I have tried several methods to automatically monitor how long it takes to charge each time. It looked simple, so I purchased a 110 volt DPDT (Double Throw Double Throw) relay and connected the normally off poles to one out terminal of the big relay that is thrown when the cable is connected to the car. I put the relay in a box with a a 110 volt socket. I plugged a non digital clock to that plug-in-spot and set the hands to 12:00. I plugged the cable into 030 and WHAM. The clock stated keeping time! I thought I had my problem solved. NOT! I went a few hours later and to my surprise the clock was still running! Oh oh. The cable was still connected and the green light was on, so the relay was still on. I checked all of terminals in the charger, but nothing turned off when the charger was done with its job.
Next, I looked in vain for a light sensing switch that triggers "on" with light. Sorry, they only sense dark, so I bought one of those. I put the sensor on the flashing yellow light and plugged in the clock, figuring that the clock would stop when the light flashes. Oh oh again. The clock does not use enough power to trigger the switch. I connected a light in the circuit. Too bad! The light would go off but the switch passed through enough current to keep the clock running even when my light was off.
The only possible way I can figure how to accomplish my goal is a suggestion to use a video camera on the flashing yellow light with the clock showing. By setting the clock at 12:00 & finding what the recording says when the light goes out I could have an accurate record of the time required. I have not yet set that up. But it appears that it uses about 6.5 KVA per hour of charging, just by checking the readings on the hour--