Test your 120V charging cord on occasion. My plug end went bad. While not used often I do you the 120V cord often at a hotel/B&B. The last 4 times I used it I came back to the car to find the charging stopped about an hour into the charge and thus I missed out on a good 9+ hours of charge. First hotel I attributed to a rather long extension cord and the rain. But that was not the situation at the last B&B. It turns out the GFC head of the plug had gone bad and actually partially melted the plastic around one prong. The end is quite easy to replace and found this one on Amazon Leviton 16693 15-Amp, 120-Volt, Grounded, Compact Automatic Reset Right Angle GFCI, RoHS Compliant, Black - Amazon.com and I have found it to work well so far. Weird how the plug end just went bad after 4+ years.