Recommended Vehicle and Trailer Wiring Change from 4-Way to 7-Way for Battery Maintenance Charge

Question:

I have a 2017 Mazda CX-5 with a 4 pin connector. I just bought a small tear trailer that also has 4 pin. I want to be able to charge an AGM 12v battery in the trailer when the vehicle is running and have read I need 7 pin for the battery charge wire as well as some isolation/cutoff device to the vehicle. I’ve already purchased a mock genius 3500 converter. I am dumb when it comes to electrician stuff, what’s the simplest way for me to accomplish the above? Thanks in advance

asked by: Dean

Expert Reply:

If I understand correctly, the Noco Genius 3500 is what you have and that is an AC battery charger and so it will help maintain your trailer battery when stored but will not assist with charging when towing.

For your 2017 Mazda CX-5, the best way to charge your trailer battery is to use the Hopkins Adapter 4-Pole to 7-Pole and 4-Pole # 37185 as you stated and connect the black 12v power to # 10-1-1 wire sold by the foot. Then you will use circuit breaker # 9510 and then solenoid # PK5231201. You will also want ring terminals # DW05705-1.

You will run wire from the battery positive terminal to the circuit breaker from the circuit breaker to the solenoid, then from the solenoid to the black wire on the adapter.

On your trailer side, you will simply use the 7-Way Molded Trailer Wire Connector, 6' Long # H20044 and connect based on the attached chart. Then you will simply connect the black power to the positive terminal on your trailer battery. You can use butt connectors # DW05745-10 for these connections.