You will not get a better, cleaner source of DC, than from a battery. PURE as...A dead straight line....Nada, zip, NO ripple, etc etc...
What are you trying to do exactly? If just running t'scope n gear, then your chosen battery will suffice. To charge it, use at least a 4 Amp unit, but do not charge whilst using t'scope/laptopetc, unless the charger is a switch mode/regulated one. (actually, I would not recommend doing it anyway).
HTH.
L.