By Jim Ringold
The Road to Solid State EVs — Part One
The first step is to tell the mandatory joke about computer-controlled cars. How do you restart a stalled electric vehicle (EV) using Microsoft software? You close and open the windows of course!
But this joke makes a point. The EV computer (controlling the entire vehicle in the case of Tesla), the central processing unit (CPU) and the associated software/firmware that tells an EV’s solid-state devices how to operate, has to keep the EV running without fail. The computer simply cannot freeze up at 60 miles per hour! To help explain how this works, this is a multi-segment discussion of the “solid state” devices, including the central controlling CPU(s) and the supporting Firmware (instructions embedded in the CPU) and Software (instructions written to the computer that can be changed when desired) that make an EV possible.
All of this central control is necessary and operates through commands and feedback from all the other solid-state devices to perform an EV’s operational functions. A few vital operations are a) keeping the battery pack happy, b) starting, steering and stopping, and c) operating the lights, wipers, turn signals, horn, etc. You get the drill. Then there are the secondary functions that are not vital for life safety — power windows, door locks, environmental controls, and displays showing vehicle status, navigation, entertainment, and so on. (Note: Displays do have their own processor to put the images on the screen.)
It is good to keep in mind during this discussion that when Mr. Musk lays out designs, he tries to always utilize “first principles thinking.” Tesla design goes back to the basics at the beginning, starting from scratch. He disregards “this is the way we have always done it” to form fresh ideas and make clean design/configuration decisions.
Also remember that first principle thinking is extremely unfair to existing vehicle manufacturers because they don’t immediately have that first principle thinking luxury. These manufacturers have a huge investment in existing tooling and designs. They have to build the new requisite computer engineering staff, establish new suppliers, and worst of all they have to keep building internal combustion engine (ICE) cars in the meantime. This is all so seemingly unfair and presents even more of a challenge for a vehicle company management team that does not possess the new “solid state” EV evaluation skillset that is required to chart the best path into the EV future for their company.
Much had to set the stage to make the current crop of EVs possible. Batteries had to evolve well beyond the long-standing lead and acid batteries that have been used to start fossil fuel cars since the electric starter was invented, to the lithium-based series of batteries that made the laptop computer practical, but even a step beyond them. Solid-state switches (relays) had to be perfected to control the high power supplied by the new lithium-ion batteries.
Solid State — Discrete Transistors — 101
Before the term “solid state” was coined, these switches were called transistors, invented in 1947 by Bell Labs in Murray Hill, New Jersey. A bipolar junction transistor (BJT) entered the market in 1950. A whole lot of pocket “transistor radios” in 1955 entered the market (note that $49.95 then equals $350.00 today). The low power requirement of these little three-legged discrete transistors allowed the use of series AA batteries for power. Up until then, red, glowing, glass vacuum tubes provided the switching for radios and early primitive computers.
A quick word about logic switching in the world of Boolean Algebra: First developed in 1874, it is one of the first developments by man leading toward the creation of the EV. Boolean deals with two states, true and false, noted as 1 and 0. In the 1930s, it was discovered that Boolean Algebra could be applied to switching circuits. This matured into two types of transistors. The first transistor switching uses “and” gate — as in, “this and this” allows the electricity to continue to flow. The second is an “or” gate — as in, “this or this” allows the electricity to flow. There is also a “not” gate that we shall ignore here. To this day, all computers and control devices use these rules but in more sophisticated and faster ways.
Early solid-state computers (early 1950s) used these little three-legged “discrete” transistors to perform the functions. They still took up space, but not nearly as much as the vacuum tubes that needed a whole room. Vacuum tubes created a lot of heat, so a lot of air conditioning was also required. IBM announced its first discrete transistor computer in 1955.
The first transistors used germanium as the switching medium. Bell Labs discovered by chance that silicon dioxide worked better. It was also learned how to layer materials to make better and higher voltage transistors. Next came MOS, and then in 1959, MOFSET transistors were developed. MOS transistors advanced into the first home computers in the 1970s.
While good for processing 1’s and 0’s, the early transistors could only switch up to about 22 volts DC. You could not turn a 110V lightbulb on and off with a transistor. You had to use a mechanical switch relay with the low 22VDC transistor voltage to operate the magnetic coil and the relay contacts to conduct the 110VAC to light the bulb.
The higher heat and voltage that a MOFSET transistor could handle began to invade the power supply industry. This brings us up to the 1970s. There is a whole alphabet soup of transistors developed in the following years. They got faster, lower cost, more reliable, and could handle higher voltages. But still nowhere near what it would take to turn a high-voltage, high-amperage battery on and off in a variable way to control an electric motor like an EV.
The next step needed for an EV was smaller devices where thousands of transistors would be required for the 1 and 0 logic. The integrated circuit that could “integrate” hundreds, thousands, and more transistors into integrated circuits would be needed. But that is the story for Part Two, technological advancements needed on the way to to building a useable EVs.