# [EVDL] Hydraulic regen



## EVDL List (Jul 27, 2007)

http://www.valentintechnologies.com/

Here is an entire car based on that idea.

As for having a system like this on an electric car, it seems like it could easily complicate things to a level that would negate the efficiency gains. It could have the potential of adding a considerable amount of weight as well. 

Chris Leone
University of Florida
Student of Mechanical Engineering
352-278-1176



----- Original Message ----
From: storm connors <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Friday, October 17, 2008 8:31:07 AM
Subject: [EVDL] Hydraulic regen

At our last EV meeting (thanks Bob Rice) we had a discussion about
hydraulic regen. My take is that you attach a hydraulic motor/pump to
the driveline feeding an pressurized accumulator tank. To slow down,
pump the fluid into the tank. Use the pressurized fluid for power when
needed.

It was asserted that this would have a better energy return than
electric regen.

The idea has been keeping me awake at night. I live in a very hilly
area. The first 3 miles from my house are downhill.

Anybody know anything about it?

-- 
http://www.austinev.org/evalbum/1059
http://stormselectric.blogspot.com/
Storm

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## EVDL List (Jul 27, 2007)

There was an article in an engineering magazine about it back in May or
April??? You could do it with air too but there might be more pumping
losses. That article even had a series hydraulic hybrid featured which was
a Ford F350 I think and towing they got really good economy.

http://www.designnews.com/article/1152-Hydraulic_Powertrains_Propel_These_Hy
brid_Trucks.php

http://www.controleng.com/article/CA6561952.html

http://fluidpowertalk.blogspot.com/2008/06/hydraulic-hybrid-tested-in-bmw.ht
ml

http://fluidpowertalk.blogspot.com/2008/06/hydraulic-hybrids-part-two.html

http://www.designnews.com/article/7232-Hydraulic_Hybrid_Cars_No_Batteries_Re
quired.php

"The simulation results showed the Passat's hydraulic drive train was about
95 percent efficient, once you add in the vehicle's regenerative braking
energy. That efficiency is only about 4 percent better than a conventional
mechanical drive train. Yet, thanks to the hybrid's engine optimization and
engine-off operations, total fuel conversion efficiency jumped from 18
percent with the traditional vehicle to 38 percent with the hydraulic
hybrid. "The engine always runs at a high-load, where it's most efficient,"
Achten says. And the engine only had to be on about 9 percent of the time in
simulations of the New European Driving Cycle (NEDC). Achten says the
overall efficiency gain would improve gas mileage to 6.6 ?$/100 km for the
hybrid from 2.9 ?$/100 km for the conventional vehicle and would also result
in an emissions reduction of more than 50 percent." from the last link at
designnews.com

As far as energy recapture goes we should be much closer to perfect compared
to battery systems. I was at one time considering hydraulic or pneumatic
recapture system on the front wheels and DC drive on the rear however does
it make more sense to go for a series electric to hydraulic system? Who
knows? There is much movement in this direction though so google around and
you will find more than what I posted. These types of hybrids don't lend
themselves to conversions very well though so if you are up for the big
challenge of building a car then you are in this ball park.
Jeff

-----Original Message-----
From: storm connors [mailto:[email protected]]
Sent: Friday, October 17, 2008 6:31 AM
To: Electric Vehicle Discussion List
Subject: [EVDL] Hydraulic regen


At our last EV meeting (thanks Bob Rice) we had a discussion about
hydraulic regen. My take is that you attach a hydraulic motor/pump to
the driveline feeding an pressurized accumulator tank. To slow down,
pump the fluid into the tank. Use the pressurized fluid for power when
needed.

It was asserted that this would have a better energy return than
electric regen.

The idea has been keeping me awake at night. I live in a very hilly
area. The first 3 miles from my house are downhill.

Anybody know anything about it?

--
http://www.austinev.org/evalbum/1059
http://stormselectric.blogspot.com/
Storm

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## EVDL List (Jul 27, 2007)

Thanks for the references. Interesting comment: "Kargul maintains
hydraulic hybrids are much more efficient at recovering braking
energy. He says a hydraulic hybrid with a properly sized accumulator
ends up returning about 70 percent of the braking energy to the wheels
while a typical electric hybrid returns something around 21 percent."

The question. Is there such a thing as a hydraulic pump/motor? One
device that I could attach to the shaft of my motor and control with
valves to provide either function?

storm



> Jeff Miller <[email protected]> wrote:
> > There was an article in an engineering magazine about it back in May or
> > April???
> 
> ...


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## EVDL List (Jul 27, 2007)

Yes. Some are quite small but can do a lot of work. We have tree 
shakers around here and they are operated on hydraulics and the pumps 
and motors are pretty small but they can shake a tree down in seconds. 
Very powerful.




> storm connors wrote:
> 
> > The question. Is there such a thing as a hydraulic pump/motor? One
> > device that I could attach to the shaft of my motor and control with
> ...


----------



## EVDL List (Jul 27, 2007)

http://www.eaton.com/EatonCom/ProductsServices/Hybrid/index.htm
maybe here?
http://hydraulics.eaton.com/products/trans_medium_duty.htm
Eaton is one of the leaders in this field. There are a couple of others.

-----Original Message-----
From: storm connors [mailto:[email protected]]
Sent: Friday, October 17, 2008 8:20 AM
To: [email protected]; Electric Vehicle Discussion List
Subject: Re: [EVDL] Hydraulic regen


Thanks for the references. Interesting comment: "Kargul maintains
hydraulic hybrids are much more efficient at recovering braking
energy. He says a hydraulic hybrid with a properly sized accumulator
ends up returning about 70 percent of the braking energy to the wheels
while a typical electric hybrid returns something around 21 percent."

The question. Is there such a thing as a hydraulic pump/motor? One
device that I could attach to the shaft of my motor and control with
valves to provide either function?

storm



> Jeff Miller <[email protected]> wrote:
> > There was an article in an engineering magazine about it back in May or
> > April???
> 
> ...


----------



## EVDL List (Jul 27, 2007)

FORD uses it in some of the Trucks and SUV "hybrids" not sure however if it still is available or even made the price was about $3,500 for the system that captured the braking energy to help initial acceleration.




-----Original Message-----
From: storm connors <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Fri, 17 Oct 2008 5:31 am
Subject: [EVDL] Hydraulic regen



At our last EV meeting (thanks Bob Rice) we had a discussion about
hydraulic regen. My take is that you attach a hydraulic motor/pump to
the driveline feeding an pressurized accumulator tank. To slow down,
pump the fluid into the tank. Use the pressurized fluid for power when
needed.

It was asserted that this would have a better energy return than
electric regen.

The idea has been keeping me awake at night. I live in a very hilly
area. The first 3 miles from my house are downhill.

Anybody know anything about it?

-- 
http://www.austinev.org/evalbum/1059
http://stormselectric.blogspot.com/
Storm

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## EVDL List (Jul 27, 2007)

I looked into this for an electric motorcycle project. I had heard
that hydraulic pump/motor systems could be very efficient, and I
thought it would be a good solution for a unique motorcycle problem:
most of the braking power of a bike is in the front wheel, so that's
where you need the regen to happen if you're going to do it. But it's
mechanically difficult to capture that energy. If you had a
lightweight pump/motor in the front wheel hub, then you could both
drive the wheel to go, and brake the wheel to stop. The hydraulic
hoses accommodate the front suspension movement (the forks).

I've since put that part of the project on the back burner, because
I'm not sure regen will buy me enough to cover the cost (weight,
complexity, expense) of putting it in. But someday I'll buy a couple
of hydraulic pump/motors and hook 'em up, just to see what's what.

d.

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## EVDL List (Jul 27, 2007)

My vision was to run a hydraulic pump/motor off my electric motor
shaft. It would pump into the accumulator to slow the vehicle and act
as a motor to use the accumulated energy to move the car. I don't see
any DC power involved in the system. What did you envision?

> DC powered hydraulic pump was the third
> level of redundancy on a two (or three) engine airplane. Accumulators would
> also be available from aircraft salvage.

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## EVDL List (Jul 27, 2007)

There are pump/motor, usually they are radial piston, although some are 
gear.


The typical vickers pump is vane, they start without load the vanes fly 
up to the surface and begin to build pressure and the pressure elevates 
the end plates to create a seal and build pressure. I could see where 
this is exactly the wrong style pump for this application, we need 
positive displacement.

A cylindrical piston has the added benifit of being easy to chenage 
displacement.

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## EVDL List (Jul 27, 2007)

The best mechanical air compressors are less than 25% efficient. You 
loose almost as much on the expansion motor side.

This is easy to tell, compressor head will take your skin off and an air 
wratchet gets cold in your hand.

Heat: the bullshit detector of effiency claims

There is no cold, just the absence of heat. (there is no spoon)

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## EVDL List (Jul 27, 2007)

25%? I know of a few that are close to 80%.

Sent from my iPhone



> Jeff Shanab <[email protected]> wrote:
> 
> > The best mechanical air compressors are less than 25% efficient. You
> > loose almost as much on the expansion motor side.
> ...


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## EVDL List (Jul 27, 2007)

----- Original Message ----- 
From: "Jeff Shanab" <[email protected]>
To: <[email protected]>
Sent: Friday, October 17, 2008 9:22 PM
Subject: Re: [EVDL] Hydraulic regen


> The best mechanical air compressors are less than 25% efficient. You
> loose almost as much on the expansion motor side.
>
> This is easy to tell, compressor head will take your skin off and an air
> wratchet gets cold in your hand.
>
> Heat: the bullshit detector of effiency claims
>
> There is no cold, just the absence of heat. (there is no spoon)

And ALL the Laws of Physics are in effect til further notice.They can 
trash the Constutution BUT the Physics stuff is Non Negotiable<g>!
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## EVDL List (Jul 27, 2007)

----- Original Message ----- 
From: "Jeff Shanab" <[email protected]>
To: <[email protected]>
Sent: Friday, October 17, 2008 9:17 PM
Subject: Re: [EVDL] Hydraulic regen


> There are pump/motor, usually they are radial piston, although some are
> gear.
>
>
> The typical Vickers pump is vane, they start without load the vanes fly
> up to the surface and begin to build pressure and the pressure elevates
> the end plates to create a seal and build pressure.

Ahhh! THAT'S how they work? As soon as I tried to operate the bucket 
truck's boom the poor little motor labored down to a count-the -rev's thing, 
EVen though it was at rest, later? Takes power just to TURN that Vickers 
pump with NO load. Ballsier motor is in order! Series Golf cart one awaits 
my trial and terror, er, I mean error?Permags just wont hack it! I'm 
surprised how much power a crappy Briggs and Scrapiron GAS engine can put 
out on a log splitter!

I guess there are a buncha designs for hydralic pumps? This is an EV 
List, what do I know?I figgured the truk was born with a itty-bitty Vickers 
pump.

Seeya

Bob

I could see where
> this is exactly the wrong style pump for this application, we need
> positive displacement.
>
> A cylindrical piston has the added benifit of being easy to chenage
> displacement.
>
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## EVDL List (Jul 27, 2007)

> On 17 Oct 2008 at 12:17, henry buehler wrote:
> 
> > Thank you for reply I don't get many.
> 
> ...


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## EVDL List (Jul 27, 2007)

> On 18 Oct 2008 at 5:01, EVDL Administrator wrote:
> 
> > Perhaps because the thread is off topic for the EVDL.
> 
> ...


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## EVDL List (Jul 27, 2007)

> Jeff Shanab <[email protected]> wrote:
> 
> > Instead of a bypasvalve for excessive output, the displacement needs to
> > vary. Otherwise initial application will either nearly lock the wheels
> ...


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## EVDL List (Jul 27, 2007)

>
> Compressed air about the same as hydraulics (just another fluid) 

I would say compressed air is worse, it is a compressable fluid. By 
seperating the system into an incompressable working fluid and a 
compresable storage we eliminate a lot of losses of useing a 
compressable fluid to do work. And it is more controllable. Hydraulics 
can move rapidly then slow down with approach control, you can set the 
rate precisely, With air the rate varies with the osscilations in load 
as it compresses and uncompresses the fluid in the lines and rest of the 
system.

Id say we are wandering a bit off topic, but I can see were electric 
regen is best for regen acrros large amount of time at high speeds, say 
down a hill.
I can imagine where a smaller hydraulic and accumulator (or clockspring 
and a clutch) would work better for just restoring momentum lost stopping.

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## EVDL List (Jul 27, 2007)

I am guessing here, but since planes use electricity to operate
(fly by wire) I guess they send a voltage to the DC powered
hydraulic pump, the hydraulics then control whatever is needed
to be moved (rudder, flaps, ...)
Cor.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of storm connors
Sent: Saturday, October 18, 2008 5:27 AM
To: [email protected]; Electric Vehicle Discussion List
Subject: Re: [EVDL] Hydraulic regen

My vision was to run a hydraulic pump/motor off my electric motor shaft.
It would pump into the accumulator to slow the vehicle and act as a
motor to use the accumulated energy to move the car. I don't see any DC
power involved in the system. What did you envision?

> DC powered hydraulic pump was the third level of redundancy on a two 
> (or three) engine airplane. Accumulators would also be available from

> aircraft salvage.

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## EVDL List (Jul 27, 2007)

Analogue to the motor controller in an EV which avoids
sending full pack voltage to the motor to give a smooth
and controlled acceleration and protect both motor and
pack, you would want the same for a hydraulic system.
On a Forklift I can see that the operators are also
making small/slow adjustments, apparently the (manual)
control levers they have allow a restriced flow of
hydraulic fluid, essentially the same that you are
suggesting for regen and take-off on a hydraulic regen
system. Often this kind of control is achieved by a
PWM (Pulse Width Modulation) of an electric control
signal to the valve, so it can be wired into the
system you already have for motor control (throttle
and brake pot) but you may need to add a little
controller to give the correct (PWM?) drive signal
to the valve(s).

What I wonder about is if the weight and bulk of
a hydraulic reversible pump/motor attached to the
front wheel would be much different than a hub motor
which does exactly the same thing, maybe a little
limited in max torque/regen power but you can
control it by a small controller attached to the
*front* wheel brake lever and the normal throttle
and your regular battery pack, so you do not need
a dedicated "accumulator" that adds to weight and
size - neither of which is a good thing on a bike.

Regards,
Cor.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Jeff Shanab
Sent: Saturday, October 18, 2008 6:42 AM
To: [email protected]
Subject: [EVDL] Hydraulic regen

I have played with hydraulics a bit. And thought about this concept
myself.
I think the trick would be to get efficient hydraulics and they are
expensive.
Instead of a bypasvalve for excessive output, the displacement needs to
vary. Otherwise initial application will either nearly lock the wheels
or dump a lot thru the relief valve back to tank, wasting energy.

It seems to me electric could be better, but a similar caveot applies,
right kind of motor and controller is needed, certainly the analog of
voltage and current is pressure and Gallons per min.

We had machines with nitrogen charged accumulators, they were a piston
that compressed the nitrogen precharged to about 100 bar up to 160 bar.

The machine then ran off the charge in the accumulator until the next
cycle opening the dump valve wide open and taking the load off the
motor.
These were 100hp 460V motors and they had an amp guage on the front
panel that climbed to 120A just before full charge then idled under 20A.

Off the shelf components could be found through grainger. Rebuilt
hydraulic motors and pumps are not to bad and they are very compact for
their torque.
Most the stuff is low rpm, so just feeding into the differential is
pushing rpm limits on this stuff.

Now here is the real trick. What do you do with the change in hydraulic
volume? I was thinking maybe two accumulators and we go from one to the
other.

think accumulator = capacitor(or battery) gpm = amps pressure = volts

Motors are optimized to motor and pumps are optimized to pump, The
valves are what is gonna kill you.
To control 2000psi + fluid in a 2" pipe (55gpm) you are gonna need a two
stage valve in which the oil pressure is used in the second stage of the
valve.

Valve = IGBT, BIG IGBT

For a comparison point, the 750Ton clamping force machine shooting 120oz
of plastic, weight in at 120,000 lbs and had 3 variable voluumn kawasaki
pumps.
These were controlled with very special amplifiers and allowed that
machine to use less than 1/2 the power of the machine exactly half it's
size, 4x difference in effiency!



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## EVDL List (Jul 27, 2007)

Thanks Henry. Though all the references ar to big vehicles, it should
be possible to do regen on a typical EV using this technology. Cost
and weight ar the 2 problems to be overcome it would seem.



> henry buehler <[email protected]> wrote:
> > http://en.wikipedia.org/wiki/Hydraulic_launch_assist
> >
> > link to what was being discussed
> ...


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