[EVDL] Why doesn't regen work with DC
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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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
_______________________________________________
For subscription options, see
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1 - 20 of 20 Posts
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
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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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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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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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
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
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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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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