Thanks useful information: 
Another way to tackle the issue could be from the coming persepctive ...
obviously the weight and space taken up by the batteries and chargers is the issue.Originally Posted by mikew09
have you thought to try converting to LiIon AA batteries?
I know a lot of folks are scared of them in one way or another, but so far I've had them in my Nikon SB800 and they work a treat.
In terms of usable power they eat 3 sets of rechargeable AAs for breakfast(as all Lithiums do anyhow).
I've had them sitting in my SB800 now for nearly a year I reckon and I just checked and they're still at full power.
And it's important to note that full power for a LiIon is nothing like full power for a rechargeable or alkaline AA battery.
With the normal AA's on the SB800, I think(memory a bit vague) but I get maybe 1 or 2 continuous flashes in succession before the flash needs to pause a moment due to recylce times. No such issue with the lithiums. Ever!!! .. as in ever ever.
They just put out so much more power that I had the flash continuously cycling as fast as the camera could shoot. The again and because the camera pooped out long before the flash did, I re-did the test this time using the modelling flash for about a minute so it sat there flashing it's quick strobe like output for a botu a min, then I quickly shot at 4fps for about 17 frames .. and I still couldn't find a recycle time limit for the batteries.
My conclusion is that these batteries are beyond the ducks guts(whatever euphemism that may be) .. the geeses guts maybe
Only and main problem is they output 3.6v, and people are scared of this voltage rating .. and it's unknown if such a voltage rating is safe via the internal battery pocket. I know that they use lithium power via an external source tho.
An 'almost problem' with them too tho is that the batteries can heat up if used excessively. I have no idea what excessive use requirements most strobist have, but in my durability/recycling testing doing minutes of modelling light testing and wayyy too much boring exposure recycling testing they never got warmer than luke warm. But they did get warm, where the normal AAs stayed cold.
I used the term 'almost problem' only to alert the issue of possible overheating and if you shoot at 10fps for more than two minutes there could be an issue with heat. Havign held the modelling light down for about a minute(I got tired and copped out and the flash wanted to keep going!) .. I didn't think they heated up as much as they got warmer.
So far, so good tho. And my testing now is to see how much self discharge they exhibit .. and it turns out that after a bit of use to deplete them a little and having sat now for about a year, they did discharge to the point where the flash wouldn't turn on.
Because your main gripe was weight, these batteries do save an enormous amount of weight over normal AAs. And as they have about 3x the power ability, you may not need charges and suchlike.
Note that if you do look into them they are called AA when they're lithium, the battery model number is the 14500. And be careful about some makes as they can be a bit taller than the standard 50mm height that an AA is supposed to be.
I got stung with some AAAs that don't fit a lot of my devices as they were taller than std AAAs, so when I searched for these AA/14500's I made sure that the size was 50mm.
So far with both the AAs and AAAs I'm using in various devices I've never had any issue with heating up, nor over voltage issues. But note that some devices simply can't tolerate higher voltages than the specs state should be used.
Hope that helps.
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