PowerGenix PGX-4AAZiNc-1.6v High Voltage Rechargeable AA Batteries - 4 Pack

by PowerGenix

Product Details

• Product Dimensions: 0.8 x 3.8 x 4.5 inches ; 8 ounces
• Shipping Weight: 1 pounds (View shipping rates and policies)
• Shipping: This item is also available for shipping to select countries outside the U.S.
• ASIN: B0029LHXG2
• Item model number: PGX-4AAZiNc-1.6v
• Average Customer Review: 3.4 out of 5 stars  See all reviews (30 customer reviews)
• Amazon Best Sellers Rank:
  • #93 in Electronics > Accessories & Supplies > Batteries, Chargers & Accessories > Household Batteries > AA
• Date first available at Amazon.com: June 5, 2009

Product Description

From the Manufacturer

PowerGenix has developed a high-energy density, high-cycle life and low-cost nickel-zinc (NiZn) battery ideal for applications that demand high discharge rate capabilities. The technology offers compelling performance advantages, most notably a 30% weight and size reduction coupled with higher power and superior low temperature discharge behavior. Two of the more prominent features of the PowerGenix NiZn battery are its small size and low internal resistance, which enables the delivery of significantly more power during periods of peak demand than a nickel-cadmium (NiCd) or nickel-metal hydride (NiMH) battery of comparable size. Although the design and construction of the cell is similar to NiCd, the higher voltage of PowerGenix's NiZn cell results in a 25% lower cell requirement in multi-cell packages, representing significant space and cost savings.

NOTE: These batteries cannot be recharged in a standard NiMh recharger. Please use a PowerGenix or other Nickel Zinc charger.

Product Description

PowerGenix 4 Pack AA 1.6v High Voltage Nickel Zinc Rechargeable cells 2500 mWa

Customer Reviews

Most Helpful Customer Reviews

172 of 180 people found the following review helpful:

3.0 out of 5 stars Marketing Hypes vs. Technical Facts of Nickel-Zinc Batteries, July 19, 2009

By 

NLee the Engineer (Nashua, NH) - See all my reviews
(HALL OF FAME REVIEWER)    (TOP 10 REVIEWER)   

This review is from: PowerGenix PGX-4AAZiNc-1.6v High Voltage Rechargeable AA Batteries - 4 Pack (Electronics)

On first glance, the PowerGenix Nickel-Zinc Rechargeable Batteries seem to offer many advantages over ordinary rechargeable NiMH cells: higher voltage, higher energy density, lighter weight, longer cycle life, and so on. But before you rush to replace all your rechargeable batteries with NiZn type, let's examine each claim carefully to separate marketing hypes from technical facts:

"30% Higher Voltage" [FACT]
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!

"33% Higher Energy Density" [HYPE]
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

"30% weight and size reduction" [HYPE]
The weight of each NiZn AA cell (25g) is about the same as NiMH AA cell (27g for eneloop). For certain applications, it is possible to use three NiZn cells (3*1.65=5V) to replace four NiMH cells (4*1.25V=5V). But doing so also shortens run time by 25%.

"Longer Cycle Life" [HYPE]
PowerGenix claims that service life of NiZn cell 'meets or beats' that of NiMH cells. However, technical data found on PowerGenix web site says NiZn cell is rated for 200 cycles (at 100% deep-discharge), shorter than the 500-1000 cycles cited for most NiMH cells.

"Longer shelf life" [HYPE]
It is probably true that NiZn cell offers longer shelf life than Lead-Acid batteries (which are notorious for high self-discharge rate), but how does it compare against low-self-discharge NiMH cells? In the PowerGenix "Charging Procedure" section, it says you have to recharge the NiZn batteries once every 30 days!


In summary, 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. For example, the light bulb in a typical two-AA flashlight is only rated for 2.3V. But a pair of freshly charged NiZn cells produce 1.85*2=3.7V, which is enough to burn out the bulb. If you intend to use those NiZn cells in your digital camera, make sure the latter is still covered by warranty!

Finally, NiZn cells cannot be recharged using ordinary NiMH chargers. You have to purchase the special PowerGenix ZiNc 4-Position Charger, and be careful not to mix up different types of AA batteries and chargers. So unless you are desperate for higher battery voltage, it is probably not worth the extra expense and risk.

[Update on Nov 21, 2010]
My original review was written more than one year ago. At that time, I was just pointing out the marketing hypes surrounding the release of this product. Since then, I also found NiZn cells to be very poor in terms of quality and longevity.

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!

36 of 37 people found the following review helpful:

1.0 out of 5 stars Unacceptable failure rate, February 5, 2010

By 

Gregory King - See all my reviews
(REAL NAME)   

Amazon Verified Purchase

This review is from: PowerGenix PGX-4AAZiNc-1.6v High Voltage Rechargeable AA Batteries - 4 Pack (Electronics)

I'd love to love these batteries, but they haven't solved the quality control problems. My first set had a cell stop charging after only a few uses. I had them replaced, but am still having problems. Used in sets of 4, one cell will invariably die out early. Since most devices won't complain since the voltage is still higher than 4 NiMH cells, that weak cell gets overdischarged. Then, it won't charge properly.

The Powergenix charger exacerbates the problem. It charges in pairs, but only has one indicator light. So put in a bad cell with a good cell, and it won't charge either. But put in 3 good cells and one bad cell, and the light will indicate. However, only TWO of the cells are being charged. The light turns green, but two cells are still uncharged. The dead cell can only be rejuvenated by a high voltage pulse, but you may not know which "paired" cell to charge with. Pair it with a good cell, and it will either not charge completely, or overcharge the good cell.

So now I'm forced to baby my cells to avoid overdischarging any of them, and possibly starting to mark cells and track them to find stragglers. Now if I'm lucky, I'll have ONE working set after buying two...and it's a laborious science project every time I need to recharge them to make sure I actually get out anything useful. Maybe if I'm lucky the remaining cells will put themselves out of my misery

14 of 14 people found the following review helpful:

1.0 out of 5 stars Safety warning - hydrogen outgassing from NiZn cells, December 27, 2010

By 

R. Clark - See all my reviews
(REAL NAME)   

This review is from: PowerGenix PGX-4AAZiNc-1.6v High Voltage Rechargeable AA Batteries - 4 Pack (Electronics)

These NiZn batteries produce significant amounts of hydrogen gas under some conditions that are normal operating conditions for other types of AA batteries such as nickel metal hydride (NiMH) batteries.

First, these NiZn batteries operated well for a few dozen cycles in a one-cell flashlight with about a 0.5 watt power draw.

But a couple of days ago I put them in a two-cell flashlight with about a 1.75 watt power draw. This light is waterproof, sealed with o-rings. The batteries worked fine when I used the light to walk through the woods a few times and for other short duration uses.

Tonight I used the light for about an hour and a half to two hours. While working on some plumbing I noticed that the flat rubber switch cover was distended into a hemisphere, bulging out half an inch above its housing. This happened during a period of a few minutes since the time I had last handled the light. The rubber cover felt hard when touched, and I couldn't press the switch to turn the light off. Subjectively, it felt like pressing my thumb on a 10-speed bicycle tire to check its tire pressure. The head of the milled aluminum flashlight was somewhat more than lukewarm, but that is its normal operating temperature. The lamp was operating at normal brightness. Nothing else seemed unusual.

I was wearing safety glasses at the time, and unscrewed the tailcap next to an air vent. The gas pressure escaped with a pop. When removed, the batteries were slightly warm. There was a small drop of clear liquid at the base of one of the batteries, but no other visible residue. The batteries themselves were not bulged, which means that they must have effective gas vents built in. One of the batteries measured 1.62v no-load voltage shortly after being removed from the light, and the other measured 1.58v.

Reading up on this, I found that the gas is hydrogen, generated by the nickel-zinc chemistry in these batteries under the "right" conditions.

If I hadn't noticed it, these batteries would have kept producing hydrogen until something stopped them. This particular flashlight has a weak point as far as pressure buildup is concerned, which is its on-off switch.

But I have another flashlight that's machined from heavier aluminum alloy, and it doesn't have an on-off switch, for reliability and ruggedness reasons. You turn it on and off by turning its waterproof sealed tailcap. The failure mode on that one would be blowing the head or tail off.

These batteries are going in the garbage bin in the next few minutes.

Powergenix needs to start printing an informational warning on the packs of these batteries about a substantial pressure buildup of explosive hydrogen gas, that these batteries produce in significant amounts.

Amazon also should include an informational safety note on the product page about this. Granted, few people will use these batteries in sealed units where the gas can build up to high enough pressures for something to give way, but it's not a vanishing number of people either.

Update: Dec 28, 2010 - According to an e-mail I received from "N. Lee the Engineer," who has also reviewed these batteries, the hydrogen is generated when two or more batteries are used in series, and one battery becomes more discharged than the other(s). Hydrogen is generated by a NiZn battery whose voltage falls below 0.42 volts, as electricity flows through it from another battery that is at its normal voltage.

In short, using only one of these batteries, in a one-cell device, could not cause the battery to produce hydrogen.

He included a link to a better explanation of this. From that article:

"So if you are discharging your series string of NiZn cells at 1 amp, and one cell drops to <0.4V, hydrogen is being generated at a rate of 14ml/minute. ... You can see that the internal pressure of the cell can rise rapidly if a NiZn cell is overdischarged."