Originally Posted by barondla 
Great info miniman82. Never knew how to neutralize different types of batteries. One of your cautions does present a problem. How does a K10/20D(lith-ion battery) owner carry a 360 0r 540(aa nimh) flash in the bag? Two different power sources are supposed to be a no no.
. My bag has 4 Li50 batts in it and 12 Sanyo Eneloop nimh AA. That could really do something.
Dammit!
How come everytime I type a long winded reply, I get kicked off, and asked to re-enter my info even though I obviously already have????
Here I go again, shorter this time....
OK, flashes typically operate on 4 cells connected in series. This provides 6 volts to the flash, since each alkaline cell is 1.5 volts. With NiMH/NiCAD, you end up with 4.8 volts, because each cell is only 1.2 volts. A Li-Ion AA cell is about 3.6 volts, so if you only used 2 of them, you'd have 7.2 volts. 4.8 volts is 80% of 6, and 7.2 is 120%. That's 20% on each side of 'normal' operating voltage for a normal 4 cell flash, so I doubt there would be any damage. If anything, the flash would charge up faster, due to the increase in voltage.
Anyone want to loan me a 360/540 to try out some mods?
Of course I would replace it in the event of failure, and also foot the bill for the cells and charger if anyone out there is interested? If successful, it would mean less batteries to carry around (more room for LBA!!!!!), and also less charging time (since you can now charge twice the needed amount of cells to power your flash with a typical 4 cell charger).
PM me, or post up here if interested.