Hypermiling the Aptera

[Knix]

Great work!

I’ve also been wondering low you can get the consumption of the Aptera. I think the rolling resistance is also affected by speed to some degree. The engineeringtoolbox website has an estimate for rolling resistance which I think is more accurate which includes tire pressure and a small contribution from the speed squared. I may play around with it tomorrow.

[curtis-cibinel]

I suspect the wheel covers at the front are unsprung mass which move directly up and down with the front wheels. This would make changing the ground ground clearance essentially require remaking them or adding a lower piece. Until they release more details (especially for the offroad kit) we are still guessing.

[john-malcom]

Interesting! Deterministic point calcs at this point. If you care to give me your estimated ranges for each of the variables I will put in a Monte Carlo with triangular distributions so we can see what it is like with variation accounted for

[curtis-cibinel]

Unfortunately I am not a mechanical engineer and I’m sorry if I failed to describe that. I simply found calculations accounting for air resistance, weight and rolling losses and plugged it into a targeted spreadsheet I converted (originally for a GEO metro EV). The numbers are “back of the napkin” estimates. The 2000 mile claim was a bit sensationalist I admit and perhaps when someone really tried to stretch it the real value might be 1700-1800 miles which is still an impressive feat.

Even when released most production vehicles don’t provide all specs for all of the values needed for high speed efficiency calculations so they are estimates. Frontal area for example is not available as a shown spec but can be estimated and has little impact at low speed (I used the spec for an F150 to approximate the Rivian as a point of comparison). The data seems to fit real world measured values for the reference vehicles well enough to be a point of comparison (varies only 1-3%). See https://teslike.com/

I now realize one fundamental flaw was failure to account for engine efficiency losses and my coefficient of tire resistance may not be precise enough. I do not know the efficiency of the wheel motors (apart from the reasonable assertion they are above 90%). For rolling friction I simply took the assumption from articles that low rolling resistance tires with coefficients in the range of 0.006 and 0.008 were available (low rolling resistance tires) and plugged the higher (worse) into the equation. From Wikipedia this seems to be the case but I could not find specific low rolling resistance tires rated measured in coefficient of rolling resistance for the specific size for Aptera (195/45 R16).
https://en.wikipedia.org/wiki/Low_rolling_resistance_tire

I believe that a ultralight car with ~45% of its mass being high density batteries (based on the rough 10lb / kwh number that is often quoted) can reasonably be assumed to have strong hypermiling potential. It stands to reason that if a Tesla driven slowly can exceed its rating by over 70% that an Aptera can similarly. Controlling all variables and maintaining a constant low speed at high elevation with a lightweight operator would logically exceed what can be done with two guys driving a loop on a public road.

One thing in the numbers that I find non-intuitive (potentially wrong) is that when I compared the range degradation at speed between the model 3, rivian and entry level aptera (with some assumptions for both) they are nearly identical rates of degradation. This could be a coincidence in the data given the areas, weights and drag values or a flaw in my equations.

Here are my operating assumptions for the Aptera:

1. The described 1800 lb aptera is the 600 mile version. The weight be kwh being ~10lb would result in the 1000 mile version being ~2200lb +-100lb

2. The testing would be performed at a high elevation track reducing air density. This accounts for a ~2.5% (65 mile) increase in range but could be ignored due to practical challenges.
3. Tires for the Aptera with coefficients of road friction of 0.006 to 0.008 (see linked wikipedia are available). This seems reasonable given the common assertion of typical tire-road friction being 0.01. I actually used 0.12 for most of my charts as it seems to better align with mileage ratings but those losses are more likely due to breaking efficiencies. Small differences in this value result in huge swings in effective mileage at speeds where aerodynamics are negligible.

4. The frontal area of the aptera is ~20 ft squared. Honestly this might be high but the model 3 is 25 and it is clearly less than that. I believe it should be in the 17-22 range.

5. Coefficient of air drag is exactly 0.13 as stated. This could be higher or lower in reality but at low speed is relatively minor. +- 0.05 ?
6. The driver is 90lb. Honestly this is just me putting a 90lb jockey into the calculations for my own amusement. If the driver is 150lb instead this accounts for ~50 miles in the calculator which tracks within reasonable error with the statements that 30lb = 1% range.

7. For engine power conversion efficiency I would defer to anyone with more engineering background. Currently my chart fails to account at all which is obviously flawed. Not a ton of detailed specs exist for wheel motors in general. 95%?

8. I also made the assumption that ~8% of the pack would not be available to the user to preserve longevity. This was used more or less in all the numbers presented. At the end of the day actual pack sizes are not something we know for most EVs. By tuning based on other vehicles 55 mile theoretical ranges to exceed their epa ranges by approximately 7-10% the data seems to track with this fairly well.

In general I found most vehicles I entered exceeded rated ranges by too wide a margin but by a fairly consistent amount for each. This seems reasonable given the pure physics rather than real world nature of the calculations vs practical driving (turning = losses, breaking = losses, etc).

[jennifer-sensiba]

I’ve got an interesting idea that I’d like to explore more: going far more than 1000 miles by trying to keep power levels closer to what the panels are generating. I know this would likely be very, very slow. Like college student solar racer 20 MPH slow.

I do remember seeing in a video (can’t remember which one) that the Aptera pulls 1500 watts at 60 MPH. I may have the figure wrong on that, but it’s close to that. Because aero drag increases proportional to the cube of speed, going half the speed should produce 1/4 the drag. Combined with other hypermiling techniques, I’m thinking it may be possible to make the solar become a significant portion of the vehicle’s power.

I know you’ll rarely get the full 700 watts from the solar panels, but if you can keep the power to move on average under 500-1000 watts, it could get some insane range.

• This reply was modified 1 year, 9 months ago by  Gabriel Kemeny.
• This reply was modified 1 year, 8 months ago by  Gabriel Kemeny.

[steven-g-bueche]

This is above my paygrade but please do continue or at least contact someone at the home office. I’m sure the fan base would love to hear about anything that will extend their range.

[Riley]

Theoretically you can travel forever it would just take a long time 35 or so miles of recharge a day. Weight plays a huge role in your calculations as well so if you were to attempt pushing the limits you could rip out most of the interior and dramatically increase range.

[joshua-rosen]

At the height of summer in Texas, circling an empty parking lot around a football stadium or an oval track at 20MPH you might be able to drive all day on solar power alone. That would prove nothing but it would make a good article for you on Clean Technica and a YouTube video. I’m sure that Aptera would be willing to lend you a car for the attempt next summer. You would want to do this in the 250 mile version not the 1000 mile version, the 1000 mile car is going to be very heavy.

[OZ.]

Joshua, I would guess that since the optimum solar charge (Over whatever time frame Aptera used for its calculations. 8hr? 12hr? ?) is 44 miles, to drive on solar alone at 20MPH might be a bit optimistic.

[kerbe2705]

I believe that it was over a 12 hour, cloudless, southern California day…

[BUG]

North of the Arctic Circle, Mid Summer, 90 Pound Driver, passenger seat removed, etc…Drive all Day, as in 24 Hours!

[curtis-cibinel]

I spent a lot of time looking into this and the potential definitely exists (ignoring solar). On a track with a 90lb jockey and low rolling resistance tires could very likely go over 2000 miles. Maybe 1700 could be possible on roads. Obviosly totally pointless but that doesn’t stop people.

https://docs.google.com/spreadsheets/d/1Tuu7avKH2dS_JPk7aiP2av09a1f1WE0OvvNH6fdHpiQ/edit?usp=drivesdk

note: I make many assumptions. Feel free to grab a copy and play with the numbers.

[ray-holan]

Hi, Jennifer. You have an intriguing idea there. I’m sure once Apterae hit the road next year (fingers crossed!) hypermiling will be an active discussion and there will probably be friendly competition for “how far did you get on your last charge?” Taking the batteries down to their last few percentage points of energy would maximize your range, but, as others have pointed out elsewhere on the forum, this would negatively affect the life of your pack.

I have had extensive hypermiling experience with several Honda Insights. Once you eliminate the energy penalty of stops and starts by picking an uninterrupted stretch of road, your main enemies to greater MPG ( = greater range in our case) are weight, rolling resistance, and drag. Aptera is head and shoulders above other ICE vehicles and other EV’s in each of these areas already. Not much more weight can be removed from the vehicle.

You can reduce rolling resistance by pumping up the tires to 45 psi or thereabouts — ride will be noticeably harsher but vehicle will roll more easily. Keeping the speed down reduces drag. So slow and steady is about all you’re left with as far as optimizing range.

[ari-colin]

Well I managed 81.8 miles on one charge in my 2012 Volt. Average speed was 23 mph. Volt was rated at 35 miles and ended up with 8.34 miles / kWh. Also had tires way over spec at 60 psi. There is an article about this drive on InsideEVs. Would love to try an extreme test in an Aptera.

[ray-holan]

Quite an achievement, Ari. I had a 2014 Volt and my best was only 46 miles. I didn’t have the patience for an avg. speed of 23 mph though. You’re a better man than I. Or at least a more patient one;)

[ari-colin]

I found the perfect spot for the hypermile run, FedEx field in Landover, MD, where the Redskins or whatever they call themselves now play.

It is a giant traffic circle, plus there are EVgo chargers there so I could top off before the run. I also waited until my tires had 50K miles on them to reduce rolling resistance. I waited too long and it got dark before I completed and I could see a noticeable drop in efficiency due to the lights.

https://insideevs.com/news/321962/just-how-far-can-a-chevrolet-volt-go-on-electricity-how-about-818-miles/

[JRWiley]

Just curious as to what some of you would guess the Aptera would do in the wake of a semi. Would it benefit a lot, a little or not at all. Btw, I tried this once when I was young for a very short distance before I lost my nerve.

[glenn-zajic]

There will be very little benefit to drafting a semi. First, there is little frontal area to diminish the wind resistance, remember the two hands out the window? That is the most amount you would be blocking. Second there isn’t much surface area for the air to grab ahold of to drag the vehicle. It may offer some slight benefit to the semi, but I even doubt that would be measureable.

[ImAlwaysMIA]

Let’s not also forget about all the rocks and debris that the semi tires kick up right into the front end of your vehicle.

[Mike-Mars]

Yep. I used to hypermile a bit, back in the day (over 1000 miles on a tank in my Passat).

The more aerodynamic the vehicle, the less advantage there is in drafting something. There’d barely be any effect at all on the Aptera.

I think the key to getting the most miles out of the Aptera is the simplest hypermiling principles of don’t brake unnecessarily, don’t go too fast (but not dangerously slow for the conditions either), plan ahead, make sure your tyres are good, never use A/C or heater. The advanced techniques are probably mostly irrelevant since it is an EV not an ICE, there is no freewheel, there is no transmission …

• This reply was modified 11 months ago by  Michael Marsden.

[ROMAD]

Was it a TDI and how big was the tank? I’ve been able to get up to 600 miles on the 16 U.S gallon (60 L; 13.3 Imp Gal) tank of my Jetta TDI.

[Mike-Mars]

Yes, a TDi. That tank was was 1015.1 miles (90 miles into the reserve)

60.5 litres (16 us gallons) brimmed & vented – (I hope this is right because I had to back-calculate it from the MPG I have written down)

Year 2000 model

My current car can get higher MPG, but it has a much smaller tank. Best on that one was 649 miles at 87.7 ukMPG (73 usMPG), 33.6 litres.

[ROMAD]

And a manual tranny I suspect. I have a automatic.

Speaking of transmissions, since the Aptera will have the motors in the wheels, I guessing they will feel similar to a CVT?

[Mike-Mars]

Yes manual. No use of the A/C or heater. And no DPF either …

Hypermiling techniques included engine-off pulse&glide (which I don’t recommend, it puts a lot of strain on the clutch and transmission). It was quite a relief when I stopped hypermiling, there’s so much to keep track of, and you are constantly working.

A major factor which people forget is also the daily commute. Mine was 28 miles each way, fairly flat. If you drive shorter distances (for example, to the shops or dropping the kids off at school), or on hilly terrain, then the MPG will be noticeably less.

[OZ.]

I got a 780 plus on my 2003 Golf TDI once, I had to do a weekly commute for a while Sacramento to L.A. and I finally decided the crazy competitive way I usually drove would kill me at some point, so I just set the cruise to 70mph one trip, puttered around L.A. and then 70mph on the way back, I lost my nerve and filled up in Gustine. (Low fuel light wasn’t on but I was beat and didn’t want to press my luck till the next stop, I did, however, always burp fill the tank with the 2 extra gallons you could sneak in whenever I fueled up.)

[ROMAD]

Best I’ve ever done was 617 miles. Have you done the ventectomy?

[OZ.]

No, thought about doing that, but ended up selling it when I retired. (It had an annoying glitch that no one was ever able to remedy, causing it to drop into the limp mode randomly, usually at an inconvenient time.)

[Mike-Mars]

I had that a number of times on different TDIs:

* Leak in air intake tubing (looked like someone had used an angle grinder nearby)

* Dirty MAF sensor

* Bad MAF sensor

* Incorrect MAF sensor (from the wrong revision, after the intercooler was changed)

[UnidentifiedDrivingObject]

Didn’t realize the TDI’s “breathing issues”, has the same exact issues I encountered on my longitudinal ATW 1.8T. Bad or dirty MAFs, vacuum tube/check valves leaks or cracks. On top of pronation to sludging (added the oil capacity using the “Mannolator” & prompt 5kmi German Castrol 0W40 OCIs). Sold it, after 13yrs/130kmi not because of these given issues. But interior and engine plastic parts are literally crapping out/falling apart on me. Lol.

[Mike-Mars]

I’ve had some similar problems with plastics too. The trouble for me is that they stopped manufacturing that particular model in 2005, so spare parts are becoming difficult to get. My current car is a 2002, 280k miles, quite a few modifications. New suspension better able to cope with the endless potholes here, swapped the 16″ wheels for 15″s for the same reason, some aero components from the A2 ‘3L’ super-efficient variant, added a 6th gear to the gearbox and made the 5th gear higher, remapped, swapped out the centre console with a higher spec one with an mpg gauge, added in a module so that the centre console can read error codes & other engine parameters and display them in real-time, swapped the interior (I prefer dark colours).

• This reply was modified 11 months ago by  Michael Marsden.

[mark-rooney]

Mythbusters tested this: https://pressbooks.bccampus.ca/technicalwriting/wp-content/uploads/sites/296/2018/10/Drafting-Behind-Big-Rigs-Mythbusters-Report.pdf

This is with a dodge magnum and they had to drive unsafely to get significant improvement. A realistic minimum 50 foot distance would be single digits improvement. 5% isn’t worth it.