AA and AAA NiMH low self-discharge tests--Round 2

Four Week retention

update to add Radio Shack AA 4-week results

AA NiMH low self-discharge sets

batt mAh var

ENL 1811 0.013
TPE 1795 0.020
HYB 1870 0.007
ACC 1790 0.016
RHY 1795 0.018

DPC 1857 0.011
ENO 1854 0.012
KPC 1950 0.021
AMX 1856 0.031
IME 2008 0.030
GRY 1938 0.024
RSK 1808 0.012

conventional AA reference cells

KOD 1673
RAY 1273
NEX 978
TI24 836
TI26 1495
LC20 1498
SY23 1615
PW20 1677

AAA NiMH low self-discharge sets

batt mAh var
HY8 696 0.007
IM8 791 0.024
AC8 697 0.007
EN8 765 0.017
DP8 757 0.003
GR8 824 0.028

Among the AA cells the Maha IMEDION have the best 4-week results. The Kodak are respectable second, and low price and high availability will make them the preferred choice for many.

The GP Recyko AAA cells exceeded their name-plate capacity after four weeks! It appears that in general the AAA market has had less of a capacity horsepower race than the AA market, leading to more concervative ratings.

The only good thing to be said about the Radio Shack AA cells is that they are very widely available, at last in the USA.

Actually, there is one more good thing--even though they are the worse of the second batch, they still exceed the 4-week capacity of every single one of the eight different conventional NiMH AA cells from my personal inventory included in this test as comparison references.

You don't have to wait a year for the low self-discharge NiMH batteries to have a clear advantage--just a month will do.

Thanks for all these updates. Are you going to keep going with these for another month or are you going to stop the test and actually use the batteries? I just purchased a BC-900 charger and some Imedion batteries, I am charging and testing some of my older batteries now, but I took the new imedions and put them right into my flash because I needed them today. Hope they are as good off the shelf as many say.
--
studio5photo

studio5photo wrote:

Are you going to keep going with these
for another month or are you going to stop the test and actually use
the batteries?

All the batteries listed as second round are currently sitting through a 3-month retention period. I expect to provide a report covering all save the Radio Shack AA's about April 18.
--
new 350D user July 1, 2005

technicsplayer. wrote:

One thing I have not seen publicised much in manufacturers
descriptions is whether a BC900 refresh cycle benefits these cells,
or even a more simple full discharge and charge every few months if
not being used regularly. You would assume that they are the same as
standard NiMH in this respect, just have the low discharge chemistry?

I don't think the manufacturers say much about what they think treatment like the BC-900 refresh cycle does to even conventional NiMH, let alone the low self-discharge types.

The one comment I've seen is, from Eneloop. They say that if you store the cells in a discharged state, it may require multiple cycles to get capacity back.

The sticky part about cycling is that, whatever good it may do for some cells, it does harm to all cells. You are unambiguously using up some of the cycle lifetime of the cell when you put them through a cycle, whether that cycle is useful use of the cell in its end application, or theoretically therapeutic cycling in a device that provides that as a service, as both the BC-900 and the MH-C9000 do.

My personal suggestion is to use intentional cycling very sparingly. Repeated cycles clearly are indicated as a rescue method when a cell with much less than hundreds of cycles is not accepting anywhere near a full charge (I had one such battery arrive brand new in this set of tests, and the rescue brought it up to nearly as good performance as the other three in the set).

A single intentional cycle once every few months (not to deep discharge, but, say, down to about 1.2V) may actually help long-term life. If done with any form of monitoring or measurement, at the very least it will help build confidence and knowledge, so you don't get caught with a dying flashlight on a dark and snowy night while you are trying to mount tire chains.
--
new 350D user July 1, 2005

Three month retention

AA NiMH low self-discharge sets

batt mAh var

battery 3 month var
ENL 1746 0.010
TPE 1590 0.065
HYB 1808 0.007
ACC 1696 0.019
RHY 1716 0.022

DPC 1821 0.012
ENO 1768 0.017
KPC 1874 0.034
AMX 1784 0.034
IME 1940 0.041
GRY 1872 0.029
RSK 1705 0.009

conventional AA reference cells

KOD 1012
RAY 605
NEX 533
TI24 0
TI26 781
LC20 1212
SY23 888
PW20 1259

AAA NiMH low self-discharge sets

battery 3 month var
HY8 594 0.062
IM8 758 0.024
AC8 632 0.024
EN8 734 0.019
DP8 734 0.001
GR8 788 0.029

Among the AA cells the Maha IMEDION have the best 3-month results by a clear margin. The Kodak and GP Recyko are essentially tied for second place. The low price and wide availability of the Kodak cells with that good performance will make them an excellent choice for many.

The GP Recyko AAA were clear victors in the AAA category. As their availability is a bit difficult, it is comforting that the IMEDION offering was quite competitive, with the Duracell and Eneloop models only moderately less capable.

The only good things to be said about the Radio Shack AA cells are that they are very widely available, at last in the USA, and that the cell-to-cell matching of the particular set of four I had under test was excellent--the best seen in my test.

The clear advantage of ALL of the low self-discharge models over ANY of my historic conventional AA NiMH cells is even more dramatic in the three month readout than it was at the 4-week readout.
--
new 350D user July 1, 2005

Mark K wrote:

archae86

I am currently using Maha c801D charger

1. I have some 40 Sanyo 2500mAh, 4 Energizer 2500mA, 12 Sanyo 2300mA,
and 4 GP 2700mA AA batteries. I have been puzzled by their almost
instant discharge property. Question
a. Will there be any chance I bought fake NiMH batteries or
b. Is the the universal physical property of NiMh batteries or
c. The chemicals inside are exhausting

I don't have a full picture of your situation, but it seems to me that the two most likely issues are either:

1. your usage pattern has simply consumed much of the useful lifetime of many of your batteries. It is typical of batteries with appreciable usage to lose both capacity and retention lifetime. Manufacturer's claims of 500 or 1000 cycles should be viewed with much skepticism, as they generally assume benign use conditions, and allow very considerable loss of capacity.

I've not kept formal cycle counts on my batteries, but would hazard a guess that in general my NiMH batteries have ceased to be of good use to me after perhaps a hundred cycles, and sometimes far less.

If your usage style routinely runs a set to full depletion, then, depending on the device, it probably drives at least one cell in the set to reverse voltage. In that case the cycle life is likely to be far, far less than 100. You might get considerably better lifetime out of newly purchased batteries if you can find a way to avoid running the set down so far (maybe charge every night, or, if the device has a battery meter, change out the set at a higher reading than has been your practice).

or:
2. your charger is terminating charge too soon on many of your batteries.

This second point is far from impossible, in fact none of the "smart" chargers I've owned with the possible exception of my Maha Powerex MH-C8000 have been entirely free of this fault. If you have a simple "stupid" charger--the sort which does not sense the voltage on the batteries at all, but just charges at something like 0.1C forever, or possibly something like 0.2C for a time limit of 5 to 10 hours, then you can try charging the same battery on the stupid charger. If it gives substantially better service, then your c801D terminated prematurely on that battery (it tries to sense the negative delta-V point, and sensing that can be a problem--which may be as much the fault of the battery or of your usage as of the charger).

As my experiments did not explore cycle life, I have no basis in my own data to recommend the low self-discharge units for your situation. Nevertheless, I think you'll probably find them better in your service. As I imagine you have heard, it is well to keep the batteries in sets--this makes it less likely that a mismatched battery will get prematurely destroyed by reverse voltage in service.

I've not kept up with comments on the Maha Powerex MH-C9000 charger which I used for all charging and measurement in this exercise.

After reviewing the relevant thread on the Candlepower Forum today, I think I should mention that the particular MH-C9000 I used had the date code:

0FAB01

on the back. This makes it a very early model, preceding some firmware and possibly hardware revisions on later models. In particular it seems that the charge termination condition was altered in later models to make missed termination less likely, but with the consequence that termination occurs earlier on at least some batteries than on my model.

Separately the measurement and termination condition, and possibly the compliance limit on discharge was changed. On my model the voltage during discharge is measured after a (very) short pause at zero current, with the termination limit being 1.0V. Also the compliance limit is 0.8V (in other words if 0.8V applied gives less than the specified discharge current, but at zero current the voltage is 1.0 or greater, discharge continues--sometimes for a very long time as I saw with several of my long-service conventional cells).

On the updated models, the discharge termination condition is under load, not open circuit, and the limit is 0.9V. For many cells, particularly the long-service ones mentioned above, this is a tighter limit, so they will terminate discharge sooner and a lower capacity will be reported.

So, in summary, my test methods with my model of the charger probably reported slightly higher capacities than would the same methods applied using a newer model of the same charger. I think this would generally just be a very few percent.

It is also possible that changes in the charger may have eliminated the problem of this charger having trouble recognizing Maha IMEDION cells plugged into it (on my sample the middle two channels hardly ever recognized these cells, though they did not have this trouble with any other cells in the test). I've not seen information on this point.
--
new 350D user July 1, 2005

You are correct regarding the slight over-estimation of battery capacity by the 0Fxxxx versions of the MH-C9000. Maha have advised me that the measurement inaccuracy of thae first versions was approximately 6% optimistic.

The relative measurement and comparison between the different battery brands remains unaffected by this. I mention it only so that those comparing results of their batteries charged and discharged with a 0Gxxxx or OHxxxx version of the MH-C9000 can take the variation into consideration

Jeff Servaas
Servaas Products - Australian Distributor for Maha Powerex
http://servaas.com.au

See the range of Powerex products on display at the PMA Australia Photography Exhibition in Brisbane, May 30-June 1, Stand 217. http://www.pmaaustralia.com.au

Eric_K wrote:

With the Radio Shack Low Discharge currently half off, would that
change your recommendations? Just wondering. I can't find Eneloop's
locally.

The RadioShack AA cells of the low self discharge sort rated extremely low among the other competitors. Nevertheless, they appear to me fully qualified as low self discharge types, with all the good things that implies. So, if you find them quite a bit cheaper, rather than more expensive, the remaining concern I have is just whether you can tolerate about 10% less capacity than most of the competitors.

For most applications, I think the answer to that last point is probably "yes". The one alternative I think you might find readily available in your neighborhood, possibly at a competitive price, is the Kodak alternative. If you live in the United States, surely there is a Wal-Mart near you. My impression is that they generally were carrying the Kodak entry at a pretty good price last time I knew. That alternative would give you one of the best at a pretty good price rather than one of the worst at a quite good price. While the Eneloop actually ranks pretty low, you might find them at the local camera store. I think Ritz carries them here in Albuquerque.

Since I just praised the Kodak entry, this may be the place to make a negative note. After I wrote my review, I started actually using the batteries in my GPS receiver. It is a Garmin GPS V. it takes four AA cells, and the battery compartment is a pretty snug fit regarding cell diameter. Out of a couple of dozen brands/types that I've tried before, maybe two have had trouble fitting in. The Kodak was not the worst fit (meaning largest diameter) that I've had, but it definitely was uncomfortably tight.

The two issues seem to be that the diameter of AA cells is not really precisely defined by universally observed spec and that rechargeable cells swell slightly when recharged. Anyway, if you have an application for which you know that ordinary AA cells are sometimes a tight fit, the Kodak may be a poor choice. The diameter difference is extremely small, and I think the great majority of applications won't care at all.

Thanks for the time invested in this !! Wonderful job.

If I may add some basic background about rechargeable batteries...

(I've been into the radio control airplane hobby for 35years now, and rechargeable batteries have always been a lifeblood of our hobby.)

Rechargeable consumer batteries of the 80's never had mAH numbers marked on them, or it was a microscopic marking. Today, we see these numbers plastered on the battery like it's a horsepower rating on a sports car.

To put more capacity in that same AA package started by packing it with a bigger "jellyroll" of the plate/separator/electrolyte assembly. I have disassembled my share of NiCd and NiMh batteries for childish reasons (warning: fire can result) and remember the old 500mah AA battery roll would just fall out of the shell. The new 2100+ is so tight its hard to remove. This is why size C and D batteries exist; more room for more jellyroll.

Over the years the layers got thinner in order to get more winds on the roll - and put bigger numbers on the package. However, a thinner separator will accelerate self discharge. But they don't tell you that on the package do they? Now you could try to sell a 1600 mah cell with good thick separator and say it lasts 2x longer in storage, but which blister pack will get grabbed at the point of sale... the 1600 or 2600? Battery makers had painted themselves in a corner. This what drove the development of a better separator material. Is also coincidence that these new cells have fallen back in capacity 20%? Notice too that the mAH rating is obscure once again on many of the pre-charged store brands Kodak, Eneloop... hmmm.

I think they actually took 2 great steps forward in separator technology, and had to take one step back in capacity to make the advertised long term storage benefit marketable at point of sale. Either way, its all good.

(Personally I'm still waiting for Mr. Fusion)

Sorted summary capacity mAh data:

AA low self-discharge NiMH
battery initial 1-hour 1-week 4-week 3-month 3m/1h%
IME 1831 2186 2053 2008 1940 89% MAHA IMEDION 2100 mAh
KPC 1723 2124 2021 1950 1874 88% Kodak Pre-Charged 2100 mAh
GRY 1687 2116 1992 1938 1872 88% GP Recyko 2100 mAh
DPC 1515 2010 1906 1857 1821 91% Duracell Precharged 2100 mAH
HYB 1619 2026 1918 1870 1808 89% Hybrio by Ultralast 2100 mAh
AMX 1645 2078 1936 1856 1784 86% Ansmann Max-e 2100 mAh
ENO 1189 2017 1904 1854 1768 88% Nexcell EnergyON 2000 mAh
ENL 1438 1980 1847 1811 1746 88% Eneloop by Sanyo 2000 mAh
RHY 1738 2021 1867 1795 1716 85% Hybrid by Ray-O-Vac 2100 mAh
RSK 1505 2024 1868 1808 1705 84% Radio Shack pre-charged 2000 mAHr
ACC 1737 2022 1899 1790 1696 84% Acculoop 2100 mAh
TPE 1009 1932 1847 1795 1590 82% Titanium Power Enduro 2100 mAh

AA ordinary NiMH
battery initial 1-hour 1-week 4-week 3-month 3m/1h%
PW20 * 1963 1804 1677 1259 64% Powerex 2000 mAh NiMH
LC20 * 1727 1595 1498 1212 70% LaCrosse 2000 mAh NiMH
KOD * 2072 1917 1673 1012 49% Kodak 2100 mAh NiMH
SY23 * 2091 1899 1615 888 42% Sanyo 2300 mAh NiMH
TI26 * 2001 1745 1495 781 39% Titanium 2600 mAh NiMH
RAY * 1579 1471 1273 605 38% Ray-O-Vac 1600 mAh NiMH
NEX * 1239 1211 978 533 43% NEXcell 2200 mAh NiMH
TI24 * 2109 1859 836 0 0% Titanium 2400 mAh NiMH

AAA low self-discharge NiMH
battery initial 1-hour 1-week 4-week 3-month 3m/1h%
GR8 723 912 846 824 788 86% GP Recyko 800 mAh
IM8 727 870 810 791 758 87% MAHA IMEDION 800 mAh
EN8 600 838 783 765 734 88% Sanyo Eneloop 800 mAh
DP8 622 833 780 757 734 88% Duracell Precharged 800 mAh
AC8 543 779 724 697 632 81% Accupower Acculoop 800 mAh
HY8 593 799 738 696 594 74% Hybrio by Ultralast 800 mAh

-500 hours capacity as delivered
0 hours zero-time capacity after at least three cycles
168 hours--one-week capacity
672 hours--four-week capacity
2184 hours--three-month capacity

MisterBG wrote:
Thanks for the update.

I read these results as indicating that there is very little
difference between the "Low Self Discharge" types, whereas the
"Regular" NiMh cells show huge variations in performance.
I will make sure I get Low Self Discharge types for my next purchase.
--

To Err is Human, To really foul things up you need a computer.

Yes, so far the pretty large number of low self-discharge brands I've tested have been pretty close. For the most part you might as well buy the least expensive among the ones you find readily available. If you happen to have a device with snug battery wells, the slightly larger diameter of the Kodaks could be an issue (mine have found their home in my Canon 580EXII, which has enough clearance, and for which I especially value it working if I snatch off the shelf after a long rest).

If your usage pattern is to charge the night before and use the next day, and you are especially sensitive to total capacity, then a standard NiMH with a high capacity label from a brand that does not lie too much may well be superior. For most of the rest of us, I think the low self-discharge generation is a good thing.

Let me add my thanks for the great and tireless work you've done on this... and then add to the load by asking whether you've had a chance to evaluate the Delkins?

Nill

Nill Toulme wrote:

Let me add my thanks for the great and tireless work you've done on
this... and then add to the load by asking whether you've had a
chance to evaluate the Delkins?

Nill

I only spotted the Delkin 2300 product when I visited Thomas distributing sometime a few weeks ago. Perhaps after the holidays I'll look around and see if there's anything else new around worth looking at, but have not started any new work at the moment.
--
new 350D user July 1, 2005