Many people believe that car manufacturers could (as soon as they wanted to) simply replace the internal combustion engine with an electric motor, and the fuel tank with a battery.
This text tries to explain why this is not the case. Let's start with a few seemingly simple questions:
Cars with Internal Combustion Engines can simply use their excess heat. Because these engines have such a dysmal efficiency that they produce much more heat than propulsion (the efficiency is typically less than 10% in city driving, around 20% on the highway).
Good Electric Motors have an efficiency between 89% and 97%. They do not produce nearly enough heat for cabin heating. And you cannot simply use an auxiliary heater that burns gasoline, because you also just threw out the gasoline tank to make room for batteries.
So you switch to an electric heater.
But how exactly do you fit that into the existing system? That has a hose which delivers hot water from the engine to a heat exchanger, which sits in the air flow. Will the electric heater be a drop-in replacement, or will it require further modifications?
An internal combustion engine can directly drive a compressor of an air conditioning unit. Because the engine needs a gear shifter anyway, to keep its speed always within a range of a few thousand revolutions per minute (regardless of whether the car drives with 5 or with 75 miles per hour). Internal combustion engines work only within that limited rage.
Electric motors do not have this limitation, and thus do not need/have a gear shifter. But the AC-compressor will not survive the speed of the electric motor when the car drives at highway speed.
You cannot simply use a constant reduction gearbox. Because then the compressor would not get enough power in city driving. A gear shifter just for the compressor? Much too expensive.
So you switch to an electric compressor. Which is also more efficient anyway. But that will definitely have a different form factor than the mechanically driven one.
You just noticed that you must put in a bunch of electric devices. Where do you run their thick cables, such that they are well protected?
Will these cables run the high voltage of the battery, or do you put in an a high power (i.e. expensive) voltage inverter? If you directly use the high voltage, how do you make sure that all these cables pose no risk to first aid people and firefighters in case of an accident?
Batteries are heavy. Batteries for a decent range weigh much more than the internal combustion engine and a full fuel tank combined.
Most car chassis cannot simply take that additional mass. What about the wheels, the suspension, and the brakes? Are they ready to handle the additional load? The payload capacity should better not be reduced either, because it is already ridiculously small for many cars.
Batteries, unlike the engine, do sometimes also want heating. So all of a sudden you have two items in that car which need heating, not just the passenger cabin. And during fast charging the batteries like higher temperature than the passengers. Ha, you thought that if would be that simple? No!
And, unlike the fuel tank, batteries also want cooling. Even much more urgently than heating.
You have the option to simply ignore that. But then you would get bad press when owners in hot climate need to replace batteries already after three years.
So you probably want thermal control for the batteries. How to you want to provide that in wherever place in the car where you did put the batteries? Oh, by the way:
The former space of the fuel tank is neither sufficient, nor is it in a safe place in case of a rear accident. But even if these issues would not exist:
What would a placement of so much mass in that place do to the center of mass of the vehicle? How do you prevent that this heavy back overtakes the front when the car must brake in a corner? Will the existing ABS handle that? With the same suspension and wheels?
So you spread the batteries out. Some under the back seat, some in the transmission tunnel. Not the easiest solution for the manufacturing process. Also what a pity that you cannot eliminate the transmission tunnel now that you have no transmission and no exhaust pipe any more.
But even so: how do you evenly (and cost-efficiently) heat and cool these battery chunks, when they are differently sized and spread-out?
Back to climate control: The electric motor needs a powerful high voltage inverter. Yet another thing that needs cooling. Where do you put it?
Sometimes the motor needs cooling, and the battery needs heating. Sometimes the battery needs cooling, and the passenger cabin needs heating. If you inherit existing systems from a car with internal combustion engine, can you transfer heat from anywhere to wherever it is needed?
So you have ripped out the engine block. How do you give the front of the car its stiffnes back? And would it not be phantastic to use the freed space for a much bigger crumpling zone, making the car a lot safer? Is it possible to do both? Not to mention the possibility to put a second trunk there.
Turns out is is not such a good idea to put the electric motor in the same place where the internal combustion engine was. It is so small that it could be put between the wheels. That would free up space, and further lower the center of mass.
But it requires some more mechanical modifications.
Let's face it: An electric car needs a very different chassis than a car with an internal combustion engine.
You should by now have noticed that it would be beneficial to lift everything a bit up, and put the battery block underneath the whole passenger cabine.
A newly designed optimized chassis could extend the stiffness of the battery compartment upwards, to create a much improved side impact protection. The rest of the car (pillars and roof) should be adapted such that all these parts work together in an optimized way.
The Tesla Model 3 is the safest car ever tested by the NHTSA. Because its chassis is not a compromise. All of it is optimized to be a fully electric car. You cannot get the title safes car back when you build only compromises. I'm looking at you Volvo and Mercedes.
The Tesla Model 3 is the best selling electric car for a reason. People just don't want bad compromises.