Gregory J. Hassler

Bigger Batteries Win

Why battery size matters more than charging speed, and why fast charging exists to serve it

A popular prediction inside EV circles is that battery packs are going to get smaller. The reasoning goes like this: charging keeps getting faster, chargers keep getting more common, and eventually a small, cheap, light pack topped up in six minutes beats a large expensive one you never fully use anyway. It is a tidy story and it is backwards. Fast charging absolutely needs to keep improving, and it needs to keep spreading. But it improves in support of larger batteries, not instead of them. The physics, the ownership math, and a century of consumer expectation all point the same direction, and it is not toward smaller packs. The number on the window sticker is not the number you live with An EV's rated range is a best case. It is a new battery, in mild weather, charged to 100 percent, driven to zero. Nobody owns that car for long. Start with a 300 mile EV and apply the things that actually happen: Degradation. Call it 12 percent by year eight, which is typical and better than the 30 percent floor most warranties allow. You are at 264 miles. Winter. Recurrent's study of more than 30,000 vehicles actually on the road puts average range loss at roughly 22 percent at freezing. That figure reflects today's fleet, in which heat pumps are standard on most new EVs and are worth about ten points on their own. Older EVs with resistive heaters do worse, and so does anyone driving in genuinely deep cold rather than at freezing. Take the 22 percent and you are at 206 miles. The charge window. Daily charging to 80 percent, and not planning to arrive on empty, leaves you a working window of about 70 percent of the pack. That is 144 miles. So a 300 mile car is a 144 mile car on a February morning in year eight. On a road trip, where you charge to 100 percent and run it down to 10, the same car covers about 185 miles between stops. None of these derates are exotic. I have argued elsewhere that corner cases matter and that the industry should stop waving them away, but this is not even a corner case. Cold weather, an aging battery, and a charge limit are just the normal conditions of owning a car for ten years in a place that has seasons. A pack has to be sized for the worst realistic day of its tenth year, not the best day of its first. Gas set the baseline, and it did it on purpose Almost every gas vehicle on the road covers 400 miles or more on a tank, and plenty of them go far past that. A Ram 1500 EcoDiesel with the big tank is EPA rated near 860 miles. A Panamera has been tested at 750. Half ton trucks with optional 33 and 36 gallon tanks routinely clear 800. The exceptions are rare enough that you can name them off the top of your head, a Miata and a handful of other small sports cars. Those numbers are not accidents of packaging. Fuel tank size is a deliberate engineering decision, and automakers chose those sizes because that is what buyers demanded. Nobody was forced into a 400 mile baseline. The market picked it. The harder part for EVs is that the gas baseline barely moves. A gas car loses maybe 10 to 15 percent of its range in deep cold, not 22 to 40. It does not lose capacity as it ages, because the tank is a plastic box and the tank does not degrade. There is no charge limit, no reserve strategy, no 20 to 80 habit. You use the entire tank, every time, in any weather, in a car that is twelve years old and has never been treated kindly. That is the expectation EVs are being measured against. And it is why the answer is a bigger pack rather than a smarter charging strategy. Larger packs live easier lives This part is not about babying the battery. Owners should not change their behavior, and the data increasingly says charging habits matter far less than we once believed. This is about how the pack is sized before the car ever reaches a customer. Cycles. Drive 12,000 miles a year in a 300 mile EV and you have put roughly 40 full pack equivalents through it. Do the same 12,000 miles in a 150 mile EV and it is 80. Same driver, same miles, double the cycle count over the life of the car. C rate. A 250 kW charge into a 100 kWh pack is 2.5C. The same 250 kW into a 50 kWh pack is 5C. Same charger, same number on the screen, more stress and more heat on the cells. Heat. More capacity means more cells sharing the same current, and resistive heating scales with the square of the current per cell. A larger pack also has more mass and more cooling surface to absorb whatever heat does get made. The identical charging session that a 100 kWh pack shrugs off is a thermal management problem for a 50 kWh one. Cycle life. Put those three together and the picture is simple. A larger pack does fewer cycles, does them at lower C rates, and runs cooler doing it. Cycle life goes up directly, and because heat and high C rate stress feed back into calendar aging too, the clock ages a little more slowly as well. I will be honest that this is the smallest point in the article, because in practice modern packs are already outliving the cars they are bolted into. But it is still technically better, and nothing about battery life is being traded away to get it. A bigger pack is not buying range at the expense of longevity. What it does cost you is weight, and weight turns out to matter far less than people assume. Charging speed is downstream of pack size What a driver actually cares about is miles added per minute, not kilowatts. Those are different things. Efficiency is what turns kilowatts into miles, and it is arguably the bigger lever, but that is its own conversation. What pack size does is allow the high charge rate in the first place. Adding 200 miles in 15 minutes at 300 Wh per mile means moving 60 kWh in a quarter of an hour, or 240 kW on average. On a 100 kWh pack that is a 2.4C average across a 10 to 70 percent window, which sits in the fat part of the charging curve. On a 60 kWh pack it is the entire battery, at 4C, which no chemistry on the market will do. Small packs are also forced to use more of their curve. Every stop has to take a bigger percentage of the pack, which drags the session up into the taper where the power falls off a cliff. That is the same mechanism I wrote about in "The 10%-80% Myth." A big pack does not just charge faster in kW, it gets to spend the whole session in the part of the curve where fast charging works. The weight objection is smaller than everyone thinks The most common pushback on bigger packs is weight. A bigger battery makes the car heavier, a heavier car uses more energy, and so you spend the extra capacity hauling the extra capacity around. It is intuitive, it is theoretically true, and in normal driving it is close to immeasurable. Two reasons. First, regenerative braking gives most of it back. The energy you spend accelerating a heavier car is largely recovered when you slow it down again, and the same is true climbing and descending a hill. Weight is a loan in an EV, not a purchase. Second, and more importantly, weight is simply not where the energy goes. At highway speed the large majority of an EV's consumption is spent pushing air out of the way, and aerodynamic drag does not care what the car weighs. Add a few hundred pounds of cells to a crossover and the change in highway consumption is a rounding error next to what a roof rack does to it. Weight matters for performance driving, for tires, for brakes on a heavy truck, and for what a vehicle does to a guardrail. It barely matters for range. Which means the central objection to a larger pack mostly does not survive contact with the data. The honest counterargument Efficiency is a real substitute for capacity, and I would rather say so than pretend otherwise. A 75 kWh pack at 250 Wh per mile delivers the same miles, the same cycle count, and the same miles per minute as a 100 kWh pack at 333 Wh per mile. Anyone who cuts drag or drivetrain losses gets the benefits I described above without adding a kilowatt hour. The data is not ambiguous about which way this is going. US average battery electric pack size reached about 90 kWh in 2025 and is still climbing. Some market data shows the average flattening for a stretch while range kept rising, which is efficiency doing the work, and that is real. But efficiency is a lever with a hard stop and we are already close to it. The best production cars are down around a 0.20 drag coefficient, motors and inverters are north of 90 percent efficient, and tires can only be made so hard before they stop being tires. Battery technology has no ceiling in sight by comparison. Energy density keeps rising and cost per kWh keeps falling, and that is exactly what keeps the weight and the price of a larger pack in check. Packs keep growing because capacity is the lever with room left in it. There is a second problem with leaning on efficiency, and it is the part the efficiency argument tends to skip. The more efficient a car is, the harder it gets hit by any inefficiency you introduce. That roof rack from a moment ago costs roughly the same watt hours per mile no matter what it is bolted to, which means it takes a far bigger percentage bite out of a 250 Wh per mile car than out of a 350 Wh per mile one. Same with a headwind, a trailer, winter tires, or four adults and their luggage. Efficiency is smart range, and smart range is conditional. Capacity is dumb range, and dumb range does not care what you did to the car this morning. There is no replacement for displacement, and in an EV the displacement is in the pack. There is a cost ceiling, but there is no physics ceiling, and the cost ceiling keeps moving. The 200 kWh consumer vehicle is not a thought experiment. The Hummer EV carries about 212 kWh and the Silverado EV is not far behind, and those are products you can buy rather than concepts. For now that much capacity belongs to expensive trucks, while mainstream vehicles sit somewhere in the 75 to 120 kWh band, already roughly double where they sat a decade ago. But capacity that starts out as a premium feature has a habit of becoming standard equipment. If cells keep getting cheaper and denser, and they are, there is no particular reason 200 kWh does not become ordinary. The shrinking pack theory has the arrow pointed the wrong way. So what is faster charging for It is for the batteries. Charge time is capacity divided by power. Double the pack, hold the charger constant, and you have doubled the stop. The only way to keep growing capacity without stretching the length of a charging stop is to grow the kilowatts right alongside it. A 100 kWh pack needs roughly twice the power of a 50 kWh pack to put the same percentage back in the same minutes, and a 200 kWh pack needs twice that again. Charging speed is not competing with pack size, it is what makes a larger pack livable. There is a second reason, and it belongs to a particular group of people. If you have a driveway, public fast charging is a road trip tool you use a handful of times a year. If you park on a street or in an apartment lot, it is your entire fueling life, and it happens in the same February weather that just took 22 percent of your range. For them the battery is not something that quietly refills itself overnight. It is a fuel tank. It gets filled on a trip made for that purpose, and how far it goes between fills is the whole question, exactly as it is for a gas car. That population is why chargers also need to be more numerous and more reliable, not merely faster, and it is why their cars need bigger packs rather than smaller ones. Those two needs are not in competition. They are the same need viewed from two sides. The question is whether the car still covers the trips you actually take, in the cold, in year ten, with a battery that has aged the way batteries age. You do not solve that with a faster charger. You solve it with a bigger battery, and then you make the charger faster so the bigger battery is no inconvenience at all. More at curiousaboutevs.com