# Re: [EVDL] Overvoltage during regeneration



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*

This is the biggest problem with regenerative braking. You've got two 
options: use it or stop generating it. A big resistor will do the job, 
but it has to be a BIG resistor. After all, you're dissipating the same 
power to stop the vehicle as the start it with the same (but opposite) 
acceleration.

The better option is probably to disable regen when the batteries are 
too full. 

I believe the Prius and its mates solve this problem by never allowing 
the batteries to get too full.

Jude



> W9IP-2 wrote:
> > What happens when you have regenerative braking but your batteries are
> > already fully charged? I have an AC24/DMOC55 w/144 V of lead acid
> > batteries. I can see the voltage soar (pegs the meter) and lot 'o amps
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*

It all depends on how much power your batteries can accept.
Thunderskys are supposed to be able to be charged at 3C.
I decided to test this out today with my 90AH cells.
I charged one from 3 others.
It accepted 160A (just shy of 2C) at 3.6v at SOC %90.
I was using a carbon pile to regulate the charge current, but it was eating
too much voltage.
I didn't have time to wire it up for a faster charge current.
Given that it normally isnt recommeneded to give these "cheap" cells 100%
charge every charge, it seems it is fairly reliable at accpeting big charge.

Out of curiosity MRO, what charge current does your AC24 put out?

Matt 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Jude Anthony
Sent: Friday, 5 September 2008 11:54 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Overvoltage during regeneration

This is the biggest problem with regenerative braking. You've got two
options: use it or stop generating it. A big resistor will do the job, but
it has to be a BIG resistor. After all, you're dissipating the same power
to stop the vehicle as the start it with the same (but opposite)
acceleration.

The better option is probably to disable regen when the batteries are too
full. 

I believe the Prius and its mates solve this problem by never allowing the
batteries to get too full.

Jude



> W9IP-2 wrote:
> > What happens when you have regenerative braking but your batteries are
> > already fully charged? I have an AC24/DMOC55 w/144 V of lead acid
> > batteries. I can see the voltage soar (pegs the meter) and lot 'o
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*



> Jude Anthony wrote:
> > This is the biggest problem with regenerative braking. You've got two
> > options: use it or stop generating it. A big resistor will do the job,
> > but it has to be a BIG resistor. After all, you're dissipating the same
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*



> Rick Beebe wrote:
> > That might effect drivability if you're slowing the car with regen and
> > it suddenly cuts off. Sort of like having your brakes go out suddenly.
> > It would be better if it gradually went away as the batteries got close
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*

The Kelly KDH controller documentation mentions a regen switch that goes
on the brake pedal, much like the throttle cutoff that goes on the
accelerator pedal (which prevents motor start when the pedal is
floored). There is also an analog regen control input for "continuous
variable regeneration". However, the docs don't really go into detail
about how exactly that works. Perhaps a full battery flag can flip the
regen switch status electronically? My initial thought is that the brake
pedal can be adjusted such that the first 1/4" of travel can close the
regen switch to the controller without starting the hydraulics to the
brakes, and further travel engages the master cylinder.

Haven't found the Curtis controller docs (but then, haven't looked yet).

On the Highlander Hybrid, I can feel the difference between regen
braking and wheel disk braking. I'm not exactly sure how that is - maybe
it's how my posterior can sense the dipping of the vehicle, or lack
thereof?

Best Regards,

- Gene


-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Lee Hart
Sent: Friday, September 05, 2008 11:54 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Overvoltage during regeneration



> Rick Beebe wrote:
> > That might effect drivability if you're slowing the car with regen and
> 
> > it suddenly cuts off. Sort of like having your brakes go out suddenly.
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*



> W9IP-2 wrote:
> > What happens when you have regenerative braking but your batteries are
> > already fully charged? I have an AC24/DMOC55 w/144 V of lead acid
> > batteries. I can see the voltage soar (pegs the meter) and lot 'o amps
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*

Ack my post is confusing... what I meant to say is, if the analog regen
control input to the controller is 0 volts = full regen and 5 volts = no
regen, and the battery status is 0 to 5 volts empty to full, then you
could just tie the battery status out to the regen control in and you're
good to go. Of course that's in a perfect world of complementary
components. If that's what it really does but the range/direction is
different, you can invert and/or scale as needed. I wish the docs went
into more detail.

Best Regards,

- Gene



The Kelly KDH controller documentation mentions a regen switch that goes
on the brake pedal, much like the throttle cutoff that goes on the
accelerator pedal (which prevents motor start when the pedal is
floored). There is also an analog regen control input for "continuous
variable regeneration". However, the docs don't really go into detail
about how exactly that works. Perhaps a full battery flag can flip the
regen switch status electronically? My initial thought is that the brake
pedal can be adjusted such that the first 1/4" of travel can close the
regen switch to the controller without starting the hydraulics to the
brakes, and further travel engages the master cylinder.

Haven't found the Curtis controller docs (but then, haven't looked yet).

On the Highlander Hybrid, I can feel the difference between regen
braking and wheel disk braking. I'm not exactly sure how that is - maybe
it's how my posterior can sense the dipping of the vehicle, or lack
thereof?

Best Regards,

- Gene



_______________________________________________
General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*

I can tell I'm getting hooked. I was walking between buildings here at
work today, pondering about how a series wound DC motor would work as a
generator, since a classic generator has the field coils excited by a
separate circuit. Ran in and googled it - seems that it's iffy for
series motors due to commutator damage?

Still thinking about a suitable vehicle. It's gotten to the point where
when I drive around, I see other cars like a hungry cartoon wolf sees
sheep - as dressed cooked turkeys on plates!

Best Regards,

- Gene




> W9IP-2 wrote:
> > What happens when you have regenerative braking but your batteries are
> > already fully charged? I have an AC24/DMOC55 w/144 V of lead acid
> > batteries. I can see the voltage soar (pegs the meter) and lot 'o
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*

The first controller that I had in my EV call Transformer I from the EFP Co. 
in Troy, Mich. had a regenerated braking circuit that was tested back then. 
It use a 900 amp Cable Form controller which the main contactor open and 
close like the Curtis controllers do.

There was a micro switch inside the large accelerator control and a micro 
switch on the main contactor that operated a small control relay that made 
sure that the main contactor was off that was on the main positive battery 
feeder line and shut down another battery contactor that was on the battery 
negative power line.

The motor is a GE series 32 hp 6000 rpm 165 to 230 vdc at 175 amp continuous 
running. It has four commentator coils that are in series with the 
commentator.

To make this a generator, it had to be rewire from a motor to a generator by 
use of a two double pole transfer contactors that was mechanical interlock 
and electrical interlock, it is something like a reversing contactor.

These double pole contactors, reverse the leads of the commentator circuit 
to the field circuit and inserted a 300 amp free wheel diode. It left the 
existing 300 amp free wheel diode alone that was in the controller. The 
controller also had a shunt contactor, that bypass the motor controller for 
regen back to the battery if needed.

Then there is a resistance braking contactor that has a large 2 inch 
diameter by about 12 inches long power rib resistor that was in parallel 
with this contactor. When this contactor was open, the generate energy went 
through this resistance which went to another very large resistor which is a 
fin type that is 10 inches square and 30 inches long. The resistance was 
0.5 ohms and had 0.25 ohm tap on it.

When this resistance braking contactor open, then the full motor generating 
energy went though this large resistance. I do not remember what the 
wattage of these resistors was, but the large one had to be hung off the 
front bumper got red hot when coasting down a long 2 mile hill at 75 mph.

This is all old school electrical circuits which took five 600 amp 
contactors and one double 2 pole reversing contactors, micro switches, one 
300 amp diode, a shunt resistor, a load bank power resistor, indicator 
meters and a Auto - Off- Manual switch which was use to control these 
circuits.

I do not use this system with my Zilla controller, but use a 
alternator-inverter that is power off the main motor pilot shaft with a 
electric clutch. This clutch engages when I let up on the accelerator which 
then turns all the accessories units during the coast down or what I call 
MECH REGEN. At this time the motor and battery amps is reading 0 amps while 
the alternator-inverter is generating 14.5 volts up to 100 amps and 6 KW 120 
VAC 60 hz which runs the heating system.

While the main motor is engage by the electric clutch, the DC-DC converters 
go off line that is use to power the electric motors for these accessory 
units.

In the winter time, I can go down a steep icy hill with no problem. It 
holds better than a ICE does. In the summer time, I switch this system off, 
because I can gain more distance after coming down these hills at 80 mph and 
can run out another 2 to 3 miles with no additional energy.

Roland


----- Original Message ----- 
From: "Gene Stopp" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, September 05, 2008 5:22 PM
Subject: Re: [EVDL] Overvoltage during regeneration


> I can tell I'm getting hooked. I was walking between buildings here at
> work today, pondering about how a series wound DC motor would work as a
> generator, since a classic generator has the field coils excited by a
> separate circuit. Ran in and googled it - seems that it's iffy for
> series motors due to commutator damage?
>
> Still thinking about a suitable vehicle. It's gotten to the point where
> when I drive around, I see other cars like a hungry cartoon wolf sees
> sheep - as dressed cooked turkeys on plates!
>
> Best Regards,
>
> - Gene
>
>


> > W9IP-2 wrote:
> > > What happens when you have regenerative braking but your batteries are
> > > already fully charged? I have an AC24/DMOC55 w/144 V of lead acid
> > > batteries. I can see the voltage soar (pegs the meter) and lot 'o
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*

Hi guys,
I gotta jump in here. After 8 years of driving a Prius and never even 
wondering how regen is done, I must say that it acts like down shifting and 
using compression to slow you down as in a ice. There is a fairly constant 
drag on regen. If the frictions do not kick in the car is under almost all 
slowing conditions slowing down due to the regen drag. This means that you 
regen less and less as you slow down. If you are not slowing at the rate 
that you desire you step harder and this engages the engine to add a bit 
more drag and harder yet you engage the frictions. Getting great mileage 
from the Prius requires driving like an old lady. Usually there are no 
situations where the change over is a problem. In fact if the system wants a 
lot of regen it will try to get as much drag as it can even as it reaches 
stop. In that case you actually ease up or stop short. I would think that 
regen should be on at some level whenever the throttle is all the way out. 
and increase when braking is required. The throttle would allow coasting 
when just barely depressed and accelerate as you press down past coast. Just 
a thought. For high performance you might want a different set up. By the 
way I am at 156k and still 2/3 original pads left.
robC
----- Original Message ----- 
From: "Gene Stopp" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, September 05, 2008 1:08 PM
Subject: Re: [EVDL] Overvoltage during regeneration


> Ack my post is confusing... what I meant to say is, if the analog regen
> control input to the controller is 0 volts = full regen and 5 volts = no
> regen, and the battery status is 0 to 5 volts empty to full, then you
> could just tie the battery status out to the regen control in and you're
> good to go. Of course that's in a perfect world of complementary
> components. If that's what it really does but the range/direction is
> different, you can invert and/or scale as needed. I wish the docs went
> into more detail.
>
> Best Regards,
>
> - Gene
>
>
>
> The Kelly KDH controller documentation mentions a regen switch that goes
> on the brake pedal, much like the throttle cutoff that goes on the
> accelerator pedal (which prevents motor start when the pedal is
> floored). There is also an analog regen control input for "continuous
> variable regeneration". However, the docs don't really go into detail
> about how exactly that works. Perhaps a full battery flag can flip the
> regen switch status electronically? My initial thought is that the brake
> pedal can be adjusted such that the first 1/4" of travel can close the
> regen switch to the controller without starting the hydraulics to the
> brakes, and further travel engages the master cylinder.
>
> Haven't found the Curtis controller docs (but then, haven't looked yet).
>
> On the Highlander Hybrid, I can feel the difference between regen
> braking and wheel disk braking. I'm not exactly sure how that is - maybe
> it's how my posterior can sense the dipping of the vehicle, or lack
> thereof?
>
> Best Regards,
>
> - Gene
>
>
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>


--------------------------------------------------------------------------------



No virus found in this incoming message.
Checked by AVG - http://www.avg.com
Version: 8.0.169 / Virus Database: 270.6.16/1654 - Release Date: 9/5/2008 
1:24 PM

_______________________________________________
General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Overvoltage during regeneration*

There are a lot of tricks to driving a Prius for maximum fuel efficiency, 
but the EVDL is not the place to discuss them. There are many Prius forums 
and a couple of good Yahoo groups for those who're interested.

What we as EVers should take note of, though, is that Toyota's engineers 
deliberately set up the Prius so it drives like a "normal" ICE with slushbox 
car, right down to the annoying (to me; some may like it) simulated 
automatic transmission creep. There's a bit of regen braking on accelerator 
release, but no more than the engine braking, such as it is, that you 
usually get with an ICE and slushbox. There's more regen when the brake 
pedal is depressed, varying quite smoothly with pedal pressure, but again 
you're not supposed to even notice. ;-)

There's a reason for that -- it makes the Prius more comfortable and 
familiar. And even as diligent as Toyota were, there are still new owners on 
the forums from time to time who complain that the Prius "drives funny." 

This might be a lesson of sorts to anyone who is building an EV for a 
novice. While most of us as experienced EV drivers probably wouldn't want it 
this way, when building for others there's a significant comfort, 
convenience, and maybe even safety factor in having the car behave as 
expected (that is, as much like a boring ICE as possible). 

The Solectrias were set up a bit differently. The accelerator has a 
definite coasting spot where there's no motoring and no regen, like the 
Prius's. However, with further release of the accelerator, regen quickly 
becomes more aggressive than the Prius's. At least some of them turn on the 
brake lights at 60 amps or more of regen. In fact, if you drive gently, a 
Force or E10 can almost be a one-pedal (wig-wag) vehicle. You only need the 
mechanical brakes for the final stop from where the regen drops out -- just 
a crawl -- and to hold the vehicle once it's stopped. 

The prototype Pivco Citibees used in the Alameda Station Car project in the 
mid 1990s used a drive almost identical to the Solectria's, but their regen 
was on the other extreme. IIRC, they had little or no regen on pedal 
release. The regen was primarily if not solely controlled by a potentiometer 
on the brake pedal.

IIRC, the Brusa inverters used in these cars (Solectria and Pivco Citibee) 
could support either regen on accelerator release, or regen controlled by a 
separate pot. One could certainly configure two pots, one on the 
accelerator and one on the brake pedal, to achieve that middle ground, a 
familiar engine-braking feel plus seamless brake-pedal regen, for the same 
level of driver familarity the Prius has. I imagine the same is also true 
of most current AC drives.

IIRC, the mid-1990s Zapi H2 and H3 series motor controllers with regen 
occupied a middle ground of sorts. As crude as they were by today's 
standards, they were at least theoretically capable of simulating an 
"ordinary" car's ICE braking. They had adjustable accelerator release regen 
braking, and additional more aggressive regen braking controllable from a 
brake pedal device (either switch or pot, I don't recall which now). 

As an aside, regen doesn't come naturally to series motors, and the Zapi 
series motor regen controllers tended to release their smoke distressingly 
often when used with full regen. The H3s were especially troublesome in 
this regard. The H2s generally could support release regen OK, but were 
still iffy when asked to provide the greater current of brake regen.

David Roden - Akron, Ohio, USA
EVDL Administrator

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


_______________________________________________
General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


----------

