Longer KL1 run time - 3 123 vs. 2 lithium AAs?

I was just wondering which combo will give KL1 longer run time - 3 x 123 batteries or 2 x Energizer lithium AAs?

Why not do a bit of calculation?

Assuming all batteries are Energizers...

1 Lithium AA L91 (not those already 2 in a pack type) - 2900 mah @ 1.5 volts
1 Lithium 123 - 1300 mah @ 3 volts

If 123s.. = 3 x 1300mah x 3 volts = 11700mah
If AAs... = 2 x 2900mah x 1.5 volts = 8700mah

Therfore 123s should theoretically have the advantage, added to the fact that it's more efficient to step down than the step up (I think..) 123s should have alot more advantage than AAs.

Anyone wanna burn some $$$ and do some real world testing?

Nerd, amp hour capacity does not accumulate in a series hook up; (3) 3Volt 1.3 amphour batteries in series (ie. end to end) will give you 9 volts for 1.3 amphours of use. (2) 1.5 volt 2.9 ah batteries in a series will give you 3 volts for 2.9amphours..to compare them multiply amps X volts to get total watts available;
3 Lithiums= 9v X 1.3ah = 11.7 watts
2 AAs = 3v X 2.9ah = 8.7 watts

...the lithiums still win...
<edit> - or is it 'watthours'?..so a '5watt' LS would burn for about 2.34 hours, compared to 1.74 hours for the AA's..I think..real world figures will vary)

When you calculate total watt/hours of a battery or group of batteries, it really doesn't matter if you compute them by series or parellel. Multiplication rule follows through. Voltage and current under load will vary the numbers greatly, though... So it doesn't always necessarily mean that the watt/hours apply hand in hand to application. Especially when you factor in regulation and/or direct drive into place...

Ah hah, not mah.. wrong measurement unit.. lol! My bad...

Nerd, nothing wrong with mah, I just divided by a thousand; converting it to ah... don't tell pah...

Falcon, right, that's why a watt is a watt is a watt...
..the rest is correct of course..