I HAVE A 1970'S 4 WHEEL 36 VOLT HARLEY DAVIDSON GOLF CART, THE CART HAS LACK OF POWER WHEN GOING UP A SMALL GRADE, IT IS HAS AHARD TIME TO LOAD ON MY TRAILER, THE CART HAS 3 BRAND NEW BATTERIES,THE OTHER TESTED GOOD,DOES ANYBODY HAVE AN IDEA WHAT MIGHT CAUSE THIS? THANKS, 3RACER