would that be to air-freight your pan-handle? ;-) 250kg = £50 or something silly. might as well take a " declaration of dangerous goods" with you. not sure they'll want to take your battery and very sure you won't find a replacement in Tamanrasset.
Omar - the head of flights in Djanet - is a top chap with limited resources so you'd probably need to find a way to crate it yourself. everyone in Djanet is ace so you'll get help with crating.
are you aware there is a 20km(?) break in the road between Tamanrasset and In Salah? I haven't been that way so I don't know how bad it is, but I heard it got washed out in the October rains and doubt its been fixed yet.