected to high current.

These batteries just don't last.

In comparison I have 40+ Enloops around, some 3 - 4 yrs old, and every one is working.

Buy at your own risk. I do not recommend them.
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5 of 5 people found the following review helpful
on July 10, 2010
I was very disappointed with the life of these batteries. They do not last very long at all powering flashes for my camera. I did a test with these batteries in one Lumpro 120 flash vs fresh Duracell alkaline in another identical one for a model shoot in studio. I went through all 24 of these batteries I had in the same time I changed the Duracells once (8). I hoped these would have been the answer to power draining flashes, but they are not, even at 2500mWh. Good power when they are charged though, providing good recycle times.
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4 of 4 people found the following review helpful
on September 13, 2011
Regardless of any problems that I've had with these batteries, I still need them for several devices which have never funtioned properly on NiMH (vs. alkaline), especially for my favorite waterproof GPS which never locks on to satellites using NiMH. Also, I have a 2xAA travel razor which works like gangbusters using the NiZ (while rather wimpy on NiMH), I've used the NiZ AAs daily for over a year in the razor which still works fine. I have several LED flashlights which are quite a bit brighter using the NiZ, and since they are relatively cheap I'm willing to risk the higher voltage (I've probably cut the life-span of the LEDs by quite a bit). Last but not least, I use it in my Sonicaire electric toothbrush which also works better with NiZn vs NiMH.

That being said, other than the high voltage they provide they are generally inferior in every way to the better quality NiMH low self-discharge types such as Eneloop. First a warning about battery voltage. They are not just higher than NiMH and alkaline cells, they are MUCH higher. As much as 1.9V straight out of the charger. The obvious workaround for this is to mix NiMH and Ni-Zinc batteries so they average out to a typical "alkaline" voltage. Be very careful not to allow these cells to drain to zero, or worse, charge them in reverse through by mixing them in series with fully charged batteries in "dumb" devices such as flashlights. In one years use, about a quarter of the batteries I've bought have failed completely (approx. 10 to 15 charge cycles).

You must buy a PowerGenix charger to go with these batteries. Definitely choose the charger that can charge 1,2,3, or 4 batteries and NOT the one that requires charging in pairs. Very often if you charge in pairs you will end up with one barely charged battery, since the charging electronics are heavily biased towards safety (which admittedly is a GOOD thing), but does a terrible job of actually charging batteries :( Also, as others have stated, if you have a battery that has gone down too low in voltage, neither charger may be able detect them and they will remain uncharged. You need to partially revive them in a NiMH charger first for a few minutes (NOT LONGER), so the PowerGenix charger will detect them and charge properly.

I don't know why the price has dropped by as much as two thirds on these batteries, but I suspect that it might be a good idea to stock up on them if you really need them (and they still end up being cheaper than alkalines in any case), in case PowerGenix folds or they pull them from the market.
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