Hi all , its there an external battery pack that works with the A7r? , I've recently bought a motorised rail for Timelapse and the a7r batteries are the weak link , I see Sony have a mains powered pack but need a battery powered version , I've also seen some DC couplers but they seem to just mention the A7s not the a7r? Ive also seen a thread where a guy sauys these work with his a7s but not his R
Any ideas? I'm not very electrical so I really need plug and play if possible..
Thanks in advance