Energizer AA lithium vs. alkaline same capacity?!?

[milkyspit]

I just noticed something very strange in the battery data found under "Technical Info" on the Energizer Web site. According to their published specifications, the Energizer AA alkalines have 2850mAh capacity, while Energizer AA lithiums have 3000mAh. What gives!?! I thought the lithiums had much greater capacity per battery, and my own experience using both types in my flashlights would seem to support my assumption. So why the spec stating that they have virtually identical capacities!?!

 

[lemlux]

The stated capacity of the alkalines is at a low drain. As the current increases, alkaline capacity drops precipitously and lithium only slightly.

Also, lithium will but out considerably higher voltage for longer at any current. The watt hours capacity of the lithium cell is consderably higher at any current. The ratio of watt hours of lithium vs. alkaline increase steadily as the current increases.

 

[zmoz]

Yeah, you aren't going to get 2850mah out of an alkaline in anything but a remote control. /ubbthreads/images/graemlins/smile.gif The lithium will probably give you the full 3000mah in almost anything.

 

[Pi_is_blue]

The difference in voltage can easily be seen in an Inretech 2AA adapter (DD). The lithiums make it about twice as bright as the alkalines.

 

[milkyspit]

So, if I'm understanding correctly (and please pardon the analogy), if I visualize a tiny power generation plant with a pile of coal sitting next to it, the mAh capacity is akin to the amount of coal in the pile -- in other words, it is related to the total potential for electricity generation -- but the speed at which the plant can burn the coal matters, too, in that one plant (lithium) can scale up tremendously if necessary and make electricity from the pile of coal very quickly, but the other plant (alkaline) only has the capacity to burn the coal fairly slowly, and if forced to burn it quickly will end up wasting a lot of the coal.

I know it's a corny analogy /ubbthreads/images/graemlins/rolleyes.gif , but is this something like the difference between these battery chemistries?

 

[JohnK]

Milkyspit- I couldn't have said it better myself..........I think you are splendidly correct.

 

[lemlux]

Milkyspit:

I would add the following to your analogy. There is also a difference in the quality of the two coals. Alkaline coal generates fewer BTU's per ounce (lower average voltage and watt hours [ = average voltage times mAh] per mAh)than lithium coal.

 

[milkyspit]

Okay. It seems that lithium in general is a battery chemistry that matches well with high output lights like Surefires or the 5W Luxeons in general. Is it the alkaline chemistry that doesn't perform as well under high load, or is it specifically the AA size? For example, is an alkaline D cell designed for high current output, or does it suffer from the same types of limitations on current draw as the AA alkalines?

 

[Brock]

Or another way to think of it is the alkaline coal plant cant keep up with larger loads so you get a brown out. The power is still there, but who wants lower voltage. While lithium will keep putting out that full voltage till they run our of coal /ubbthreads/images/graemlins/smile.gif In reality most alkaline lights run longer, but at a much reduced level almost from the get go.

 

[paulr]

Alkaline batteries in general aren't so great at high current, though you can get higher current from D's than AA's just because of their larger size.

If you want low operating cost and high current, use NiMH or (for even higher current) NiCad designed for fast discharge. Capacity will be lower than alkalines but you can discharge at very high rates with the right cells (e.g. the sub-C nicads in cordless power tools).

 

[danno]

Try going to the "Technical Information" section of Energizer's website and looking at the battery datasheets, which contain runtime graphs of alkaline AAs and lithium AAs. Look at the "digital camera" graphs for lithium and alkaline AAs. These graphs show that, at 1 amp of current drain, the alkalines will last approximately forty minutes until the voltage drops to 1.0 v, while the lithiums will last about 160 minutes. On the other hand, on the "remote control" test, which is based on intermittent use a low-drain device, the alkalines last 50 hours until they drain to 1v and the lithiums only last 45 hours.
As I understand it, this is due to the high "internal resistance" of alkaline batteries. This concept of internal resistance is based on modeling a battery as a voltage source and a resistor. Due to their battery chemistry, alkalines have higher internal resistance than lithium, ni-mh or ni-cads. In fact, for some applications (like flash photography) the effect is so great that you will get better runtimes from an old ni-cad AA than from an alkaline AA. (although ni-cads have low capacity, they have the lowest internal resistance of common battery chemistries).
BTW, alkalines are great for some flashlights if you are interested in long run time. Due to their high internal resistance, when used in direct drive or resistored LED lights, they tend to dim faster but last much longer than ni-mh or lithium cells. On the other hand, if you're using a regulated circuit or want max brightness, use lithiums or ni-mh.

 

[FalconFX]

The curve for discharge currents for alkalines make them undesirable for hungry devices. One of my digicams would be lucky to last 60 minutes with a couple of alkaline AAs, while getting almost 2 hours with NiMHs...

 

[JohnK]

On this same vein, what is the effect of having EIGHT series/parallel AA's; as in the PT Surge.

Surely this is why it is so durn BRIGHT.

 

[FalconFX]

4 in series, 2 packs in parellel: Basically, to divide the current load between 2 parcels of battery packs for longer runtime, if you want to think of it that way...

Similar design purpose to the M6, which can run off of 9V, but uses a series/parellel configuration to provide the necessary current to maintin a 500lumens bulb...

 

[Charles Bradshaw]

Re: Energizer AA lithium vs. alkaline same capacit

The Lithium AAs can deliver more for longer, plus have a longer shelf life, and work better than alkalines at low temperatures.

Illustrative Example:

My Rev1 Arc LS gets 3.5 hours bright light on a Ge-Sanyo CR123A (1200 Mah), 3.5 hours on 2AA alkalines, and 7 hours on 2AA Lithium.

The point is that Alkalines have less usable capacity than lithiums.