Can Breakaway Kit Battery Be Charged from Main Trailer Battery Without Depleting It

Question:

I have a tandem axle trailer with a Pro Series break away kit. The trailer has an auxiliary battery and electric pump to fill a water tank. The break away kit is charging off the pump battery. How fast will this drain the battery? Will this change once the break way battery is fully charged? Does a diode have to be used?

asked by: Jake A

Expert Reply:

It is permissible to have your trailer breakaway and water pump wired in the way you describe - under certain circumstances.

As long as your water pump battery is substantially larger in current capacity than the breakaway battery, and as long as BOTH batteries are in good condition and fully charged before you head out, then the 12V maintenance charge from your vehicle 7-way wiring harness should be able to maintain both batteries without either becoming depleted.

I suggest you apply a charger such as the CTEK Universal 12-Volt Battery Charger # CTEK56353 to both batteries, one at a time of course, to ensure a full charge when you depart. The low-level maintenance charge from your vehicle's 12V power feed will be able to MAINTAIN the two batteries, but it will NOT be able to charge them if they become depleted. Please refer to the linked video for details about this excellent charger. By the way I have owned one for almost 2 years and it continues to work well on my old Harley's battery.

You do not need a diode kit for this application. The key is ensuring both batteries are in good shape and well-charged before you go.

expert reply by: Adam R