Why is the capacity of CR123A batteries so low anyways?

[InfidelCastro]

Or is it not?

Looking at them next to my 2500mAh Energizers, I don't understand why CR123A batteries have such low rated capacity. Volume wise, they are similar in size. Definitely larger than AAA's. They are shorter, but fatter than AA batteries.

I see them rated around 800mAh. Is this because their ratings are based on much higher current drains? Or is there something else going on here?

AA batteries are easily capable of putting out the 1A or so that a decent flashlight demands. So why the big disparity in Ah ratings?


My G2 takes a little over an amp of current and runs for less than an hour on two new batteries.

My 2D takes around an amp of current and runs for many, many hours. And doesn't suddenly go dead either.

I thought lithium is much more energy dense?

 

[chevrofreak]

Higher voltage. 1300mAh at 3v and 2600mAh at 1.5v are about the same capacity.

 

[billw]

By my calculations, an AA has about 25% more volume than a 2/3A
battery, which is pretty significant.

Most of the non-rechargable cr123a batteries are rated about 1000 to 1200mAH,
aren't they? Are you talking about these, or rechargables?

And lithium batteries are much lighter than NiMH, so depending on whether
you measure energy density as energy per gram or energy per volume,
you get different comparisons.

However, the big part of what you're missing is that the lithium battery
has 2.5x the voltage of the NiMH batteries, so a 1000mAH Li cell has
about 3WH of capacity, and the 2500 NiMH has (also) about 3WH of capacity.

On the third hand, a 2500mAH NiMH battery in something like a flashlight is
pretty much a state-of-the-art modern battery in heavily used "showcase" size,
used in the discharge realm where it was designed to be used, while the cr123a
is a 15-year old battery and technology (with little customer demand for improvement)
designed (maybe) for pulse applications (cameras, right?), that just happens to almost
work OK in flashlights as well...

 

[InfidelCastro]

Yea, I've often wondered why we don't see C or D sized lithium batteries for flashlights (in any quantity). It would be alot cheaper to feed a Surefire M6 type light with 3 lithium D's instead of 20 (or whatever number it takes, don't remember) CR123A's.

 

[paulr]

3 volt Lithium D's (basically giant 123A's) are available from hdssystems.com at something like $11 each in quantity.

CR123A's (17mm dia, 34mm length) and AA's (14mm dia, 50mm) have about the same volume.

 

[InfidelCastro]

Right, that's crazy. Somebody should develop higher powered lights that take these batteries. But then they couldn't sell a bazillion 123A's to put into D sized lights like the M6 though...

$11 a battery is ridiculous. If manufactures started making lights based on something other than 123A's, the price on C and D lithiums would come down. But there's no incentive, because they make so much money off of batteries that only run the lights for 20min-1hour (typical light)

 

[chevrofreak]

The Surefire M6 uses 6 batteries.

You cant compare Ni-MH and Li-Ion, they are completely different chemistries.

To know the true capacity of a battery you need to go by watt-hours rather than amp-hours. Watt-hours combines voltage and current, which will give a number that can be compared between chemistries.

 

[HarryN]

Right, that's crazy. Somebody should develop higher powered lights that take these batteries. But then they couldn't sell a bazillion 123A's to put into D sized lights like the M6 though...

$11 a battery is ridiculous. If manufactures started making lights based on something other than 123A's, the price on C and D lithiums would come down. But there's no incentive, because they make so much money off of batteries that only run the lights for 20min-1hour (typical light)

The price is certainly not as attractive as one would like, but I am not sure if they are out of line or not. The capacity of a Li (not Li Ion) C / D cells is quite impressive when you consider their ability to deliver voltage, current, and capacity in a relatively small package. The ones HDS carries (SAFT) are protected, approx 7.5 AHrs, and very high quality.

As a useful comparison, in terms of CR 123s, which are nominally 1 - 1.5 A HRs, it would take 5 - 7 in parallel to be equivalent to 1 of these. That makes the $ 15 / each price seem a bit more reasonable.

There are cells from other brands that have impressive performance as well.

 

[idleprocess]

Amp-hours is not the best standard to be comparing things...

2500mAH NiMH cell * 1.2V == ~3 watt-hours
1400mAH CR 123A cell * 3V == ~4.2 watt-hours

...thus, there's more energy in a CR123A cell than a 2500mAH NiMH cell.

 

[TooManyGizmos]

.
Now this is a very good thread ! :rock:

It's very informative and I'm learning a lot !

I've been wondering the same thing lately (AA v/s 123) , but just forgot to post it .

This forum is great - with a lot of friendly , helpfull , smart people !


Thanx.. "InfidelCastro".. for posting this good question .

We need more like it - for educational purposes .


Thanks ALL - for sharing !


Cheers......:buddies:
.

 

[greenLED]

Agree, TMG!

It's nice to see "technical" threads back. In enjoy them more compared to the "what lights should I buy?" ones, although I do try to help on those too.

 

[tvodrd]

Well done Idle! (That was the post I didn't make last night. ) Here is one of several sites with ampacity numbers. (My "Bunny" one seems to be dead.) I personally don't care for the self-discharge characteristics of NiMH chemistry. For Watt-hours per cubic whatever, lith primaries still have a major edge over anything else. (Yeah, ampacity is discharge-rate-dependent!)

Larry

 

[greyfox]

the same question

 

[chimo]

the same question

I'm not sure if the question is the same as the original poster but I will attempt to answer.

My answer:

the same answers as above

 

[TooManyGizmos]

!
Is that all there is ?




:nana:



What about .......... how much more capacity does an 18650 have than a 2600mAh AA cell ?

Does anyone make primary 18650 size Lithium's ?


.

 

[idleprocess]

Amp-hours * nominal voltage == watt-hours. This is highly dependent on the load, since voltage typically sags as current draw increases, also causing a reduction in the number of actual amp-hours any given cell can provide.

Lithium-ion cells have a nominal operating voltage of ~3.6V at loads up up to ~1C, thus 2200mAH 18650 * 3.6V == ~7.92 watt-hours.

I don't know if there are any 3V lithium primary 18650 cells being made. The 18650 is close to the "4/3 fat A" cell (18670). A cells are 17500s.

Battery size chart at the CPF wiki

 

[Handlobraesing]

Amp-hours * nominal voltage == watt-hours. This is highly dependent on the load, since voltage typically sags as current draw increases, also causing a reduction in the number of actual amp-hours any given cell can provide.

Lithium-ion cells have a nominal operating voltage of ~3.6V at loads up up to ~1C, thus 2200mAH 18650 * 3.6V == ~7.92 watt-hours.

I don't know if there are any 3V lithium primary 18650 cells being made. The 18650 is close to the "4/3 fat A" cell (18670). A cells are 17500s.

Battery size chart at the CPF wiki

Your simplified equation can only be used for batteries with a perfect discharge curve. The further the discharge voltage curve deviates from perfectly flat, the greater the error introduced.

For the alkaline or the lead acid or anything else with less than a flat discharge curve will have a substantial amount of error.

The correct calculation for energy capacity is:
∫power(t,0,end)

If you could plot the current and the voltage simultaneously over time, its just a matter of integrating the product over time with a software.

I'm not sure what graphing software you can use to integrate hundreds of datapoints though.

 

[Spacemarine]

I'm not sure what graphing software you can use to integrate hundreds of datapoints though.

If you have the datapoints, there is no need fo a graphing software, even Calc from Openoffice (or Exel if you can't get Openoffice) would be enough. Just multiply the current with the voltage with the time between each measurement and sum them all up. That's it.

 

[monkeyboy]

There is much greater demand for AA's than 123's since practically everything uses AA's these days. I guess this gives manufacturers more incentive to develop new technology for rechargeable AA's.

I like that fact that you can just go into a shop and buy the latest Sanyo 2700mah AA rechargeables with the knowledge that you're actually getting a battery with 2700mah wheras the R123 would probably require buying some dubiously labelled 800mah cell off ebay which is probably more like 500mah and comes with a charger that only charges it up to 200mah.

OK that's a slight exaggeration but you get my point. (I've had bad experiences of buying batteries/chargers on ebay before)

 

[idleprocess]

Your simplified equation can only be used for batteries with a perfect discharge curve.
[...]

Of course. Integrating the curve will give you a very precise measurement.

We don't need to go through the exercise of integrating a voltage curve since we just need a nominal comparison of faceplate values.

Given the relatively flat curves for lithium-ion, lithium-primary, and NiMH, using a nominal "working" voltage that dominates most of the curve (~3.6V for lith-ion, 3V for lithium primary, and 1.2V for NiMH) will get us close enough for a better apples-to-apples comparison. I expect an acceptably small error margin using this method; differences in actual vs rated amp-hour capacity will probably be a much larger error than our approximation.

Even with lead-acid, alkaline, and other chemistries with less-than-flat discharge curves, one need only choose a good "midpoint" voltage that's close to the statistical average voltage over the entire curve. With PbA, that seems to be ~2V/cell; with alkaline, it seems to be the same 1.2V we use for NiMH.