low battery can stand for a lot of shit! it basically means "all out of" a certain thing or just unwilling to continue. there can be: emotionally low on battery , physically low battery, financially low on battery ,or any other stupid thing anyone could use!!!
emotionally low batt- stressed, mad,emo, sad,lovesick,lonely,...(anything regarding emotions)
physically low batt- tired,sick,hungover(from over night partying),too drunk to stand up,stoned,jaded,or just f***ing sleepy...
financially low batt- broke(like britteny spears ever since she lost her underwear!),out of money(im sure you already get it... right?)
low battery can also mean "turned off" or what a girl says when shes not horny!!!