mine is a 3phase @ 21AHr x 14.3V is 300W
going through the book's list of bulbs as stock on my 03 R* Midnight
looks about 200W total (both directionals, high beam, brake) current draw.
maybe a useable 100W (~7AHr), more if you change out the bulbs for LED's.
i been thinking about a rewire myself.
if you have saddlebag space, adding another stock 18AHr battery
would get you a lot more time to run power accessories. alternately
you can get pretty 'large' (as in AHr) battery pack's like those
NiMH or LiPO for a toy RC car. ie 7.2V 4.5AHr. 2 would cost ~$40
give you 14.4V @ 9AHr. ofcourse that comes down to how you can
charge/maintain them but im sure somone could put 4 of them in
inside pockets of the heated jacket or pockets on the sleeves.

<P>03 R* Midnight<br>04 mag wheels chromed,
V&H Pro pipe, HyperCharger intake, relocated FPump,<br>8" risers with 42" 1.25 beachbars 'upside down'!,<br>hand stretched the control sw wiring 8" and perewitz made me an 8" over brake line<br> bunch of other crap with chrome too...