How To Prevent Tow Vehicle Battery From Draining Trailer Battery

Updated 04/19/2018 | Published 04/18/2018

Question:

I am installing a Lithium battery on my RV trailer. I am being told that because the voltage of the Lithium battery is higher than the wet cell in my RV that the Lithium battery will try and charge the wet battery and therefore needs to be isolated. Typically the isolators your sell are for the reverse situation Trailer discharging the RV battery. Could they be used to provide a solution for this problem? This problem has been brought to my attention by people who have installed lithium batteries in the the RV trailer. I intend to monitor and confirm that this is an issue for me before taking any action. Thanks.

asked by: Larry P

Expert Reply:

As you mentioned, this is normally the accessory battery draining the starting battery (tow vehicle) and most of our products like the Battery Isolation Solenoid, Item # PK5231201, are focused on preventing this situation.

It is possible to set this up in reverse but we do not have much experience with it or customer feedback about it.

The best solution for preventing your tow vehicle from draining your trailer battery is to have the same type of batteries. In a multi-battery situation, the lower state of charge will drain power from the battery with the higher state of charge so eliminating this difference with "like" batteries will help prevent battery draining.

I also talked to one of our battery manufacturers and another option they suggested was to disconnect the RV connector from the vehicle connector so that no power exchange possible when not towing.

expert reply by: Brint H