AA NiMH

mete

mete

Joined
Jun 10, 2003
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I need some info on AA NiMH batteries .I'd like top quality ones for low self discharge rate .That does limit power rating though that is also a function of impurities in the battery.Any suggestions ?
 
Sanyo Eneloops
You won't be sorry: I know I haven't been.

Here's a CPF subforum dedicated to batteries:
http://www.candlepowerforums.com/vb/forumdisplay.php?f=9

This thread in particular might be helpful:
NiMh Battery Shoot Out

I recall a thread there where a guy left a charged set of Eneloops in his car's glove compartment (I believe) and after many months (if not a year) they still had a good charge on them and were in great shape. My memory of the specifics are hazy and I can't find that thread at the moment but I'm sure you could find it in that subforum with a little searching around.

The LSD batteries these days are great. Not saying that Eneloop is the only game in town but they have a great reputation and they are the only ones I have personally used and can recommend.

The reduced capacity is a worthy trade-off for the storage time, in my opinion. When I used to go on vacation (or even out to a special event) with my camera and its external flash, I would have to remember to charge all my NiMH cells (including spares) beforehand. What a P.I.T.A. Now I just know that the spare Eneloops in my camera bag are good-to-go. I'll throw one set of the spares into the flash, and whatever was in the flash gets charged to become another set of spares. This keeps each set in rotation.

Even if I were to go for a year without using that flash (ha, yea right!), all the cells would still have great capacity left. With the older high-capacity NiMH's that would be a joke for a mere fraction of that time span.

I also use them in any of my AA flashlights.

Not only are they guilt-free, they are stress-free. No longer do I have to run around topping things off :jerkit:
 
I use Eneloops, but have recently discovered easier-to-find alternatives. Any rechargeable battery the comes "precharged" will have a low self-discharge rate.
 
I use the Rayovac Hybrids, which I believe were developed jointly with the Eneloops(which are made in Japan, IIRC, while the Hybrids are made in China).
I had 12 Energizer 2500mAh NiMh cells, and bought 4 Hybrids. I've since thrown away all of the Energizers. The Hybrids are MUCH better, particularly in digital cameras and camcorders, in spite of a 2100mAh rating.
 
ThinkOfTheChildren said:
How often are you charging them? Those have a pretty awful reputation as far as self-discharge rate goes.

http://www.candlepowerforums.com/vb/showthread.php?t=204139&highlight=Energizer+2500
http://www.candlepowerforums.com/vb/showthread.php?t=160139&highlight=Energizer+2500
Click to expand...

I have the energizers too with the fast charger (the one with the big wall wart). My camera is battery hungry and i find i get quite a bit of time with the energizers. They recharge in 15 minutes so i'm really not worried about discharge. I rotate thru 3 sets of 4, always have fresh batts. :thumbup:
 
Currently of all the rechargeable NiMH - the LSD (Low Self-Discharge) are better for most applications. They retain their charge much longer than most regular NiMH - so they are more or less "ready to use".

There are good arguments for higher capacity NiMH - but mostly for applications where the batteries are going to be used shortly after charging. But often higher capacity NiMH start to lose their charge quickly even the best known brand like Energizer 2500mAh, Duracell 2650mAh and even the Sanyo 2700mAh have been reported to have high self-discharge

Usually after more than about 2 months' storage LSDs show better usable capacity.

Most well known brands LSD batteries have been reported to perform well.

But of all the LSD's the eneloop stand out as the best by test and reputation.

I did some ad-hoc testing in comparison to Kodak Pre-Charged (which I suspect are re-badged GP ReCyko)
and in certain applications eneloops were much better -
please see summary post #57 (link) in eneloop vs. Kodak Pre-Charged Voltage Maintenance .

There are confirmed re-badges of the eneloop -

Duracell Pre-Charged - but only the made in Japan with white top surrounding the +ve button.

Sony CycleEnergy (blue)

Personally I would buy eneloops or confirmed re-badges over any other unless there is a real non-trivial price difference -
however Duracell Pre-Charged (nicknamed "DuraLoops") are sometimes on sale locally and can be as low as $7.99/4.

--
Vincent
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Thanks for the replies ,I've decided to try the eneloops considering my usage.
The higher the mAh rating the faster the self discharge rate .That's why the eneloop is only 2000 mAh.
My batteries had worn out so I needed something.
 
define hi discharge? is it that battery self discharging after a day or two? or months and months of no use. I dont know anyone that leaves batteries that long without using them. Are we talking daily use or charging them and leaving them for a year??? . hell i used and recharged my AA batts 7 times already today.

part of the problem with listing "discharge " rates is people do not factor in how often the batts are used.
 
The thing about batteries is they are more or less the same. Yes I know that brands capacity and design can vary a lot, and there are lemons out there; but my point is batteries all react pretty similar to the way they are treated.

If you use a ton of batteries buy a ton of rechargeables, all batteries have a finite cycle life, meaning any old battery can only be charged and discharged so many times.

If you are using cells daily and recharging them daily, get high normal capacity cells, but get enough that you can use 1 hour or greater charge times, charging batteries in 15 minutes destroys them, and they will quickly become useless.

LSD NiMH cells are designed for the devices that last months on one set of cells. Sure they are just as good as the others for high drain (maybe better, from what I've read LSD are just high tolerance "cleaner" batteries) devices that you recharge often.


Bottom line, buy quality brands and treat them right, don't charge them faster than 1 hour, yes you can do it; but it will cost you money in the long run. Extra cells and less charging of individual cells will make them last longer.
 
I don't know what the agreed upon definition of high-discharge is, but some of the hi-cap cells can get to the point where they won't even hold a decent charge for a couple days.

You recharged cells 7 times in one day? Good lord man, what were you doing?

Are you sure that your devices are really that power hungry rather than your batteries being in bad shape? It might be worth experimenting... buy one set of Eneloops and see if they require a charging just as quickly as your hi-cap cells. Or at least buy a new set of your favorite NiMH's: your current cells may be well past their peak life. I could be way off base though: maybe you are cranking through that much juice legitimately.

It's worth noting that in addition to the low-self-discharge property of Eneloops and similar cells, they have shown in testing (and real world use) to have much better lifespan compared to the hi-caps. They also can handle heavier load (like some flashlights demand) with less voltage sag so even though their capacity is "decreased" some devices might perform better and longer on them.

Brand new hi-cap cells will still have a higher capacity before sitting 1 or 2 months than an Eneloop, as noted by UnknownVT, but that is when they are still at the peak of their life. After enough cycles and usage that becomes less and less so. After a few months (maybe a year?) of use, the self-discharge rate becomes worse. That is when you start to hear the stories of, "I charged my cells on Friday and when I tried to use them on Tuesday they were dead."

A lot depends on how often and how hard you use your cells, of course, as well as your charging methodology.

Bushman5 said:
part of the problem with listing "discharge " rates is people do not factor in how often the batts are used.
Click to expand...
Well I would hope people are smart enough to factor that in on their own. Same with primaries: I would hope someone wouldn't look at the advertised 10 year shelf-life of lithium cells and think that it will run a device for 10 years.
 
By the way, I agree that there are certainly applications for hi-caps. I hope I don't come across as trying to advocate replacing all NiMH's with Eneloops. If you are definitely using devices quickly then yes your usage may require hi-caps. But that's the thing: you better constantly be using them that way. If you use them hard a couple days but then let them sit a while, you're going to start seeing trouble.

I don't let my cells sit for months and months, but usage is not constant. Maybe I'll use the external flash or a certain flashlight heavily a few days, and then not at all for two weeks. I don't want to have to worry about lots of care and attention to the cells: making sure they don't self-discharge too far and get damaged, conditioning them too often, etc. That's one of the reasons I like Eneloops.
 
On a slightly different but related topic- Eneloops are available in a complete kit which includes charger, AAs , AAAs, hollow adapters for converting its AA to C and D cell applications! I' ve never seen this in any other recharge kits/packages.

N.

www.dozierknives.com/forum
 
ThinkOfTheChildren said:
I don't know what the agreed upon definition of high-discharge is, but some of the hi-cap cells can get to the point where they won't even hold a decent charge for a couple days.

You recharged cells 7 times in one day? Good lord man, what were you doing?



Brand new hi-cap cells will still have a higher capacity before sitting 1 or 2 months than an Eneloop, as noted by UnknownVT, but that is when they are still at the peak of their life. After enough cycles and usage that becomes less and less so. After a few months (maybe a year?) of use, the self-discharge rate becomes worse. That is when you start to hear the stories of, "I charged my cells on Friday and when I tried to use them on Tuesday they were dead."
Click to expand...

the batts are all less than a month old, with the exception of the orignial ones that came with the charger. I'm running 33 frames a second on the camera, averaging about 2000 frames per session, or Hi Def movie mode or my power hungry flash unit. Not to mention my flashlights. I have charged up all 24 of them before a hike or trip and have never had a "charge on friday, dead on Tuesday" issue....

as for 15 minute charge times killing bats i cry foul here (keep in mind this has been my own experience with the batts i have, ymmv) .....the batteries and charger i have is designed for fast 15min charging. It discharges, checks, conditions and charges the batteries. its fan cooled to prevent heat buildup . I have some AA's (the original ones that came with the unit) that are over a year old and they have all had daily charging, use/discharging and they last just as long as the new ones (same brand, same capacity). I've also stored them for weeks and never seen this issue of discharge. Not knocking eneloops, they are great, but there is nothing wrong with hi cap energizer AA NIMH either.

sure on a bench test (controlled environment) the discharge rates can be measured and compared. But its virtually impossible in real world use of the batts to measure such rates, there is FAR too many variables. Temps, item the batts are in, frequency of use , power demands etc etc etc etc.

that being said I know the eneloops have recieved a pretty high rating by the CPF crews. I just dont want to buy YET another set of batteris and YET another (different) charger
 
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I said that for a while, at first, when I got into the rechargables market for use in my bike lights. Then It got to the point where the energizer 2500's would nee changed out halfway through a 20-30min commute. Eventually switched to Duracell Pre-charged (white top, supposedly re-branded enelope) and since then I've been getting absolutely fantastic results.

If you search, especially over on CPF, you'll find that while some people have had good results with the energizers, they have a long and well documented history of poor performance.
 
I had been doing a bit of battery work with another person on their usage in a pretty battery fussy dSLR (Pentax K100D and K200D) - by careful measurement it was determined that the cutoff voltage threshold in the K200D was about 1.15V with a max current demand of ~1.5Amps

conventional high capacity NiMH batteries will outperform eneloops if they are recently charged (ie: not stored for too long before actual usage).

Here are the comparisons - again using the discharge curves by SilverFox taken from NiMh Battery Shoot Out

I drew the same horizontal 1.15V threshold cutoff red-line
then noted the points at which the 2Amp and 1Amp discharge curves crossed that red-line and found the mid-point between those (this should approximate where a 1.5Amp curve would cross the 1.15V red-line - not exactly right but probably close enough for this look-see comparison)
and dropped a vertical red-line to the horizontal axis to note the actual Amp-Hours delivered.

eneloop
EneloopAA2000K100D.gif


Energizer 2500 mAh
EnergizerAA2500K100D.gif


Duracell 2650 mAh
DuracellAA2650K100D.gif


those readings were approx

Sanyo 2700mAh = 2.265 A-h
Duracell 2650mAh = 1.881 A-h
eneloop = 1.66 A-h
Energizer 2500mAh = 1.61 A-h
GP ReCyko = 1.54 A-h
RoV Hybrid = 1.43 A-h

So the high capacity Duracell 2650 mAh (and Sanyo 2700mAh) do beat the eneloop when they are recently charged and in good condition.
But the Energizer 2500mAh is lower than the eneloop even when recently charged.

However when aged high capacity NiMH are notorious for developing high rates of self-discharge and can lose their capacity (eg: Ref1 Ref2 Ref3) -
so that the LSD (Low Self-Discharge) batteries eventually will cross-over and perform better in longer storage before use situations.

To be fair when one is going to use the K100D/K200D a lot - then charging up a set of those better performing high capacity NiMH on the day or night before probably will show better performance from eneloops under the same conditions.

But if the batteries are stored or partially used for anything over a month or 2, then the eneloops are probably going to do better at that point.

--
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I was trying different NiMH batteries a few years ago and kind of lost track of what's currently out. I will say that I ordered pre-chargend Eneloops back in Summer (June/July) of 2007 when I was in Iraq, but had them shipped to my home. I have since returned and forgot about the batteries and found them right before Christmas. All the batteries will still charged and working...not sure how much they dishcharged over the previous 18 months, but I put several in some LED lights to see how long they would last (mostly Fenix LED lights) and they lasted several hours before noticing the drop in output. I'm pretty well sold on the LSD Eneloops for long term use/storage.

ROCK6
 
I think Eneloops are currently the best bet in cells right now. Personally a 700mah capacity drop for longer charge shelf life and likely more charge cycles is very much worth it.
 
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