Troubleshooting Trailer 12V Charging Circuit That Does Not Re-Charge Batteries Fully

Question:

Batteries on trailer dont seem to charge when going down the road. power at truck plug and wiring to batteries looks ok. checked breaker it is ok. am I missing something?

asked by: Jack H

Expert Reply:

The 12V auxiliary power feed on your truck's 7-way can deliver a maintenance charge to the trailer's on-board batteries, but it does not carry enough juice to re-charge a battery that is depleted.
A depleted battery really needs to be re-charged by a shore-power charger like one of the CTEK units, such as their # CTEK56353. I own one of their chargers (for about 6 years now) and it works well in my always-on 24/7/365 duty cycle on my motorcycle and lawn mower batteries.

Another possibility is that there is corrosion, on either or both the vehicle or trailer side connectors, that could be impeding current flow to the trailer. Check your connectors inside and out for any signs of corrosion or build up and clean as needed. You can protect good connections with dielectric grease like # 11755.

expert reply by: Adam R