no capacitor, sorry
coures 40 amp alternator cant bear the strain
Listen
before i upgraded my alternator, my 2 far stinger, used to keep voltage high for a 4-5 second span of boom.
Then alternator failed to charge it and voltage dropped to like 11.5 and permanently stayed there .
After upgrade. idle voltage is 15.6 , 15.4 . With max boom like 10 mins strate doesnt go down below 14.
SO, no cap, Just proper 4 guage wiring, good ground wire same as pwer wire, and 0 guage big 3 is the best choice trust me