EV energy losses (college thesis)

[gone-ot]

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

[EVmetro]

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.

[gone-ot]

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.

[EVmetro]

Originally Posted by Old Tele man

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.

[oil pan 4]

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

[thingstodo]

Originally Posted by oil pan 4

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 ...

[jjackstone]

Originally Posted by EVmetro

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.

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

[EVmetro]

Originally Posted by jjackstone

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.

[freebeard]

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.

[EVmetro]

Originally Posted by freebeard

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.

.