EV energy losses (college thesis)
 

For the EV readers: http://scholar.lib.vt.edu/theses/ava..._LR_T_2011.pdf

Interesting read. Is this your paper, or a link to something that you liked? I have studied regen extensively via real world testing of EVs that I build, and have come to some simple but solid conclusions. What people like to focus on is the beautiful concept of capturing waste energy that is available in EVs, but they rarely look at one of the most important considerations, which is the proper management of kinetic energy. Just as wind turbines and alternators seem like great things to attach to a car for people who do not understand perpetual motion and thermal dynamics, off-throttle regen looks appealing to those who do not understand the conflict that it imposes on proper management of kinetic energy.

Braking regen is very effective, just as alternators and wind turbines can be if they are left behind when you drive away, but this regen needs to be utilized only when there is energy that is truly going to be wasted as heat from the friction brakes. If regen is deployed when the car should be staying in motion, then energy will be wasted. In the case of off-throttle regen, wasting energy is what happens. Off-throttle regen is a fantastic way to make an EV feel like an ICE, but everything that was changed to get get that ICE feel was an important part of how an EV can be so much more efficient. There is a distinct difference in how a DC sytem with no regen feels out on the road compared to how an ICE or EV with off-throttle regen feels, and this feeling is a vehicle that is not encumbered. If you program an AC sytem with regen to have no off-throttle regen, you can get this same thing.

Once you have an AC system that is programmed for no off-throttle regen, the next step is to set the car up with regen on demand, so that it can be used only when it is needed. Only the driver can choose when the best time to use regen is, since the road conditions are ever changing. In my most recent build, I have found an ergonomically correct location for my variable on demand regen system, and it is a potentiometer that is set up so that I can easily control ALL of the regen capability, not just the 10% to 15% that is typically available in off-throttle applications. This variable on demand regen system allows me to use regen to satisfy ALL of my braking needs. No blend with the friction brakes at all, although the original friction brake system is in tact and standing by as a redundant braking system. Regen can be a fantastic way to harvest waste energy, but the timing of when it is used is critical when efficiency is the goal.

No, it's not my paper, just my continuing education. However, I did teach automotive technology at Arizona Western College, Yuma, AZ, as an adjunct faculty member for 8 years before I transitioned into defense/aerospace employment.

That paper had some great information in it, and I would consider it ongoing education for myself as well. Regen has been one of the things that I have focused a lot of time on, which has been one of the reasons why my latest build is so much more efficient than the OEM offerings and other DIY conversions. When I did my first conversion, I had got a weird conspiracy theory type of feeling as to why the rest of the world does not all drive electric, and it felt like I was getting away with something. After doing another build after that and a lot more homework, I got that same feeling about my variable on demand regen system that I now run on my latest build. The efficiency compared to other EVs is breathtaking, but conveying the concept to other people is generally a lost cause.

To boost EV efficiency just stop pushing wireless chargers.
For some reason people think electric vehicles are like their cell phones.

IMHO, There is only one positive to wireless charging - you don't have to worry about the cord being cut off when you get to a public charger.

I'm told you can get a few bucks for the cord at a scrap metal yard ... instead of the $$$ that they actually cost.

I have seen very few EV charge stations in Canada (Saskatchewan). Thankfully I have not seen a missing cord thus far.

As for whether the stations are working .. I don't have a running EV yet so I have no data ... :(

EVmetro,
Have you done any testing to show how much energy or additional range the regen provides? Always interested in that type of information. Also, other than the potentiometer and additional wiring needed, are there any other components necessary to control the amount of regen available?
JJ

I am running a Curtis 1238 controller, which is very programmable. I can program it to regen at any percentage of the full 650 amps, which allows me to use a lot more regen than with off throttle applications. Typically, off throttle regen is set around 10% of full potential, so the other 90% of available waste energy gets wasted on friction brakes. All I have is the "thumb pot" and two more wires going to the controller to allow using regen for my primary braking system.

As far as additional range, I see little advantage when driving 55mph on flat ground, since I am playing by the same rules of nature as a manufactured EV does, but the more hilly an area is and the more braking is needed, the more profound the efficiency compared to what off throttle would be. The efficiency improvement comes from two things. The first is having the vehicle maintaining a less disturbed motion", by having the vehicle "freewheel" like a ten speed bicycle or DC drive system, and this is what prevents a largely unrecognized loss of efficiency. The second thing that improves overall efficiency is harvesting every last drop of waste braking energy, which comes from never using friction brakes for anything other than holding the vehicle at traffic signals.

I still do lots of testing, and my conclusion is that off throttle regen is as useless as putting a wind turbine on the roof, or alternators on the wheels. It is possible to drive an off throttle configuration in a way that might get a small return if the driving conditions are right, but at the cost of electricity, the negligible returns would not be worth the trouble. To make any substantial use of regen, the kinetic benefits of a DC system have to be there to separate "waste" energy from "wasted"energy, and then regen needs to be used to harvest every last drop of the now isolated "waste" energy.

I admire the build quality your Metro conversions have, so that adds credibility to your statements.

So where is the 'thumb pot' ergonomically located? In a VW Beetle it could be the handbrake lever on the center tunnel. With the regen in the first seven or so clicks of the handbrake, the mechanical part would still be available for hill-holding and as a parking brake.

http://i1242.photobucket.com/albums/...ejpg1-1871.jpg

http://i1242.photobucket.com/albums/...ejpg1-2361.jpg

http://i1242.photobucket.com/albums/...age.jpg1_7.jpg

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Thanks. I see where it is, very near to the handbrake, but beyond that I don't have a clue.

So the lever shaft is cut and welded in a way that allows the top right corner of the Fluke to fit between them? Maybe the pot is a bias control and the button on top the shift lever is normally used?

Maybe I confuse easily?

That pic with the fluke in it was just a pic to show how the top half of an automatic buick shifter was grafted onto the 5 speed manual shifter that I use. The button on top of the shifter is no longer used to release the shifter interlock to take it out of park as it did on the buick that I got it from, now it controls the potentiometer below it that is mounted to the shifter shaft. The big button allows very precise control of the regen, from no regen at all to emergency braking power. The linkage is set up so that it gives progressively more regen the further I push it. So the sequence is that I push the button down, which turns the knob on the potentiometer, and the potentiometer changes determine how much regen is applied.

I found that setting the "off throttle" regen to just a tiny little bit made it so that the motor does not free spin so long. When the off throttle regen was set to zero, I could put the transmission in neutral and rev it up, and the motor would free spin for about a minute before finally coming to a stop. By playing around with tiny amounts off off throttle regen, I was able to come up with a setting that feels like no off throttle at all, but lets the motor idle down in just a few seconds. I was also able to fine tune it so that I have really nice clutchless shifting. I do have a heavy duty and very functional clutch, but it is nice to not have to use it if I don't want to. With just the right amount of off throttle regen, clutchless shifting is a little sweeter than clutchless shifting in a DC set up.

The driving experience is a lot nicer when you don't have to use the foot brake or the clutch. The thumb pot gives more precise braking action than the foot brake, and with far less effort. When I built this set up, I was not sure how easy it would be to adapt my driving habits to it, but it turns out that it is a lot easier for humans to adapt to things that are easier to do in the first place. I am finishing a Cadillac EV conversion right now, and am installing the same system, since the theme of this build is luxury. This build won't have a traditional shifter to use as a control location, so I am building a custom mount for it that is easy to use.

Got it. The Buick half has an internal rod the button actuates. So you stop the car with your thumb. :thumbup:

In principle, the button could be anywhere (or everywhere) you might have your thumbs. The steering wheel, the driver door window sill...

Exactly. The key is locating the thumb pot in a location that is really easy and natural to use. What would be really cool, would be a ring around the back side of the steering wheel, so you could squeeze it in any position

Thanks for the detailed information. I know that ranges will vary with all the normal factors such as speed, stop and go traffic, hills etc. Care to venture a guess as how much energy the regen saves you as general percentage?
JJ

Interesting that this company is showing the brake specific energy consumption efficiency of their 125 PowerPhase motor as a vertical line at low rpm. Might as well floor it on take off.
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https://scontent-ord1-1.xx.fbcdn.net...16&oe=571B97BC
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In my first conversion, I run an off throttle set up in a Metro, and in my second conversion, I run a DC set up with no regen capability at all, again a Metro. The variable-on-demand system is in my third metro conversion, again a Metro. During my 10 mile commute each way in heavy city traffic, I use at least 15% less energy with the variable on demand system than what I use for either the DC or the off throttle Metros. If I really push the limits of eco driving, there is no way that I can get home on as little energy with the off throttle or DC Metros, compared to what I can do in the variable on demand one. The DC and the off throttle Metros are remarkable, and use about the same amount of energy for that commute, but they just can't compete with the variable on demand.

I also do 55 mph range tests on my Metro conversions here in the flat Sacramento valley, and all three conversions use about the same amount of energy. The variable on demand system still does a little bit better, but I also did more things on this build to reduce the weight, and I also have an economy switch to limit maximum amps when it is switched to that position.

I also drive a lot in the foot hills where I have several 6% to 8% up and down grades, and lots of twisting roads with switchbacks and such. This is where the variable demand system shines the best, and it is also the type of terrain that I have to use my friction brakes the most on my ICE Metros. I know these roads well, and I make no effort to conserve energy at all. These roads are recreational driving to me, and I push the EVs to their limits. The variable on demand system makes this kind of driving really fun compared to having to use friction brakes, and it collects large amounts of braking energy

Regardless of the type of driving that I do, the variable on demand regen proves to be the ultimate eco mod, and yields superior efficiency compared to what is available in manufactured EVs. Here in CA, the difference in registration fees between a 20 year old Metro and a new manufactured EV is enough by itself to pay for 15,000 miles per year in electricity, so between that and the variable on demand system, I don't see myself owning a manufactured EV. Eco mods rock.

Thanks once again. Flat highway negligible gains were expected. I would have guessed between 8 and 10% difference for stop and go traffic so the 15% is impressive. Really didn't have a guess at all for hillier terrain so if it's better than heavy traffic that is truly great.
JJ