Eneloop Cells Lifespan Analyssis

[scott1981]

Much has been said about Eneloops 1000 cycles, and so much has already been said about its capacity retention.

In this sense, if Eneloops are not that used you can count on them not loosing charge (under certain conditions), but there is a question:

If they can hold charge for so long and someone used them once or twice a year and then topped them off until next use, it seems as if they would last for MANY years, right? However the question that arises is: Isn't there a natural degradation of the battery or its internal components even if it is used under the best conditions, or as in my example, used very little or not used at all? (the "very little use" scenario could be the case of a TV remote or a single cell operated clock, now that Sanyo says these cells could replace alkalines in such low drain devices. I don't think that if you used them in such appliances, they could actually replace 1000 alkalines each. I really wish it was like that, however Should we be considering other variables like natural degradation non related to charge-discharge cycles which in cases like these may be the first cause of battery end of life?

This would be a good way to eventually predict the Eneloop cell's lifespan on something else but number of cycles. Li-Ion cells suffer from this, and they being to degrade whether you use them or not after 2 or 3 years.

 

[SilverFox]

Hello Scott1981,

Good question...

Li-Ion chemistry has changed a little, and now it seems that the life span is more like 5 - 7 years. NiMh chemistry is more stable, if that counts for anything.

By slowing down the chemical process, they may have also slowed down the degradation process. I think the greatest degradation occurs during self discharge during storage. So far, cells that are 3 years old perform as well as new cells, so we have a little data to go on.

Tom

 

[Curious_character]

Some time back I had three pairs of non-LSD NiMH cells I used in my digital camera -- one set in the camera and two spare sets. The camera got only occasional use, so I'd usually have to recharge the cells before going on a trip where the camera would be used, because of self discharge. (I'd often discharge them the rest of the way before recharging, but not always.) After two or three years of this, with no more than a dozen or so cycles, the cells were all shot, with very low capacity. Cycling and "reforming" (16 hour charge at 0.1 C) wouldn't recover them. They were around 2 Ah capacity -- state of the art at the time -- and three different brands. My conclusion was that ordinary NiMH cells were unsuitable for this kind of use, where they repeatedly self-discharged then recharged, with only occasional actual intentional discharge.

Because LSD cells self-discharge at a much slower rate, I'd expect them to last a great deal longer in this kind of service. So far I haven't seen any evidence either way, but my money's on the LSD cells.

c_c

 

[Mr Happy]

I have the impression that as long as NiMH cells retain a charge, their deterioration over time is much slower than if they are allowed to self-discharge in storage.

I have tested new out of the package Eneloops that were two years in storage after their manufacturing date (i.e. manufactured August 2006, opened and tested August 2008). After two years in storage they still held a good charge, and after a conditioning cycle on the C9000 showed a capacity as good as any other sample of the same vintage (i.e. about 1950 mAh). This compares with non-LSD cells that have been reported as unusable after two years shelf storage without maintenance.

So my prediction is that if Eneloops are used just a few times a year and are kept charged while not being used, they will last a very long time.

 

[scott1981]

Yeah I had the same experience with some Sanyo 2500 AA I got 2 or 3 years ago. Since my camera uses 4 AAs and I use it every now and then, I would do the same thing c_c did: I would only recharge them before use and then store them in a cool place and all that....

However after 1.5 years of having them and with less than 30 recharges on it (I was using a single channel smart charger at 1000 mA charge current and batteries were really cool (only slightly warm) while charged - and they would not be left for over 1 hour in trickle charge which was around 50 mA) I noticed that they would be 0.95/0.90V after lets say 10 days. They would loose charge TOO rapidly.

At first thought that it would be more than normal for these new high capacity cells (>2300 mAh) to loose charge rapidly, and you would only be able to use their full capacity right out of the charger. But after doing research I came to the conclusion that even though self discharge was in fact an issue, users reports did not mention cells running flat in 1 week! So I thought that maybe I had just had bad luck and had ended up with a defective batch of 2500s.

My dad bought Sanyo 2700s and he had the same problem, same for his Sony 2500's and so on. Today, everyone I know that owns 2500s or 2700s are subject to my questioning about how much they last for them, and usually they will say "not that much"

So Yes, self discharge is a problem and you have to keep charging them once an over again, but on the downside you are using up another cycle, so one way or the other you end up loosing.

I wonder how is Sanyo planning to make good profit of these batteries, because if they are so good and last many years as we all suppose, people will not need to buy batteries so often, and also, as I read somewhere else here at CPF, R&D is moving towards Li-Ion. Personally I don't like Li-Ion for many reasons, and I think NIMH is a well developed technology, but still there is more room for improvement. I don't think that in any near future we will see AA or AAA operated devices running on Li-Ions, so as long as there are devices using these batteries, there will be NIMH. But Yes, R&D may not bring anything new to the table, still I don't see NIMH going away for good.

 

[Eugene]

I have some sanyo 1600's from 2001 that are holding around 80% of their charge still and now get used in my kids toys. That long term data is one of the reasons I've standardized on eneloop. I have Rayovac, radio shack, etc cells that are all at less than 80% with at 4 years of age.

 

[scott1981]

I have seen many people saying that old NIMH's were indeed better at keeping charge. I think that the NIMH technology has a limit (probably set by its energy density), and whenever you try to cross it, you just try. You can increase capacity but at the expense of shortening the cell lifespan or dramatically increasing its self discharge rate.
As s student of chemistry my guess is that a thinner separator allows ions to travel easily through it specially those as little as hydrogen ions. In other words the chemical reaction that happens when the battery is being discharged (eg when it is conected to a circuit), is now happening through the separator as if it was some kind of "chemical short". Lets bear in mind that we aim to control that reaction (to some extent) and we can decide when it happens (eg when we use the battery), but with such a thin separator ions may be flowing more easily resulting in an undesired reaction that takes place 24/7 and it only gets worse with time.

 

[scott1981]

Has anyone seen this??

http://batterydata.com/

That site recommends using NIMH in full charge/discharge cycles, whereas LiIon is better suited for shallow discharges.
I was under the impression that if you should not run your NIMH cells all the way down preferring a recharge after some usage. Is this true for everyday use or for storage?

Also,

Constant Level of Self-Discharge During the Life of the Battery

Li-Ion batteries have a self-discharge rate that remains constant during the life of the battery, regardless of the cycle count. NiMH batteries, including the new eneloop and Hybrio cells, have a steadily increasing level of self-discharge as the cycle count increases.

"High cycle count and aging has little effect on self-discharge on lithium-based batteries."

"NiCad and NiMH battery chemistries exhibit a high level of self-discharge. If left on the shelf, a new NiCd loses about 10 percent of its capacity in the first 24 hours after being removed from the charger. The rate of self-discharge settles to about 10 percent per month afterwards. At a higher temperature, the self-discharge rate increases substantially. As a rule, the rate of self-discharge doubles with every 10°C (18°F) increase in temperature. The self-discharge of the NiMH is about 30 percent higher than that of the NiCd.. A major contributor to high self-discharge on nickel and lead-based batteries is a high cycle count and/or old age. With increased cycles, the battery plates tend to swell. Once enlarged, the plates press more firmly against the delicate separator, resulting in increased self-discharge."

So it seems that LDSs like Eneloops will experience higher discharge rates as the battery is used?

Thanks!

Nick.

 

[baterija]

Has anyone seen this??

http://batterydata.com/

That site recommends using NIMH in full charge/discharge cycles, whereas LiIon is better suited for shallow discharges.
I was under the impression that if you should not run your NIMH cells all the way down preferring a recharge after some usage. Is this true for everyday use or for storage?

It has some interestingly mixed guidance.

Try to completely discharge the batteries prior to charging. Some chargers can do this automatically (LaCrosse BC-900) and some can do it manually (Maha MH-C9000).

Do not use the "discharge" button on your charger (if it has one) for every charge cycle, because this unnecessarily shortens the battery life.

Do a full discharge/charge of NiMH batteries every few months (most cameras won't completely discharge the batteries)

If you read the first point and stop, it sounds like you should discharge all the way everytime. The second then modifies the guidance for a vague not "every charge cycle." Finally it says do it every few months. These are listed as separate tips but really seem like one tip - occasionally you should fully discharge before charging, but not too often.

I think you question is answered by the second tip...fully discharging NiMH everytime "unnecessarily shortens the battery life." That seems to be supported by the testing I have seen here. As far as affecting storage, it's best not to let the cell completely self discharge and stay that way.

 

[scott1981]

Yeah I guess it is a little bit mixed up. There is a paragraph stating why Li Ions are better than NIMH and that is based on the first being barely discharged whereas the latter should be discharged.
On another paragraph they state that nimh should not be run all the way down like in SLAs... confusing huh?

What is even more disturbing if their statement that Eneloops do loose their LSD capabilties as they see more cycles during their use... is that true?????

Nick.

 

[Mr Happy]

What is even more disturbing if their statement that Eneloops do loose their LSD capabilties as they see more cycles during their use... is that true?????

Probably...but given all the other nitpicks about their advice, I'd say it is more of a wild-assed guess than an evidence-based statement.

 

[Bones]

...
A major contributor to high self-discharge on nickel and lead-based batteries is a high cycle count and/or old age.
...

Gosh, what a profound observation...

High milage and old age will also contribute to my car burning more gas and oil. If it starts to happen at one year and 30,000 miles that's bad, if it starts to happen at five years and 150,000 miles that's not bad at all.

The Eneloop was introduced almost three years ago now, and reports of any type of diminished performance remain exceedingly rare, so I think the latter age and milage is the better analogy.

Anyway, the two recommendations I emphasized with italics may tell us all we really need to know about this site:

Recommended AA NiMH batteries:

Sanyo 2500 mAH 4/$8.97

Sanyo 2700 mAH 4/$11.97

Sanyo eneloop 8/$19.99

Recommended NiMH Charger:

Maha International World MHC401FS Charger Kit

 

[Eugene]

WRT batterydata.com anyone can put up a web page, that doesn't mean all the facts on the web page are accurate.
For example:

20 Advantages of Li-Ion Batteries over NiMH Batteries

2. More charge/discharge cycles

We know thats false, NiMH usually can be used far more cycles than a lithion ion, thats one of the tradeoffs when going to lithiumm ion

20 Advantages of Li-Ion Batteries over NiMH Batteries

8. Faster shot to shot times, especially when using flash

This isn't true either, canon is a good example, they will have a lot of models that are the same except for battery type and comparing an equiv model the charge time is the same. in fact when we were looking at a good camera last year the top in the flash charge time (non dSLR) was powered by AA's.

Advantage #12, I've seen plenty of lithium ion cameras with battery doors that can pop open so this one is a stratch also.
#17 is false, a cel in a pack can very well, thats the common failure of a lithium ion pack.

AA batteries Limit You to Low-End Products (for Digital Cameras), this isn't true either, our AA powered camera is the high end.

So don't trust everything on a web site.

 

[scott1981]

Well I came across this CNET review:

http://asia.cnet.com/buyingguides/digicams/0,39059880,39380882-7,00.htm

Stating that low end cameras are AA (or AAA) powered, whereas Li Ion batteries come in high end batteries. Is this actually becoming a trend?

Thanks,

Nick.

 

[Disciple]

• Is there any new information on this subject from the last five years?
• Are infrequently used Eneloops from 2006 still good today?
• Has anyone tested how they hold up to storage under variable temperature such as in a vehicle?

 

[Norm]

• Is there any new information on this subject from the last five years?
• Are infrequently used Eneloops from 2006 still good today?
• Has anyone tested how they hold up to storage under variable temperature such as in a vehicle?

My 2006 cells fit into your description, I bought too many, so they don't see a lot of use, on average they have lost about 100mAh.

Norm

 

[jtr1962]

• Is there any new information on this subject from the last five years?
• Are infrequently used Eneloops from 2006 still good today?
• Has anyone tested how they hold up to storage under variable temperature such as in a vehicle?

I've been using two sets of four 2006 Eneloops in my bike lights until recently ( I replaced them with 2400 mAh Duraloops ). When I ran them through a break-in cycle on one of my MH-C9000s one set still had about 97% of original capacity. All of the cells in the other set had at least 90%. Both sets have at least 100 charges, possibly as high as 250. I suspect the capacity degradation isn't due to the number of recharges but rather because I mostly charged at the default 1000 mA rate. The cells were always pretty warm (but not hot) at the end of charge because my C9000s were the early ones which had a more aggressive charging algorithm. I'm sticking to recharging the Duraloops on one of my two newer C9000s.

I also have some 2006 Eneloop AAs which have been sitting around unused since I bought them. I ran a break-in cycle to determine the capacity when I first bought them but other than that they haven't been touched. I may run another break-in cycle on them in a few years time just to see how they fared. I'm not sure exactly when I bought them, although I think it was no later than 2008.

 

[StorminMatt]

Well I came across this CNET review:

http://asia.cnet.com/buyingguides/digicams/0,39059880,39380882-7,00.htm

Stating that low end cameras are AA (or AAA) powered, whereas Li Ion batteries come in high end batteries. Is this actually becoming a trend?

Thanks,

Nick.

I know this is an old post. But now that this thread has come back from the dead, I thought I would comment. Anyway, I wouldn't say that only low end cameras use AA batteries. This may be the case with point and shoot cameras. But things are different with DSLRs. DSLRs almost always use Li-Ion batteries as well. But at the same time, it is usually possible to buy a battery grip for a DSLR that uses AA batteries.