Is a Battery Isolator Needed when Adding a Battery to a Trailer

Published 07/31/2013

Products Featured in This Question

Starter Solenoid - SPST - 12 Volt - 100 Amp - Continuous Duty - Grounded

(14)

$35.41

CTEK MULTI US 7002 12-Volt Universal Battery Charger w/ Pulse Maintenance and Backup Power

(98)

$199.99

Question:

If I add a battery to a trailer and have the truck 12v power wire charge the battery, would I need an isolator for any reason, such as, overcharging the trailer battery and getting hot or what would be the purpose for it if needed or not needed?

asked by: Tom H

Expert Reply:

First, the 12 volt circuit from a trailer connector, and most factory alternators on vehicles, are not able to charge up a trailer mounted battery. What they will do is provide a maintenance charge and keep the trailer battery at its current charge level.

A battery isolator will only send power back when the vehicle is running. This will help to keep from draining the vehicle battery. Or you could just disconnect the trailer from the tow vehicle when you stop for long periods of time. If you want to add an isolator use # PK5231201. I have included a picture that shows how the isolator gets wired.

To charge a battery properly I recommend the CTEK battery charger # CTEK56353. Several of us here at etrailer own this charger and it works beautifully to not only charge a battery quickly but also help to recondition a battery.

expert reply by: Michael H