I have been using a old 12vDC 24w Auto trouble light that has a couple of alligator clips to do my pre-charges (image below). It works but is not elegant. So what I am thinking of is a hard wired around the battery disconnect breaker lamp/socket with On/Off button to handle the task. If someone could point me to an item I would appreciate it. I like using a light versus a resistor since it gives me a indication with light coming on and going off as charge happens.