# [EVDL] Regen Not Efficient....



## EVDL List (Jul 27, 2007)

Hello everyone, 



Looks like Jack Rickard has done some tests of Regen in his two EV
conversions and come to a startling realization. That Regen is actually a
NEGATIVE!!



I'm sure the discussion list would love to talk about this subject.



Here is his blog.



http://jackrickard.blogspot.com/2010/07/more-regenerative-braking-results-it
.html#comments 



Sincerely;



Douglas A. Stansfield

President

www.TransAtlanticElectricConversions.com 

973-875-6276 (office)

973-670-9208 (cell)

973-440-1619 (fax)



ELECTRIC CAR PRODUCERS





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## EVDL List (Jul 27, 2007)

Actually Jack just posted a Followup and there may have been a problem with his data collection. Regen MAY work after all.

Peter Flipsen
-----Original Message-----
From: "Douglas A. Stansfield" <[email protected]>
Sender: [email protected]
Date: Sat, 24 Jul 2010 15:24:32 
To: 'Electric Vehicle Discussion List'<[email protected]>
Reply-To: Electric Vehicle Discussion List <[email protected]>
Subject: [EVDL] Regen Not Efficient....

Hello everyone, 



Looks like Jack Rickard has done some tests of Regen in his two EV
conversions and come to a startling realization. That Regen is actually a
NEGATIVE!!



I'm sure the discussion list would love to talk about this subject.



Here is his blog.



http://jackrickard.blogspot.com/2010/07/more-regenerative-braking-results-it
.html#comments 



Sincerely;



Douglas A. Stansfield

President

www.TransAtlanticElectricConversions.com 

973-875-6276 (office)

973-670-9208 (cell)

973-440-1619 (fax)



ELECTRIC CAR PRODUCERS





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## EVDL List (Jul 27, 2007)

Well if Jack retests I will be interested in the follow up.

While I don't have regen in my EV right now since it uses a DC 9 inch spiral
wound motor, I appreciate the ability to coast since I live in a VERY hilly
area. If I was able to regen downhill it will slow me down and I will have
to expend another increase in energy consumption to push it back up the next
hill. Whereas if I coast downhill and actually use gravity (32 feet per
second squared) that helps me pick up speed to get back up the next hill. 

I am extremely interested in seeing Jacks results. It will be good to have
some published data on this subject as well as AC vs. DC which still
constantly comes up for discussion.

Enjoy the dialog.


Sincerely;

Douglas A. Stansfield
President
www.TransAtlanticElectricConversions.com 
973-875-6276 (office)
973-670-9208 (cell)
973-440-1619 (fax)

ELECTRIC CAR PRODUCERS







-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of [email protected]
Sent: Saturday, July 24, 2010 3:40 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Regen Not Efficient....

Actually Jack just posted a Followup and there may have been a problem with
his data collection. Regen MAY work after all.

Peter Flipsen
-----Original Message-----
From: "Douglas A. Stansfield" <[email protected]>
Sender: [email protected]
Date: Sat, 24 Jul 2010 15:24:32 
To: 'Electric Vehicle Discussion List'<[email protected]>
Reply-To: Electric Vehicle Discussion List <[email protected]>
Subject: [EVDL] Regen Not Efficient....

Hello everyone, 



Looks like Jack Rickard has done some tests of Regen in his two EV
conversions and come to a startling realization. That Regen is actually a
NEGATIVE!!



I'm sure the discussion list would love to talk about this subject.



Here is his blog.



http://jackrickard.blogspot.com/2010/07/more-regenerative-braking-results-it
.html#comments 



Sincerely;



Douglas A. Stansfield

President

www.TransAtlanticElectricConversions.com 

973-875-6276 (office)

973-670-9208 (cell)

973-440-1619 (fax)



ELECTRIC CAR PRODUCERS





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## EVDL List (Jul 27, 2007)

Thirty plus years of EV research and design by thousands of engineers all 
over the world shows that regen extends range, thus improving efficiency as 
measured in Wh/mi. Now, how much, and whether that's worth the hardware and 
software cost - that's another matter. But this is the first time I've 
heard of anyone suggesting that regen >reduces< efficiency or range.

Generally, when your data contradict that much established research, you 
stop and look again before you publish, no?

David Roden - Akron, Ohio, USA
EVDL Administrator

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## EVDL List (Jul 27, 2007)

David,

It is very interesting research. Using 30 year old EV technology might have
different results and since we are using different technology today it makes
sense to retest once in a while to verify our initial conclusions. 

Jack is using off the shelf current technology so I am very interested in
his results. Especially in the same car.

This is going to be an interesting discussion. I don't think it is a closed
issue so I welcome his research.


Sincerely;

Douglas A. Stansfield
President
www.TransAtlanticElectricConversions.com 
973-875-6276 (office)
973-670-9208 (cell)
973-440-1619 (fax)

ELECTRIC CAR PRODUCERS






-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of EVDL Administrator
Sent: Saturday, July 24, 2010 5:04 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Regen Not Efficient....

Thirty plus years of EV research and design by thousands of engineers all 
over the world shows that regen extends range, thus improving efficiency as 
measured in Wh/mi. Now, how much, and whether that's worth the hardware and

software cost - that's another matter. But this is the first time I've 
heard of anyone suggesting that regen >reduces< efficiency or range.

Generally, when your data contradict that much established research, you 
stop and look again before you publish, no?

David Roden - Akron, Ohio, USA
EVDL Administrator

= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
EVDL Information: http://www.evdl.org/help/
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = 
Note: mail sent to "evpost" an "etpost" addresses will not 
reach me. To send a private message, please obtain my 
email address from the webpage http://www.evdl.org/help/ .
= = = = = = = = = = = = = = = = = = = = = = = = = = = = =


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## EVDL List (Jul 27, 2007)

> Douglas A. Stansfield wrote:
> 
> > While I don't have regen in my EV right now since it uses a DC 9 inch
> > spiral
> ...


----------



## EVDL List (Jul 27, 2007)

As was stated earlier, Jack jumps to conclusions rather quickly and
not completely following a sound scientific method in doing so. He
tends to attack when someone disagrees with him on his conclusions but
he does sometimes come around and when he sees he made a mistake he
admits it. The regen "issue" is one such time. He has, however,
uncovered a possible error in how some claim the range extending
gained by regen. If one measures Ah out of the pack and then Ah into
the pack and uses that as their measure of regen efficiency it is
entirely possible to come to the conclusion that regen provides range
improvements in all situations. This is not always the case as Jack's
data have shown. For example, if using regen consumed 100Ah and the
regen put back 10Ah one might conclude from this alone that regen put
back 10% or extended range 10%. The problem is that if using no regen
only consumed 85Ah then the regen drive was worse. Bill D summed it up
quite concisely on how this could be the case. Some of us have been
saying he needed to use Wh not Ah because of the different voltages
involved. In one of my comments I said I was more interested in the
amount of energy consumed from the wall and not Ah in or out of the
pack. He initially attacked back at the idea but then has decided that
maybe he was a little hasty in rejecting the notion. Measuring the KWh
taken from the wall would give another measurement instrument for
energy consumption even though it may not be very precise. Over
multiple drives and charges the "noise" will tend to average out. If
there is a difference between the two "modes" of driving it should
start showing up. Of course, as Bill D pointed out, the system and the
driver have to work _efficiently_ together. I think that the easiest
regen setup to get used to after driving a non-regen vehicle is one
where the regen is operated independently from the throttle and the
brake. Jack's rigs don't have this setup (yet?) so he will have to get
more experience hypermileing with regen like he does with his
non-regen vehicle.


-- 
David D. Nelson
http://evalbum.com/1328

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## EVDL List (Jul 27, 2007)

> On 24 Jul 2010 at 23:21, Douglas A. Stansfield wrote:
> 
> > I am fascinated by this and long to see
> > published results.
> ...


----------



## EVDL List (Jul 27, 2007)

To be clear - Jack is no longer say "regen doesn't work" - he has backed off
on and that and now says it may well do so. And he has openly admitted his
error. He is however (as some have pointed out to him) suggesting that
it might be better to measure the efficiency gains of regen using Wh in and
out of the wall. The regen set ups he is using and the driving conditions
he is testing them under may or may not be the best ones for the test but
his latest preliminary results NOW do show that regen results in gains in
efficiency.

Peter Flipsen



> EVDL Administrator <[email protected]>wrote:
> 
> > On 24 Jul 2010 at 23:21, Douglas A. Stansfield wrote:
> >
> ...


----------



## EVDL List (Jul 27, 2007)

I think any discussion on regen needs to
count the reduced brake wear.

My current car is a Prius
(paritally electric car, but does not plug in...yet! ),
and I have got pretty good control of the regen -
turning it on and off with the accellerator.

In a car with regen, brakes are for panic stops.
I just don't need new brakes as often as I did
in my ICE car. Note, brakes are both a financial
issue and a green issue, as there is material being eroded.

My first EV (hopefully to go on the road "soon")
won't have regen, but my next likely will.
(When I turn over a new Leaf?)

STOP means make electricity.

Seth

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## EVDL List (Jul 27, 2007)

"Generally, when your data contradict that much established research, you
stop and look again before you publish, no?"

Exactly. I've also done a similar comparison test. I drove about a 5 or 6
mile closed loop with 6 stops signs, no stop lights, and some small hills. 
Battery pack fully charged initially both times. Once with regen on, once
with regen turned off (0%). AC50 motor/Curtis 1238-7501 controller,
neutral_braking parameter setting % regen. I "hypermiled" with regen off,
coasting as much as possible while remaining fairly close to the speed
limit. Result was about 12% less charged used with regen on. I used a TBS
gauge to track Ah used. The difference in Wh used should be similar, as the
pack was fully charged for each run, so voltage was similar.

Using the neutral_braking parameter to control regen, the control is all in
the accelerator pedal. I can control this well, usually holding the current
within +/- a few amps of what I want, so I can hold it at zero to coast. 

The only way you could possible get less efficiency with regen would be to
modulate the vehicle's kinetic energy more than you do without regen. This
could happen if you have poor control of the throttle/controller, so that
you are regularly over-regen'ing, slowing too much, then accelerating to
compensate. Think about it, if you drive a vehicle using regen to stop, and
you drive with the same exact acceleration/deceleration as without regen,
using friction to stop, there is no way it can be less efficient with regen. 
Even if the regen has very poor efficiency, it will put some energy back
into the pack, whereas with friction it all goes to heat. The changes in
vehicle kinetic energy will be the same for both cases - but in the regen
case some gets converted to potential energy in the batteries.

In normal driving you typically have to keep pace with traffic, so you can
only "hypermile" so much without impeding traffic flow or riding the bumper
of the car in front of you. You have to regulate speed, regularly slowing
and stopping. You either do that with friction, or regen. If with regen you
will get some kinetic energy converted to potential energy, with friction
you can only generate heat.
-- 
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Regen-Not-Efficient-tp2301226p2301605.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

* "Regen is counterproductive"
* "BMSs kill packs"
* "Street light go off when you walk under them"
* "Condoms cause pregnancies"

Yes: you can find data that corroborates all the above.

For example: "I never used a condom before, and never made any woman
pregnant. The one time I used a condom, she got pregnant. I therefore can
prove that condoms cause pregnancy. I have the data to prove it." OK. But do
you have *all* the data? What if some of your lovers did get pregnant, but
never told you? What if, because you never used a condom before, you didn't
know how to use one properly?

Now substitute "BMS" for "condom" and "killed pack" for "pregnant". Or,
substitute "regen" for "condom" and "efficiency" for "pregnant". You get the
idea.

Sure, data are great, I love data! But just because you have data doesn't
mean you have all the data, nor that you know how to interpret them. The
worse is when someone approaches you and offers to help you make sense of
your data, and you send them away because you say: "I have data, and you
don't, so go away and don't come back until *you* have data.". (Yes, that is
what I was told when I went to the holder of the data that "proved that BMSs
harm packs" and offered to explain what those data were really showing. )

It would be easy to dismiss such people; so what if one day they'll learn
the hard way: it's just one EV that may be damaged.

What really worries me is the crowds who listen to the most controversial
voice, just because of the fact that it is controversial, the crowds who
distrust the system ("The government is behind 9/11"; "The oil companies are
suppressing free energy information"), and will latch onto a voice of
dissent for no other reason that that voice is "being silenced". I am not
worried about a "regen is counterproductive" statement: an EV without regen
is not dangerous. What I am worried about is people who will refuse to use a
BMS with a Li-Ion pack (or to wear condoms) based on such voices of dissent;
I am worried because of the dangers of an unprotected Li-Ion pack (or the
consequences of unprotected sex). 

(Don't get me wrong: I am all for dissent. Dissent is good. Following
dissent just because it's dissent, without questioning, is what concerns me.
I really don't want to be in a pissing contest.)

Initially I dismissed the "bottom balancing without a BMS" issue as a non
starter. Sure, a bottom balanced pack without a BMS can be protected from
over-discharge by looking just at the pack voltage, that's undeniable. But
to ignore what happens at the top end (charging with a CCCV charger and no
BMS), which can result in a fire hazard from severely overcharged cells, is,
in my mind, unconscionable. 
I wasn't too worried, as it affected only one person: its proponent. But
then I started hearing from others who seriously considered bottom balancing
without a BMS as a viable option. This is when I have to speak up, and say: 

A CCCV charger without a BMS >>>> WILL OVERCHARGE CELLS <<<< 
and an overcharged cell can be a fire hazard.

And, no, I am not trying to sell you a BMS for your Li-Ion pack. Go buy
someone else's BMS, I don't care; just as long as you have one, one that
actually works. 

/ rant

P.S. The technical details about my statements above are too involved to
include here. Let me refer you instead to the following:
1) This white paper explains why CCCV charging a Li-Ion pack gives a false
sense of security:
http://liionbms.com/php/wp_cccv_charging.php
2) The book "Battery Management Systems for Large Lithium Ion Battery Packs"
lists 7 reasons why top balancing makes sense, and finds not a single one to
do bottom balancing (section 3.2.3.1). Here is a screen capture of the
relevant section:
http://lithiumate.elithion.com/smf/pictures/bottombalancing.gif










-----
Davide Andrea
http://liionbms.com/php/index.php Elithion 
-- 
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Regen-Not-Efficient-tp2301226p2301608.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

> Elithion <[email protected]> wrote:
> 
> > What really worries me is the crowds who listen to the most controversial
> > voice, just because of the fact that it is controversial
> ...


----------



## EVDL List (Jul 27, 2007)

Just did a Plug In Enginer Prius kit conversion last week for a client and
boosted mpg considerably.

Turns out that the Enginer Kit can actually end up charging the stock Prius
battery from the wall outlet not just the Enginer battery pack. Usually
takes between 3 and 7 minutes to fully charge the 1kw stock Prius pack. 

This allows him to leave every morning with both a full Prius battery (two
green bars) and the Enginer supplemental battery.

Glad your regen is working well Seth.

Sorry I had the meeting on Saturday and missed you this month. Maybe next
month I will hold the NJ EAA meeting someplace by you on a Sunday. Actually
aren't there blue laws still in effect on Sunday so that all the big mall
parking lots are empty? Maybe we can hold one at Garden State Plaza on a
Sunday afternoon in August? Do you think that will work?


Sincerely;

Douglas A. Stansfield
President
www.TransAtlanticElectricConversions.com 
973-875-6276 (office)
973-670-9208 (cell)
973-440-1619 (fax)

ELECTRIC CAR PRODUCERS





-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Seth Rothenberg
Sent: Sunday, July 25, 2010 11:20 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Regen Not Efficient....

I think any discussion on regen needs to
count the reduced brake wear.

My current car is a Prius
(paritally electric car, but does not plug in...yet! ),
and I have got pretty good control of the regen -
turning it on and off with the accellerator.

In a car with regen, brakes are for panic stops.
I just don't need new brakes as often as I did
in my ICE car. Note, brakes are both a financial
issue and a green issue, as there is material being eroded.

My first EV (hopefully to go on the road "soon")
won't have regen, but my next likely will.
(When I turn over a new Leaf?)

STOP means make electricity.

Seth

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## EVDL List (Jul 27, 2007)

The scientific thing to do when you want to present a (new) 
theory is to first establish the rules by which your proof
must be executed.
Luckily one does not even need to actually build or run an
EV with or without regen if the rules show clearly enough
how you measure, how it is an apples-to-apples comparison
and one just has to apply logic and laws of physics to be
able to see that under practical and comparable situations
the regen will always result in lower energy use.
To clarify:
- rule is that the EV must be driven in the same way with
and without regen, so same speed, same acceleration and
same deceleration. The fact that deceleration (regen) will
recoup some energy must not be the reason to drive faster
or brake harder, because then it is not apples-to-apples.

Since the same energy is needed for the acceleration and
coasting of the EV, the only difference will be during
the periods of deceleration. In the non-regen EV all
energy will be turned into heat and brake pad wear.
In the EV with regen a part of the kinetic energy of the
vehicle is turned into electric energy and stored into
the batteries.
You can debate about how much of the original energy that
was needed to accelerate the vehicle will make it back
into the battery and can be pulled out again for the next
acceleration - I have seen numbers for lead-acid batteries
and AC drivetrains that estimate about 50% of the original
energy is available for the next cycle, so that means that
coasting is much preferable to accelerate-regen cycles, so
it is mandatory to either be able to disengage regen or to
get a "feel" for the accelerator to allow your EV to coast
without drawing power from battery or wheels, because
either will prevent you from maximizing your efficiency.

But by simply applying logic and laws of physics, you can
make a water-tight case of regen reducing the energy that
your EV consumes, in all practical cases.
There is a theoretical case where you never brake until
you reach the end of your journey where you glide to a
halt on an incline. In such a scenario it does not matter
whether you have regen or not, the consumption is the same
in both cases.

Please also note that many batteries do not accept large
charge currents until they are below approx 85% SOC.
So the first few miles of your journey you should not
expect any benefit from regen if you charge your pack to
100% SOC every night. I know from my own experience how
the first few traffic lights were always a frustration
when you missed the green, because of wasting all that
energy in the brake pads... The Prius was much smarter
by keeping the max SOC below the acceptance level and
always allowing the electric deceleration... I think that
the Li-Ion batteries will also allow charging to less than
100% if you are either on top of a hill and can recoup a
lot of that energy during the start of your trip and
still offer enough energy to complete the trip up at the
end, so you know that at least half the energy of the trip
up the hill comes from the trip down and not from the wall.

Regards,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of tomw
Sent: Sunday, July 25, 2010 9:04 PM
To: [email protected]
Subject: Re: [EVDL] Regen Not Efficient....


"Generally, when your data contradict that much established research,
you stop and look again before you publish, no?"

Exactly. I've also done a similar comparison test. I drove about a 5 or
6 mile closed loop with 6 stops signs, no stop lights, and some small
hills. 
Battery pack fully charged initially both times. Once with regen on,
once with regen turned off (0%). AC50 motor/Curtis 1238-7501
controller, neutral_braking parameter setting % regen. I "hypermiled"
with regen off, coasting as much as possible while remaining fairly
close to the speed limit. Result was about 12% less charged used with
regen on. I used a TBS gauge to track Ah used. The difference in Wh
used should be similar, as the pack was fully charged for each run, so
voltage was similar.

Using the neutral_braking parameter to control regen, the control is all
in the accelerator pedal. I can control this well, usually holding the
current within +/- a few amps of what I want, so I can hold it at zero
to coast. 

The only way you could possible get less efficiency with regen would be
to modulate the vehicle's kinetic energy more than you do without regen.
This could happen if you have poor control of the throttle/controller,
so that you are regularly over-regen'ing, slowing too much, then
accelerating to compensate. Think about it, if you drive a vehicle
using regen to stop, and you drive with the same exact
acceleration/deceleration as without regen, using friction to stop,
there is no way it can be less efficient with regen. 
Even if the regen has very poor efficiency, it will put some energy back
into the pack, whereas with friction it all goes to heat. The changes
in vehicle kinetic energy will be the same for both cases - but in the
regen case some gets converted to potential energy in the batteries.

In normal driving you typically have to keep pace with traffic, so you
can only "hypermile" so much without impeding traffic flow or riding the
bumper of the car in front of you. You have to regulate speed,
regularly slowing and stopping. You either do that with friction, or
regen. If with regen you will get some kinetic energy converted to
potential energy, with friction you can only generate heat.
--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/Regen-Not-E
fficient-tp2301226p2301605.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

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## EVDL List (Jul 27, 2007)

One thing about the Prius - it tells you how much regen you have had in Wh.
If you can get 200 Wh in a stop (10km) trip you are doing well, it does not
seem like much, but that's more than 1km free, or +- 10%.
I think regen is great, you just have to use it as little as
possible! As you say, the Prius is set up to regen if you take your foot off
the accelerator, this means you are either using power or regenerating, it's
very hard to get it into a neutral zone, or at least, I can't. This report
we talking about, one of the tests he did was to accelerate them regen over
and over, if you accelerated then brake (not regen) power consumption would
be far higher than with regen, however, regen overall is not an efficient
process, so it's better to drive so you don't use it.
The regen with no accelerator of the Prius is meant to simulate the
engine braking of a normal automatic car, I think it would be better without
it and I am trying to find a way to implement this. I have considered a
throttle stop, but this would result in more "creep" at low speeds, the way
it is set up. Another way would be a micro that could control the gear lever
switch between "D" and "N". I have tried driving like this, putting it into
N when I don't need power, but of course, then it gives a tiurtle in short
order as it never charges the battery.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of tomw
Sent: Monday, 26 July 2010 3:34 a.m.
To: [email protected]
Subject: Re: [EVDL] Regen Not Efficient....


"Generally, when your data contradict that much established research, you
stop and look again before you publish, no?"

Exactly. I've also done a similar comparison test. I drove about a 5 or 6
mile closed loop with 6 stops signs, no stop lights, and some small hills. 
Battery pack fully charged initially both times. Once with regen on, once
with regen turned off (0%). AC50 motor/Curtis 1238-7501 controller,
neutral_braking parameter setting % regen. I "hypermiled" with regen off,
coasting as much as possible while remaining fairly close to the speed
limit. Result was about 12% less charged used with regen on. I used a TBS
gauge to track Ah used. The difference in Wh used should be similar, as the
pack was fully charged for each run, so voltage was similar.

Using the neutral_braking parameter to control regen, the control is all in
the accelerator pedal. I can control this well, usually holding the current
within +/- a few amps of what I want, so I can hold it at zero to coast. 


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## EVDL List (Jul 27, 2007)

"Heat is the bullshit detector for efficiency claims." me.
"If a salesman says a powers supply is high efficiency and you can't put your hand on it, then he is inclusing it's use as a hot
plate in his calculation" also me.

"Energy is never lost, it is just transformed." My thermodynamics book.


There is such a huge difference in energy depending on driving styles, it is possible to slant results without meaning too. It seems
that other people jump on his initial reporting and blow it out of proportion.

If you accelerate to speed and coast to a stop, brakes are cold. (The guy behind you may be a little "hot".)
If you accelerate to speed, maintain speed until the last possible moment then apply the brakes firmly the brakes get hot. There is
energy being used to create that heat. The energy used to maintain the speed a little bit longer. If you use a generator and put it
back in the batteries and the result is cooler brakes, you have proved it's effectiveness. But a good volts and amps graph could
solve this if speed snd elevation is also included. The trip totals are just to cumlative.

Minor elevation changes might cancel on a loop, but Hills don't. The direction of the loop may make a difference.

I didn't read all of the text, I find it painful as it reads to me like a commercial but did anyone see a statistic of how many stop
lights in each iteration of the loop?

I have seen proof of regens usefulnesss With full charts on a rav4 and GPS for a college. It had multiple readings per second and
the level of detail is more telling.

I also have trouble with the early conclusions on BMS's. Again way to many conclusions based on way to little data. :-(

I do love his conversions and his tenacity


----------



## EVDL List (Jul 27, 2007)

"Please also note that many batteries do not accept large
charge currents until they are below approx 85% SOC.
So the first few miles of your journey you should not
expect any benefit from regen if you charge your pack to
100% SOC every night."

The only time I have had the controller not give regen (you can tell because
the car doesn't slow when you release the throttle, and the TBS gauge reads
0 A), was just after full charge, and I had just added a cell to the pack,
but forgot and left my regen voltage limit programmed for 35 cells rather
than 36. It occurred as I dropped about 200 ft about 1/5 mile after leaving
my driveway, where I would normally get around a max of 60A regen. You can
program this limit to what value you like on the Curtis controller. If I
recall correctly, I have it set at 125V or about 3.48V/cell. Even when
stopping fairly suddenly for a traffic light after driving only 4 or 5 
miles I have gotten 160A regen without the controller limiting it. But of
course that is the max, and it only occurs for at most a few seconds before
dropping quickly.

I think we all know results with regen certainly depend on driving
conditions - stops/starts, slowing for traffic and curves, and hills. I have
it programmed at 55%, which gives fairly strong braking if you completely
release the accelerator. Enough that I hardly use my mechanical brakes. I
just ease the throttle up/down to decelerate/accelerate for curves and
traffic. At fast deceleration for a traffic light I have had a spike of
over 190A regen.
-- 
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Regen-Not-Efficient-tp2301226p2301828.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

>Now substitute "BMS" for "condom" and "killed pack" for "pregnant". Or,
substitute "regen" for "condom" and "efficiency" for "pregnant". You get the
idea.

I am lost...Does this mean if I use regen my wife will get pregnant??










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## EVDL List (Jul 27, 2007)

>>Now substitute "BMS" for "condom" and "killed pack" for "pregnant". Or,
substitute "regen" for "condom" and "efficiency" for "pregnant". You get the
idea.

>I am lost...Does this mean if I use regen my wife will get pregnant??


Hey, I have 8 kids and I don't use REGEN....something is amiss
here....(grin)







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## EVDL List (Jul 27, 2007)

Tom,

The fact that your controller can regen immediately after
you start out of your driveway and drop 200ft in elevation
*proves* that your batteries are not fully charged.
Apparently you charge your Lithiums pretty conservatively
and that was what I was hinting at also with the remark
about the Prius - NiMH and Li-Ion allow this type of
not-fully-recharge at home to capture this energy.
Lead-acids won't take a large current if they are fully
charged, they will just boil it off.
Even if they have dropped to 95 or 90% SOC and you hit
them with 200A regen, their voltage will go through the
roof and you better had programmed the max regen voltage 
before the critical error level (I had my controller go
over 420V and execute a panic shutdown on the freeway
when I hit the brakes hard for a Yahoo merging short in
front of me, after I reprogrammed the regen parameters.
So, I put them back to wait for SoC below 85% before
allowing so much regen and setting the max voltage
level a tad lower... I had a 312V nominal pack (26x12V)
So pushing it over 420V meant 2.7V per cell...)

Regards,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of tomw
Sent: Monday, July 26, 2010 6:07 AM
To: [email protected]
Subject: Re: [EVDL] Regen Not Efficient....


"Please also note that many batteries do not accept large charge
currents until they are below approx 85% SOC.
So the first few miles of your journey you should not expect any benefit
from regen if you charge your pack to 100% SOC every night."

The only time I have had the controller not give regen (you can tell
because the car doesn't slow when you release the throttle, and the TBS
gauge reads 0 A), was just after full charge, and I had just added a
cell to the pack, but forgot and left my regen voltage limit programmed
for 35 cells rather than 36. It occurred as I dropped about 200 ft
about 1/5 mile after leaving my driveway, where I would normally get
around a max of 60A regen. You can program this limit to what value you
like on the Curtis controller. If I recall correctly, I have it set at
125V or about 3.48V/cell. Even when stopping fairly suddenly for a
traffic light after driving only 4 or 5 miles I have gotten 160A regen
without the controller limiting it. But of course that is the max, and
it only occurs for at most a few seconds before dropping quickly.

I think we all know results with regen certainly depend on driving
conditions - stops/starts, slowing for traffic and curves, and hills. I
have it programmed at 55%, which gives fairly strong braking if you
completely release the accelerator. Enough that I hardly use my
mechanical brakes. I just ease the throttle up/down to
decelerate/accelerate for curves and traffic. At fast deceleration for
a traffic light I have had a spike of over 190A regen.
--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/Regen-Not-E
fficient-tp2301226p2301828.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

_______________________________________________
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----------



## EVDL List (Jul 27, 2007)

> Glad your regen is working well Seth.

Better than regen in a Prius is Lithium in a Camry.
(inching along, just think of that 2-year snail joke 

This morning, I planned to sleep in, but my kid had another plan...
so I finished cabling the BMS on my LiFePO4 pack.
That's not "finished" but it's close. The controller sees 49 cells.
(though not all at once; need to build more harnesses 

The 50th cell is at .8 volts...oh well.

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## EVDL List (Jul 27, 2007)

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----------



## EVDL List (Jul 27, 2007)

> shred wrote:
> 
> > I believe a shunt (passive) balancing BMS system waists too much energy
> > making an expensive active BMS the only practical choice for me. Let???s say
> ...


----------

