He's travelling by backpack - you're suggesting bringing along a car battery in the backpack!
No. Im suggesting that unless he gets extra triple remote (which he may be) people who live in huts usually use Photovoltaics (solar panels) or wind for power
how do they do this
thay have the renewable source charge a (or a bank of) lead acid batterie(s) typically in poorer countries car batteries - it no good using solar for your lighting without beingable to store it till its dark
So if you have a 12v hookup then your OK
I understand the OPs situation they may not work due to extra remoteness or the mountain politics (but then dollar bills are light and will sort the politics)
Incedentally you talk about the weight of a lead acid - well carrying energy is heavy (hense no almost electric cars on the market) so even a pile of D3 batteries for an extended trip would be heavy
the lightest fuel is petrol or parafin (and also possibly for sale up there)- which brings me onto another idea - I wonder if there are any superlight petrol generators with engines the size of a remote control car !
Having done extended remote trips in the era of film I am genuinely interested in this subject
My own thoughts so far are
-to get a 'digital camera battery' (no D3 version yet?) , thier solar charger and also a 12v charger for same with clamps attached
-Also to get a custon D3 charger without the transformer fabricated by a tech geek that runs off 12V or whatever th output of the DCB is
-And to take an FM2
A further thought. Solar only works in the day - wind works 24/7 so anovernight wind charge could be preferable
(before I was stupidly pulled into photography my career was going to be in low tech engineering for the third world BTW - far more lucrative)