Full charge, no power: the software behind EVs

**Akshara** (0:04)
In today's episode, we'll break down two important stories. First, we'll talk about the software behind EVs, and then we'll talk about where the priorities in India's priority sector lending norms are. Welcome back to The Daily Brief by Zerodha, where we cut through the noise to help you understand what's actually happening in the most important stories from business and markets. I'm your host Akshara, and today is Wednesday, 15th July.
Coming to the first story. So recently, a weird series of videos had surfaced from across India. E-rickshaws weaving through traffic were coming to an abrupt halt. The driver would have no idea why.
Nothing would appear broken.
As it would turn out, a few people on a nearby footpath had choked the ride from their phones.
And this became enough of a menace that India's IT ministry had to act. Officials initially said two applications had been removed, and shortly thereafter, the ministry directed Google and Apple to remove seven battery management apps, including BAT, BMS. So these apps linked through Bluetooth to the vehicle's battery management system, which is the onboard software that watches over a battery pack. They were originally meant for maintenance, but they became a portal for wider misuse. To us though, this triggered a more interesting question. Why did this vulnerability even exist? Why could these vehicles be stopped so easily? Turns out, while modern petrol cars use software to the incoming era of electric vehicles, software is everything. It is the lifeblood these cars need to run, and it could also become a liability.
This is the shift we wanted to explore. Let's think of an old petrol car. You press the accelerator, a physical process follows. A cable pulls open a valve inside the engine, injecting fuel where it can be burned. There's a mechanical link between you and the engine. But things are different in an electric vehicle. So here, the accelerator sits atop a sensor. So when you press the accelerator, it measures exactly how far you've pushed it, and turns that measurement into an electrical signal.
It's that electrical signal and not mechanical ones that the battery and the motor respond to. There's nothing inside that your hand or foot physically moves. So in many modern EVs, the signal from your accelerator goes into something called the Vehicle Control Unit or VCU, which is a component that decides what a vehicle should do next. In simpler two and three wheelers, like the e-rickshaw in this story, that job often falls to the motor controller instead, which directly controls how much power reaches the motor. Either way, there's a component between the accelerator and the engine that checks whether the vehicle should actually do what you're asking for. It looks at your speed, whether the brake is pressed, whether the battery or motor is too hot or too cold, and whether anything else has gone wrong. Only then does the vehicle decide how much power to deliver. And then there's the BMS or battery management system. So if you don't know what you're looking at, this can just seem like a fancy battery percentage detector. But when XP and Texas Instruments, the two major suppliers of this technology, the BMS is actually a safety system. Even if the rest of the vehicle asks for full power, if the battery itself isn't in a safe state, the BMS can say no. So this is what it's believed were behind the e-rickshaw cases. So the apps reportedly connected to the system over Bluetooth and triggered a command that stopped it from supplying power. When the vehicle asked the battery for power, the tampered BMS refused it. Now, there are other software systems too that can limit power. The motor, for instance, can cut back if it's overheating. Traction control can do the same if a wheel starts slipping and so on. So all of these systems, the VCU, the BMS, and others, carry information. But having information localized to one component isn't enough. That information must quickly reach the rest of the vehicle. If a vehicle is skidding, for instance, that information can't remain in the wheel. It must be carried to the VCU so that it can adjust what's happening. That's the job of the CAN bus or the controller area network. Now, in modern EVs, controllers like the VCU and the BMS pass messages to each other over one or more of these networks. And these work a little like a shared line that every part of the vehicle can read from. The battery, for instance, might post that available power is reduced. The brakes might post that they're not being pressed, and any component that reads that information, then reads it off the same line, avoiding the need for a private wire running to every other part. Simpler vehicles work a little differently. Basic air-rickshaws, for instance, may use simple analog wiring instead of a CAN network. So once the VCU and the BMS agree on how much power to allow, that power has to reach the motor in a form it can actually use. And this again is the domain of software. Now a battery only gives out direct current or DC. Picture it like water flowing steadily and one way down a pipe. Basic electric vehicles, including simple e-rickshaws, use this power directly, with DC motors running on a simple motor controller. But modern EVs need alternating current or AC. So picture this current like water alternatively being pushed and pulled rapidly in both directions instead of flowing one way. And so, something has to sit between the battery and the motor, converting the DC power to AC power. That something is the inverter which Texas Instruments describes as the main power processing system inside an EV. And it adjusts current thousands of times a second. Only once the inverter has done its job, does the motor actually turn, in turn spinning the wheels. Even then, the system keeps watching itself. Sensors report back how fast the motor is spinning, how much current is flowing, and in more advanced vehicles, whether a wheel is slipping, and the car adjusts accordingly. These decisions get revised many times a second, and all of this is orchestrated by software. An EV doesn't simply receive one instruction and carry it out. It keeps measuring, calculating, and correcting for as long as the wheels turn. And the same works in reverse when you slow down. Lift the accelerator or touch the brake, and the motor now acts as a generator. Electricity goes back into the battery rather than flowing out. And this is called regenerative braking, a standard in most modern passenger EVs. So where it exists, it takes the same kind of coordination as speeding up. The BMS decides how much energy the battery can safely take in, and the motor controller decides how much regenerative braking the motor can produce. In more advanced EVs, software decides how much the vehicle slows because of the motor winding down, and how much comes from the actual brake pads. And software also checks when the battery is full or too cold, cutting off the motor and letting regular brakes do more of the work. So slowing an EV down, in other words, is partly a software decision too. Likewise, even charging an EV takes software. You can't plug in an EV the way you fill a tank. The vehicle and the charger first exchange safety and power information, working out whether the connection is safe and what the battery's temperature and charge level allow. A battery, for instance, can only take in DC, but the power from a wall socket is AC. Something has to convert it. During ordinary home charging, the vehicle does this conversion itself. But during DC fast charging at a public station, the station does that conversion itself before the power reaches the car. But because these chargers push more power, the car and charger keep exchanging information throughout the session, checking things like current and temperature again and again as the car charges. Meanwhile, the BMS keeps monitoring the pack throughout, looking for any issues that might need charging to stop midway. Now, all of this takes connectivity. And there is, of course, connectivity inside the vehicle, as its components talk to each other. But the vehicle also communicates with the outside. EVs plug into nearby wireless Bluetooth or Wi-Fi, matching with things like a diagnostic tool, phones, keys, or a battery app. This is the kind of link the BAT-BMS app used. And many are also connected to the Internet or the cloud, usually over a mobile network. And this supports things like navigation, remote monitoring, fleet tracking, and software updates sent from much further away. Now, this connectivity isn't inherently a flaw. In fact, it's usually a feature. It's what lets an owner check charge remotely or have a fleet operator track dozens of vehicles at once.