Is a Battery Isolator or Diode Needed When Charging a Trailer Battery from a 2007 Ford F-150

Updated 10/25/2017 | Published 10/24/2017

Products Featured in This Question

Deka Battery Isolator - 120 Amp

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$103.68

10 Gauge Wire - Blue Primary - Per Foot

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$1.65

Deka Battery Isolator Installation Kit for Standard Alternators - 8 Gauge Wire

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$38.30

Question:

I have a 2007 Ford F150 with the towing package. On the 7-way connector it has one of the wires labeled as Trailer Battery Feed Hot with Key in Run Only. Can I connect directly from this to the trailer battery or do you reccommend any sort of additional Battery Isolator or Diode be installed on the trailer side of the connection? The information that I have says that this needs to be at least a 10 AWG wire max of 50 ft on the trailer side and has a 30 Amp fuse in the trucks fuse panel. Thanks for the advice.

asked by: Bob G

Expert Reply:

The 12V Power pin on your 2007 Ford F-150 (which you said is labeled as Trailer Battery Feed Hot with Key in Run Only) will provide a maintenance charge to the battery on your trailer. The only time that a battery isolator or a diode is needed is when the 12V Power would be running while the trailer is hooked up and without the tow vehicle on. Since your F-150 will only be sending power to the 12V pin you will not need an isolator or diode.

If you were wanting your trailer to pull power from the 12V Power pin constantly you can replace the wiring on your truck by running 10 Gauge Wire # 10-1-1 from the positive terminal on your battery back to the 12V Power pin on your 7-Way. If you choose to go this route then I do recommend using a battery isolator like the Deka # DW08771. You can use the Deka Battery Isolator Installation Kit # DW08769 to complete the installation.

I have attached a helpful article on routing the power wire that you can reference as well.

expert reply by: Jon G