How to Install a Trailer Battery Isolation Solenoid to Prevent Starter Battery Discharge

Question:

I have two questions.. Looking to add a battery isolator for a dual battery setup for my RV so I can leave connected and use power from truck. Its a 2015 Silverado 4WD LT with a 170 amp alternator... So I need a 200amp isolator? Do you know where the post is for the trailer harness power as I will need to disconnect this and wire to 2nd battery on other side of the ioslator.

asked by: Tom

Expert Reply:

You want to choose a battery isolator based on the amperage capacity of the trailer power battery it will be controlling, not based on the alternator output.

For instance, the Battery Isolation Solenoid # PK5231201 is rated for 100-amps. +12V power from the trailer-power battery connects to either side terminal and the other side terminal outputs that power ONLY WHEN the center terminal detects voltage. This center terminal connects to a key-controlled circuit to get that trigger signal. A power antenna circuit is an example of one that could be used to trigger the solenoid. You can use a simple fuse tap kit # F2526 to give you the required "key on" signal to close the solenoid so it can send power to the trailer.

The linked photo shows the circuits on a 7-way trailer socket. The contact at the one-o-clock position carries the 12V trailer power circuit.

expert reply by: Adam R