Troubleshooting Trailer Battery Connection and Issues if Connected Wrong

Updated 06/26/2020 | Published 06/24/2020

Question:

I disconnected both my batteries awhile back and don’t remember if their series or parallel. I took my test light and found a throw switch underneath the trailer. What and how exactly is that for and if I hook the batteries up wrong will it hurt anything?

asked by: Mark S

Expert Reply:

Thanks for the photos. The batteries are connected in parallel which means the power output remains the same but the capacity doubles. The throw switch in this wiring is simply to connect the two batteries together and makes removing one battery easy if needed. The Deka 2/0 Gauge Overmolded Battery Cable Harness Assembly - Red - 7" Long # DW04362 you asked from is a better connection with thicker gauge wire for better transfer which also makes connection and disconnection easy and less confusing as well. I personally wouldn't want that live power switch mounted to my frame/ground connection or be exposed to elements. If you parked in tall grass it could even start a fire so I'd remove that for sure.

If you wired them in series, the power output would jump to 24v which could be an issue with any electric component rated for 12v use. See attached diagram.

expert reply by: Jason S