Powergenix NiZn Poor Performance

About 2 months ago I purchased 12 Powergenix NiZn batteries as a result of many reviews both here and on other internet sites. Used them in my wife's reading light which she uses on a regular basis. After this short period of time, about half of them will no longer hold a charge. I just took 4 of them out of her light tonite which had been used about 1 hour or maybe even less, and 2 of the cells measured 1.5V and 2 measured .3V. The weak cells will charge, but loose their capacity almost immediately.
Has anyone else seen this poor durability?

I don't use NiZn batteries, but I've read here on the forums that they are very fragile and die if reverse charged, and it looks like the two strong cells in your 4 cell setup have reverse charged the 2 weak ones..

It's possible that they would last better if recharged at first sign of dimming or diminished light output from the reading light instead of running it down all the way.

One thing about NiZn is they are not a general replacement for alkaline batteries. Their use should be carefully judged for those applications where the high voltage is really needed.

For almost all everyday applications of rechargeable batteries an NiMH battery like the Eneloop is best.

Mr Happy said:

One thing about NiZn is they are not a general replacement for alkaline batteries. Their use should be carefully judged for those applications where the high voltage is really needed.

For almost all everyday applications of rechargeable batteries an NiMH battery like the Eneloop is best.

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I have used them in only in incan lighting applications. In my wife's reading light as mentioned earlier, and in a Mini-mag. Where should they be used? Duraloops yield a much weaker light in these applications.

sterr11 said:

I have used them in only in incan lighting applications. In my wife's reading light as mentioned earlier, and in a Mini-mag. Where should they be used? Duraloops yield a much weaker light in these applications.

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Well, it seems you have a handle on this. The usual recommendation for the NiZn is in certain brands of digital camera that refuse to work properly with NiMH. If you put the higher voltage NiZn in incan lights I suspect you will be shortening the bulb life. When you put regular NiMH in a Mini-mag, for example, the bulb is as bright as it is "supposed" to be, IMHO.

As to the durability problems, several others here have made the same observation. One thing that may help is to check the usage pattern. The golden rule with rechargeable batteries in multi-cell devices, and with NiZn especially, is never fully discharge the battery. As soon as there is the slightest hint of the bulb losing brightness it is time to recharge. If you let the bulb start to go yellow you are running into the danger zone where one or more of the batteries can be damaged.

sterr11,

Mr Happy said:

......The golden rule with rechargeable batteries in multi-cell devices, and with NiZn especially, is never fully discharge the battery. As soon as there is the slightest hint of the bulb losing brightness it is time to recharge. If you let the bulb start to go yellow you are running into the danger zone where one or more of the batteries can be damaged.

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What Mr H says here is especially true with NiZn cells. Actually, from what I've seen personally, and what others here have observed, you really need to stop the discharge of NiZn cells well before an incan light starts to go dim. The drop off in voltage is so quick with these cells when they run down, that it would be nearly impossible to catch it in time to not have damaged one, or more cells. And, as already mentioned, they are damaged really easily.

My 3 cents. (adjusted for inflation)

Dave

A different kind of recommendation, but for the reading light I'd suggest trying to find an LED light that takes a single AA cell. In that instance a Duraloop can be left to run completely empty with no harm at all.

Mr Happy said:

A different kind of recommendation, but for the reading light I'd suggest trying to find an LED light that takes a single AA cell. In that instance a Duraloop can be left to run completely empty with no harm at all.

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I thought the jury was still out? I know it was looking that way, but I'm not sure that's true. I can't see how "stretching" the cells internal components by over discharging the cell frequently, wouldn't cause more wear, LSD or not. LSD cells may be more resilient, but it still doesn't sound like a good idea.

Dave

45/70 said:

I thought the jury was still out? I know it was looking that way, but I'm not sure that's true. I can't see how "stretching" the cells internal components by over discharging the cell frequently, wouldn't cause more wear, LSD or not. LSD cells may be more resilient, but it still doesn't sound like a good idea.

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That's a fair point, but in this case I think it is OK. The boost driver in a single cell LED light will stop working long before the voltage gets down to zero (perhaps at 0.6 V or higher). This is not something I believe is going to present any problem to the battery, certainly not compared to the problems evident with the NiZn cells.

One of the reasons I like NiMh, in conjunction with a charger that gives me a ballpark figure of how much charge had to be put back into a used cell, is that I can easily judge a regular charging pattern that will prevent any likely over-discharge issues.

I have a set of devices that I swap charged cells into on a weekly basis, and others on a monthly basis. A couple I change immediately after use. I don't like cells to get down to much more than half used, especially in items that don't have a voltage cut-off.

As delicate as I'm reading these NiZn cells are about over discharge, I would be making some kind of effort to find a charging routine that is safe for them. I don't have any idea if there's a NiZn charger that gives you any feedback, however. You would probably just have to guess based upon the amount of time the charge took.

At least with a single cell device, there is no risk of reverse charging occurring so I would think the risk of over discharging NiMH cells is greatly reduced, even if one runs them down all the way.

Btw, a very nice single AA cell light with a perfect floody beam for reading that performs great on Eneloops is the Zebralight H501w.

Probably one reason the Nizn are more easy to reverse and damage are due to the higher voltage range it runs at. Being considered discharged at 1.3v with a full voltage over 1.8v, users may still see high brightness when one or more are totally dead and reversed. And they are more likely to be in the reversed state a much longer amount of time because the other cells are able to make up the voltage difference and maintain brightness in a light.

If you prevent them from dropping below 1.3v at any time, they should last much longer. How long, who knows. I haven't put enough cycles on mine to really tell you.

bcwang said:

If you prevent them from dropping below 1.3v at any time, they should last much longer. How long, who knows. I haven't put enough cycles on mine to really tell you.

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Good points, bc. It seems that NiZn cells definitely are prone to damage when over discharged. The question is still somewhat of a mystery with LSD NiMH cells, as I pointed out previously. I agree with Mr H however, that the over discharging problem will be less significant using LSD NiMH cells, as opposed to NiZn cells.

Dave

ive had a set of 4 for a while and they probably have about
15-20 cycles on them after being used in a 4AA headlamp.
Ive been pretty good about not running them down super
low... no problems here but Ill have to get out the DMM and
see what each one says.
Ive got a new HL (H51) so they'll be used one at a time from now
on.
I like that they have a little more kick than an alky or eneloop.
Im more into max lumens than runtime since I have 4 of these
I can bring 3 spares if necessary :devil:

good to know they're a bit prissy with the over discharge- Ill
keep it in mind tho honestly Im not too worried about it.
thanks for the report!

Mr Happy said:

A different kind of recommendation, but for the reading light I'd suggest trying to find an LED light that takes a single AA cell. In that instance a Duraloop can be left to run completely empty with no harm at all.

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Good point. Now that you mention it, my move toward 1xAA lights, following as it did my embrace of NiZn AAs, is probably no coincidence. I've had bad luck charging more than 1 NiZn cell at a time.

But don't try to use NiZn in a Shiningbeam RC-29 II. The NiZn's resistance is so low that the RC-29 II draws upward of 4 amps, making the body blazing hot. I suspect that similar excessive amperage is what caused my ShiningBeam RC-G2 II's clicky tailcap to fail in the first hour. (But Bryan quickly replaced it for free.)

Paul_in_Maryland said:

But don't try to use NiZn in a Shiningbeam RC-29 II.

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Isn't that more a driver/cell voltage issue than a straight internal resistance issue?

If the driver was both current-regulated for output, and roughly constant efficiency at different input voltages, it should take less current from NiZn than from NiMH.

Shiningbeam RC-29 II
http://www.shiningbeam.com/servlet/the-180/**NEW**-Romisen-RC-dsh-29-II/Detail
RC-G2 II
http://www.cpfmarketplace.com/mp/showthread.php?t=195708&highlight=romisen

weird, they are high potency lights for a single AA, and the driver item seems to be one of the looser styles, going up and down more with the voltage. which sometimes can be better than torturing a battery when it is mostly dead, and mght be a bit higher in efficency too, if its just a simple power Pump

Kilgor
The driver does NOT appear to be regulated (i.e it gets dimmer and dimmer as the battery runs down, rather than maintaining a steady brightness level until the battery is fully drained).

gsin123
I got 2.8 Amps with primaries and 1.2Amps with rechargeables

uk_caver said:

Isn't that more a driver/cell voltage issue than a straight internal resistance issue?

If the driver was both current-regulated for output, and roughly constant efficiency at different input voltages, it should take less current from NiZn than from NiMH.

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I can't speak to how or why the RC-29 II doesn't like NiZn. But my findings are confirmed by another CPFer, who posted current drawn from several kinds of cell. Sorry, I can't recall the thread, the forum, or the CPFer; I think it was Buffalo Bill; it's someone who frequently posts lumens vs current charts, including one or more in the thread on the Malkoff M31.

I now use an Eveready L91 lithium cell in my RC-29 II and my RC-G2 II. It lasts at least twice as long as the NiZn and doesn't make the lights hot.

Paul_in_Maryland said:

I now use an Eveready L91 lithium cell in my RC-29 II and my RC-G2 II. It lasts at least twice as long as the NiZn and doesn't make the lights hot.

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does it make the battery hot on the top? because some lithium AAs have PCT that kicks in at ~2amps, effectivly giving you current max control at the battery, which can heat up the battery.
i donno , but from reading other stuff, i would want to check more of what happens using bench supply , before the rare chance that it goes BONK!

if a PCT was kicking in the light would be a tiny bit brighter when you first turned it on, surging for very short time.
when you pull the battery quickly after having used it for a long time, it could be slighly warmer or even hot on the top
any strobe modes could be brighter than normal modes
the light operates differently in different actual temperatures
stuff like that might be spotted without meters bench supplys and loads and all??

and yes i AM talking about the PCT on a Primary lithium AA cell.

When I first started testing the PowerGenix NiZn cells, I fell in love with them. Their ability to deliver power is only surpassed by the Elite 1700 NiMH AA cells. And their high voltage opens up the possibility of some interesting flashlight mods. For example, seven of these AA cells will power an FM1909 bulb in a 2D Mag, making a very impressive little light.

However, after performing a lot more tests on these cells I have found them to be too unreliable for use in a flashlight. I have had several cells leak in controlled testing where they were definitely not over discharged or mistreated in any way. I have also had cells simply die by what appears to be internal short circuits.

It is also a PITA that they cannot be charged in series like NiMH, and that they can only be charged with the PowerGenix charger (although you can charge them with a CC/CV powersupply).

Unfortunately, I have a ton of these things since I found a very good deal on 8 packs shortly after I started testing them. I am still using them around the house in various electronics, but I won't be designing any flashlight mods that use these cells.

I sincerely hope that the reliability problems can be fixed by PowerGenix. I don't know how expect to use these in EVs and PHEVs given the current reliability issues.

Cheers,
BG