I virtually STOPPED making stupid connection errors on multiple battery setups by color coding battery posts (the top where there is no connection to anything) and lugs and terminals.
RED Positive
BLACK Negative
GREEN No Touchee
Green is used on series interconnects. I then slop preservative over everything but the colors are still very legible.
But yes, as Mena points out, connection is not complicated at all. When I connect, I'll drive the truck over and shut it off. Raise the hood, open the battery compartment on the trailer. First connect the Positive jumper clamps at both ends. Then connect the negative at the trailer. Last comes the negative for the truck. I'll then start the engine and note the time.
For extra insurance ELECTRONIC (as opposed to electric) devices are shut off in the trailer. Things like inverters, stereos, etc. OK to leave the fridge on, and hot water heater controls enabled.
It is normal for the alternator to get too warm to touch when it is charging. The opened hood will help keep it cool. Ignore warnings from folks who don't understand that alternators powering today's cars driving across the desert get a lot warmer than your alternator ever will charging your trailer batteries. Do not disconnect jumper cables until the engine has been switched off.
Hundreds if not thousands of people have charged batteries this way for decades.
