Eneloop XX Vs Turnigy 2400 Cycle Testing

Out of curiosity, I decided to run a cycle life test to compare the high capacity Eneloop XX to the Turnigy 2400. In Australia at least, the Eneloop XX cells are quite expensive - about 30% more than regular Eneloops and they rarely go on special. Regular Eneloops are often on special at less for an 8 pack than the Eneloop XX cells cost for a 4 pack! The Turnigy 2400 cells on the other hand are quite cheap. Ignoring shipping costs, they're cheaper than regular Eneloops even when the Eneloops are on special.

To begin my testing, I took a single Eneloop XX cell and a single Turnigy 2400 cell and placed them both in the same charger. For this test, I decided to run both charging and discharging at only 1 amp - as the cells are only rated for 500 cycles each, I decided that it was worth running the test at a lower rate.



To my surprise, despite being more expensive, the Eneloop XX cell lasted for a significantly lower number of cycles than the Turnigy cell. I then decided to run another test with a pair of Eneloop XX cells to make sure that there wasn't something unusually wrong with the first cell that I tested:



One cell performed very similarly to the first test, but the other lasted for a significantly larger number of cycles. The pattern of capacity decline is pretty much the same, just over a longer number of cycles. It's hard to say what the cause of this difference is - it could be that there is some variation between cells, but I wouldn't expect this considering that normal Eneloops are very consistent, and I would have expected that consistency to carry over into the Eneloop XX line as well.

As a follow up, I decided to run yet another test to compare a Eneloop XX with a Turnigy 2400 cell:



In this latest test, I ran both charges and discharges at 2 amps. In this case, the Eneloop XX survived for more cycles than 2 of the 3 previously tested - despite being run at twice the current. The Turnigy cell managed to last for more cycles, but at no point did it manage to beat the Eneloop XX in capacity.

Overall, I'd say that this is a disappointing result for the Eneloop XX. Unless the absolute maximum capacity is required, I would generally recommend the Turnigy 2400 cells ahead of the Eneloop XX cells - particularly considering the large price difference!

Do you know what causes the abrupt end of life for NiMH cells?
I always thought that there will be a continous decline of capacity, not an abrupt end.
What is the behaviour of the cells when they switch to zero capacity: short cirquit or high ohmic?
Were there any temperature problems during testing?

I have a lot of the Turnigy 2200 cells. I have never compared them with my Eneloops, but they seem to do just as well.

Interesting, any chance you could do this test with regular eneloops as well?

LessDark said:

Interesting, any chance you could do this test with regular eneloops as well?

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Like this one?
http://www.ultrasmartcharger.com/phpBB3/viewtopic.php?f=5&t=69

Tobias Bossert said:

Do you know what causes the abrupt end of life for NiMH cells?
I always thought that there will be a continous decline of capacity, not an abrupt end.
What is the behaviour of the cells when they switch to zero capacity: short cirquit or high ohmic?
Were there any temperature problems during testing?

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There weren't any temperature problems during this testing - the tests were done a few months ago over winter (in Australia) - it has taken me a while to get around to posting the results.

The cells aren't completely dead when they hit zero on this test. What happens is that as the cells age, their internal resistance increases - it eventually gets to the point where as soon the discharge starts, the voltage drops below the 0.9V cutoff. Prior to that, the voltage drops significantly, but as the cell warms up, the internal resistance drops and the voltage recovers. A normal discharge has the voltage starting high and constantly decreasing. With high current discharges on cells with high internal resistance, the voltage curve ends up looking like an upside down U:

Very interesting results. I am surprised at the results.

A couple of ideas here:

- Could the differences you're seeing in the same battery be due to differences in the two slots of your charger? If the voltage sensor is off in one, you could be overcharging in one slot and not the other which would dramatically reduce cycle life.

- Maybe the inflection point termination is not working well on the XX cells and causing an overcharge.

- The fact that the 2amp charge resulted in better cycle life performance than 2 of the 1amp charge rate cells, points to some evidence the termination might be working better at 2 amps, and/or that charge rate also helps the termination end more reliably with less overcharge.

- Due to eneloop voltage profile during charge being quite different from other nimh cells, the charging mechanism could be overcharging XX and correctly charging your turnigy cells leading to these results.


Those are just some ideas on what might be going on here. Maybe do a log of charge and discharge in the ultrasmartcharger of both slots, trying both types of batteries, including voltage, current, and temp data and we can spot if anything is amiss. The data is pretty random for very consistent cells which points to not a cell problem but a setup problem in my opinion.

Thanks for the tests!
Very interesting.
its almost as bad as swearing against eneloops
just kidding.

I`m quite surprised. Its also very strange to see they just die with even so much juice in them....... I would imagine they would go much worse before totally giving up..
It could definitely be the rest time between the cycles?
How many of those charger/discharge setups do you have?
would be interesting to see, how long they last if they have longer rest time between each cycle. Just like in a real life situation.

can you post pictures of both the XX cells and Tunirgy cells? Are the XX 1st gen?

At least till now, the Std. eneloop seem to be the better option..

bcwang said:

A couple of ideas here:
...

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I could also add the case the XX eneloops used to be fake.

bcwang said:

A couple of ideas here:

- Could the differences you're seeing in the same battery be due to differences in the two slots of your charger? If the voltage sensor is off in one, you could be overcharging in one slot and not the other which would dramatically reduce cycle life.

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There is a single external 18 bit ADC used for both channels. The ADC has an internal 2.048V reference that is used for all channels. IMHO, a faulty voltage reference would be the most likely cause of incorrect voltage readings, but that would affect all channels the same. There are other possible causes for ADC errors of course, but they shouldn't actually matter too much as long as the error is consistent.

Absolute voltage is critical when charging Lithium Ion cells, but isn't as important when charging NiMH cells because NiMH termination is done based on changes in the voltage rather than the absolute voltage. (let me know if this isn't clear and I need to do a better job of explaining it)

The first 2 tests were done in the same charger. The cell that performed worse was in slot 1 in one test and in slot 2 in the other test, so that pretty much rules out any difference between the channels. I did move the charger to a different location though, so maybe there was some external environmental condition which affected one channel more than the other (i.e. if there was air moving from one side to the other, you would expect that the side on the receiving side would run a bit cooler than the other)

- Maybe the inflection point termination is not working well on the XX cells and causing an overcharge.

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The inflection point ALWAYS occurs before a -dV signal occurs (by definition) If inflection termination causes overcharging, then -dV termination (which always incurs overcharging) is always going to be worse! Having a quick look at the charging data from the first test, I can't see any cases where the cells appear to have been overcharged.

Inflection detection is very reliable - I haven't had a single missed termination in all of the testing/charging that I've done with the UltraSmartCharger - and that includes some cells that were in really bad condition.

This is the first charge for the Eneloop in the first test:


This is the last charge for the Eneloop, again in the first test:


The last charge heats up more at the end, but still terminates OK. I suspect that the increased heat generation is due to lowered charge efficiency caused by damage to the separator increasing the internal resistance.

- The fact that the 2amp charge resulted in better cycle life performance than 2 of the 1amp charge rate cells, points to some evidence the termination might be working better at 2 amps, and/or that charge rate also helps the termination end more reliably with less overcharge.

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Inflection termination should work reliably at pretty much any current (unlike -dV detection) I haven't done any testing at ultra low charge rates, but I could do that if anyone is interested?

The lower discharge current allows for a more complete discharge. I'm wondering how much damage is actually being done at the end of the discharge as opposed to the end of the charge. I'm thinking about running some tests to see if that if it's possible to work out if deep discharging does more damage than slight overcharging...

- Due to eneloop voltage profile during charge being quite different from other nimh cells, the charging mechanism could be overcharging XX and correctly charging your turnigy cells leading to these results.

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I can't say that I've noticed any significant difference in the voltage profile when charging Eneloops. Do you have any information that you can point to which shows that there is a difference?

Those are just some ideas on what might be going on here. Maybe do a log of charge and discharge in the ultrasmartcharger of both slots, trying both types of batteries, including voltage, current, and temp data and we can spot if anything is amiss. The data is pretty random for very consistent cells which points to not a cell problem but a setup problem in my opinion.

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As I mentioned above, I'd be inclined to think that an external environmental issue might have been a factor - that seems more likely than inconsistent Eneloops...

ChibiM said:

I`m quite surprised. Its also very strange to see they just die with even so much juice in them....... I would imagine they would go much worse before totally giving up..

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It seems that increased internal resistance is the cause of these failures and in this case it has happened before much capacity has been lost.

The cells are still usable with good capacity for low current devices.

It could definitely be the rest time between the cycles?

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Shorter rests does mean that the cells don't have as much time to cool down, so yes, I would expect that to have some impact on the results. Checking the data, it's quite clear that the cell temperature haven't had a chance to fully stabilize after each charge/discharge. Ironically, in the short term, the higher cell temperatures will generally mean that the cells will give better performance during the discharge, but in the long term, I wouldn't expect it to be good for their longevity.

How many of those charger/discharge setups do you have?

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I've currently got 3 chargers running testing 24/7. I've got a 4th charger that I'm planning to put into cycle testing service fairly soon.

would be interesting to see, how long they last if they have longer rest time between each cycle. Just like in a real life situation.

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Might be worth running another test to see what the difference is - I agree. It will mean that the test will take longer of course!

can you post pictures of both the XX cells and Tunirgy cells? Are the XX 1st gen?

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Not just at the moment, but I'll try to do it later... I'll have to check which generation they are. Checking the date codes, it looks like 2 of them were made in 2012 and the other 2 were made in 2014...

At least till now, the Std. eneloop seem to be the better option..

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As long as there isn't a pressing need for the increased capacity (and swapping cells isn't an easy option) then, yes - I definitely agree!

apagogeas said:

I could also add the case the XX eneloops used to be fake.

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That did cross my mind.

Fakes generally have way less capacity that they're rated for, so I think that makes it unlikely that they're fakes.

I also purchased them from **** Smith Electronics - probably the biggest retailer of Eneloops in Australia. Although fakes can creep in, I wouldn't think that to be too likely since they should be being sourced from the official distribution channels.

I also tested cells from 2 cells each from 2 different packs with different date codes to ensure that I didn't have cells from a faulty batch.

Well, a greatly reduced number of useful cycles has always been a drawback of Eneloop Pros (or XX). Despite this fact, I have still chosen to use nothing but Eneloop Pros in all my applications (except for a some early, non-LSD, Panasonic NiMH cells which I am still using until they finally "die off" completely and can be recycled).

Another commonly mentioned drawback is the higher cost of Eneloop Pros. Neither the higher cost, nor the low number of cycles has ever concerned me, however. (In my opinion, the question of whether or not you should be concerned about these two issues depends on how often you intend to recharge your cells, and how many years you hope to keep using them.)

I live in Japan where Turnigy 2400 cells are not a practical option. Turnigy is hardly sold here at all, and almost all "hits" I could find on the internet pertained to "Turnigy" branded multi-cell packs in both Li-Ion and NiMH chemistries for Remote Control hobbyists.

The only Turnigy AA cell I could find was a 2200 mAh version which were available for purchase at 210 Yen each from one single R/C Hobby Shop. That price is in comparison to 199 Yen for a Standard Eneloop, and 249 Yen for Eneloop Pros. (At the moment, the Yen Dollar exchange rate is fairly close to 100, so you can think in terms of US$2.49 per Eneloop Pro cell.)

While Panasonic literature written in Japanese claims "approximately" 500 cycles (based on the JIS C8708 standard) for the Eneloop Pro cells, it also includes the caveat "depends on your device and device usage -- actual performance may vary." I think it is a well known issue here in Japan that 500 cycles is a rather optimistic claim.

The following is a graph titled "Eneloop Pro Cycle Endurance based on JIS C8708 standard testing methods" that I found on the internet and have partially translated into English:



As you can see, 250 Cycles, or perhaps 300 Cycles (depending on your performance needs) is the most that you can expect. At 350 Cycles the Eneloop Pro has deteriorated very significantly.

The following is a portion of the raw data associated with the above cycle tests:



The JIS C8708 testing involves charging the cell at 0.25C for 3 hours and 10 minutes, then discharging the cell at 0.25C until the cell reaches 1.0 Volts. In order the pass the test, the cell must take longer than 2 hours and 20 minutes to reach 1.0 Volts. Every 50 cycles, the cell is charged at 0.1C for 16 hours, rested for 4 hours, then discharged at 0.20C until it reaches 1.0 Volts.

As the above printout shows, the 376th cycle was the last cycle to "pass" this test. (It took exactly 2 hrs. 20 mins. to reach 1.0V) The cell failed on the 377th cycle because it reached 1.0V in only 2 hrs. 19 mins. The rest of the handwritten notes on this printout refer to the fact that at 400 cycles and 450 cycles, this cell "instantly" registered less than 1.0V (it took "zero time").

As I mentioned at the beginning of this post, I (personally) am not particularly troubled by these results. I am willing to accept 200 or 250 cycles as the practical life of my current Eneloop Pros. (That doesn't mean that they cannot still be useful in many low drain applications, even after they have begun to deteriorate significantly.) Since I rarely recharge more than once per week, in my case, 200 or 250 cycles translates into 4 or 5 years. (It is hard for me to predict that far into the future, but I suspect I will be willing to re-invest in whatever the "latest and greatest battery technology" is at that time.)

Without getting into great detail, if you assume 200 or 250 cycles, you will quickly find that the initial higher cost of the Eneloop Pros is trivialized over time. What should not (in my opinion) be trivialized is the nearly 29% increase in capacity. The current Japanese language Panasonic Eneloop website claims "min. 1,900 mAh" for Standard, and "min. 2,450 mAh" for Eneloop Pros.

Furthermore, the Eneloop Pro has 22% more capacity than the Standard even after 1 whole year, despite its lower 85% capacity retention rate (90% for Standard). To me, these capacity increases are significant. I have recently read where some on this forum have posted that you will see only a very slight increase in capacity, but I wonder how factual that is.

I do not have any Standards to compare with my Pros, so I cannot say from any firsthand experience, but I do know that Sanyo claimed a 31% runtime increase in an LED flashlight driven at 300 mA. And, to my mind, 31% longer runtime for your flashlight, available every day, whenever you may need it, is pretty significant. (But, I am sure that this depends on your application.)

In summary, I use Eneloops Pros in every device, whether they are needed or not, because that is where I am keeping my "emergency stash" of backup flashlight cells. If my power goes out for any real length of time, I can rob cells from countless "nonessential devices" and use those cells to power more important things like flashlights. I figure that, so long as I make sure and recharge everything (even "nonessential devices") at least once a year, I will always have the "maximum" emergency capacity (always greater than the same number of Standard cells).

Therefore, quite a few of my Eneloop Pros may only get recharged once a year (= 250 to 300 year cell life?) Others will get recharged about once a week (= 4 to 5 years), but only a very few will get recharged much more often than that. I try to keep my cells in matched sets, and occasionally make note of their measured capacity in an Excel spreadsheet that I keep. I am interested to find out for myself when (if ever) I will notice a significant drop-off in capacity.

Some may argue that I shouldn't have spent the money on (made the investment in) Eneloop Pros. But, as previously noted, the cost difference between Standards and Pros is trivial when amortized over time and even "only" 200 cycles. And, in the meantime, I have never purchased another Alkaline cell, I am able to enjoy the highest possible capacity (longest possible runtimes) on a day-to-day basis, and I also have the greatest amount of capacity available for emergency use (should I ever need them). Whats not to like? (Besides initial cost...)

Think about it, though... How many of us are spending hundreds of dollars on flashlights? Why not invest some of that money into the cells that power those flashlights? Eneloop Pros are not all that expensive when compared to the cost of a quality flashlight.

(Lets say a good 6 x AA flashlight costs around $100 or so, and the difference between Pros and Standards is $0.50 each. That means 6 Pro cells + 6 spare Pro cells are only going to cost you $6.00 more over Standard Eneloops! You may pay a greater premium for Pros in your market, but I still don't see it as very likely that using Pros is ever going to increase the cost of your flashlight by more than 20%, and even that huge premium seems worth it to me, assuming you are going to experience an appropriate increase in runtime in your application.)

I agree, however, that those who are recharging several times a day, or even once a day, might be better off with Standard... although in my mind even that is still "debatable."

Very interesting tests! Thanks!

Thanks for the great post Rosoku!

I should have reiterated that my recommendation against the Eneloop XX cells is largely based on their significantly higher cost (at least in Australia)

If I could get Eneloop XX/Pro for only 25% more than the regular Eneloops, I'd do the same as you and standardise on them despite the lower number of cycles that they're capable of. Even for devices that require regular recharging, it might still make sense to use Eneloop XX/Pro cells despite a slight price increase just for improved convenience. Their higher capacity slightly offsets their lower number of cycles as well.

Unfortunately, though, in Australia at least, we have to deal with not just a 25% increase in price but a minimum of 40% more. When the regular Eneloops are on special (which is quire often), the price difference works out to 180% more! Even when the XX/Pro cells are on special they're generally still double the cost of the regular Eneloops on special!

For a handful of cells, the price difference isn't that big a deal, but when you've got over 700 rechargeables in service, the (Australian) price difference makes a huge difference unfortunately!

BTW, I have an Eneloop XX in my EDC torch...

Power Me Up said:

...For a handful of cells, the price difference isn't that big a deal, but when you've got over 700 rechargeables in service...<snip>

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Wow, that really is a whole lot of rechargable cells!

Sorry to hear that Eneloop Pros are so much more expensive in your market. I noticed that Eneloop Pros (in particular) are being sold on eBay.com.au from Japan, but the prices being charged for them are indeed very high.

In the case of Japan, it seems that the price of Standard Eneloops has gone down. Not too long ago, it was occasionally possible to purchase Pros for less than Standards. (I guess this was because, in general, Pros are not as popular and don't tend to "sell through" quickly enough for some online retailers.) But today, Standards seem to always be cheaper than Pros by a minimum of about 25%.

In any case, I still tend to believe that the difference in cost is overblown, when you take into account that you are likely going to eventually use your cells for at least 200 cycles. Even if you pay twice as much for Pros, that difference amounts to fractions of a cent per cycle... (Of course, Standards probably can achieve well over 1,000 cycles, so their per cycle cost gets ridiculously low, but to me that is beside the point.)

However, as you noted, the difference initial investment cost looms pretty large when you must purchase 700 cells! (I guess you are kept pretty busy recharging all those cells?)

Rosoku Chikara said:

However, as you noted, the difference initial investment cost looms pretty large when you must purchase 700 cells! (I guess you are kept pretty busy recharging all those cells?)

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It's not that bad. There are a lot in kids toys that don't get used a lot, so they just get recharged when they go flat. I've also got quite a few unopened in packs (bought at ridiculously low prices) so it's probably a bit over the top on my part to complain about the cost of that many Eneloop XX/Pros when I don't actually need that many in the first place...

Power Me Up said:

I also purchased them from **** Smith Electronics - probably the biggest retailer of Eneloops in Australia. Although fakes can creep in, I wouldn't think that to be too likely since they should be being sourced from the official distribution channels.

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I was thinking you had fakes too but if they are from ****ies then they are genuine. At $27 for four, that is some expense to pay for this experiment.

Now the questions is if Jaycar's XX's are the same or better ... (seriously, don't go out and buy them just for this test)

I guess we don't really buy XX's just for the cycles but the ability to handle high loads but this does put a little perspective on it. Still buying the XX AAA's though

Mr Floppy said:

I was thinking you had fakes too but if they are from ****ies then they are genuine. At $27 for four, that is some expense to pay for this experiment.

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Just going from memory, I think I managed to get at least one of the packs for about $20 on special...

Now the questions is if Jaycar's XX's are the same or better ... (seriously, don't go out and buy them just for this test)

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Wasn't planning to. Maybe I should ask Panasonic if they are interested in donating a couple of packs for testing purposes...

I guess we don't really buy XX's just for the cycles but the ability to handle high loads but this does put a little perspective on it. Still buying the XX AAA's though

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Capacity wise, the XX AAA cells are of even less value than the regular Eneloops - 900 mAh min vs 750 mAh min is only a 20% capacity increase compared to 2450/1900 = 29% increase. DSE at least doesn't give a discount on the AAA cells compared to the AA cells even though there are less material costs. (Lower demand for AAA would offset some of these savings of course)

Of course, with the capacity of AAA cells being so low, any increase in capacity could be considered worthwhile in a lot of cases...