if you add an extra battery you run the risk of loosing volts IF they are not the exact same kind of battery installed at the same time...... see my 2nd to last post - https://www.tamparacing.com/forums/s...03#post1312503

if you're alternator can keep up with the demands of the amp w/ out the cap then a 20 dollar cap wouldn't hurt IMO.....and it looks cool.....