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Customer Review

47 of 48 people found the following review helpful
1.0 out of 5 stars Unacceptable failure rate, February 5, 2010
Verified Purchase(What's this?)
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
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Showing 1-10 of 11 posts in this discussion
Initial post: Mar 11, 2010, 5:49:19 AM PST
Last edited by the author on Mar 11, 2010, 5:50:14 AM PST
The PowerGenix '5-hour' charger is a very poor design because it charges in pairs only. Based on what I heard, NiZn cells are less forgiving when overcharged compared to NiMH cells. You should use the PowerGenix '1-hour' charger. It charges individually, and is faster (but it is actually a '2.5-hour' charger).
PowerGenix ZR-PGX1HRAA-4B 1 Hour Quick Charger with 4 AA 1.6v NiZn Rechargeable Batteries

In reply to an earlier post on Mar 12, 2010, 5:50:06 AM PST
Gregory King says:
That is the charger I have, but it still doesn't work well. Apparently, it DOES charge individually, but it still won't charge overdischarged cells. It's very hard to tell when a cell is charging...apparently you have to count the blinks of the red light or something. Often times, I pull batteries out of the "complete" charge cycle and they are still dead. I have to jumpstart the cells in another charger.

And even with four full cells I can't use them completely, because inevitably one will overdischarge before the rest. The higher voltage causes the device electronics to think there is still battery capacity even when there isn't, so they keep going until one cell is completely dead.

In reply to an earlier post on Mar 15, 2010, 12:13:23 PM PDT
The PowerGenix '1-hour' charger trys to reject NiMH cell if you insert one accidentally. My guess is that when you first insert a cell, the charger injects a small current and monitors the cell's terminal voltage. If it is lower than 1.5V (for example), the charger thinks this is a NiMH cell and stops charging. So that's why it may have mistaken your completely exhausted NiZn cell for a NiMH cell.

If you have a voltmeter, measure the terminal voltage of each NiZn cell and make sure that it is above 1.0V before charging. If it is too low, use a dumb NiMH charger to charge it for a few minutes (watch for signs of over-heating if the charing current is high). Then re-check the terminal voltage.

In reply to an earlier post on Mar 15, 2010, 1:07:01 PM PDT
Gregory King says:
Exactly my trick. I have a cheap USB charger that provides good feedback of the charging current. It will charge the cells for 20-30 seconds before it gives up. But that's enough to trick the PG charger into charging the cells.

Unfortunately, after less than a day sitting unused, the failing cells are empty again. Talk about rapid self-discharge. I isolated it down to 3 or 4 of the 8 cells I LEAST. It may be worse. I have an RMA from Powergenix to replace the cells, so I'm going to make sure the ones I keep are all viable. These cells were bought in November and I started noticing anomalous behavior almost immediately.

Frankly, I would be surprised anyone gets a year of use out of these things.

If you want a good laugh, read their testomonials.

The first guy got 25 WHOLE PHOTOS out of a set without them dying. How few photos did he normally get? Fewer than a roll of film, apparently. ;-)

In reply to an earlier post on Mar 16, 2010, 7:55:56 AM PDT
Last edited by the author on Mar 16, 2010, 8:00:31 AM PDT
NiZn cells are recharged in a 2-stage process, just like that for Lithium-ion cells. It is known that Li-ion cell can be easily damaged when over-charged (over 4.2V), or over-discharged (under 3.0V). So I suspect that NiZn may be susceptible to the same problem.

NiMH cells are more robust in this aspect. I have some 3-year-old Sanyo eneloop and Rayovac Hybrid cells that have been discharged to 0.00V many times. Yet they still recharge to like-new conditions.

In reply to an earlier post on Jun 7, 2010, 7:07:12 PM PDT
Gregory King says:
Apparently they are. Powergenix replaced a set, bringing me back up to eight. Four (two new, two old) have failed already, after 2-3 months.

Basically, they are similar to those alkaline batteries that you used to be able to get that could be recharged 10 or so times. At $1-2 a pop, these may cost a bit less than alkalines, but not much. I am considering going back to alkalines for my Rat Zapper.

Posted on Aug 21, 2010, 10:13:28 AM PDT
Robert Ramey says:
Have to agree with this post.

These batteries have caused me nothing but grief. From the comments here it seems it might be possible to "convince them to work" but who's got time for that.

The 2500 mWATTH is sort of tip-off that the company is in the habit of over-hyping. That is, intentionally mis-leading customers to cover up for the fact that the product doesn't work as advertised.

Posted on Dec 24, 2010, 1:56:14 PM PST
Check out this article:

According to the analysis, out-gassing occur when NiZn cell is over-discharged (terminal voltage drops below 0.42V). This is very likely to happen whenever you use two or more NiZn cells in series. In contrast, over-discharge of NiMH requires its terminal voltage to be negative (below -0.1V), so it is less likely to happen.

Posted on Oct 19, 2011, 10:26:55 AM PDT
I got an e-mail from PowerGenix admitting that there are known issues with their v1 batteries. Fortunately, they're willing to give you a gift certificate them under their one year warranty so write to them at if that applies to you. Unfortunately, their v2 batteries aren't ready so it's hard to say when you'll be able to cash in that certificate.

BTW, I concur with the charger design flaw. Round-robining batteries in pairs to determine which one if bad is a poor user experience.

In reply to an earlier post on Oct 19, 2011, 6:26:56 PM PDT
Gregory King says:
Ken, thanks for the input.
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