I am going to do a third test;
How much MPG does my Volt get me on just "gas alone" doing 75mph with the hood latch sensor disconnected? and how much will it charge my battery? and how much gas will it take to fully charge my car while I am driving it?
Before you take the time to disconnect the hood latch sensor, take a half hour or so and find out if the battery is recharged by doing so.
When your battery state of charge is low or fully depleted, and you car is turned on and parked:
Pop the hood. The engine will start.
Helpful if you can use an OBD reader and app to obtain the raw state of charge for the battery to see if it goes up and by how much.
After ~10 minutes, the SOC should be a little above where it was when you opened the hood.
This adds some range to the range estimate, and gives the impression that the battery is recharging when the hood is open. Many people draw this conclusion after 5-10 minutes, and close the hood and turn off the car.
Don’t do that. Keep the hood open and the engine running. After an additional ~15 minutes with the hood open and the engine running, is the SOC any higher than it was 10 minutes earlier? I suspect it will not be.
After another additional ~10 minutes with the hood open and the engine running, is the SOC any higher than it was ~25 minutes earlier? I suspect it will not be.
When you pop the hood, the system draws power from the battery and uses the smaller motor MGA as a "starter motor." The engine starts.
The system is programmed to maintain the state of charge where it was when you "switched to gas," which you did when you opened the hood, so the system then attempts to recharge the power used to start the engine in order to "sustain the SOC where it was when you chose to start the engine."
The system then slightly overcharges that amount of power, and results in a state of charge a little above where it was when you popped the hood. This could result in a small increase in estimated range. The system then tries to sustain the SOC at that point as long as the hood is open and the engine is running.
Of course, you could then shut the hood at that point and turn off the car. The state of charge is now slightly above where it was when you first popped the hood.
So, start the car, then pop the hood, wait until the system over-recharges the power used to start the engine, and then turn the car off and close the hood.
Repeat this cycle enough, and indeed, you will recharge your battery (someone did it in a Gen 1 Volt on the Facebook Volt Owners page within the last year).