lights flicker under acceleration

[dropkicknick]

sorry if in wrong sub forum, this is my first post

got my 2012 1500 sport used with 110k

my problem is if i put engine under heavy load (spin tires, steep hill) all electrical flickers ie lights exterior and interior

i popped hood and found battery ground on D/S fender wall loose. tightened it. issue remains

realized current battery was small and unmarked (no date or cca specifics etc), bought new walmart brand H7 battery and installed. issue ramains

dont like throwing parts at problem (would have replaced battery regardless after i seen it) and not sure where to go from here, any tips? i understand alternator could be failing but only way i know to test is free test at autoparts store and ive heard they can be unreliable.

i have a multimeter and average understanding of basic mechanical/electrical theory of operations so just point me in a direction and ill follow

i also bought a couple extra 4g wires for a hyper ground install just havent gotten to it yet.

this is newest vehicle ive owned, used to 80s and 90s super basic systems.

thank you

 

[dropkicknick]

also no codes or warning lights. headlights do seem dim during normal operation, fogs are much brighter and almost a necessity during normal nighttime driving. they outshine headlights like night and day