Mark Sanders

There are few people arguing to replace jet fuel in planes with batteries so I assume your argument relates to cars? So some simple physics for you. Petrol - Energy content: ~8.9–9.5 kWh per L - Density: ~0.74–0.76 kg/L So: - 34 kWh ≈ ~3.7–3.8 liters of petrol - Mass ≈ ~2.8–3.0 kg - Specific energy ≈ ~12 kWh/kg Lithium-ion battery Typical pack-level energy density: ~150–300 Wh/kg So: - 34 kWh battery weighs ~110–230 kg - Specific energy ≈ ~0.15–0.30 kWh/kg Petrol is still about 40× higher energy density by mass. But for cars, this comparison is misleading. Unlike aircraft, cars are dominated by efficiency, not just energy density. 1. Drivetrain efficiency flips the story - Petrol engine efficiency: ~20–30% - Electric drivetrain: ~85–95% So usable energy: - Petrol: 34 kWh × 25% ≈ 8.5 kWh useful - Battery: 34 kWh × 90% ≈ 30.6 kWh useful Electric delivers ~3–4× more usable energy from the same stored energy. 2. Real-world range comparison Let’s convert that into driving range. Typical consumption: - Petrol car: ~6–8 L/100 km - EV: ~15–20 kWh/100 km From ~34 kWh: - Petrol: 3.8 L → ~50–65 km - EV: 34 kWh → ~170–220 km Despite being ~40× heavier, the battery goes ~3× farther. 3. Weight matters much less for cars than planes Cars are not nearly as sensitive to weight as aircraft: - Rolling resistance and aerodynamics dominate at speed - Regenerative braking recovers energy in stop-start driving - Extra mass has much smaller penalty than in flight So the “battery is heavy” argument is far weaker for cars than for planes. For cars, improving efficiency and cost often matters more than pushing extreme Wh/kg. In summary, Petrol has about 40× higher energy density than lithium-ion batteries by mass, but electric drivetrains are about 3–4× more efficient. As a result, an electric car can travel significantly farther than a petrol car using the same amount of stored energy, despite the battery being much heavier. For planes (and some cars) the answer lies perhaps in synthetic fuels. For the majority of cars, it lies in batteries. It’s just maths and physics. I’ll ignore the politics of war, but simply state that the more origins of energy that we have (oil, gas, solar, wind, nuclear, synthetic fuels, etc), the more unlikely we are to fight over them.