I am a new owner (within about a week) of a 2013 C-Max Hybrid SE. I absolutely love it but am realizing there is a lot more to driving a hybrid than I thought.
My initial impression was simply that; braking charges the battery, as long as there is battery power the car will have no reason to use gas. It will only switch to a gas engine when you have been unable to charge the battery and do not have enough power.
But, over the last few days I took a small trip (about 75 miles) and between the trip there and back and some city driving during, I used about a half a tank of gas. While this is better than what my previous car would have used, I was confused because the battery was about half full the entire time. Why wouldn't it have used the battery instead of gas?
I don't know all the terms everyone seems to be using and apparently there is clearly a lot more to owning a hybrid than I thought.
Can anyone offer me a SIMPLE breakdown of how the engine vs battery thing works/what I can expect from my car/what I should be doing to get the best gas mileage/anything else I should know...it would be very much appreciated!
The general engineering concept behind Ford hybrids is similar in concept to Toyota's hybrid system. Identical, no! But there are only so many ways you can skin a cat and there are only so many ways you can successfully hybridize a vehicle. Most of my knowledge comes from over 10 years of living with a Prius and becuase there is engineering similarity I felt supremely comfortable purchasing Ford hybrids. I need to find some links to the varous Prius based explainations of how this hybrid system works as it is a good baseline for explaining the mechanicals behind the C-Max (and the current Fusion Hybrid, and the previous generation Fusion Hybrid and the former Escape Hybrid).
The remainder of my comments will be very general.
Inside the transmission case are 3 major components which make this whole hybrid thing work. There are two motor/generators and a planetary gear pack (this is where a graphic would be useful). Let's define some terms (I tend to use Toyota's definitions as that is what I'm most familiar with). Motor-generators are electric motors which also act as generators depending on what the on-board computers want them to do. A planetary gear pack consists of an outside ring gear, a series of planet gears and in the center a sun gear. All the gears are meshed together permanently.
A hybrid of this design has 3 potential sources of motive power; motor/generator 1 (MG1), motor/generator 2 (MG2) and the gasoline engine (internal combustion engine or ICE for short). All three of these motive devices are connected to the three major components of the planetary gear pack. The two motor/generators are of different physical sizes. There is a large, lower RPM motor generator (MG2) and a smaller higher RPM motor/generator (MG1).
MG1 is connected to the sun gear at the center of the planetary gear pack. The ICE is connected to the planet carrier which is connected to the planet gears at the center ring of the planetary gear pack. MG2 is connected to the outer ring gear and in turn the outer ring gear is connected to the wheels through the final drive. The only motive device which is actually connected to the wheels of the vehicle is MG2. MG1 and the ICE cannot independantly motate the vehicle unless MG2 is instructed to move the vehicle by the onboard computers.
To muddy the waters further, a hybrid vehicle gets its motive power from two sources, gasoline and stored electricity. The stored electricity all comes from the ICE or regenerative braking. So effectively a hybrid vehicle gets all of its electrical power from gasoline, no matter how you cut it. The engineering and science behind all of this is that a hybrid system that is programmed properly gains its increase in fuel economy over a conventional vehicle by doing numerous activities which optimize the efficiency of the varous components of the system.
Internal combustion engines have efficient sweet spots, most easily described as RPM levels in which the best performance is achieved with the least use of fuel. The programming of the hybrid system works hard to operate the ICE at RPM and power levels which are the most efficient. The hybrid system also reduces or eliminates idiling of the ICE which is the least efficient running state of a conventional engine.
Going down the road the onboard computers are taking in numerous factors to make wholeistic powerplant operating decisions. How much throttle demand? How much resistance on the vehicles forward momentum (environment, geography, vehicle weight, drag)? How much and what kind of demand from the A/C system? Accessory power utilization? And many other factors which I can't even imagine. The computer takes into account all of these factors and then combines the most efficient combination of gas and electrical power to acomplish that task. These decisions and transitions between power sources or the relative combination of power sources are occuring continuously.
In some drive states the vehicle might make a decision to run the ICE while moving, but will direct most of the ICE power through MG1 to generate power to place in the battery while MG2 does most of the motive work. In a high demand situation, such as heavy acceleration the system might instruct all devices, MG2, ICE, MG1 to combine forces to put power to the wheels. When coming to a stop the vehicle will turn MG2 which typically moves the vehicle forward into a generator and will use electrical resistance to slow the vehicle and gain energy from the stopping process (rather than turning it into heat which is what conventional brakes do).
There is no spot where the vehicle is all electric or all gas, it is an ongoing combination of the two which maximizes the efficiency of the two energy sources with the overriding goal of reducing tailpipe emissions and increasing fuel economy.