2011 Chevrolet Volt plugged into Coulomb Technologies 240V wall charging unitEnlarge Photo
We have greatly enjoyed our 2011 Chevrolet Volt range-extended electric car since its delivery early in January 2011, and it has seen much more use than the Nissan Leaf battery electric car that arrived about a month later.
However, 15 to 20 percent of the time we've connected our Volt to the Coulomb 240-Volt wall charging station to charge itself late at night using the delayed-charge setting, we would find that it had failed to charge when we came out in the next morning.
At first, I thought the problem was some kind of mistake on my part concerning how I inserted the charging handle. But we also used the Coulomb charging station with our Nissan Leaf, and we never experienced a charging failure with that car.
After more than a year of frustration, I concluded that the problem was between the Volt and the wall unit.
About two weeks ago, I had the Volt fully checked out by my local servicing dealer (Hanlee’s Chevrolet in Davis, California), which found no faults recorded in the Volt’s black box.
So now it seemed that the problem was located in the wall charger, so I sent in a problem report to the Coulomb website.
This is the response I received:
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.
Coulomb Technologies CT-500 electric vehicle charging station
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.
Clearly, any Volt owner with the Coulomb 240V home wall-charging system who has experienced ANY failures to charge--particularly with delayed-charging time settings--should contact Coulomb quickly and report the problem in full detail.
Using delayed charging, for both cost and environmental reasons, is one of the primary advantages of electric cars. No owner should have to avoid this option due to of a design shortcoming in a wall-charging station.
If you have experienced more than a single such failure to charge, it's possible that you too may have a technical problem in your Coulomb wall charger.