Electric Aircraft: Battery Life Just As Important As Capacity


Battery limitations continue to stunt the potential of electric aircraft, but Uber is betting that current technology is good enough to make urban air mobility workable now and will only improve as the vehicles mature.

At this week’s Uber Elevate Summit in Washington, D.C., the company’s Mark Moore said battery capacity and longevity drives both the design of the aircraft and how they’ll be flown when UAM goes operational. “Everything points back to the batteries. We’ve got a very severe energy constraint, so you’ve got to design the entire aircraft around the battery if it’s going to work well,” Moore said. Moore spent years at NASA as electric vehicle expert and joined Uber Elevate as the company’s vehicle director of engineering.

Although Uber is relying on five companies to develop potential UAM aircraft, it’s intimately involved in evaluating and testing battery technology, including which chemistries work best and how to charge and maintain batteries. As the wider electric aircraft industry looks at applications for these aircraft, many companies are considering hybrid drive designs to extend range. For now, Uber is sticking with pure electrics.

That means that UAM aircraft have to accommodate the inevitable in-service degradation of batteries and factor those costs into the operating economics. “You have to design the aircraft for the end of life of the battery, not a new battery,” Moore said.

In fact, battery longevity may be just as economically important as the aircraft’s basic range limits. As a result, Uber is developing charging and maintenance strategies aimed at extending battery life. Moore said vehicle range is less important than stage lengths, which are estimated to be typically about 25 miles.

“With these batteries, you have to be able to recharge to keep these vehicles productive on the network,” Moore said. So the typical trip that might best extend battery life is 25 miles, followed by a seven-minute charging period, followed by another short charging period.

“One of the key things to look at is state of charge. We’re not necessarily looking to charge to 100% and we don’t want to take them to zero,” said Celina Mikolajczak, who oversees Uber’s energy storage systems.

Under some duty/charging cycles Uber has simulated, she said, the packs would have to be changed every three months. But a short duty cycle followed by a short charge cycle might extend that to a year. “That starts to look a lot better,” she added.

Because of both range and battery life limitations, commercial electric aircraft will live in a narrow sweet spot that will depend, in part, on flight hour costs. Moore offered a glimpse. Against the Bell 407 GXi that might be used in the just-announced UberCopter service from Manhattan to JFK airport, operating costs for the electric vehicle are estimated to be $700 compared to $1192 for the helicopter.

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  1. Ironically, just the other day I saw some Teslas on the ‘SuperChargers’ in Oshkosh. Never having seen any there, I engaged the drivers in a Q & A to which they were happy to oblige.

    I watched as a driver backed his ride into the charging station. My first question was, “How do you pay for the recharge?” A: The car communicates it’s ID to Tesla and you have an established account … kinda like an Apple account.

    Q2: “How long does it take to charge up?” A2: ” The charge rate varies during the recharge but a typical charge is about 30 minutes.” For reasons I couldn’t fathom, one driver says they rate the recharge in miles per hour which made no sense to me but ?? He further stated that there’s an APP so you can see how the car is doing while you’re off shopping or ? I asked, “Could someone yank the plug out of the car?” A: “Once the car is locked, the plug is — likewise — locked to the car.”

    Q3: “How far can you drive?” A3: “You ‘tell’ the car where you’re going and it decides your route so you can pass a recharging station IF the drive isn’t local.” I then asked what if a charging station isn’t available. A: They come with a 110VAC plug BUT … “the charge rate is borderline dismal and useless.”

    Q4: I then asked the BIG question … “How is this thing gonna do in the dead of winter in Oshkosh?” A4: “THAT is the $64,000 question. IF it won’t work, I can work from home.” Great, I thought.

    One driver of a pre-2017 car told me that those vehicles get free recharging for life. I then asked, “How long is the battery pack good for?” He said they think 200,000 miles? The next natural question … “How much will a new pack cost?” A: $20,000 !! YIKES !!!

    And THIS is gonna save the planet, I thought. To be fair, one driver — a Navy musician from Great Lakes said — “IF you know anyone with a Tesla, take a drive. You’ll be amazed at the smoothness. Better still, try to get one to drive.” Fair enough, I thought, but if I’m always worried about the state of charge and how far it is to the next Supercharging station, what good is that. Utility transcends smoothness in MY mind.

    SO … apparently the Uber flying machines are gonna have the same problem. And on today’s AOPA Today video, they’re saying that there are now 155 companies trying to build such machines. Maybe all those Light Sport companies have changed direction and are now building flying UberMobiles ??

    Meanwhile, a snowbird pilot I know mentioned that he had averaged 65mph heading back from Texas. He mentioned that Prius’ were passing him at 80mph. Moral of the story for Uber … look into HYBRID !!