Why Is There A Charge Line Voltage Drop When Connecting To The Towed Vehicle Battery

Updated 06/23/2023 | Published 06/11/2023

Question:

I recnetly bought and installed a roadmaster charge line kit on my Jayco 26y. I do not think it is charging my toad. I have 14 vdc on the wire coming from the 6 pin connector center pin when the RV is running and it is not connected to the toads battery. But when I connect it to the toads battery it s to the toads battery value 12.3vdc. Stumped. All wiring has been checked and the RVs 7 pin connector measures 14V on the AUX when the RV is running. There is 14V on the wire up to the battery but when I connect it to the battery it s to the battery voltage.

asked by: Don J

Expert Reply:

A possible reason that you're seeing the voltage drop from 14v to 12v is being the alternator is charging the motorhome battery and it's now being placed under a higher load having to charge the towed vehicle battery. The best way to check that your vehicle's battery is actually being charged by the Roadmaster Battery Charge Line Kit for Towed Vehicles # RM-156-25 would be to hook everything up but remove the connection to the towed battery and test the voltage on the wire to see that voltage is flowing in from the motorhome.

expert reply by: Kevin C