Customer Reviews

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

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1 star:		(9)

 

 

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!

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

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."

Yes, they are rated in milliwatt hours not milliamps. However, my digital camera loves them since they are much closer in voltage to the 1.5v of alkalines, my portable ham radio loves them (uses 6 to get over 10 volts), my GPS loves them due to higher 1.6 volt vs. 1.2 of NiMh.

Almost all of my Nimh cells are in various states of degradation, won't charge, won't hold a charge for long etc. Nimh cells are terrible for self discharge and internal self-shorting. With the NiZn cells in it, my ham radio has been sitting for over a month and the display still says 10.6 volts.

I just order 8 more of these. You will love them too.

Since I bought the 8-pack in Nov 2011, 3 of the cells will not hold a charge. Likely additional cells are defective and will die shortly.

PowerGenix Customer Service: 858-652-3228 immediately goes to voicemail, and they do not call back. PowerGenix email powergenix@antennagroup.com does not respond. I have for 6 months been trying to reach a live human...good luck!

There was a news item in late 2010 that indicated PowerGenix terminated their consumer product line (AA NiZn cells), and was focusing on automobile NiZn batteries in the OEM market.

Expect early failures with the PowerGenix cells. Others have reported similar failures. Don't rely on PowerGenix cells in critical situations...such as GPS receiver in backcountry.

I own an expanding collection of Sanyo Eneloop batteries that serves most of my power needs. They work great for almost everything of at least moderate sophistication, and have a slow discharge rate for a rechargeable. However, they don't always excel in very basic children's toys with lights and motors that are sensitive to the lower 1.2V nominal voltage of NiMH. For those I have found an advantage in using the 1.6V Powergenix cells. The extra voltage boost makes them run a bit livelier and longer than NiMH. In one case I had a 6 AA bubble blower that wouldn't operate for more than a few minutes on NiMH -- the fan motor would slow until eventually it couldn't even blow a bubble. The Powergenix cells allow it to run strong for as long as needed.

The new cells do come with some downsides though. First, only the Powergenix charger can charge them, and it isn't very sophisticated in comparison to the best NiMH chargers from LaCrosse and Maha. No voltage readouts, refresh mode, or charge rate controls. This is a little frustrating at times as I've had a couple cells begin to fail within the 6 months since I bought them. The provided charger says that they're charged, but I have seen evidence of otherwise when hooking up my multimeter. I even had one cell that reversed polarity. The self-discharge on the NiZn cells also seems to be faster than good NiMH ones, so they're not so good for things that sit on the shelf for a while.

I have been using these NiZn batteries for nearly a year. As an EE, I was intrigued by the higher open-cell voltage.

Indeed, this higher voltage allows for better performance in applications where battery voltage has a significant impact; e.g. Digital Cameras, electric razors, electric toothbrush, flashlights, fans, etc.

The only drawback is that you MUST use a charger designed for these batteries. The higher voltage and charging characteristics require special circuits.

Be aware also that their mAh rating may not last as long as NiMh cells with the same rating, as the higher voltage means they deliver higher current as well (depending on your application). However, with many digital cameras shutting down at about 1.15V, these batteries will outlast NiMh due to the higher 1.4V knee as the batteries become depleted.

I have 12 of these AA cells; at this point they have performed as expected. I recently returned from a trip, using only one set of two AA cells in my digital camera. I never needed my spares.

There are basically two reasons for using this chemistry, environmentally friendly and higher voltage. An advantage to this chemistry compared to regular Ni-MH is that it has a low self-discharge rate. Reportedly, similar to the low self discharge Ni-MH batteries. The higher voltage may or may not be suitable for any particular device. I suggest that things with high current draw or that were designed for 1.5 V alkaline cells will like the higher voltage. Flashes (more on that later) and digital cameras are good candidates.

The down side is that NiZn do not have quite as much capacity as Ni-MH, even when the higher voltage is factored in. The other negative is that they have about half the rated life compared to Ni-MH, so expect to replace them sooner. This is mitigated by them being cheaper and environmentally friendly. Besides, 500 charge/use cycles is not bad at all.

I bought these to power my Vivitar 285HV & non-HV flashes. This was an experiment, but has gone well, so I intend to get a another set soon. The big bonus is not with capacity, but that the higher voltage kind of super charges the flashes. Essentially they almost cut the recharge time in half. Here are my findings, comparing NiZn against fresh, high capacity Ni-MH.

285 non-HV Full power
Ni-MH 6.5 sec
NiZn 3.5 sec

285HV
Ni-MH 7 sec
Ni-Zn 4 sec

These batteries would be great in my Apple Magic Mouse if they had dependable behavior. But some of the batteries seem to have much more internal resistance than others, and for the fifth time in six months, I've had to discard a battery. When my mouse loses its connection to the computer, one of the batteries will typically test at 1.6+ volts while the other has dropped to 1.2 volts. Of the two, it's always the same one with the low voltage, and after this happens two or three times I throw out the one with low voltage. I'm going back to non-rechargeable lithium AAs. They're expensive, but they last a long time and don't cause this hassle.

I've got eight of these, and was running a run-time test on a flashlight, and the usually flush rubber switch cover inflated. When I turned it off and checked for leakage (strangely, no explosion, no leakage) there was quite a bit of gas expelled (audibly).

Their claim of "high-energy density" is not even funny, and a downright falsehood. At 1,560 mAh they are about 53.9% of the top of the line NiMH rechargeable (2900 mAh). Fresh off the charger they measure about 1.9V+, so be careful what you put them in.

After this first run, one of the cells was 0V. I had to rejuvenate it manually to get some voltage on it so the charger would recognize it.

What I mean is, I use a clip lead, readily available at Radio Shack (an insulated wire with an alligator clip at each end). I clip one side on a large coin and use this for NEG. Then stack two cells in series (about 3V) in my hand with the other gator clip on the NEG of that stack. Set the questionable cell Neg down on the coin, and then touch the two POSITIVES together. All you are doing here is putting a battery of two series cells (about 3V) in parallel with the dead cell. Electrons are flowing into the dead cell.

For NiMh You may have to hold this position for a minute or so, but for this NiZn, the cell got warm after about 1 sec. I did three 1 sec. "bursts", then the charger recognized it.

Overall, I don't know where these will fit into my AA cell arsenal.