This column goes out to all the engineers out there, armchair or otherwise, who, like me, try to make sense of a complicated world through the deciphering of numbers. The subject for today’s treatise in motorcycle engineering will be energy density; more specifically, the energy density that motorcycle lithium-ion batteries will have to attain to offer the equivalent weight and range of a comparable gasoline-fueled motorcycle. And, by way of example, I’ll be using what we all must presume will be the world’s most advanced electric bike: Ducati’s new MotoE racer.
The reason for that is two-fold. For one thing, like I said, the Ducati MotoE bike is brand-spanking new and therefore will have all the very latest in technologies. Just as importantly, Ducati has the very best MotoGP bike — the infamous Bologna Bullets — to compare it with.
Bologna’s battery-powered bike will, according to the company’s own reckoning, weigh in at 225 kg. Of that, 110 kg are accounted for by its 18-kilowatt-hour battery. Those six kilograms per kilowatt-hours — a rough approximation of the real-world energy density I promised we’d discuss — is about typical of the highest-tech batteries available. By comparison, Ducat’s GP22 tips the balance at 157 kilos. Throw in 14 kg for a full tank of fuel and that means the GP22 weighs some 54 kg less than the company’s MotoE effort.
So, if Ducati has any hopes of making a MotoE racer as light as its MotoGP bike, it will have to find a way to make its battery more energy dense. Yes, there are always other weight savings available. But Ducati claims its silicon carbide MOSFET inverter weighs only five kilos, the electric motor itself but 21 kilos and, thanks to its 800 Volt architecture, even the cabling is as slim as possible. In other words, almost all of the weight savings of any future e-racer will have to come from its batteries, and that aforementioned 54-kg difference would seem to require a doubling of energy density — an improvement, if recent history is any indication will take at least the better part of a decade to achieve.
But even that is not really a fair comparison. The electrified Duke, by all reports, makes around 150 hp, a far cry from the 280 hp — maybe 300! — that the 1,000-cc GP22 squeezes out. A more apt comparison, then, might be the 765-cc Moto2 bikes that make about the same power.
Unlike MotoGP, Moto2 weight regulations set a total for bike and rider — the better to keep the single-engine series competitive — of 217 kg.
Assuming a 70-kg rider and a full tank of gas, that leaves a Moto2 Kalex or whatever weighing about 160 kilos. That is 65 kg lighter than the MotoE. In other words, for the electrified Ducati to match the weight and power of the Triumph-engined Moto2 bikes, the battery would have to weigh 45 kilos. That’s almost a third of the weight of what’s currently being used – a huge ask even for the advocates that always claim a battery revolution is right around the corner.
“But wait,” as Ron Popeil of Veg-o-Matic fame used to say, “there’s more!” MotoE races are limited, depending on the circuit, to six or eight laps. MotoGP and Moto2 events are typically twice as long. In other words, our hypothetical just-as-competent-as-gasoline racer would need twice the Duke e-racer’s 18 kWh to complete the same distance.
Factor it all in and a MotoE bike would need somewhere like as six times the energy density of the new Duke to be able to match the power, weight and endurance as a Moto2 bike. Go through all the literature you want — even those brimming with pie-in-the-sky optimism — and you won’t find anyone claiming such a radical upgrade in technology will occur anytime soon. And, of course, that still leaves us a long way from the capabilities of the pinnacle of motorcycling efficiency, Ducati’s own GP22.
So, who cares, you ask? What a MotoGP bike does on a racetrack has little in common with how we ride our motorcycles on the street.
Well, the thing is that racing is not only a crucible of future engineering development, but also a signal of a technology’s current state of art. In other words, the same issues that make a MotoE slower, heavier and less able to run long-distance also have limitations in everyday life.
Recently, for instance, Rideapart wrote a glowing story about Bruce Smart riding his Energica to the four corners of the United Kingdom in “under” 96 hours. This was quite a feat, implied the website. Much congratulation ensued.
The only problem of course, is that British Iron Butters regularly do the same ride in less than 36 hours on ICE-powered bikes. Smart himself has done it in less than 48 hours and thought it not “terribly difficult.” And while as many of us are as likely to ride 32, 48, or 96 hours straight as we are to race a Moto2 Kalex, that same problem of energy density — and, of course, the eons it takes to replenish said energy — dramatically affects anyone grinding out ordinary, everyday touring miles.
In other words, Ducati is going to have to make incredible advances in battery energy density if they want even ordinary tourers — let alone their MotoE racers — to compete on an even footing with their fossil-fueled counterparts. The lesson I got from the introduction of the most advanced electric racer in history is that we are still a very long way from BEVs matching the performance of ICEs.
