# The regen dabate



## evmetro (Apr 9, 2012)

I just read Jacks EVTV blog about how regen does not really do anything. It was a pretty interesting read and his findings were pretty compelling. Apparently, regen makes it too difficult to maintain a consistent speed, and we end up overcompensating for the regen by speeding back up, and then overcompensating for the speeding back up to using more regen. This cycle eats up the trivial amount of braking energy that we harvest and perhaps uses even more, decreasing our range. It seems that there is braking energy to be had, but we are not able to effectively trap it. Anyway, his blog debate was never really concluded, so I was wondering if this debate made it over here to this site (I have searched and not found it, but that does not mean that it is not here) or if anybody has any thoughts on this. From what I have read so far, it sounds like I need to shut down the regen on my AC conversions to get the best range.


----------



## major (Apr 4, 2008)

evmetro said:


> I just read Jacks EVTV blog about how regen does not really do anything. It was a pretty interesting read and his findings were pretty compelling. Apparently, regen makes it too difficult to maintain a consistent speed, and we end up overcompensating for the regen by speeding back up, and then overcompensating for the speeding back up to using more regen. This cycle eats up the trivial amount of braking energy that we harvest and perhaps uses even more, decreasing our range. It seems that there is braking energy to be had, but we are not able to effectively trap it. Anyway, his blog debate was never really concluded, so I was wondering if this debate made it over here to this site (I have searched and not found it, but that does not mean that it is not here) or if anybody has any thoughts on this. From what I have read so far, it sounds like I need to shut down the regen on my AC conversions to get the best range.


I don't know what you're talking about but regeneration has always worked effectively for me. In the BEV, it may not account for much in the way of increased range, but certainly does not detract. And there is no argument that it saves a bunch of wear on the service brakes.

I don't read Jack's blogs or watch his TV stuff. But I suspect he has misapplied the feature if it is causing the problems you mention.


----------



## evmetro (Apr 9, 2012)

Here are some links of what I was reading that suggests that regen is a myth.

http://blog.evtv.me/2010/07/more-regenerative-braking-results-it-gets-worse/

http://blog.evtv.me/2010/07/regenerative-braking-entirely-a-myth/

From what I can tell so far, it looks like the people who say that regen works only think it works because they want so badly for it to be true.


----------



## ga2500ev (Apr 20, 2008)

I took a quick look. Part of the discussion seems to center around "throttle regen", which does regen when you release the accelerator, but before you press the brake. This certainly can lead to the overcompensation that the OP alluded to because releasing the accelerator causes the vehicle to slow down faster than simply coasting.

I believe that most of us think of regen only in braking situations. Clearly this will harvest back some energy. The questions are 1) is the amount of energy recovered worthwhile? and 2) is the savings to the wheel brake system worthwhile?

ga2500ev


----------



## major (Apr 4, 2008)

evmetro said:


> From what I can tell so far, it looks like the people who say that regen works only think it works because they want so badly for it to be true.


We've been through this before: http://www.diyelectriccar.com/forum...tive-braking-energy-85108.html?highlight=tomo 

There have been plenty of quantitative studies on regeneration. It sounds like Jack needs cruise control. But you? First the J plug; then anti hybrid; now regen. What gives? You must not like things which work well for the masses


----------



## Arlo (Dec 27, 2009)

On my electric bicycle my regen gives 8-10% more range its only used when you are trying to slow down. It doesn't matter if you have throttle regen or regen attached to the brakes.

You don't need to use the throttle to compensate for regen because you are not using acceleration and deceleration at the same time.

I now have regen on my Electric YSR (motorcycle) and will on my next one a cbr 250r and then my Honda CRX as well because its a proven way to capture some of the energy and put it back into the batteries while you are trying to slow down instead of using brake pads that simply destroy them self's to slow you down.


----------



## evmetro (Apr 9, 2012)

Major, thanks for that link. As I re read that thread, I was pretty distracted by my own hijacking of that thread and my distaste for the prius, but as I looked at the primary focus of the thread I was still unable to find anything really quantitative to compare to the two links that I provided above. Did you read those links? Can you explain how cruise would fix his situation?


----------



## Arlo (Dec 27, 2009)

evmetro said:


> Major, thanks for that link. As I re read that thread, I was pretty distracted by my own hijacking of that thread and my distaste for the prius, but as I looked at the primary focus of the thread I was still unable to find anything really quantitative to compare to the two links that I provided above. Did you read those links? Can you explain how cruise would fix his situation?


 _Im going to go ahead and say this is user error. I mean he is either reading the numbers wrong or his controller is not actually regening its plug braking._


----------



## evmetro (Apr 9, 2012)

Arlo, LOL! You sound like me before I took the time to read those links that I posted above! I was on the other side of the debate yesterday, and have a shop full of AC conversions with regen. I have had some questions forming about regen that lead me to this information.


----------



## PStechPaul (May 1, 2012)

I think it would be more convincing if Jack (or anyone) would use a datalogger as suggested, to determine if more energy was used when regeneration was enabled, as he speculates. This would require only the raw data which could be recorded at 1 second intervals and then a spreadsheet could be used to totalize separately the positive and negative current readings.

One possibility with the AC drive is that, for regeneration to work, the VFD must be powered, while without regen it can simply be turned off and the ACIM can just coast. But, still, if current is going into the batteries, it seems that the net effect should be recoupment of energy and a net gain. What may be happening is that there is no "coasting" configuration with any of the regen schemes so that the VFD is always on, and there are significant periods of time where the drive controller is using energy when it should be simply turned off. 

Regeneration with a PMDC motor, and perhaps even a BLDC, may be more effective because the motor generates voltage on its own and the drive circuitry can be completely shut down during regen. 

Perhaps as a side note, I wonder what would happen if a three phase induction motor would have DC current applied to two of the windings (by connecting A to C and putting current into B), or by using just A and B which would put, say, 10 amps into the A-B winding and 5 amps into A-C and C-B. I'm considering doing that for braking on my tractor project, which will use one or two 12V batteries and one or more inverters to get the high voltage for the VFD. To get regen I would need to convert the DC bus voltage to a 12/24 VDC charging current which would require a separate circuit or a specially designed VFD.


----------



## Tesseract (Sep 27, 2008)

evmetro said:


> ... Apparently, regen makes it too difficult to maintain a consistent speed, and we end up overcompensating for the regen by speeding back up, and then overcompensating for the speeding back up to using more regen.


This is likely to be true if "off-throttle" regen is enabled. That is to say, regen braking occurs whenever throttle is near/at zero. It is very difficult to coast when the drive system is setup this way, as compared to, say, only enabling regen via the brakes. 

In other words, the best efficiency is obtained by coasting as much as possible, and the worst efficiency is by repeatedly cycling between acceleration and deceleration, particularly if deceleration is only via mechanical brakes.



evmetro said:


> From what I have read so far, it sounds like I need to shut down the regen on my AC conversions to get the best range.


No. AC conversions should always use regen. I think it is smartest to make the regenerative braking effort proportional to brake system pressure, but that's a personal preference on my part.

BTW - I happened to write an article about regen braking for Charged EVs magazine a few months ago:

http://chargedevs.com/features/a-closer-look-at-regenerative-braking/


----------



## Arlo (Dec 27, 2009)

evmetro said:


> Arlo, LOL! You sound like me before I took the time to read those links that I posted above! I was on the other side of the debate yesterday, and have a shop full of AC conversions with regen. I have had some questions forming about regen that lead me to this information.


 No I read the "tests" and his test data is lacking.
I use a Cycle Analyst it shows me HARD PROOF regen is working and extending my range by 8-10% every time I ride.


----------



## evmetro (Apr 9, 2012)

Arlo, I am pretty interested in learning the truth here. Could you fill me in on what his test were lacking?


----------



## rwaudio (May 22, 2008)

evmetro said:


> Arlo, I am pretty interested in learning the truth here. Could you fill me in on what his test were lacking?


Having driven an AC EV with regen on the throttle I found the driving experience quite nice, however it's very difficult to coast but you could likely "get use to it" and if careful drive quite efficiently. 

My other experience is a DC powered 944 that coasts incredibly well, so well that you catch up to everyone else that simply lets off the gas and has a big of engine braking. It's rather annoying actually, wasting momentum because they let off the gas.

I'm in the process of swapping in an AC drive system into the 944, so I should get some comparative data on AC vs DC.


----------



## Caps18 (Jun 8, 2008)

My Dad's Ford C-Max Energi says it has about a 10% regen rate with it's AC motor.

But, I think it is a lot like hypermiling. Individual experiences will be different. If you are coasting to stops with no one behind you and you don't care about time, it will be the best. If you need to maintain a normal driving speed and then can regen in the last 500 feet, it would be better than an EV with only friction brakes. If both types of vehicles need to make a quick emergency stop, then it doesn't matter. And if you are driving on flat deserted highways in Nevada, and you are only going to stop once or twice during your trip, then it also doesn't matter. But, if you are driving in Ohio, and there are 8 stop lights in the 3 mile trip to the grocery store, let alone across town, then it probably does. More research would be needed to find out how much of an impact it will have, but I would bet there is some. And when you have a 50 mile range, those extra 5 miles might come in very handy.


----------



## evmetro (Apr 9, 2012)

Rwaudio, I really enjoy using regen, but I am thinking of switching it over to a momentary switch on my shifter so that I can use my discretion to activate it. In the tests that Jack did to determine that regen does not add up, he tested regen on the throttle, on the brake, and none at all, only to find out that regen is not more efficient. The problem is the cycling between accel and regen. It would seem to me that the concept still makes sense, but that the only time it would actually help in extending the range would be when it is used with user discretion. We are unable to control our driving to enough utilize neutral, off throttle, or brake pot, or transducer induced regen. I have seen many opportunities to harvest braking energy, but they are limited to long downhill grades. I am thinking that a momentary switch on the shifter would allow me to tap it when it is obvious that there is a good opportunity.


----------



## subcooledheatpump (Mar 5, 2012)

I understand normal production EVs may not work this way, but I've always thought of the accelerator pedal as sort of a cruise control reference speed input. You tell the car how fast you want to go. Going down hill, regenerative braking automatically activates to maintain speed, you don't lift. If you lift the pedal, the car knows you want to stop so regenerative braking is activated and you come to a complete stop. 

Same for cruising or whatever, just keep the pedal in the same position if you want to maintain the same speed. The cars controller just keeps the car moving at the same speed. This eliminates over and under compensation. 

I don't see how this would not recover energy. If you lift the pedal, energy goes back in. I do see how this is generally ineffective for highway driving, you simply aren't stopping for a very long time. Maybe changing speeds, although that shouldn't be too often. 

I find regenerative braking more of a convenience, greatly assists in stopping. I disagree about not saving the service brakes. It helps me. I can completely stop without using the regular brakes. (yeah some of it is DC braking but none the less)


----------



## IamIan (Mar 29, 2009)

evmetro said:


> In the tests that Jack did to determine that regen does not add up, he tested regen on the throttle, on the brake, and none at all, only to find out that regen is not more efficient





evmetro said:


> I am pretty interested in learning the truth here. Could you fill me in on what his test were lacking?


That is what he claimed ... not what his tests showed... his initial bias caused him to see what he wanted to see ... not what it was.

It works like this.

#1> Any time you would brake anyway ... Mechanical Friction brakes give you 0% back ... all 100% of the braking energy is lost.

#2> Any time you would brake anyway ... Regenerative brakes give you more than 0% back ... ie , some % of the forward motion gets back to the battery ... thus they are better for net energy efficiency... than using an equal amount of mechanical brakes.

- - - - - - - 

The error Jack made was that he did more braking with the Regen than he did with the non-Regen ... ie he did not use an equal amount of braking in both tests.

The only thing Jack's test showed is that Regen is not more than 100% efficient ... which we already knew... ie additional braking when you don't need to brake , does not increase your range.

- - - - - - - -

Jack Started off with a 100% completely incorrect assumption



Jack said:


> Obviously, we expected maximum efficiency from the more aggressive regen derived from brake and throttle both


More additional braking mechanical or regen ... or any other kind of braking ... can only increase the net total amount of energy ... the only way his initial claim like this would be possible is from a over 100% efficient regen ... which doesn't exist.



Jack said:


> Drive 1 76.6km 78.2 AH or 1.02088 AH per kilometer ---* Regen Type A*
> Drive 2 75.2km 77.7 AH or 1.03324 AH per kilometer --- *Regen Type B*
> Drive 3 76.6 km 78.0 AH or 1.01827 AH per kilometer --- *No Regen.*
> 
> This shows the LEAST amount of energy used to accomplish the 76.6 km drive to be when using NO regenerative braking at all


*Bold Added
*
He made 4 errors

#1> Ah are not energy ... 1.2V at 10Ah is 12wh , 1.34v at 9ah is 12.06 wh ... less Ah but it is more energy.

#2> He forgot to include the additional acceleration he had to do in drive #1 and drive #2 ... to recover from the additional braking that he did in those 2 tests ... braking that he did not do in Test #3 ... accelerating up to speed takes energy.

#3> He incorrectly assumed equal trip time on the same route would be equal energy consumed ... when that is not the case ... a fluctuating speed uses more energy than a steady speed , even if they both have the same average speed .... ie average of 40MPH swinning +10 to -10 of that will take more net energy than just a straight 40MPH without the +/-... or with a smaller +/- like 1 instead of 10.

#4> He did not log the speed ... 2nd gear is not enough information to know if he was at an average of 30MPH for Test #1 and only 25 MPH for Test #3.

- - - - - - - - - 

So as I said ... his additional braking test only showed that it was not more than 100% efficient ... but the control ... that he did not include .. was an equal wh energy amount of mechanical braking as he did with the regen ... and then see how much better the regen braking was from the mechanical.

But we all know what the general results would be ... like it or not ... Mechanical brakes give back 0% ... Regenerative Brakes give back more than 0% ... more than nothing is better than nothing.


----------



## Arlo (Dec 27, 2009)

evmetro said:


> Arlo, I am pretty interested in learning the truth here. Could you fill me in on what his test were lacking?


What IamIam just said and the fact we don't have any data logs. Its not a scientific test at all.



> Cars and drivers interact. Adding regenerative braking absolutely alters the driving characteristics of the car. It is my observation that with regenerative braking on the throttle, you really don’t coast along very much. You are always either accelerating or decelerating. There is a bit of a sweet spot at around 0 amps but it’s a little tricky to find and stay in. And it is just easier to accelerate and decelerate as traffic demands. You quickly adjust to the car and you do indeed drive it differently because of that


Then he says this...


> On a second drive, we accelerate to 50 mph. At the moment we hit 50 mph we immediately decelerate to 40 mph. Once at 40 mph we immediately accelerate again to 50 mph. And we continue this oscillation until the end of the 5 miles, averaging 45 mph for the entire distance.


You must realize this idoit cant drive his way out of a paper bag. I drove a leaf and a Miev if you hold your foot slightly on the throttle it will stay going a certain speed. You don't coast down to 40 using regen then back up to 50 with the throttle this is a major if not the whole reason he had worse efficiency. Its not the same test. This guys whole test is BS!


----------



## tomofreno (Mar 3, 2009)

Here is some data I took a few years ago:
http://www.diyelectriccar.com/forums/showpost.php?p=192084&postcount=552

Turned out it was right around the time of the Great Regen Debate on Jack's blog which JRP3 mentioned, and I responded to:
http://www.diyelectriccar.com/forums/showpost.php?p=192152&postcount=559

Some further comments:
http://www.diyelectriccar.com/forums/showpost.php?p=192247&postcount=562

Some more data:
http://www.diyelectriccar.com/forums/showpost.php?p=208464&postcount=621

Here is some more recent data:
View attachment South Lake Tahoe, summary with gps.pdf

Note going down from Spooner Summit it recouped about 49% of the potential energy the car had at the top, which was about 24% of the energy used going up. (note going up the 5% grade it used about 2.5x as much energy as the average over the route).

I also estimated how much energy was recouped from braking here:
http://www.diyelectriccar.com/forums/showpost.php?p=280765&postcount=14
and further comments on it here:
http://www.diyelectriccar.com/forums/showpost.php?p=280832&postcount=16
-that is from this thread where I data logged a bunch of data for JR (regen on that short run was a bit over 11%):
http://www.diyelectriccar.com/forums/showthread.php/ev-trip-program-68530.html

My conclusion on Jacks tests were that his throttle was set up too touchy and he wasn't used to driving with regen, so he was modulating K.E. of the vehicle as I described in one of the above posts. I can hold the motor current to +/- 0.3A no problem (TBS gauge read out) on my car, and coast as long as I want by holding it a 0 +/-0.3A. I never read his blog, just responded to what others told me. I thought it was silly. Most of the above posts are from my build thread here on diy.


----------



## major (Apr 4, 2008)

tomofreno said:


> Here is some data I took a few years ago:
> .............snip.....
> Most of the above posts are from my build thread here on diy.


Thanks for chiming in. I remembered you having done some tests; just didn't know where to find them.

Work that I did years ago on heavy commercial EVs and HEVs showed regeneration very effective. Regeneration on the battery race vehicles has also been quite effective however was never shown to be much of a range extender due to the fact it decreased lap times. But I never saw a case where there was any evidence of regen decreasing range.

I did have this article bookmarked: http://proev.com/LLPgs/LLei0005.htm


> Our data is showing that regen is worth a 10-15% improvement in range in Miami city traffic and a 15%-20% gain at the track.


And I did read thru some of those referenced Jack blogs. Saw this:


> On a drive with no regen – SPENT 78AH RECOVERED 0 AH – NET 78 AH
> On a drive with regen – SPENT 86AH RECOVERED 7.8 AH – NET 78.2 AH.


It is obvious he has used 8Ah more charge for motoring on the second drive. It may not have been intentional on the drivers part, but it was used. Having recovered most of that 8Ah supports the benefit of regeneration. What he needs to properly analyze the tests are recordings of distance and speed vs time. This could be done on a controlled course of say 1 mile with like 4 stops and starts, each direction, w & w/o regen. Then compare the energy profiles, both kinetic and battery.


----------



## evmetro (Apr 9, 2012)

Tomo, I have always been impressed with your observations on various things, and your quantitative nature. I too need to get to the bottom of things, so it appears that I will need to do some testing of my own to see what the truth is. If you or anybody else has any good ideas on how to conduct a proper test I am very interested. As it stands right now, I have a pretty ridiculous regen to weight ratio with the AC74 in the Metro, and something needs to be done, but perhaps I should gather all the important data first as a reference. Does anybody have suggestions? I have not played with data logging yet, but I see that my Orion has this, and my Torque app keeps data files of all my trips with dates and times. I do not understand what all the stuff means, but maybe it could be relevant data. When I have a laptop linked into the Orion, I can select any number of pid to make live graphs...


----------



## onegreenev (May 18, 2012)

A lot of regen recovery is quite dependent upon HOW you drive your vehicle. I have been driving my Leaf now for over two years and wished I could turn off the throttle regen and only use it during braking. So to implement brake only I'd need to use a brake transducer and hook it up. The Curtis will now allow this input. Being that the larger motor has stupid amount of regen you would need to deal with how much you actually use. I am sure you could use the brake quite well and have excellent control and still have a stupid amount of regen. 

I am not expecting to GAIN distance but I do want good brake control and if I ever find myself on the mountain road coming down I could both coast or regen. 

Making your vehicle more like a car with a gas engine in it would mean you need a tiny amount of regen with throttle then more with the brake. But you'd need to match the throttle regen with the brake regen. You would not want good regen with throttle then start back at zero regen with the brakes when you apply the brakes. It needs to transition from throttle regen and then keep going from there to brake regen. It is possible with the curtis. 

Then you will have a car that is more like it was with the ICE. 

However I like my Diesel VW Bug and diesel engines really have very little engine braking action. Best to use exhaust braking for good engine style braking. The Diesel more or less just coasts when you lift your foot off the throttle and then you must have good brakes. With brake regen you can have excellent braking and very very long life of your brake system. 


My DC motor has no regen action and I need excellent brakes. Wish I had Regen on my VW Bug. But that Kostov just wont ever see regen. I must coast and then apply my excellent all wheel disc brake system to stop. 

Pete


----------



## onegreenev (May 18, 2012)

I have driven two conversions with Brake Regen only. Excellent. Exactly what I am going to do. Coasting will do wonders for your range.


----------



## PStechPaul (May 1, 2012)

FYI, I just tried putting DC current into a 4 pole 1.5 HP three phase motor, and it does put significant drag on the shaft. With about 1 amp it is enough to keep the motor from coasting freely, and at 2 amps it is quite apparent. It has somewhat of a "springy" feeling and it reverses slightly when I stop turning the shaft, and the power supply ammeter rises and falls. At 4 amps (and about 6 volts) I can barely turn the shaft. 

This is of course not very scientific, but it shows that it might be possible to connect the 12V battery to the induction motor as a brake, which might be useful if the VFD fails. This is a special case for my tractor project and not quite on topic for this thread, but it is a useful fact. I wonder if a similar thing could be done for a series wound motor, by using the 12V accessory battery (or even maybe a single lithium cell) applied in reverse (essentially "plugging") for dynamic braking.


----------



## Arlo (Dec 27, 2009)

To be clear if you want to average 45mph you hold the throttle at 45mph and you will get your best efficiency. If you accelerate to 50 then regen to 40 and acceleration to 50 again you will have an average of 45 but you are wasting energy.
For the same reason you can't hook an alternator to the drive system to REGEN as you drive. You have inefficiencies in regen and acceleration causing the whole slowing down and speeding up process to waste energy.


----------



## IamIan (Mar 29, 2009)

evmetro said:


> If you or anybody else has any good ideas on how to conduct a proper test I am very interested.


For Net Energy efficiency to see which is better. It is straight forward and simple.

Log Volts & Amps & Vehicle speed real time ... Then drive the same route the same way in the same weather with and without.

The biggest will come from the Volts and Amps Log ... that will allow you to see the energy coming in and going out ... the speed part just tries to put that energy use in context.

If your existing parts can do it than that might be the cheapest... hook that up.

If they don't or they are giving you too much trouble ... you can hook up a data logging device ... for about $300 a high current model cycle analyst Link with the GPS enabled data logger will log DC volts , amps , watts , Ah , wh , speed max , speed average , speed real time , location ( where you went can be used on a topo map for additional detail if desired. )

For something like around ~$130 you could get two USB interface Multi-meters Link have a laptop log the data via the USB port ... one monitors and records the DC volts , the other monitors and records the volts cross a high current amp sensor ( thus telling you amps ) ... once you have real time Volts and Amps data ... just use a spread sheet program like Excel to determine Watts of power and / or cumulative Ah / Wh.

Watts of Power = Volts x Amps
WattHours of Energy = Volts x AmpHours


----------



## onegreenev (May 18, 2012)

> I wonder if a similar thing could be done for a series wound motor, by using the 12V accessory battery (or even maybe a single lithium cell) applied in reverse (essentially "plugging") for dynamic braking.


Sure but you still have the same problem with your DC motor as you would doing Regen with your DC motor. If the motor is advanced it will cook your commutator. Plug braking is common with DC forklifts. But they are moving rather at a snails pace even when moving flat out and they have neutral timed motors.


----------



## Ziggythewiz (May 16, 2010)

tomofreno said:


> My conclusion on Jacks tests were that his throttle was set up too touchy and he wasn't used to driving with regen, so he was modulating K.E. of the vehicle as I described in one of the above posts.


Are you implying that Jack would use a suboptimal implementation of a system he doesn't like to prove that it's ineffective?


----------



## Tesseract (Sep 27, 2008)

PStechPaul said:


> FYI, I just tried putting DC current into a 4 pole 1.5 HP three phase motor, and it does put significant drag on the shaft....


Congratulations - you just reinvented "DC injection braking"...

As this does not return energy to the battery pack and results in substantial heating in the rotor it's not really germane to the discussion at hand.


----------



## tomofreno (Mar 3, 2009)

major said:


> Thanks for chiming in. I remembered you having done some tests; just didn't know where to find them.
> 
> Work that I did years ago on heavy commercial EVs and HEVs showed regeneration very effective. Regeneration on the battery race vehicles has also been quite effective however was never shown to be much of a range extender due to the fact it decreased lap times. But I never saw a case where there was any evidence of regen decreasing range.
> 
> ...


 Thanks major, good to see the data in the link you gave is in the same ball park as mine - around 50% vehicle K.E. converted to P.E. in the pack. It's obvious that regen can only decrease range if you modulate the vehicle K.E. with it. So if Jack did have a touchy throttle and kept slowing too aggressively with regen then accelerating back to the speed he wanted, he indeed could have increased his energy use with regen. Edit: I fixed the attachment in my first post.


----------



## tomofreno (Mar 3, 2009)

evmetro said:


> Tomo, I have always been impressed with your observations on various things, and your quantitative nature. I too need to get to the bottom of things, so it appears that I will need to do some testing of my own to see what the truth is. If you or anybody else has any good ideas on how to conduct a proper test I am very interested. As it stands right now, I have a pretty ridiculous regen to weight ratio with the AC74 in the Metro, and something needs to be done, but perhaps I should gather all the important data first as a reference. Does anybody have suggestions? I have not played with data logging yet, but I see that my Orion has this, and my Torque app keeps data files of all my trips with dates and times. I do not understand what all the stuff means, but maybe it could be relevant data. When I have a laptop linked into the Orion, I can select any number of pid to make live graphs...


 I usually just data log pack voltage, current, and Ah used, along with gps data for vehicle position (including elevation) and speed. The product of the pack current and voltage is the power going into or out of the pack. I use a rate of one sample per second, so multiplying the current and voltage for each sample point times one second gives energy in Watt-seconds. Dividing by 3600 sec per hour gives energy at each sample point in Wh. Of course this is treating the current and voltage as constant during each one second interval, which I think is not too bad of an approximation due to the short time interval.

You can change the programming parameters in the Curtis controller to tailor regen and make it as strong or weak as you like. See Regen_Current_Limit under Current Limits Menu, and Regen Limiting Map.


----------



## kennybobby (Aug 10, 2012)

The amount of energy harvested is obviously less than that injected due to friction and other loss factors, but there is also a 'path' dependence of how much can be recovered, such as in the shaded areas below with reference to 4-quadrant motor control.


----------



## evmetro (Apr 9, 2012)

The curtis looks pretty straight forward on regen adjustments. I am going to study the data with the regen on the throttle and set too high first since it is already set this way. I have this g thingy on my dash display:










When shake the tablet a little in my hands, it looks like this:










I am thinking that I may be able to log the cycling effect of my regen if I log this at the same time that I log the rest of the data... ?


----------

