i have a couple fatmen downstairs.. but i'd have to look about anode pad.. i do not think so.. they are too big to fit in the type of light that fits a board..
Fatman will drive a luxV from a single LiON quite nicely.. good pair.. so look into the Pila 150 or 168. you will want some serious current capability. do the math.. you need to keep current in below 2A to keep fatman happy... it's a fantastic driver.. and design in a logarithmic taper pot for full dimming..
Also.. an undocumented feature is a simple potentiometer will give you a 'hack' of a low voltage cutout that works really well.. it's not 'perfect' because it'll blink sometimes but it'll save the battery and it actually doesn't just 'shut off'.. it actually dims slowly at the end of charge on the battery.
the fatman is big.. like .86 diameter and unlike the VIP.. no chance to really shave it down.. i don't think you can fit it in .75 if you try.
2 CR2 will do the trick. Each has OD of 15.6mm and height of 27mm. That will fit well within your requirement. Only downside is that you sacrifice almost half the capacity of a CR123. 1500mAh to 800mAh.
*source: Energizer website ( www.energizer.com ), Technical Information
2 CR2s won't drive 5W... not a chance. I would absoultely find a LiON solution.. biggest bat you can find.. like the 18500 or the 18650 (although that one is 65mm long).. the 18mm is perfect for your 20mm tube.. the 50mm version gives you a cm to fit your driver.. lemme calculate: .78 inches.. that's a smidge smaller than the fatman but i think it's only .80 so you should be able to sand that down.. you can put in a dial for brightness and blamo.. done deal.. build a charger from the LTC 4054 and put in a charger jack and you don't even have to ever open the thing.
-awr
ps.. oops i was just in the lab and didn't look at the bottom of the fatman.. I did design an 8-way LDO driver to put in my VIP in place of the driver in there (i want to use rechargeables).
2 CR2 will drive 5W. Just not for very long. I calculate about 1/2hr. Maybe less depending on efficiency of the converter. This will be slightly better than 3 AAA cells.
steel wolf.. when you say 'calculate 1/2 hr'.. are you talking about bawed on mah ratings ore actually measured loads.. here is an example:
I stand 'semi-corrected'... i'm a little surprised that the CR2 actually has a rating of 1A max.. i'm just aware that 123s do not like 1.5A very much.. pulling 3W out of a 123 is like pulling teeth.
if you hold back a bit so you dial the 5Wer down to 5W and not 6.5 like typical.. that is about 760mA.. than you back through the emitter efficiency you will have just about 6.0W demand at the batteries.. when the batteries are fresh that means 1.0A but the batts will drain down to 5V during the course and that means 6/5A or 1.2A from the battery..
I bet you are correct that you can get close to 1/2 hr if you use the fatman.. it's more than i expected.. but.. and 18500 single LiON has 1400mAH and the 18650 has up to 2400 (but i think that is 5mm too long sadly)..
1400mAH.. that means.. hmm. 6W / 3.7v = 1.62A.. high but way less than 2C.. so you can probably get close to the full rating of 1400mAH out of it.. or.. let's estimate 1200mAH/1600mA or 45 minutes.. but this solution costs about 1/5th of a cent to recharge.. CR2s.. $5-8 a pack.. so $8/hr or something. of course you can get them cheaper in bulk.. and get that down to S3-4/hr to operate vs 1/2 a penny per hour.. house electricity is infinitesimally as costly as batteries.
if you can cram an 18650 into your compartment.. you can expect to get the full rating out of the battery because the drain is less than 1C.. so 2400mAH / 1600mA = 90 minutes!.. again it would cost maybe 1/4 penny to recharge... that is where i would be leaning.