What you charge to build one that could handle 120 power Macbook Pro 17", with two hard drives attached to it and a digital back?
What would the size and weight be?
What would estimated time of life be? Would you eb able to make it with removable batteries?
Hi, do you mean 120W? 17" Macbook Pros should consume between 50 and 100W depending on whether processor is idle or maxed out, so the 300W for €150 model sounds like more than enough. You would add your own sealed 12V battery and charger, and the life would depend very much on the size of the battery you choose. Building your own is very flexible - the battery determines most of the weight and all the capacity, so you can choose what suits you best.
If you are drawing a constant 60W, for example, then the battery drain will be approximately 5A. If you want this to last for 8 hours then you need an 40Ah capacity battery. I would recommend getting a few smaller batteries (e.g. 40Ah) rather than one huge one. Easier to carry around and if you don't need the huge capacity you can just bring one.
Size and weight of the 300W model is 2.25kg, H=68mm, W=170mm, L=260mm
n.b. I don't know where you live but output is 230 VAC, and the socket is the standard European type. I think all Macbook pro adapters come with a euro plug and can take the voltage anyway, but just wanted to make sure you are aware. I don't know your location.