I have been experiencing failures to charge about 15-20% of the time with our Volt set for delayed charging, but NEVER with our Nissan Leaf. After confirming to my satisfaction that this problem was specific to the VOLT, I had it fully checked for any such stored information in the car's "black box," but that came up with no problem reports in the car. This tended to isolate the problem to the wall charger, an early COULOMB unit (installed in early January of 2011; we have Volt VIN # 679).
I then emailed, using the Coulomb website, a problem report to Coulomb describing this experience, and this is the response I have just gotten:
Working cooperatively with GM, Coulomb's engineering team has identified the root cause based upon extensive testing in our lab with a Volt charging system and successful testing in the field with Volt customers using Coulomb charging stations. We were able to characterize this problem as resulting from high frequency ground currents induced by the Volt on-board charger and causing GFCI trips on the EVSE when its contact relay closes at the start of a session or upon closing the relay when instructed by the Volt battery management system. This problem does not manifest itself on all Volt EVs and occurs more frequently when the Volt is set in delayed charge mode. In delayed charge mode, the Volt "wakes up" multiple times per hour and instructs the charging station to close the contact relay, thereby increasing the probability of a GFCI fault.
We made an engineering enhancement in our charging station to address this issue when charging with the Volt, and although not covered specifically under warranty, Coulomb is offering for a limited time to replace those Volt customer units affected by this problem.
Any other Volt drivers experiencing this problem should QUICKLY get in contact with Coulomb to get this new hardware installed and not blame themselves for some random glitches in plugging their cars into the charge system.