How do I battery power 12/16 track Motu Traveler/Metric Halo 2882/G4 Mac?

[jim1274]

I'm putting together a mobile rig based around a Metric Halo 2882 and Motu Traveler MKII for mid track count set-up when my R-44/Apogee Minime 4 track is not enough and i don't want to drag out the big heavy racked 24 channel HD24 based rig with 3 heavy preamps, clock, UPS, lightbridge, etc...

My plan was to use this rack:

Kaces PRO Rack Case, 4 Space, w/ Pre-wire Laptop Pocket - eBay (item 390055812194 end time Oct-25-09 11:54:55 PDT)

And fill the 4 rack spaces with my Metric Halo 2882, Motu Traveler, and 2 EWI MST-412 3-way splitters. (planning to use a Mac Powerbook G4 and Metric Halo software for tracking). That would give me 8 channels of split for stage mics, plus 4 more channels of mic pres for room mics, and 4 line ins to use for a SB feed or other line level inputs (or even use the R-44 for 4 add'l mic preamp channels if needed)

My question is, does anyone have a suggestion for portable battery only power for this set-up?

Am I better off providing separate external power to each of the MH 2882 and Motu Traveler and Mac laptop (I don't think the laptop internal battery alone will have a long enough run time, but have not tracked with it yet) Or should I get a bigger external battery for the Mac and firewire bus power the 2882? Am I correct in that I could NOT use the second firewire port on the Mac laptop for bus power only connection to the Traveler? If that was possible, then one external battery for the Mac G4 with sufficient capacity could power the whole rig? I would only be looking for, say, 3 hours run time, but more would be good unless the battery pack(s) started getting too big/heavy and expensive. There don't seem to be any cheap options for Mac laptop battery packs from my research so far.

I want to keep this as light and compact as possible.