Eneloop cycle counts explained and compared

papershredder

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May 31, 2013
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We're all familiar with the Eneloop brand 2nd gen (HR-3UTGA) and XX (HR-3UWXA) varieties in the US. They're easy to source here, despite there being slightly newer and better performing varities in other markets, surch as Japan.
The notable differences between these are:

Gen 2 Eneloop
  • 75% capacity retained after 3 years.
  • 1900 minimum mAh.
  • 1500 cycles.
  • $$

Eneloop XX Gen 2
  • 75% capacity retained after 1 year.
  • 2400 minimum mAh.
  • 500 cycles.
  • $$$


I'm going to zero in on those cycle counts today. Just what the heck does that mean? 500/1500 before what? Pigs fly?

Well, if you look on the back of the packs the cells come in, they reference IEC61951-2 per the cycle counts.

The exact test that is referenced, section 7.4.1.1 (there are other tests for different types of cells and different tests within the same types) is where they cycle the cell 49 times and check it on the 50th cycle. They're allowed to double check for a 51st cycle the results they got on the 50th cycle. If the conditions are not satisfied, they have to repeat this whole 50(/51) cycle process. The condition to satisfy, essentially, is that the cell is at 60% of its design capacity.

So, to put it in a nutshell, the cycle count means that the cell will only be able to retain 60% of its design capacity after that many cycles. (Keep in mind there are some generalizations being made here. E.g. real world use, temperature swings, etc. The real world is not a laboratory. That being said...)

So, you look at the specs above and you see the 1/3rd cycle count of the XX Eneloop... but, consider:

bbV3oBZ.jpg


On the Y axis we have mAh per cycle counts, which is the X axis.

So, you see, that because of the initially higher capacity of the XX cells, despite their more rapid degredation, they don't underperform the gen 2 cells until about 365 cycles.
Numerically, the XX degrades 1.52 mAh per cycle and the gen two; 0.506. Of course there are some assumptions made here (linearity) and generalizations. But, we can be fairly confident where those lines intersect, give or take 50 cycles or so. Work from other individuals lends itself to assumptions of linearity and no hockey stick style responses.

So, my personal conclusions is that the XX cells are still good for my applications. I only need to recharge a few times a week, meaning I'll get years and years of above-gen-2-performance out of the cells. I think the same can be said of most people.

Eneloops are good. =)
 
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jtr1962

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Numerically, the XX degrades 1.52 mAh per cycle and the gen 2 0.506.
Interestingly, a set of four regular Eneloops (2006 vintage) I've been using in one of my bike lights degraded ~3% after at least 100 cycles. This seems to be right in line with these numbers.
 

samgab

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Interesting way of looking at the data. Who knows if the degradation is linear, as mentioned by op; but presuming it is, here's another way of viewing the same data:
eneloop%2520life%2520cycle%2520projected%2520by%2520generation%2520AA.jpg

I've projected the lines a little way.

Now, let's say we deem a cell to be at throw-away state once it goes below 1500mAh capacity; In that case, the chart would look like this:
eneloop%2520life%2520cycle%2520projected%2520by%2520generation%2520AA%2520down%2520to%25201500mAh.jpg

From that viewpoint, the life span of the XX and the regular 1st Gen are very similar, and the capacity of the XX throughout the first part of their life is superior to the regular first Gen... But then there is the initial price difference to take into consideration.
But on the other hand, if we can get the 2nd, 3rd, or 4th Gen standard, and the initial cost is significantly lower than the cost of the XX type, depending on one's usage, they could work out to be much better value.
It all depends on the individual of course, but for my usage the regular 3rd gen (which are the only ones available in my part of the world) are the best value over the entire lifespan.
 

tatasal

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Jan 25, 2012
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Gentlemen, thank you very much for the graphs.

Considering my real life usage (very low frequency of charging cycles in a year, max of 4 times/year so far), low-priced Gen 1 XX, regular Eneloops and even 'Duraloops" are good enough for me.:thumbsup:
 
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samgab

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Auckland, New Zealand
Oh, and some other interesting data, this is the improvement of charge retention over # of years storage, by generation:
eneloop%2520charge%2520retention%2520by%2520generation.jpg

The 4th Generation regular eneloop "Panasonic" branded isn't shown, as it's the same as the Gen 3 in terms of charge retention in storage and initial capacity rating. The only improvement from 3rd to 4th Gen regular eneloop is the number of cycles lifespan (1800 increased to 2100).
 

Mr. Tone

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Illinois
Very nice thread and good info, thanks for putting it up. I am a huge Eneloop fan and user.
 

Floating Spots

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Sorry. Dropped my tablet and Tapatalk posted a reply. No delete that I see.


Sent from my Nexus 7 using Tapatalk
 
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