Hi Everyone. I am the owner of a RAV4 EV and a Prius, and I live near Denver, Colorado.
As far as I know I am the only person in the world to have this unique combination of vehicles and in a location such as mine. After driving a (non-plugin) hybrid for four years and a plug-in EV for a year, I have determined a few things about how the Volt needs to operate. I have mulled this over many times and realize that the Volt must have a driver-selectable mode switch to meet various conditions. The switch would have three modes, described as follows:
1. "Commute" mode. In this mode, the vehicle will drive on the battery until it is depleted, then maintain the lowest safe (non-damaging) SOC (State of Charge). The vehicle will soon be near an outlet, so there is no point in bringing up the battery. This mode also assumes that the car will not need to do anything strenuous anytime soon. This would be the default mode, the car could fall back to this everytime it is restarted.
2. "Long Trip" mode. In this mode, the vehicle will assess the current SOC. If the SOC is high, it will allow the battery to reach the happiest mid-point, either by driving on the battery alone (if the SOC is high) or by running the generator (if the SOC is low). The generator will continue to run at its most efficient opportunity while in this mode.
3. "Mountain Climb" mode. In this mode, the vehicle will take every opportunity to keep the SOC at its highest "safe" point. The generator will run vigorously to continuously supply electricity even as the battery is being drained significantly.
There are several issues that arise if these modes are not manually selectable.
The first scenario:
I live 40 miles from the base of the I-70 Westbound climb up to the Continental Divide at Eisenhower tunnel. If I drive the first 40 miles to the base of the mountain on electric, the car will then struggle to climb the mountain and the battery's SOC will become dangerously (to the health of the battery) low. This happens in my Prius, in fact, I killed the battery in my Prius, and at under three years and 29,000 miles, am one of the only people ever to have their battery replaced. The problem is that the Prius doesn't aggresively charge the battery during a mountain climb, because it doesn't know you are climbing a mountain. The Prius could easily run its generator continuously to resolve this, but if it ran this way all the time, it would kill the MPG's when back on the flats down in Denver.
The next scenario:
Let's suppose my commute is about 50 miles and my battery ran out at 40 miles. The generator kicks in and gets me home, but what should the SOC be when I get there? It should be as low as tolerable, since I'm heading towards my 240V 50A plug. However, maintaining even mildly low SOC is not healthy for a long trip, which I might suddenly need to do some time, nor is running the generator for only three minutes a day, since it wouldn't be warmed up and would be very inefficient and dirty, not to mention bad for the engine.
Yet another even worse scenario:
Let's suppose I live a the top of the mountain, and can regen all the way down to work in the morning. (Like people here in Denver do). I might need the car to charge only until halfway, then regen down the mountain until the SOC is full, then drive around Denver's front range on battery until the SOC is low, then drive up the mountain again. This is essentially an impossible situation for a fully automatic REEV like the Volt. It begs for manual control of the modes.
I worry that I am the only person in the world who has a full understanding of these scenarios because of my unique proximity to the mountains and my experience with the RAV4 EV and Prius. I'm looking for some deep thinkers to come up with an algorithm that would solve these scenarios with a fully automatic implementation, because I don't see one. If there is anybody on this site who has some thoughts on this, please share them.
Basically, how do you: Use as little fuel under all scenarios but still maintain a healthy middle point of SOC so that the battery doesn't get overly stressed and the car is able to climb a mountain with ease? Keep in mind that the air at 11,000 feet is very thin and there is less power coming out of the engine, forcing the car to rely on the battery more, or drop to a snail's pace. My RAV4 EV is very, very good at mountain climbing. It actually gets more powerful as the air gets thinner. My Prius is abysmal at climbing the mountains, but can go much further than 100 miles at a time.
The mode selector switch seems to be the only solution I can come up with.