Print 2 of the VP_tube_plug.stl and cut a sutible length of a VP plastic tube. for 4 AAA battery's you need 225mm. drill a hole in each end 7.5mm in all the way thru.
you also need 2 springs and some banana plugs.
Then hock it up to your favorite charger set it to charge NiMh and if you have like me 4 AAA at 1.2V 850mAh the charger should be set on: NiMh 4.8V and 850mAh
So if you want to charge 8 at the same time you set it on 9.6 and 850mAh and so on :-D