Overdischarge of NiZn Cells

[MarioJP]

First, and foremost. Wow great! post! you guys!:goodjob:.

Now to the cells. Total of 8 cells when they were new,and labeled to keep track of them.

Cells #1-4 was being used in my mobile charger
Cells #5-6 being used in my electric toothbrush (currently still active)
Cells #7-8 mysteriously degraded fast and got worst by venting spewing out the electrolyte, after that the voltage would stay around 0.30v does not matter if you try to charge them voltage would just sink back to 0.30v.

Have to say though At least the electrolyte on these cells are not messy compared to alkalines. Had alkalines leaked inside my multimeter, good thing I was able to catch it on time and no damage was done to the multimeter.

good thing cells #3,#4 came to rescue!!,and replaced cells #7,#8 so that now leaves me with 6 cells total. I managed to take the top off cell #8 and all I saw what looks like a roll compacted in the can,and it was dry. Did not take out the roll though, plus it was really nudge in there lol.

Now cell #4 I think its hanging to dear life now, as I am only getting capacity of 800mAh all of a sudden, and getting worst each time, while cells #1,#2,and #3 getting capacities 1200-1300 range.

No way I can't continue to use these cells in a series configuration now due to cell #4. I don't know what's really going on, but one thing for sure is cell #4 gets charged faster than the rest. Take it out the charger and voltage already 1.93v less than an hour, then let it sit there and voltage drops to 1.79v. This is just being lucky that it hit to 1.9v. Most of the time cell keeps getting charged until the cell gets burning hot,yet voltage stays around 1.79 using the multimeter.

Also thing I noticed. If you give these cells a break period between charges,they seem to charge better that way and reach their 1.9V mark much easier.

I am guessing heat=poor charging efficiency???

Lastly Cells #1-3 gets hot during charging/discharging but their capacities are holding.....yet lol.

In any case these cells reminds me of those high performance tires that Formula 1 uses. Great tires!! but boy! do they need replacing on every lap lol.

That is my experience so far with Ni-Zn cells.

Now that I thought about it. I don't think these cells are cheap in the long run. I tortured Nimh cells in the past. Does not degrade nowhere near compared to these cells. These cells are way too fragile.

One thing about the eneloops is after they have been completely drained to the point I can't turn on the device anymore. all 4 cells drains evenly. I don't think eneloops have to worry about ni-zn replacing them anytime soon.

 

[Battery Guy]

This is something that is never very clear no matter where you read about it. Are you suggesting that PowerGenix cells are at 0% SOC when their OC voltage is somewhere below 1.0-1.4 Volts, or their voltage under load is in that range?

So, 0%SOC for most batteries is going to be defined as the point where all of the capacity has been utilized. The voltage that this occurs at will be dependent on the load. If you look at the PG spec sheet that VidPro linked to above, the voltage at 0%SOC is ~1.4V for a 0.2C rate, and ~1.1V for a 3C rate. Going below that voltage is not considered "overdischarge". Overdischarge is defined as the going below the voltage where "bad stuff happens". In the case of NiZn cells, that "bad stuff" is the generation of hydrogen at the nickel electrode below approximately 0.4V. So there is a voltage window between 0%SOC and overdischarge. Think of it as your "grace period".

For example, I accidentally ran a single PG NiZn cell down to 0.9 Volts recently in an AA light. This was indicated by the lights own voltage checker. I didn't mean to go that far, but as has been mentioned, NiZn cells run down really fast near the end, and I'm sure it'll likely happen again. When I checked the cell voltage after removing the cell from the light, it was ~1.50 Volts. So, what I'm asking is, was this cell over discharged? I think not, but hey, these NiZn cells are new to me!

Nope, you should be fine. The cell ran to 0.9V under load, which is above the 0.4V point where I estimate overdischarge will start.

Curious to know what flashlight you have that comes with its own built in volt meter. Pretty cool!

Cheers,
Battery Guy

 

[Battery Guy]

Hi BG,

I read your interestin opening post with the calculation of the Nernst equation for Ni-Zn cells, you are correct.

Hi Anthony,

First, let me congratulate you for being the first person in the history of Candlepower Forums to use the term "Nernst equation" in a post! :thumbsup:

I'm higly sceptic that Ni-Zn rechargeable cells may find a widespread use, but not because the inner working of these cells is not understood or followed. The major problem of the Ni-Zn cells is the fact that they, indeed, contains Zinc.

And another :thumbsup: for Anthony!

Let me elaborate on this concept...[snip]

Excellent historical background snipped for efficiency, but everyone should go back and read it if they haven't already done so.

What is the problem with the zinc and the alkaline electrolyte? I dont' want to get in the explanation of the amphoteric behavior, which involves electronic affinities and other intricate theoretical mechanisms. The fact is that, over a long time stretch, the behavior of the zinc becomes unforeseeable.
This unforeseeability becomes compounded in nichel-zinc batteries, mainly because of two factors: the presence of impurities, and the rechargeability, which amplify the negative effects produced from those impurities.

One thing that is slightly different with a NiZn compared to a standard alkaline zinc-MnO2 cell is that the NiOOH electrode is a great scavenger of hydrogen. So if the cell is kept at a reasonable state-of-charge, hydrogen generated by the corrosion of zinc will rapidly recombine with the NiOOH, thereby preventing a build-up of pressure. In an alkaline zinc-MnO2 cell, the rate of hydrogen recombination on the MnO2 electrode is very slow, and usually cannot keep up with the corrosion of the zinc.

This said, I personally don't see the Ni-Zn consumer cells to gain a significative share of the market, unless the manufacturers don't find a way to fix the problems which are just coming to surface now. With the established Eneloops technology, I see it as a bit of a problem.

I have to say that I love the performance of the NiZn cells right out of the box. I personally have not had a problem with the original 12 I bought, but I have only been using them intermittently for a couple of months, so my personal experience probably does not mean much.

I wish that I could be optimistic about this technology, and that other manufacturers will see the potential (pun intended) of NiZn and jump into the market with their own designs and innovations, thus driving continuous improvement in the reliability of the products. Realistically though, I suspect that this is one technology that is going to die on the vine, at least with respect to consumer applications.

Keep those PowerGenix AA cells around though. They might be collectors items some day like the rechargeable lithium/TiS2 cells of the '80s, or the magnesium/MnO2 cells of the 70s.

Cheers,
Battery Guy

 

[MarioJP]

Are you saying that these cells won't be around much???

 

[45/70]

Nope, you should be fine. The cell ran to 0.9V under load, which is above the 0.4V point where I estimate overdischarge will start.

Ya OK, I follow you alright, I didn' think so. Thanks for the clarification. It's just that a lot of times when this discussion comes up about various chemistry cells, it isn't clear whether the voltages mentioned are OC, or when the cells are under load.

Curious to know what flashlight you have that comes with its own built in volt meter. Pretty cool!

It's one of the first LiteFlux LF5XT's. They aren't in production any more, I guess, but the LF5 series has been revived once, anyway. The original LF5 was a twisty, which I really wanted, but they are rare as hen's teeth. Most of their offerings have had the voltage readout, and I believe they still offer versions of the LF2xx and LF3xx, which have the same basic UI. I've always considered the LiteFlux line to be a couple notches above the rest of the low end lights available.

As for the rest of the discussion, I agree. From what I have read over the last year or so about the NiZn chemistry, it's time isn't really here yet. For example, while PowerGenix gives some really optimistic claims as to the number of cycles that are obtainable with their version, most other sources say 150 cycles is about max. I would imagine this would not include any form of abuse, such as over discharging either.

As I said in another post some time ago, my interest is strictly using them in voltage sensitive devices as an alternative to lithium primary AA cells. So far they seem to work out fine. Anthony's and your mention of the possibility of them leaking, has me worried now, however. Well, at least I have 8 of them to experiment with, anyway. If I do decide to go ahead and use them in the voltage sensitive devices that I originally planned on using them, hopefully they won't leak any worse than alkaline cells. Then again, that's why I have been using lithium's, to avoid leaking cells. :sigh:

Dave

 

[Battery Guy]

Are you saying that these cells won't be around much???

I have no inside information regarding the health of PowerGenix or their business plans.

I see two problems with the PowerGenix cells. First, I am hard pressed to find a consumer application where the PowerGenix cells will outperform an Eneloop and/or a lithium AA. For example, these cells cannot beat an Eneloop in discharge energy unless you discharge them at 4W or higher per cell. There are not many consumer applications that demand this kind of power. Second, assuming the reports from people on this forum are representative, they have some serious reliability issues.

So, unless PowerGenix can improve performance and increase reliability, I just don't see a big market for them. These cells have fantastic power capability, far more than what is needed for most consumer applications. If I were PowerGenix, I would sacrifice some power for extra energy.

That being said, I love the cells because they let me get 12-14V in a 2D mag without using lithium-ion, and I still get the advantage of having a cell with a relatively low self discharge rate.

Also, never listen to me when it comes to business advice. I am terrible at predicting which companies will fail and which will succeed. :shrug:

Cheers,
Battery Guy

 

[VidPro]

In the Idea of them replacing Lithium (throwaways), with a rechargable for the purpose of higher voltages, how many uses/cycles would it have to get to make it cost efficent even if a user discontinues them in 20 cycles (or how many cycles?)
plus unlike any primary (always) any rechargable can be topped off, so you can leave the house with no spare and a FULL charge (albiet less actual power).
when replacing a lithium primary that will not recharge at all, even if it doesnt last time , can it still beat using lithium primary?
what are its temperature capabilities ? will it work well below cold temps of ni-mh? Does it cope well with high temps?

would everyone say they can get at least 10 good cycles out of them?
can everyone buy them for less than the cost of 2 lithium primaries?

so we would be throwing these away, but to walk out with the same power at the higher voltages potentially we still throw something away

 

[45/70]

Vid, I don't know if you aimed that at me, or not, but I figure if I can get the equivalent of 2-3 full cycles out of the NiZn cells, I'll break even, as compared to lithium cells. I didn't buy a charger, but am using a bench PS, so that offsets the cost quite a bit.

In addition, since the NiZn cells can be "topped off" and basically matched up after charging, they can be used in other devices, when needed. As I said, these NiZn's I have are just an experiment to see if they can be a more versatile alternative for voltage sensitive devices, than L91's.

Dave

 

[Battery Guy]

In the Idea of them replacing Lithium (throwaways), with a rechargable for the purpose of higher voltages, how many uses/cycles would it have to get to make it cost efficent even if a user discontinues them in 20 cycles (or how many cycles?)

The PowerGenix cells cost about the same as the lithium AA (~$2.50 per cell), and they have about 60% of the total energy (2.5Wh versus 4.2Wh). So you would only need to get two cycles out of the PowerGenix to make it cost effective (assuming you already invested in the charger).

plus unlike any primary (always) any rechargable can be topped off, so you can leave the house with no spare and a FULL charge (albiet less actual power).
when replacing a lithium primary that will not recharge at all, even if it doesnt last time , can it still beat using lithium primary?
what are its temperature capabilities ? will it work well below cold temps of ni-mh? Does it cope well with high temps?

The PowerGenix cells should actually outperform the Energizer Advanced Lithium and Ultimate Lithium at discharge powers greater than 1W and 2.5W, respectively. Below that, the lithiums will deliver more energy.

Don't know about the temperature capabilities of NiZn AA cells. I would not think that they are as good as the lithium primary. Probably very similar to NiMH. Certainly the lithium primary would win out in applications where weight is an issue, or in applications like your car where the battery will be exposed to and may be required to work in temperature extremes. And of course, the NiZn cells will self discharge. The published rate is 8% per month, which isn't too bad if you are using the cells relatively frequently. Definitely not great for that emergency flashlight that sits unused for months or years at a time.

would everyone say they can get at least 10 good cycles out of them?
can everyone buy them for less than the cost of 2 lithium primaries?

I would say yes to both.

so we would be throwing these away, but to walk out with the same power at the higher voltages potentially we still throw something away

You make good points about replacing AA lithiums with NiZn in many applications. But I would ask why not replace the AA lithiums with Eneloops? Another way to ask the question is how many consumer applications would the PowerGenix be better than Eneloops? My guess is not very many.

In my mind, it is more of a "PowerGenix vs Eneloop" question than a "PowerGenix vs Lithium AA" question.

Like I said before, for my 2D mag mod I love the fact that I can get 12-14V using the PowerGenix cells without having to use lithium-ion cells. So this is definitely one application where the PowerGenix come out on top, at least for me. But I don't think that very many consumer applications exist where this would be the case.

Cheers,
Battery Guy

 

[VidPro]

i already have enloops, i would use this battery type to replace anything i thought i wanted higher voltage, ONLY, because of the enloops indeed working better in most stuff.
i have only ever envisioned it for a lithium throwaway replacement, untill they start making big improvments. A fat Zinc Air primary would be cool in standard sizes too

just like 45/70 there is some stuff that the extra voltage is SOOO usefull.
A) lights with loose drivers that punch up a bit with more voltage.
B) Motor driven things that drive faster just enough with a bit more punch.
C) how about linear regulator stuff where a tiny bit higher voltage stays in regulation better?
D) just general stuff where I the user feels they need more voltage to get the power i want to the device better
E) cell phone chargers that really wanted higher voltage to work fully, both one cell (that i have) and 2 cell that others have discussed.
F) cameras that show low battery to early with ni-my

and finnaly the lithium primary by energyser has a PCT thing that kicks in somewhere above 2amps, so really it CANT do some thing where your trying to get more amps going, and it can blow-up when the pct warms the cell item (in containment).
best rechargeable replacements for lithium throwaways.

 

[core]

You make good points about replacing AA lithiums with NiZn in many applications. But I would ask why not replace the AA lithiums with Eneloops? Another way to ask the question is how many consumer applications would the PowerGenix be better than Eneloops? My guess is not very many.

In my mind, it is more of a "PowerGenix vs Eneloop" question than a "PowerGenix vs Lithium AA" question.

I never understood this "PowerGenix vs Eneloop" comparison. If Eneloops work for your device, then sheesh just use them and quit trying to make up arbitrary silly contests between an apple and an orange and whining when the apple loses.

The point is NiMH cells don't always work properly, especially in older devices. I dunno, maybe all of you replace all your electronics every 2 years. I tend to run things until they die. My digital camera does 1024x768 (wow, that was a lot of pixels back in the day!) and it will not operate worth a darn with NiMH. My brand new 6ch hobby radio will also warn me of low voltage after practically no use. I could go on and on and on with real examples that I own.

You will say, "But... but... that means your devices aren't draining your alkalines down to the last drop! They are faulty!!" Umm ok. I'll agree that they don't drain the cells down to the last drop, but whether that means the designers committed some great sin in requiring a minimum cell voltage in order to be able to use 4 cells rather than 5 (!?) is debatable.

And this may come as a shock to some of you here, but not everybody has a regulated light. Hell there are also these things called incandescent bulbs.

As I see it, comparing a AA LSD NiMH to a AA NiZN is about as valid as comparing it to a LiIon 14500. Unless you are designing your own device or hacking an existing one, it is a meaningless comparison, and hardly falls within the bounds of "consumer application".

 

[Battery Guy]

A fat Zinc Air primary would be cool in standard sizes too

You mean like this?

But before you get your hopes up, you should know that I have never actual seen one of these batteries. Also, this website has not been updated since I discovered it two years ago. I did see a product brochure for these once, and I seem to recall that they had about 3x capacity of a standard alkaline, but only at very low discharge rates.

just like 45/70 there is some stuff that the extra voltage is SOOO usefull.

...long list of useful applications snipped...

Fair enough. I think that PowerGenix needs to hire you to lead their marketing department.

Cheers,
Battery Guy

 

[Battery Guy]

A fat Zinc Air primary would be cool in standard sizes too

More on those Aeternus zinc-air batteries that are seemingly unattainable can be found here.

Cheers,
Battery Guy

 

[MorePower]

You mean like this?

But before you get your hopes up, you should know that I have never actual seen one of these batteries. Also, this website has not been updated since I discovered it two years ago. I did see a product brochure for these once, and I seem to recall that they had about 3x capacity of a standard alkaline, but only at very low discharge rates.



...long list of useful applications snipped...

Fair enough. I think that PowerGenix needs to hire you to lead their marketing department.

Cheers,
Battery Guy

We made battery packs from AA sized cylindrical zinc air cells for the Land Warrior program a number of years ago. Unless you get a fair number of cells in a pack with series / parallel construction, they just aren't very usable at high discharge rates.

Also, there's the fact that your device would need a bunch of big holes in it for the cells to get the air they need to work properly...

 

[VidPro]

More on those Aeternus zinc-air batteries that are seemingly unattainable can be found here.

Cheers,
Battery Guy

thanks, i figured they would not have high output, but mabey it would beat stacking a rack of the small ones.
there is an app(lication) for that , mabey i can sell them on Nitch marketing

 

[Battery Guy]

I never understood this "PowerGenix vs Eneloop" comparison. If Eneloops work for your device, then sheesh just use them and quit trying to make up arbitrary silly contests between an apple and an orange and whining when the apple loses.

I didn't think I was whining. I thought we had finally honed in on a useful discussion.

The point is NiMH cells don't always work properly, especially in older devices. I dunno, maybe all of you replace all your electronics every 2 years. I tend to run things until they die. My digital camera does 1024x768 (wow, that was a lot of pixels back in the day!) and it will not operate worth a darn with NiMH. My brand new 6ch hobby radio will also warn me of low voltage after practically no use. I could go on and on and on with real examples that I own.

The discussion in this thread somehow turned towards the topic of whether or not there is a real market for NiZn AA cells. I didn't think that there were many applications where the PowerGenix cells would be advantageous, but VidPro offered several that I had not considered.

If you have applications for NiZn, then great! I want this technology to succeed and be improved upon. I just fear that in its present form, there is not going to be sufficient market to keep a company afloat. Hopefully I am wrong.

The discussion was not "which is better, Eneloop or PowerGenix". Eneloop and NiMH are established chemistries. For a new battery chemistry to get a foothold in the market, it needs to have clear, obvious advantages over the established competition. Or the company needs to have a fantastic marketing machine behind it. I just don't think PowerGenix has either of these. Like I said, I hope I am wrong.

You will say, "But... but... that means your devices aren't draining your alkalines down to the last drop! They are faulty!!"

Nope, I will not say that.

Umm ok. I'll agree that they don't drain the cells down to the last drop, but whether that means the designers committed some great sin in requiring a minimum cell voltage in order to be able to use 4 cells rather than 5 (!?) is debatable.

And this may come as a shock to some of you here, but not everybody has a regulated light. Hell there are also these things called incandescent bulbs.

My mods are mostly incans, and I love my Mag 2D mods that use 7 NiZn cells in series with a 1185 bulb.

Cheers,
Battery Guy

 

[core]

For a new battery chemistry to get a foothold in the market, it needs to have clear, obvious advantages over the established competition.

I think "Hey, my device works properly with these, I can finally use rechargeables with it!" is a pretty clear obvious advantage. Are there enough of these devices out there to keep a company afloat? Maybe not. If you browse the reviews on Amazon you can find a nice sampling of people who were overjoyed that their cameras were working.

These favorable reviews were likely written by folks who hadn't owned them for any length of time though.

And you're definitely right about them not having a marketing machine behind it -- when I have to find out about something like that through a relatively unnoticed thread a forum, that says something.

I fear you may be right about them not staying in the market for long. Which is really too bad, because I need these. Badly enough to pay $20 every other month replacing destroyed cells.

And I didn't mean to say that you personally were whining. But there isn't hardly a NiZn thread created without somebody making a direct comparison with Eneloops, whether it be self-discharge rate or capacity or current, and saying something like "seems I should stick with Eneloops".

That's missing the point. As printed in a big bold font right on the PowerGenix cell, the whole deal is HIGH VOLTAGE. Everything else is secondary, the good and the bad. Lithium primaries would be great too... if they weren't primaries.

There should be a "Godwin's Rule of NiZn Cells".

 

[Battery Guy]

I fear you may be right about them not staying in the market for long. Which is really too bad, because I need these. Badly enough to pay $20 every other month replacing destroyed cells.

Core,

So I am curious. It sounds like you use the PowerGenix cells a lot, and replace them relatively frequently (every other month). Any comments on what you see as the biggest reliability issue? Do you think that it is simply inherent to the design/chemistry, manufacturing quality problems, the device usage profile, etc....

Another question: do you have any "old" PG cells that have been used in a similar way, but still operate fine? If so, this might indicate that the design and chemistry is good, but the manufacturing process needs to be improved.

Oh, and with respect for your need for these cells, you might want to consider buying them in larger numbers and more frequently, and storing your extras in the fridge. I know that it might sound goofy or old fashioned, but the fact of the matter is that chemical reactions occur slower at lower temperature, and this includes the side reactions that cause performance degradation.

Just don't freeze them. You run the possibility of damaging the seal and the vent.

Cheers,
Battery Guy

Cheers,
Battery Guy

 

[VidPro]

BG if the original problem with the zinc and the electrolytes exists still, would they fall apart over time even without use?
i dont (ever) totally understand the interactions destroying the plates or the electrolytes getting contaminated with the metals , but if that problem had not been totally solved (whatever it was) would the problem exist in an unused cell?
that the internals would degrade over time?

or was most of the problem returning of the metals back? and the cycles are the biggest issue of the original problem.
hard pulse charging i'd get them suckers running back quick enough.
i would try a staccato pulse charge on the thing, 10%on 90%off 10ms 5+C or higher CV charging, and see what that could accomplish. (slam it hard but dont overheat) but i would have to know the max amps through the connections before damage occured. And it would have to be done on every charge not when it is too late.

could you speculate on a "storage" voltage ?? high low or medium?
like they say charge every month?, and the more charged the less stuff in the electrolytes or something?

 

[MarioJP]

Well Its now official, cell #4 has lost all it's capacity by just sitting there for 2 days. When I took the measurement, voltage idles at 1.28v.

Furthermore,I did a short and the current went from 3A to 500mA less than 10 second. Cell #4 really took a beating I don't know if this was caused by a polarity reversal during use or something.

All I can say is cell #4 has been declared end of its life. However I did decided to go ahead and completely drain this cell down to 0V and see if any improvements would happen. Won't find out until couple hours from now.