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Discussion Starter #1
Someone was surprised when I told them that regen doesn't work with a
dc motor. And I couldn't explain why. So my question is why doesn't it
work? (even though it is possible with a sepex motor or something...
right)
If someone could explain it that would be great :)

Cheers,
--
Tehben
'90 Toyota 4x4 Pickup
'hElix EV'
Website: www.helixev.com
evalbum: http://www.austinev.org/evalbum/1225

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Discussion Starter #8
Hi Ed,

I hope Peter doesn't mind me chiming in. I have
experience with regeneration, both on BEVs and HEVs.
There are a lot of issues to consider. But, with
regards to your question "how much energy is
recuperated with regen?", about half of the energy
that it took to accelerate the vehicle to the speed at
which you start braking. This assumes you have a
motor (generator) capable of high enough power.
Braking power can exceed acceleration power. Also,
you need an efficient means of storing the electrical
energy on-board. Batteries may not be suitable for
the high regen (charge) currents. My HEV work has
been using ultracapacitors.

So, 50% can be recovered. But that is just 50% of the
energy used to accelerate, not to power the vehicle at
speed. And that assumes you make fast stops.
Coasting down lets the energy dissipate to aero and
friction. So, if you brake often and hard, your net
extension of range for your energy storage could be up
to 25%. This is typical of my results for 6 stops per
mile and 25 and 35 mph speeds. What a city bus might
do.

On a PbAcid power car with lots of stops and starts,
flat ground, regeneration increase in range was barely
noticeable. What was nice was the "top-off" charge to
the battery every time you stopped, giving a little
more voltage for the next acceleration. Also,
regeneration lessened the heat into the brakes, by a
lot. Like I said, I really can't say we went further
on a battery charge, but I feel we went faster around
the track. Depends where you want to use the energy.

One thing not in my regeneration history is hilly
terrain. I'm in the flatlands. But it is obvious
that regeneration is useful with changes in potential
energy as well as kinetic. So you use extra energy
from your battery going up the hill, regen can get you
back some of that energy when you go down. How much?
Obviously not all. 50%, maybe, best case. With
normal batteries, maybe like 25% on your best day. My
guess.

Overall, for EVs using normal batteries, my guess is
even if you have a lot of stops, you might see 5%
improved range. Lots of hills, maybe up to 10%. In
the big scheme of things, you probably will be hard
pressed to quantify an increased driving range with
the addition of regeneration.

Now, should you do it? If you can, YES. I love it.
I use it even on the IUVs I do. 7 mph. Hey, it is
nice. Rarely have to use the friction brakes. And it
comes free with the motor and control (sepex). So why
not. Does it make the truck go further? My guess is
no. O.K. Maybe the DOD is a few percent less when it
is charged.

Again, should you do it? If it cost a lot, or adds a
lot weight, or damages your battery-----NO. It is not
going to be worth it.

Other advantages are primarily increased time between
brake maintenance. Which on large commercial
vehicles, can be significant. On your heavy battery
cars, could be a big plus.

No simple regen answer. Hope this helps.

Jeff M


--- [email protected] wrote:

> Peter -
> I've often thought that using a couple of
> alternators could be used as
> regen - (stepped up, and only turned on when the
> "gas pedal" is NOT
> depressed).
> Is it worth the effort?
> Does regen provide enough energy back that makes it
> worth the investment?
>
> Regen provides energy back to the batteries. If not
> done right, regen can
> overcharge and cause damage to Lead-Acid batteries
> (depending on
> panic-like stops, for example) - never mind AGM or
> other battery
> technology.
>
> Is this also why its not used?
> Would the losses in belt-driving alternators (even
> freewheeling until
> 'engaged') overcome any gains in regenerative
> braking?
>
> Finally, how much energy is recuperated with regen?
> 10%? 5%?
> There are other advantages to regen besides just
> recharging the battery
> pack: extending the life of the braking system, for
> example.
> However, are these advantages worth the effort?
>
> Thanks -
>
> Ed Cooley
>
>
>
>
>
> "Peter VanDerWal" <[email protected]>
> Sent by: [email protected]
> 08/29/2007 08:58
> Please respond to
> [email protected]; Please respond to
> Electric Vehicle Discussion List <[email protected]>
>
>
> To
> "Electric Vehicle Discussion List"
> <[email protected]>
> cc
>
> Subject
> Re: [EVDL] Why doesn't regen work with DC
>
>
>
>
>
>
>
> > It's possible with some DC motors, just not
> series-wound, which is what
> > most
> > EV'ers use.
>
> Actualy you can regen with a series motor too, it's
> just complicated to
> control and has some issues with brush advance, etc.
> It requires a special controller and extra
> contactors (expensive ones)
> Because of the added expensive and problems, plus
> the generally low
> efficiency, most folks don't bother.
>
> >
> > Basically, to do regen, you have to reverse the
> current in the motor.
> But
> > in
> > a series wound motor, the current flows in the
> same direction in both
> > field
> > and armature. So when you reverse the current in
> both, you reverse the
> > magnetic field in both. That means that any
> magnetics that were
> attracting
> > before are still attracting, and any that were
> repelling before are
> still
> > repelling.
> >
> > If you used permanent magnets instead of the
> armature, or if you could
> > reverse the connection of the field, regen would
> be possible.
> >
> > -Morgan LaMoore
> >
> > On 8/28/07, Tehben Dean <[email protected]> wrote:
> >>
> >> Someone was surprised when I told them that regen
> doesn't work with a
> >> dc motor. And I couldn't explain why. So my
> question is why doesn't it
> >> work? (even though it is possible with a sepex
> motor or something...
> >> right)
> >> If someone could explain it that would be great
> :)
> >>
> >> Cheers,
> >> --
> >> Tehben
> >> '90 Toyota 4x4 Pickup
> >> 'hElix EV'
> >> Website: www.helixev.com
> >> evalbum: http://www.austinev.org/evalbum/1225





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Discussion Starter #9
Finally, how much energy is recuperated with regen? 10%? 5%?
There are other advantages to regen besides just recharging the battery
pack: extending the life of the braking system, for example.
However, are these advantages worth the effort?


10-25% is common in AC/BLDC systems. BLDC's and AC's regen
efficiently (80-90%), and essentially it's free - it's
only software (or in a hardware-based controller, it's
only a few logic gates). So it absolutely makes sense to
use it there. At high charge rates, NiCd's will accept
maybe 85 - 90% of regen energy (the rest is heat just like
when you charge from the wall), I don't know about floodies
or AGM's, but probably less. It's still a bit more range or
a bit less DOD which may extend the battery life a bit.
I only have experience with BLDC's and NiCd's so that's all
I can comment on intelligently. I am not so sure that adding
alternators and stuff like that really makes a lot of sense to
me, but I have a bias towards BLDC systems where all of that
is included in the motor and even the most basic controller.

-Dale

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Discussion Starter #10
Peter VanDerWal wrote:

> Actualy you can regen with a series motor too, it's just
> complicated to control and has some issues with brush
> advance, etc.

I'd just like to clarify here that series motors don't have brush issues
with regen because they are series motors, but rather because most of us
use the cheapest series motors we can find, and these do not include the
interpole windings (and possibly other compensating windings) that all
sepex motors MUST have to avoid brush arcing during regen. There are
some series DC motors that include interpoles (e.g. some Kostov and GE
motors), and these can be used for regen without brush issues.

I'm only aware of one controller for series DC motors that includes
regen capability that is available new, and that is the Zapi. Curtis
made the 1221R, but I don't believe it is offered anymore. (Someone
suggested it was never offered in North America, but I believe this is
false as I know that Canadian Electric Vehicles had some a few years
back.)

As Peter notes, the roundtrip efficiency (i.e. the amount of electrical
energy that actaully makes it back into the battery) is not particularly
high, and since only part of the energy used to accelerate (or climb a
hill) can be recovered, the increase in range is typically low while the
additional cost of a series DC regen controller can be significant.
However, I think that if the most commonly used series motors (ADC,
Warp) were available with interpoles far more people would be using
regen.

Cheers,

Roger.

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Discussion Starter #11
Hi Guys,

Peter said "issues with brush advance". Roger says no
issues with brushes. Well, I think they're both
right. Most of the series wound motors used for EV
conversions do not have interpoles. Primarily because
they are (or were) low voltage forklift motors,
bidirectional, brushes on neutral. When run at
several times design voltage in battery powered cars,
the brushes are advanced to facilitate commutation at
the high voltage. Once shifted for motoring, the
brushes are shifted in the wrong direction for
generator action. So regeneration with an advanced
brush motor would arc to beat the band.

Now, if the EVers were using interpole series wound
motors, they would not need to advance the brushes and
generator commutation would be acceptable. But,
interpole motors cost more, and can be larger and
heavier than non-interpole motors. And, rarely seen
in frame sizes below 10 inch. Possible, sure. I've
seen them. They go to 2 pole designs. Which can
bring a whole new set of issues.

Even if interpole series motors were available for
EVers, the regen controls would still be difficult,
complex, more costly and I suspect unreliable. By the
time you throw all that into the regen equation, go
AC. Reliable and no sparking.

Jeff M

--- Roger Stockton <[email protected]> wrote:

> Peter VanDerWal wrote:
>
> > Actualy you can regen with a series motor too,
> it's just
> > complicated to control and has some issues with
> brush
> > advance, etc.
>
> I'd just like to clarify here that series motors
> don't have brush issues
> with regen because they are series motors, but
> rather because most of us
> use the cheapest series motors we can find, and
> these do not include the
> interpole windings (and possibly other compensating
> windings) that all
> sepex motors MUST have to avoid brush arcing during
> regen. There are
> some series DC motors that include interpoles (e.g.
> some Kostov and GE
> motors), and these can be used for regen without
> brush issues.
>
> I'm only aware of one controller for series DC
> motors that includes
> regen capability that is available new, and that is
> the Zapi. Curtis
> made the 1221R, but I don't believe it is offered
> anymore. (Someone
> suggested it was never offered in North America, but
> I believe this is
> false as I know that Canadian Electric Vehicles had
> some a few years
> back.)
>
> As Peter notes, the roundtrip efficiency (i.e. the
> amount of electrical
> energy that actaully makes it back into the battery)
> is not particularly
> high, and since only part of the energy used to
> accelerate (or climb a
> hill) can be recovered, the increase in range is
> typically low while the
> additional cost of a series DC regen controller can
> be significant.
> However, I think that if the most commonly used
> series motors (ADC,
> Warp) were available with interpoles far more people
> would be using
> regen.
>
> Cheers,
>
> Roger.
>
>



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Discussion Starter #12
I can see regen being very useful in hilly terrain. I regularly travel a
few 6% grades with speed limits of 30MPH and 40MPH. Seems like such a
waste of energy (and brake pads) when I could be waking my poor floodies
back up on the way home!

Anyone else notice how much better floodies seem to perform if used
immediately after charging? Much better than if charged and left to sit
overnight...

How about threading a small plastic tube down the battery vent and
bubbling a bit of air through the cells to keep them from stratifying?

-Adrian

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Discussion Starter #13
[email protected] wrote:
> I've often thought that using a couple of alternators could be used
> as regen -- (stepped up, and only turned on when the "gas pedal" is
> NOT depressed).

Ordinary automotive alternators are not very efficient, but they are
common and inexpensive. If all you want is "mild" regen to simulate ICE
engine braking, they will work adequately.

> Is it worth the effort? Does regen provide enough energy back that
> makes it worth the investment?

That depends on where you live, and how you drive. Regen adds perhaps
10% to your range in ordinary driving, where you rarely go down hills
and don't use the brakes very often. But if you live in a hilly area, or
do a lot of stop-and-go driving, regen can extend your range by 30% or
more.

> Regen provides energy back to the batteries. If not done right, regen
> can overcharge and cause damage to Lead-Acid batteries...

Yes. Like any battery charger, a regenerative braking system has to know
the state of charge of the batteries, and limit the current to a
suitable level for their state of charge.

> Would the losses in belt-driving alternators (even freewheeling until
> 'engaged') overcome any gains in regenerative braking?

If belt driven, the belt losses will continue all the time. So, you will
lose range if you drive on the freeway and never use the brakes or go
down hills.

But, most people's driving habits are such that even modest use of regen
will make up for the extra losses in the belt drive.

Note that *all* motors are intrinsically able to work as generators,
too. The differences are just that some types are better suited (easier
to use) than others. A DC series motor is about the hardest.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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Discussion Starter #14
Jeff Major wrote:
> Most series wound motors for EV conversions do not have interpoles,
> primarily because they are (or were) low voltage forklift motors,
> bidirectional, brushes on neutral. When run at several times design
> voltage, the brushes are advanced to facilitate commutation...
> the wrong direction for generator action. So regeneration with an
> advanced brush motor would arc to beat the band.

A good summary, Jeff.

> If EVers were using interpole series wound motors, they would not
> need to advance the brushes and generator commutation would be
> acceptable. But, interpole motors cost more, and can be larger and
> heavier than non-interpole motors. And, rarely seen in frame sizes
> below 10 inch.

Agreed. The nature of the market is such that few customers will pay for
interpoles on smaller motors.

> Even if interpole series motors were available for EVers, the regen
> controls would still be difficult, complex, more costly and I suspect
> unreliable. By the time you throw all that into the regen equation,
> go AC. Reliable and no sparking.

Here I disagree. Interpole series motor/generators have been used
successfully for a *very* long time. They are common in trucks, buses,
trains, elevators, cranes, and many other serious, big-motor
applications. Many of them were used with contactor controllers that
were fairly simple when you got down to the basics.

When you look at (for instance) a Curtis 1221R or Zapi H2 or HFM series
DC controller with regen, it is hardly any different from the same
controller without regen. There are extra contactors, but they are the
same ones that would have been there anyway if you had electric
reversing (which all purpose-built EVs have anyway).

I think is is more a matter that certain technologies become fashionable
at different times. DC had its time; now the AC induction is in vogue.
Who knows what will be next; brushless DC? Switched reluctance?
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
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Discussion Starter #15
Adrian DeLeon wrote:
> Anyone else notice how much better floodies seem to perform if used
> immediately after charging? Much better than if charged and left to
> sit overnight...

Yes. A little regen certainly perks up an almost-dead pack!

> How about threading a small plastic tube down the battery vent and
> bubbling a bit of air through the cells to keep them from stratifying?

This might help for large cells. But the ones we use in our EVs are
generally too small to worry much about stratification. Normal road
vibration and vehicle motion will keep them reasonably well mixed.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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Discussion Starter #16
--- Roland Wiench <[email protected]> wrote:

> Hello Ed,
>
> REGEN is very expensive to install in a EV and some
> ev's may not have the
> room to install it. Here is the 1985 cost of

I don't understand how this can be with today's
technology. May Gizmo EV has very little room for
extra things like you describe. To add regen to it was
just a small module about the size of an older cell
phone charger and that was it. It is all solid state,
too. This is a SepEx motor so that may be the
difference.



David D. Nelson
[email protected]


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Discussion Starter #18
On 29 Aug 2007 at 10:22, Roland Wiench wrote:

> REGEN is very expensive to install in a EV and some ev's may not have the room
> to install it.

Careful, this is only true if the EV uses a series motor and simple
controller. With a separately excited DC motor or an AC induction motor,
and possibly with other types, adding regen is almost trivial to implement
and uses very little additional space.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Discussion Starter #19
On 29 Aug 2007 at 10:20, Jeff Major wrote:

> So [if] you use extra energy
> from your battery going up the hill, regen can get you
> back some of that energy when you go down. How much?
> Obviously not all. 50%, maybe, best case.

Here's a case study of sorts - a situation in which regenerative braking
made a very substantial contribution.

http://www.brusa.biz/applications/e_mini_evergreen.htm

David Roden - Akron, Ohio, USA
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Discussion Starter #20
On 29 Aug 2007 at 21:57, Adrian DeLeon wrote:

> How about threading a small plastic tube down the battery vent and
> bubbling a bit of air through the cells to keep them from stratifying?

This is one of several tricks that have been tried for exactly this purpose.
I recall reading about a fair bit of work done in this area about 20 years
ago. I think I also recall some kind of vibrating gadget that was supposed
to implement some amount of electrolyte mixing.

One of the more interesting tricks that Robert Aronson incorporated into at
least one version of his "tri-polar" batteries was intercell connectors
located at the >bottom< of the battery. The heat from the connectors
(presumably a bit undersized) was supposed to create convection currents to
help stir the electrolyte.

I suspect that the best solution to electrolyte stratification is AGM
design. However, I'm not an electrochemist, so I might be wrong about that.

David Roden - Akron, Ohio, USA
EVDL Administrator

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