Powering arduino with 4.8V NiMH battery

Using Arduino General Electronics
19

Yeah, that is actually a pretty good point on just using a buck or boost converter.

12A, $5 shipped. http://www.ebay.com/itm/DC-DC-CC-CV-Buck-Converter-Step-down-Power-Supply-Module-7-32V-to-0-8-28V-12A-EC-/221670461819?pt=LH_DefaultDomain_0&hash=item339c96d17b

Actually, you could use a buck/boost converter to supply the arduino with a constant comfortable voltage, while running servos straight off batteries....

$2 shipped buck/boost http://www.ebay.com/itm/DC-DC-Boost-Buck-Converter-Step-Up-Step-Down-Supply-Module-3-35V-to-2-2-30V-HG/271720088700?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D32237%26meid%3Dff97540d481642989f28d171bc93103a%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D290833291375&rt=nc

No endorsement of those specific vendors - there's a huge number selling same units and similar ones.