I’ve always wondered this one. Rechargeables (well, NiMH and LiIon and most NiCd) pretty well always list their capacity (mAh) on the batteries and the packaging, so you have a good idea of how long they will last in a device given its amperage before requiring a recharge. I like that idea. At least then I know I can expect somewhere around 5 hours of use in a 500mA device using 2500mAh batteries.
So why don’t they list capacities on alkaline or lithium batteries? Is there something that prevents them from measuring capacity with any degree of accuracy? Or is it purely a marketing thing? It just seems to me that with battery companies continually putting out new battery lines and claiming that they’re longer-lasting than ever before, quantitatively backing such claims up with actual capacities would seem to make a lot more sense to me.
Industry secrets. Industry war between Energizer and Duracell far as I can tell.
Also, I don’t know how the wattage decline plays into it, but alkaline batts gradually lose their punch from minute one…a progressive drop… whereas NiMh and NiCd drop off more suddenly near the end of life. I don’t know if this factors in or not.
In the hobby world, you buy batteries based on the mA rating…1200, 1400, 3000, etc. Even in non-electric powered vehicles, simple radio/receiver batteries of all different sizes/shpes/configs advertise the mA rating. It is very useful to determine battery value and forecast how much radio time you have.
If you go to the manufacturer’s web sites and poke around for the technical specs of the batteries, you can find the exact discharge curves, mAh ratings, and pretty much anything else you’d ever want to know about the batteries.
They aren’t secrets. They just choose not to put the information where the public can easily get to it.
Or maybe it’s so they can BS the unwary? I just looked at Energizer’s website, and there’s something I just don’t get.
Standard Energizer AAA (Alkaline Manganese Dioxide Zinc): 1.5V, 1250mAh
Energizer E2 Lithium AAA (Alkaline Manganese Dioxide Zinc): 1.5V, 1250mAh
And lest we think battery format is to blame here:
Standard Energizer AA (same composition): 1.5V, 2850mAh
Energizer E2 Lithium AA (same composition): 1.5V, 2900mAh
What the heck is going on here? Their premium E2 batteries are made of exactly the same stuff and have (almost) exactly the same capacity as their standard line despite this wonderfully useless “FAQ:”
A dodge worthy of a senator. So what in the heck costs an extra $4 when you buy the E2s?
Alkaline batteries have a significant internal resistance compared with rechargables. This means the greater the current draw, the more of their energy they waste generating heat in the battery.
Additionally, alkaline batteries suppply a gradually decreasing voltage as they discharge, so for some applications they become useless even while they technically have a fair bit of energy left in them. Flashlights are a nice example - a mini-maglite goes from bright to sickly in about thirty minutes with alkalines, even though they’ll give a weak beam for a few hours after that, and run a radio for a while even after that. Rechargables tend to have a relatively flat discharge curve.
This makes a mAh figure less useful for alkalines than for rechargables, or even downright misleading.
Think you read something wrong here. Energizer makes an E2 Titanium and an E2 Lithium. The lithium is clearly a different composition and has a longer shelf life. The vanilla E2 seems to be optimized for high current drain applications like digital cameras that wipe out ordinary alkalines almost immediately. I don’t know enough about battery technology to tell you what the difference is, or why it doesn’t map into increased mAh, though.
Sorry, you’re right – I was getting the Lithium mixed up with the E2 Alkaline.
Just the same though I see the mAh is still the same even with AAA (1250mAh) and a little higher with AA (3000mAh). I am assuming then that the difference is in the discharge curve where lithiums (and possibly E2 Alkalines) hold their voltage for longer periods of time before dropping.
This brings up another question though: Why don’t NiMH rechargeables have capacities that rival their Alkalines or Lithiums in smaller sizes? I know you can get 2500-2800 NiMH AA batteries, but the average AAA only hits 850-900mAh, while alkalines and lithiums all sit at 1200+mAh. Is it because nickel-metal hydride is less dense?
are you sure about the Energizer AA being 2850mAh? that seems really high.
the lithium seems fairly close to the Panasonic 18650’s I have here, I got them from a Laptop Batteries, they’re 3.7v @ 3400mAh, or around 12.5Wh, but they are a bit bigger then AA’s (basically equal to around 3x Lithium energizers@4.35Wh). according to http://www.batteryshowdown.com/static/images/mah_large_1000mA.png theres only a couple batteries with anywhere near 3Ah and they’re all Lithium, I doubt the energizer anything other then lithium is 2500+
their data sheets are available here. Their claimed capacity for the normal Energizer AA (the standard one, silver & black label) has about 2900-3000 mAh capacity, but only at a 25 mA current draw. at a 500 mA current draw, its capacity drops by more than half. Your 18650s will have roughly the same capacity at both low and high current draws. A data sheet I found for a Panasonic cell shows fairly little capacity loss even at 10x the current draw.
The materials in rechargeables take up more physical space per mAh. But you are limited by the standard sizes of AA, AAA, etc. battery case – you just can’t fit enough rechargeable material inside the case to get up to the same mAh.
mAH is not a good measure of alkaline because the rating though a industry standard is not a good indicator of how long a battery will last since the chemistry is so dependant on how fast you withdraw that power.
Also that rating would be counterproductive to building a battery that lasts, since one can optimize the chemistry for a max mAH for the testing purposes, which would generally have lower performance in real life applications. The more you try to get better ratings, the worse it’s everyday performance.
I’ve had some Nimh AA’s that were slightly larger than standard cells, they did have a high mAH rating, but didn’t fit in some things, others very tightly.
Well it took a long time to get the correct answers didn’t it !
Well the benefit of alkaline over standard is that the standards have the high internal resistance when used at high discharge rate…
But you see its marketing, if they put the alkaline’s capacity on the package clearly, people would see that there was no point in paying five times the price for something that might be as good as three times as good, or in low current use, only one times as good.ie no improvement.
Meanwhile, consumers need the capacity of rechargeable so as to know how long to recharge them… and because there is competition in them to get higher capacities.
Not my area of expertise so I take your word for it on the above. But it does invite a question.
If the current (heh :)) battery-rating standards are A) inapplicable to the most commonly used modern battery chemistry, and B) poorly model the uses batteries are actually put to in 2016, then …
How about the industry / NIST / ??? come up with a more relevant consumer rating standard?
Yes, it’ll still be partly arbitrary / artificial. And you’re right that industry would game the new standard too. But assuming it’s well chosen to represent at least a decent hunk of the actual usages for that sized battery it’ll be better than the zero data and pure marketing puffery we have today.
