Will Enclosed Trailer Interior Lights Drain Breakaway Battery Without Power from Tow Vehicle

Updated 04/23/2019 | Published 04/22/2019

Question:

My enclosed interior lights only work with my vehicle running. The 12v auxiliary power from the vehicle also charges the brake auxiliary battery. What keeps the brake aux battery from powering the interior lights if it is all connected to the same circuit?

asked by: Scott

Expert Reply:

Unless there is a battery isolator like the Buyers Products # 3376391050 on your trailer and it is set to off then your interior lights should pull power from your breakaway battery. The only other thing that may be preventing this is if your breakaway battery is dead. Since tow vehicles only provide a slow trickle charge on the 12V power wire if your battery is dead this would make sense.

I recommend taking your breakaway battery to get it tested. If it needs to be replaced I recommend the Hopkins Engager Push-To-Test Trailer Breakaway Kit w/ Built-In Charger # 20099 because it has the built-in charger and allows you to test the battery right there.

You actually don't want your interior lights to be pulling from your breakaway battery anyways. The breakaway battery is designed for emergency situations where your trailer disconnects from your tow vehicle. If you were to drain your breakaway battery before heading down the road and your trailer were to disconnect before the battery had time to build up enough charge that could make an emergency situation worse. You really need to add an auxiliary battery if you plan on using your interior light frequently.

expert reply by: Jon G