EVcast.com is the home of the EVcast. The EVcast is a podcast dedicated to bringing consumers the latest information on electric vehicles in a non-technical, non-political, and entertaining way. Don't forget, you can also subscribe to this podcast via iTunes or your favorite podcatcher.
Watch this Blog
Notify me by e-mail any time a new post is made to this blog.
The EVcast is a podcast dedicated to bringing consumers the latest information on electric vehicles in a non-technical, non-political, and entertaining way.
Become Our Platinum SponsorProduct ID: 00000003Currently In Stock: 0
For the main sponsor, you get the big prize! A 622px wide x 100px tall banner that will appear on just about every page within EVcast.com, including blog posts. On the homepage, in place of the banner you will have a custom ... More »
August 2008 Posts
Don't just listen to the EVcast -- experience and be a part of it! Join us at 1:00pm Eastern, M-F, in our live video broadcast and chat along with us!
Bo, One of the listeners was commenting on saving electricity by not needing to refine as much gasoline as we switch to EVs. You commented that we get our gasoline from overseas so we would not be saving US electricity.
My understanding is that CRUDE OIL is imported from overseas and then refined into GASOLINE here in the USA using USA electricity. So perhaps we could save electricity by reducing gasoline refining. (I will not hold my breath).
The difference between crude oil and gasoline is an interesting one. Iran, which has tons of crude oil, has a shortage of gasoline. This is because they lack the refining capability. Iran is actually planning to switch their cars to natural gas which they have plenty of (and is difficult to export).
John C. Briggs
quote comment add new comment
The question, at what speed do you get the best mpg?
I added another column to the table Wh per mile. Work equals force times distance. Thus, a car should be most efficient at 0.001 mph. Which leads me to believe the most efficient speed for fuel economy depends on the engine manufacturer or torque curve.
How do things change with an EV? Everything! You should get better mileage at 5 mph than 10 mph and so on since the engine is efficient at all speeds.
In regards to rolling resistance, it involves wheel bearings, tires, and possibly differentials. However, based on what I have read over 90% of these losses are attributable to tires. I could be wrong! In an electric vehicle at low speeds these losses become dominant an a owner on Iwantazenn increased his mileage 5 miles by slightly over inflating his tires. You can lower your Crr to less than 0.08 by buying tires on the wikipedia rolling resistance webpage or this site below. It is interesting to note steel on steel have Crr < 0.001 and an electric car could get mileage exceeding 10 Whr per mile on steel tubular rail at low speeds. Which leads to the idea of why not having a big nationwide roller coaster. Be careful in getting too low Crr as you need it for safely braking.
In regards to air drag, it involves frontal area and streamlining. The average car has a Cd=0.34. However, the Honda Insight has a drag of 0.25.
In regards to lights, radios, wipers, and AC units. Most cars use 55w per headlight, however Xeon headlamps use 35w. This total to about 100w for headlights. Radios consume between 10w to 15000w, but most reasonable people use about 15w. Wipers are rated at 40w, however rain will also lower your rolling resistance. I am going to leave AC r out but it should be near 500w. So you use 150w, at 10 mph you will use 15 Whr per mile. At 50 mph you will use 3Whr per mile.
The fourth column lists kinetic energy. Based upon the motion of the mass. Regenerative braking attempts to recapture some of this energy.
I did my calculations based on a website to calculate your own air drag coefficient google it if you interested. I am planning to make a post at Iwantazenn for an actual car and further clean-up of this post.
Based on a 1000 kg car, frontal area 2.3 m^2, Cd=0.34 (modern car), Crr=0.01
fd=0.095*(Vmph)^2 N, frr=98.1 N
speed-rolling resistance-air resistance-energy use (Wh/mi)-kinetic energy-
Thanks for the update.
So your suggestion is that efficiency for EVs is different than for ICE vehicles and that actually 0mph might be the most effecient speed for an EV, except that the load of accessories will probably make the most efficient speed be something higher, perhaps 5 MPH.
This fits in well with the information provided by Vectrix
Constant Speed Range Miles
25 MPH 65 miles35 MPH 54 miles40 MPH 48 miles45 MPH 44 miles50 MPH 36 miles60 MPH 20 miles
So the highest efficiency for this EV is 25 MPH or less. This is very different than for an ICE car where the highest efficiency is about 45 MPH.
I find very interesting your discussion of electrical accessory loads. Because these loads are constant with time and don't change with driving speed, it is more efficient to drive faster, i.e. don't spend so much time in the vehicle using the battery for AC and lights, etc.
One small knit-pik with your post, rolling resistance actually increases in the rain, it does not decrease. I have a Toyota Prius with real-time MPG feedback, so it is painfully obvious to me that rain kills MPG (perhaps 10MPG less in the rain). I think the reason is that the car has to push the water out of its way.
I made an educated guess Crr would drop in rain since it appears it drops for bikes. Think Armstrong predicted there would be record time since the road was wet once. Also noticed the EV-1 had the lowest Cd of any production car, but Aptera broke the record at 0.11. These are theoretical numbers, and I am probably missing something or made a calculation mistake somewhere, as the Zenn uses over 100 WH/mile. However, it could be due to controller, battery, and motor inefficiencies.
In comedy they often say never do an accent or impression unless you have it down cold. I say please continue with performances! Regarding your mock survey with british consumers,...stop making fun of asians.
At the EVcast, we say do your best impression even if you sound like an idiot. To that extent, with the British accent, I have succeeded. If you or anyone other listener thinks doing an accent is the same as "making fun of", then I have to put out a blanket apology to all Brits, Asians, Texans, old guys, teenagers, people with Boston accents, Italians, Indians, stupid people, smart people, rich people, former and current presidents, Scooby-Doo and Shaggy. To all those groups, I am sorry if I offended you.
BTW- you can catch all those attempts as accents and dialects somewhere in episodes 1-53 except for the last two... I am reserving those for future episodes.
Well, I would just like to comment on the part where this video have mentioned about ford. All I know is that Ford is modifying ford f150 parts so that they can turn it electric.. I just hope this will become successful.