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http://www.cleanmpg.com/photos/data/2/AmericanFlag.jpg With MORE regen, it appeared it was actually LESS efficient???? (http://jackrickard.blogspot.com/2010/07/more-regenerative-braking-results-it.html)

http://www.cleanmpg.com/photos/data/501/GM_Stator_and_Rotor.jpgJack Rickard - BLOGSPOT (http://jackrickard.blogspot.com) - July 11, 2010

An interesting dilemma... What could cause this unexpected result? --Ed.

In our first initial drives with the Mini, we were getting apparent ranges that matched my calculations for range initially without regen. We had assumed we would get some extension in range from having our first car with regenerative braking.

After just a few drives, it became apparent to me that with 100AH pack, and just under 1 AH per mile, that our range would be limited to about 100 miles - really quite similar to the BMW MIni-E. We had a larger pack, but also a larger car as we used the Clubman. But I was assuming we would get something from regenerative braking.

The question was of course what? Most comparisons indicate AH consumed and AH recovered and the Toyota RAV-4 even has a little indicator showing you your efficiency gains from regen based on this. I rather suspected that a real world comparison didn't yield the 21-25% gains that this measurement routinely provided. But I assumed 6-8% would be "real."

In the case of the Mini, it didn't look like we were getting much.

But we were busy completing the Speedster build and we have already heard from a number of people who want to purchase it from Special Editions Inc as a finished car when they can produce it. They can't produce it until we send them the prototype and... http://jackrickard.blogspot.com/2010/07/more-regenerative-braking-results-it.html

Wow! That is really screwed up! Fortunately the regen on my Insight works better than that. If I ride the brakes slightly on a long downhill grade, the regen will dutifully charge the battery indicator to 100%. It sounds like Mini needs to go back to the drawing board.

Hi, BM -- there is no question of the regen doing its job of shoving charge back into the battery. It seems however that the car is capable of driving further without doing any regen at all. Even when still braking.

We don't have a choice in a non-plugin hybrid... we have to get that battery charged somehow and regen is the only option. In an electric car however, things are a bit different. Jack's results indicate that in spite of returning charge to the battery through recovery of some small part of kinetic energy... it is somehow less efficient than not capturing any of it. That's the headscratcher...

I'd like to see a controlled test on a closed circuit without any other traffic. Run it like a timed rally effort such that the speeds at particular points on the route are specified and braking is orchestrated to be at identical rates, over identical distances, and at identical speeds. Have that course traveled with all 3 sets of regen configurations and then see what the difference is.

I didn't read the whole post, but if the regen is aggressive meaning it slows the car down as soon as you lift off on the accelerator, then yes I can see it would be less efficient as you are throwing away momentum. Downhill gliding is always more efficienent than any energy gains you would get through regen. I have heard of some BEV cars that will use this agressive regen, that is bad news for hypermilers.

If its not agressive, meaning it only uses regen if the brake pedal is pushed then it should be more efficient.

I agree, Volton -- yet his data shows that the best range is to be had with zero regen of any sort. :confused:

When I get back from Hybridfest I want to do an ABA test in my Prius. The only issue would be disabling regen. The only way to do it is to put the car in neutral.

Side topic: places with a very steep grade like I70 just west of Denver downhill....I dream of the excess regen transmitted to a local power plant.

As a owner of a AC induction drive vehicle with throttle modulated regen (and 33000 miles) I think Jack's basic conclusion is incorrect. Regen is beneficial but the gains aren't always huge and they definitely need to be applied in the right condition.

When I'm hypermiling my Force there are some basic rules. Disobey any one of them and the amount of power used can change from an average AH per mile of <0.9 to >1.3 plus in just one stop/start. In other words it is extremely extremely hard to repeat a given drive result right down to the the 6-10% accuracy. I can be nailing at 20 mile 0.9 AH drive and one need for a extra use of power blows it. But I can recover power with regen. I can't recover power with the use of anything else in the vehicle. But I get my maximum range coasting. Pretty much a no brainer.

Coast-regen-brakes is the required order for getting the vehicle to come to a rest. Towards the end of Jack's post he also points out this. Another unmentioned point in his article is that it is in fact very hard to duplicate an exact SOC (state of charge) on a EV battery pack. So this could have a bearing on results. It is a chemical change not a specific amount of "fuel" being added or taken away.

With practice and an adjustment in driving style regen is a positive. It is certainly more beneficial in a stop and go city drive where the driver is required to do forced stops. The nice thing is it comes "free" with a AC induction drive system and makes DWB really possible. Obviously regen will not extend the range of a vehicle driven at a steady pace. And if you use it when coasting is possible it isn't as good for range as coasting. But it really beats turning energy into brake dust.

Regen is Good! But not as good as some other range extending options. :flag:

+ Charge from Regen
- Cost of Regen (Cost of applying the regneration system)
- Regen Process Effect (Side-effect of charging by regen on the battery)
- Regen Momentum Grab (Cost of undesired lost momentum)
- Inactive Regen System (Cost of having the regeneration system available for use but inactive)

Those are the negatives I can think of.

+ Charge from Regen
- Cost of Regen (Cost of applying the regneration system)
- Regen Process Effect (Side-effect of charging by regen on the battery)
- Regen Momentum Grab (Cost of undesired lost momentum)
- Inactive Regen System (Cost of having the regeneration system available for use but inactive)

Those are the negatives I can think of.

Regen costs virtually nothing in a AC induction system it is there if you decide to use it. And it doesn't add weight. Deciding not to use it also requires some active engineering.

There is a potential for battery harm if unregulated but voltage regulation is also built into the controller by default and there is a greater potential for it to be beneficial.

Unintended regen isn't anymore likely than unintended braking or anything else the driver does to increase fuel use.

As there was virtually no cost in having it, so turning it off isn't costly either.

It also greatly saves brake linings and after a few miles of using it it makes you wish all vehicles had it.

But how well it is implemented for driver use in the vehicle is going to be very important as to how well it is liked or disliked. Trying to make the vehicle behave too much like a ICE vehicle could result in misapplication.

A simple DC conversion is cheaper than a AC conversion and often some equate some of this cost to regen braking ability but that just isn't true. New production BEV's will certainly have regen capability along with efficient motors and controllers.
:flag:

Another thing to keep in mind, we as hypermilers think differently than most drivers. A typical driver (consider my wife) accelerates up to a red light then applies hard barking to stop (I have learned to keep my mouth shut). I think in that case regen would be a benefit, and the agressive (accelerator) type regen system even more so. My concern is EV manufactuers are considering that type of driver most when designing their cars. I think the Volt has two modes, and they ironically call the ECO mode the agressive type, I might be wrong about that though.

For hypermilers a brake only regen would be the desired mode. That should be more efficient than friction brake systems. So yes I agree that his conslusions are incorrect as least as far as the brake only regen being less efficient than no regen.

My Force has throttle pedal modulated regen. It is a bit strange at first but is definitely my preference after using it for awhile. I can also disable it with a simple on/off selector.

When driving without traffic "gas" pedal becomes the stop and go pedal, easily controlling both forward motion and able regen to a complete stop.

Nissan has designed the Leaf to make it "creep" put it in D and it moves if you don't step on the brake pedal. Solectria wasn't trying to mimic a gas car so the Force is like a manual transmission with the clutch in, off throttle you don't creep like automatics usually do. In fact the car is totally at the mercy of gravity once at rest. (with regen turned on any movement caused by gravity or a push will result in max regen)

Jack's test essentially compared regen to coasting and not to braking. Coasting always wins all the time! Coasting beats regen all the time but sometimes it isn't possible to coast. And some, as mentioned by others and seen everywhere, don't seem to like coasting but prefer braking.

A easily controlled and repeatable test would be for Jack to accelerate using wot to 35 mph hold for 5 seconds and then regen to a complete stop without brakes. Repeat this for 30 cycles and measure the pack capacity. Now repeat the same thing but use the brakes to stop with no regen at all and once again measure the pack capacity. (If Jack's battery pack has more capacity at the end of the brake only test don't buy the products he is using.) :flag:

As Insight 1 owners know, regen, or the need to regen, is an inefficient process. Most owners try to stay away from assist and the requirement for regen. That fact alone would seem to demonstrate the truth in the article. The benefit of hybrid drive is that one can get a bit of extra power if it is needed, although at an efficiency cost. Assist/regen is one of the features which ALLOWS us to use very small, very efficient engines. JMHO.

Hi Volton and EVUser:

As Jim mentioned about his Insight-I, the same is true of all hybrids. The extended glide is worth far more than any amount of regen that can be collected. However, when the occasional impediment arises where braking is needed, Regen at least gives you something back for whatever impedes our progress ahead.

Hypermiling a non-hybrid, HEV, PHEV, FCV or BEV all rely on the same principals with the BEV just being so efficient on the acceleration and glide side if it can be forced to glide.

I know, I am speaking to the choir here :)

Jay, there is still some back EMF being generated on the Prius even in N as the fields have been knocked out but everything is still hooked up and spinning away. You will glide much further in N then grabbing regen of course.

Regarding DC, Zero’s DC motor setup w/out regen capability is really great for the bikes because their regen capability is so useless anyway. For racing maybe there can be a benefit but a low cost DC motor with controller and series cells for the proper voltage is a heck of a lot easier than the complex inverter/rectifier or boost Transverter setups in the latest Toyota and Ford based hybrids.

I will have to read Jack’s discourse later tonight…

Good Luck

Wayne