I am not so sure this happened because I towed, but I noticed it while I was towing. Normally, I always remember seeing my batteries around 14.2- 14.4 vdc on my tuner display. I never remember seeing it under 14.0. While towing over the weekend I noticed it reading 13.7- 13.9 vdc. I had assumed maybe it was due to the load of the house batteries, brake battery, etc. Thing is, it is still under 14 vdc now even with nothing connected. I know 0.5 vdc is somewhat nominal but I am left wondering if there is something taking a dump on me. It will never happen at the right time. What are some common causes and things to check on the PSD with dual alternators and batteries? Am I crazy for being concerned about a half volt?