How To Charge Trailer Battery From a 1999 Honda CR-V with a 4-Flat Trailer Connector

Updated 04/06/2011 | Published 04/05/2011

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10 Gauge Wire - Blue Primary - Per Foot

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40 Amp In-Line Circuit Breaker - Perpendicular Mount Bracket

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$9.85

Question:

I have a 1999 honda crv and am pulling a little guy trailer with a 12 v battery attachment to run some 12 v lighting. I want to charge the trailer battery while driving. and I also need to wire the CRV for trailer lights etc. Can it be done and do you have the harness to do it? The trailer has a flat 4 connector installed. Thanks

asked by: Dennis

Expert Reply:

The Hopkins Wiring Harness, part # 43105, will fit your 1999 Honda CR-V and give you a 4-Flat connector at the rear of your vehicle. This will allow you to plug in the trailer and have lights on your trailer. I am including a link to the installation instructions on the Hopkins harness.

The best solution to be able to charge your trailer battery from the CR-V battery is to install the Hopkins 4-Flat to 7-Pole Adapter, part # 37185, on your Honda CR-V. You will plug the 4-Flat connector on your CR-V to the back of the Hopkins adapter. There will be four remaining wires on the back of the adapter.

The white ground wire will need to be attached to the vehicles frame. The black wire on the adapter will need to be connected to the vehicles positive battery terminal with a length of 10 gauge wire (# 10-1-1) using a 40 amp inline circuit breaker # 9510. This is the wire that will supply the power to charge your trailer battery.

The other two wires are blue wire for electric brake controller and the purple wire for reverse lights or auxiliary power. If these wires are not needed they can be taped up out of the way.

For the trailer you will need to remove the 4-Flat connector and install the Hopkins 7-Way Molded Trailer Wire Connector, part # H20042, to the wires on your trailer. The wires on the trailer will be attached to the Hopkins connector according to the color code listed in the product description, with the black wire attaching to the positive terminal of the trailer battery for charging.

You will want to make sure to unplug the trailer when the vehicle is not running to avoid discharging the battery on your Honda.

I am including a link to a FAQ page on trailer wiring.