EV-lutioin
Active Member
Interesting, my MX has never even come close to the range displayed... are you driving under the speed limit?
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Interesting, my MX has never even come close to the range displayed... are you driving under the speed limit?
Maximilien
Member
I made it clear in the other post in this thread that I drive mostly 65mph~70mph. Sometimes 75~80mph when I am urgent for business meetings. It still averages about 300 kw/mile, giving ~3.3 miles in each kwh.
If I drive 55 mph, I will get like probably near 400 miles.
I let autopilot on on highway most of the time, if that helps.
No, I don't drive 55 mph like some people thinks. But I use AC rarely by opening the windows. I expect that in the winter I may get a little less.
Aerodynamic drag drops as temp goes up normally. But it's actually air density that does the trick. Humidity, Temp, and Barometric Pressure all combine to become what pilots and auto racers call Density Altitude or DA for short. Pilots need low DA for shorter take-offs with heavy loads, racers (ICE) need low DA to get more oxygen in the cylinder per intake stroke. EV owners need high DA though. So one of the best places for EV range is like Wendover, Utah (Bonneville), because the DA can go over 11,000 feet (3350m) in August. Density altitude should not be confused with physical altitude, they can differ by quite a bit.
If rolling resistance is ~30% at 75 mph, and your range is 200 miles at 0 m DA (standard temp and pressure), at 3350m DA, you should improve to 226 miles with no other changes.
Trivia: As humidity climbs, air becomes lighter, and you have less aero drag. Why? Water is heavy right? No, actually it's not when it's a gas. Two nitrogen atoms make a nitrogen molecule with an molecular weight of 28, which is 78% of air, oxygen which is 21% is 32. A water molecule is 2 hydrogens and an oxygen, which only weighs 18 per molecule. Since all gasses have an even disbursement of molecules, air adulterated with water is lighter.
Agreed! I just went through several stages of grieving over that McRat post. In the end, and after consulting other sources, it's changed how I believed environment affected drag. Excellent post!
It's a small effect, but real 
E.g. 30°C (86°F) is 3% less dense (and thus about 2% longer range) than 20°C (°86F). Heat also improves battery capacity (reduces internal resistance / increases ion mobility), which usually has more of a positive impact on range than the reduced air density. This of course only applies to an extent; if it gets hot enough that you have to cool the battery, then that's wasted energy.
E.g. 30°C (86°F) is 3% less dense (and thus about 2% longer range) than 20°C (°86F). Heat also improves battery capacity (reduces internal resistance / increases ion mobility), which usually has more of a positive impact on range than the reduced air density. This of course only applies to an extent; if it gets hot enough that you have to cool the battery, then that's wasted energy.
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Oddly enough, in the winter, HRP (Houston Racepark in Baytown) has NEGATIVE DA!!! Less than sea level. Some of the records in drag racing are set at HRP because of it.
If I had to leave California, my second choice would be Texas. And my third choice would Texas.
Love Texas and Texans. I need to go back again soon to raise my spirits and down some spirits. Oh, and as for the effect of humidity: saturation vapour pressure at 30°C / 86°F is about 0,04atm, and water vapour is 62% as dense as bulk air, so the density (and thus aero drag) difference between 100% humidity and 0% humidity is about 2,5%, and thus the effect on range about 1,5%.
N5329K
Active Member
You really experience high DA effects in an airplane on takeoff and landing. Aircraft engines and airplane wings need air to work, and at high DA there's less air for the engine to make power (even worse if the pilot fails to lean to best power), and less air for the wings to "bite" for lift. Interestingly enough, the airspeed indicator remains true (IOW the airplane will rotate on departure at the same indicated airspeed regardless of DA), but groundspeed is a whole 'nother thing. It takes longer to reach the proper indicated airspeed when you are hot and high. If it's hot and high enough, there might not be enough runway available. Bent metal ensues.
Landing is the same. Your first high-DA landing can be an eye opener. While the airspeed indicator shows the same old number for landing, the ground will be moving at an alarmingly fast pace beneath your wings. More than a few pilots have been fooled by this effect into slowing down and suffering a low altitude stall and spin. These are usually non-recoverable.
Robin
Landing is the same. Your first high-DA landing can be an eye opener. While the airspeed indicator shows the same old number for landing, the ground will be moving at an alarmingly fast pace beneath your wings. More than a few pilots have been fooled by this effect into slowing down and suffering a low altitude stall and spin. These are usually non-recoverable.
Robin
SageBrush
REJECT Fascism
There are multiple effects on energy consumption from a higher ambient, but I would not be surprised if one of the more prominent is higher tyre pressures.
E.g, a 15C increase in temperature from 293K to 308K is ~ a 5.1% in pressure.
E.g, a 15C increase in temperature from 293K to 308K is ~ a 5.1% in pressure.
Oh, tires are a whole new can of worms.... more to the point tire temperatures increase while you drive over the first 15-30 minutes (if I'm remembering the timeframe right), causing a very meaningful drop in rolling resistance between cold tires and warm ones. And it's not the air pressure that does it, primarily, it's the reduced hysteresis in the warm rubber.
Here's a fun one: old tires have lower rolling resistance than new ones. The opposite of what most people would expect. But older tires have thinner tread (less flexure of the tread pattern elements) and rubber that's become harder with time (less general rubber flexure). These properties make the tire have poorer traction, particularly in adverse conditions, but they do lower rolling resistance - so your rolling drag goes up when you put new tires on.
For better performance and range. Need should probably be reworded to want.
There is a race once a year that involves high DA conditions, called Pike's Peak. EV's have the advantage over ICE race engines there, and have won the race before.
SpiceWare
Member
During family gatherings I've noticed that family members who reside in Houston, Corpus Christi, and San Antonio look quite a bit younger compared to those those in dryer states (ie: older siblings look younger than their younger siblings). My mom said it's due to the humidity as it helps to decrease/delay the formation of wrinkles.
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