Technology should have more staying power.
Is it only me who thinks it's weird how our phones got bigger, but the battery life got worse. Not improving endurance before increasing demand is a human problem.
By the time you read this, Perseverance will have already touched down on the surface of Mars. We call it the Red Planet because it’s, well, red as the soil on the Highveld, but that often gets confused with heat. The average temperature on Mars is -53 degrees Celsius, with Mercury rarely climbing above 20. That’s terrible conditions to operate batteries in.
Percy, like Curiosity before it, is powered by a nuclear energy called the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). The heat from the plutonium-238 core is transferred to a metal plate that is at a colder temperature and that creates an electron flow.
That’s called a thermocouple and you can read more about the MMRTG system in this excellent coverage.
Importantly, Percy’s generator is designed with an operation life of 14 years - which is about 4x the 3-year mission - starting at about 110W and the Pu-238 decaying each year until depletion. The electricity is stored in two lithium-ion rechargeable batteries with a total capacity of 43Ah.
Heat from the MMRTG keeps everything functioning optimally in the frigid Martian climate with Li-ion cells losing about 10 percent capacity at freezing, and only reducing discharge capacity/rate of flow from that point (dropping to 50 percent at -18 Celsius).
The problem isn’t actually discharging, which can remain functional at up to around 40-below, but rather when electron flow is reversed during charging. With less heat energy the electrons slow to a crawl and fall below the charging threshold.
Back on Earth our EVs aren’t fitted with nuclear generators and rely on batteries alone to provide the energy needed for forward propulsion. Porsche pushed the industry forward a little with 800V architecture for more consistent performance and less weight from the associated reduced wiring volume. High voltage also allows for faster charging time.
My arguments for the iPhone 12 Mini included declaring the battery endurance as fine because 15-hours operating time is more than adequate. Unfortunately, I had a blind spot in my analysis with complaints starting to come in of battery health dropping quicker than usual.
That 15-hour endurance leaves the battery at under 20 percent charge by around 20h00, which is slightly below the preferred charge levels for Li-ion chemistry. Charging from below 20 percent eats up a bigger chunk of a charge cycle than if you keep it in the mid-range charge.
Driving the Porsche Taycan hard, because that’s what the marketing says it can do consistently, will leave you in the same situation. This is a brand that is built on performance and, sadly, instead of an EV follow-up to the headline grabbing Taycan, we get yet another petrol-powered 911 to start 2021.
Apple is allegedly halting iPhone 12 Mini production to support its better selling, bigger siblings during a global chip shortage.
What does this have in common with Perseverance? Well, the current Mars mission is to collect samples which will be gathered and returned to earth in the far future. To be fair, there’s also in the Ingenuity drone which will be our first flight on another planet…
Percy is another massive leap for humanity without first building the required safety net of sustainability. Just like the Porsche pursuit of performance left it with the same old battery problems we’ve had before, rendering the current Taycan immediately obsolete when the next big battery breakthrough happens.
Of course, dedicated EV manufacturer Tesla already has an eye on the next generation of batteries and announced the carbon architecture that will support the shift to Lithium-Sulphur batteries. When you produce the batteries and the car your R&D investment is split between it. Legacy carmakers buy in batteries and design cars around it.
My read: Nasa benefits from the kind of vertical integration that is keeping Tesla ahead of the chasing EV pack. Percy will, effectively, poop out sealed soil samples on its explorations and the next generation is tasked with retrieving it to study back on earth.
While I’m not a fan of littering other planets with now five rovers and three other man-made objects since the 70s, I see the human advancement point. But does it give us the right? In the same vein, does Porsche deserve praise for producing yet another fossil fuel slurping performance machine when that development could’ve been spent on making better batteries?
Jaguar is set to become an EV exclusive auto brand by 2025, which at least shows a real commitment to sustainable forms of motoring and not merely compliance-focused marketing stunts.
Humans are very bad at seeing beyond the immediate future these “breakthroughs” create. Then, like with climate change, future generations are left to pick up the pieces. We should do better.
Something you should know about:
The current cold storms running through Texas have caused numerous power outages and forced loadshedding/rolling blackouts to counter the problem. The State of Texas doesn’t have a federal (national) power grid and is served by private players who, in the pursuit of profit, neglected some maintenance and necessary winter upgrades that was mandated on the federal level.
Hopefully this serves as a warning for the Western Cape’s ambitions to go independent with its power generation. Privatising is not necessarily the answer if there isn’t sufficient oversight.
A number that may only interest me:
The time it takes light from Mars to reach Earth. That means while the Nasa JPL crew was celebrating a confirmed touchdown, Perseverance had already been on alien soil for about five minutes after negotiating the Seven Minutes of Terror completely autonomously.