How to Charge a Trailer Battery While Towing a Tear Drop Trailer with a 2002 Volvo v70XC  

Question:

Expert Reply:

If your trailer has a 7-Way connector, then it either already has electric brakes or is set up for electric brakes. Either way, you would not want to use the pin and wiring for the electric brake to charge a battery because it is too small a gauge for this application. A 7-Way connector already has a pin for a 12 volt accessory. If you are looking at the face of the trailer side 7-Way, it is in the 11 oclock position. This wire is only large enough to maintain a battery but will not charge it.

You can add the # C59496 wiring to your 2002 Volvo v70XC to provide a 4-Way trailer connector. This will provide the basic lighting functions; right turn and stop, left turn and stop, running lights, and ground. If you added a 4 to 7-Way adapter, like # 37185, you would still only have those functions unless you hardwired the remaining wires on the adapter. If you do not intend on adding a brake controller, the blue wire can be taped up and stowed out of the way. The same goes fro the purple (may be yellow) wire which is for reverse lights. The white wire will need to be attached to the vehicle frame.

In order to have the 12 volt power wire functional, you will need to attach a length of 10 gauge wire, # 10-1-1 (long enough to reach from the back of the car to the front with some slack, it is sold in 1 foot increments) to the black wire on the adapter. You would then route it under the vehicle, avoiding areas that may pinch or burn the wire, and up through the engine compartment near the battery. Then, attach it first to a 40 amp circuit breaker, # PK54540, and then from the breaker to the positive battery terminal. You will then have all the light functions and the 12 volt accessory function which, again, will maintain a battery but not charge it.

The best solution is to use a battery charger, like the NOCO Genius Mini # 329-GENM1, to charge the battery ahead of time, and then use the 12 volt accessory function to maintain the charge while you tow. I have included a link to a video review below.

To more effectively maintain the battery while towing, there is a separate connector you can install. First you will need some large gauge wire (battery cable). Connect one end to a 40 amp breaker, # PK54540, and then from the breaker to the positive battery terminal. Route the other end under the vehicle to the back where you will need to attach it to a Pollak Single-Pole, Round Pin Trailer Wiring Socket - Vehicle End, # PK11851. So it should be positive battery terminal to 40 amp breaker to vehicle side connector.

On the trailer, you will need the same size wire and a Pollak Single-Pole, Round Pin Trailer Wiring Connector - Trailer End, # PK11852. One end of the wire will attach inside the plug, then go to another 40 amp breaker, and then to the positive battery terminal on the trailer. So it should be connector to 40 amp breaker to positive trailer battery terminal. Make sure the battery is also grounded to the trailer frame. This still will not up-charge the battery but it will more effectively maintain it. Be sure to unplug this connector when not towing as it could drain the vehicle battery.

expert reply by: Michael H

0