Red Suzi

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Post by AMPrentice » Tue, 27 Jan 2009, 05:32

acmotor wrote: Zook (Suzuki Sierra) fans would crucify it. Image

I guess neither of these are what you were thinking ?
who cares about their opinion since they are into fuel anyway.
It would be interesting though to see how it went on say a suzuki swift s2.
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Post by coulomb » Tue, 27 Jan 2009, 18:45

acmotor wrote:I am not using the brake resistor at present...

I did consider connecting the battery pack to the Danfoss via a power diode (100A , not much PIV needed) shunted by a power resistor to carry the regen. I guess you don't need a diagram there.
Use a braking resistor as normal for the controller to dump into ...
Are you thinking of this for the Rodeo too? With the Rodeo, you will have 220 Lithium cells, so if your Danfoss keeps the DC bus at 750v or less, there will only be 750/220 = 3.4 vpc. That won't be much regen into the pack, will it? Surely LiFePO4 needs at least 3.65vpc for good charging?

I'm assuming that the Danfoss regulates at 750v or less because you reduced Red Suzi from 600v to 576v, as it was attempting to use the brake resistor (which you don't have yet, right?) before the batteries went to 15v. With 48x12v, they would try to go to around 15.6v (but you would presumably only see that sort of voltage if you asked for higher regen current).

I'm not that familiar with the Danfoss controller; I'm looking at the Control Techniques (Commander series) one which attempts to keep the DC bus at 780v with the brake resistor.

It seems to be that if using a brake resistor, that sets moderately close limits on the number of cells in the pack.

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Post by acmotor » Wed, 11 Feb 2009, 23:31

Programable brake resistor voltage would be good. Some controllers have this as an option now. The new ABB series ?

For TS in Rodeo..
This regen voltage limit is one reason my BMS is designed to shunt up to 3A (depending on resistor choice at cell) although I will probably got for 1.5A. This means that a few kW can be dealt with by a full battery pack.
The TS are very flat in voltage when away from full charge. You need about 1.5C (60A) to pull the cell voltage from 3.2 to 3.4V once the cells are less than 90% or so full.

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Post by Mesuge » Sun, 15 Mar 2009, 06:26

Tuarn, any milestones ahead for your Suzi, first 1 000km or 5 000km on the same Pb batt. pack? Pls. keep us in the loop Image
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Post by Thalass » Thu, 28 May 2009, 10:31

Hey Tuarn, have you taken this little beastie off road yet? How long can the motor sustain the 300-ish-nm of torque your graphs show (for a few seconds).

Looking at my ICEmobile's workshop manual, the total gear ratio for 1st gear, low range, should be just shy of 17:1 (3.454 for 1st gear, 1.196 for "low" range, 4.111 diff ratio), and the engine puts out a maximum of 223nm of torque. I'm convinced an induction motor can beat this, but would probably need a low/high range.

I'm wavering from my two motor direct drive concept! One larger motor with a decent transfer case is sounding better every day. I think you may have found the best setup for an off-road EV.
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Post by acmotor » Thu, 28 May 2009, 18:43

Thalass,

Red Suzi has not been 'bush bashing', but has been off road quite a bit at our farm.
It is heavier than when it was ICE but never lacks for torque.

In low ratio it is 10.5:1 to the rear wheels.

Original motor was 72Nm max torque at 4000RPM (plus ~4:1 1st gear)and emotor is 300+Nm up to 1500RPM so the emotor is definitely ahead, also because it is torque from zero RPM.
In theory the 300+Nm is for 60 seconds (by controller and emotor ratings). The controller then brings you back to 72Nm. I've never experienced that yet though.

The limitation at present is the torque available over 60kmph is low since I can't maintain v/f ratio at higher frequency. The thread on AC motors, multipoles and torque covers this.
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Post by Thalass » Thu, 28 May 2009, 21:03

I'm attempting to read that thread today. Looking at your evalbum page, I was thinking perhaps a taller high range might help, while keeping it a simple hi/low transfer case (rather than a three-speed or something). But I'll try and digest the ac motors thread. I still have 13 or so weeks before the house is finished and we can move in!

I'd like to work on an open-source 3 phase induction motor controller, but it is very much beyond my level at the moment.
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Post by Lectrickery » Thu, 04 Jun 2009, 23:28

Hi, Love all the work all you guys have so pasionately put into all your vehicles. I just have a quick question on Regen so I can understand it better.
When you remove your foot from the accelerator does the motor imediately start to slow Red Suzi?
If so wouldnt it be better to allow your EV to coast when not in accel and regen kick in when breaking only, say it was activated by the brake light circuit?
Sorry am new to all this but would love to have the funds to build my own and I believe AC is the way to go. In the mean time I plan to learn from others trials & triumphs and know what I am doing before I attempt a build.

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Post by acmotor » Thu, 11 Jun 2009, 07:22

Lectrickery wrote: .... When you remove your foot from the accelerator does the motor imediately start to slow Red Suzi?
If so wouldnt it be better to allow your EV to coast when not in accel and regen kick in when breaking only, say it was activated by the brake light circuit? ....


In the speed control open loop mode that I use at present, the red suzi drives just like an ICE with engine breaking. That is, only a setup limited amount of regen is used. This is limited by the amount of current I can push back into the SLA batteries (12A). It can push 60 or more amps but that will kill the batteries. (and stop fast - too fast for RWD brakes)
ICE vehicles don't coast unless you put your foot on the clutch. They are always slowed by the motor when you take your foot off.
Driving an AC direct drive EV with regen turned off lets you know what real coasting is !

But yes, for more regen braking, the top travel of brake pedal is a good source of control (prius does that).
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Post by Lectrickery » Thu, 11 Jun 2009, 19:56

Good to see the Forum pages are back again I was suffering withdrawals.

Is it possible to do Regen Brakes on a DC Motor?
Cause as I said so far AC looks like the way to go for several reasons that I can think of.
1) Faults in the AC controller cause the vehicle to stop. No chance of unintended full accelleration.
2) Regen Brakes give regen plus save brake wear considerably by the sounds of it. (my biggest fear is being in a DC EV with no brakes & no way to stop)
3) More control options all round with AC Motors and better Life Expectancy on motor.

Is there any real advantage in keeping the gearbox with AC or DC conversions? Are better miles gained from box or no box?

Sorry I have alot of questions but you seem pretty clued in to all this EV stuff & I just want to get it rite.

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Post by antiscab » Thu, 11 Jun 2009, 20:07

keeping the gearbox allows you to use a smaller/cheaper motor and controllre to achieve the same performance.
The resulting system is heavier and less efficient for the same power output.
If you have the money, ditch the gearbox.

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Post by acmotor » Thu, 11 Jun 2009, 20:32

Firstly, regen on a series wound DC motor can be done in a limited fashion. It is not common and is complex and unreliable if done by contactors (basically windings are re-arranged as shunt mode to run as a generator) Some intelligent controllers try it by accessing the field and armature separately.
It also typically damages the commutator by arcing, although compromise fixes have been made.
Even if it can be set up then the low voltage at low revs returned is of little use for recharging battery pack.
Some """regen""" as was used on forklifts is actually 'plug braking' (driven holt) not regen.
But then that is all DC .... don't go there IMHO I don't want to debate it ! There are threads on this and other forums if you must entertain DC regen.
antiscab wrote: keeping the gearbox allows you to use a smaller/cheaper motor and controllre to achieve the same performance.
The resulting system is heavier and less efficient for the same power output.
If you have the money, ditch the gearbox.

Matt


Matt, just ditch the "achieve the same performance" bit.
kW is kW.   You can't make a 1kW motor in an EV perform the same as a 100kW motor Image
Look at it another way.... if you need a gearbox (to change gears) then the emotor wasn't big enough !
The only time a gearbox should be required is to match the emotor torque /RPM to the EV requirement in the first place.
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Post by BjBlaster » Fri, 12 Jun 2009, 03:23

antiscab wrote:
If you have the money, ditch the gearbox.

Matt


Unless it's front wheel drive, because you'd need some sort of diff to replace the gearbox...
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Post by Lectrickery » Fri, 12 Jun 2009, 18:49

There must be some kind of Diff out there that can give you at least two gears like a high & low range just so your EMotor dont have to rev off its nut all the time and to extend the speed range. I was looking at a thing called a Split Diff found mostly in trucks but I dont understand them.
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Post by Thalass » Sat, 13 Jun 2009, 10:36

I hope to use that brake pedal method on my car. But also limited (10%? 20%?) regen when the accelerator pedal is lifted. I'm not a huge fan of the external pot regen control. (I've seen slider pots as a regen control)
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Post by acmotor » Sat, 13 Jun 2009, 18:02

Yes, some regen when pedal lifted gives natural driving feel as we are used to in ICE.
I also have concerns about live driver adjustable regen e.g. slider pot. The vehicles dynamics should remain consistant and predictable, particularly if another person drives.
Additional regen off the top of brake pedal is the go since we all expect to have braking if we press the brake pedal !
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Post by weber » Sat, 13 Jun 2009, 18:26

Prius is a precedent for two settings of accellerator-back-off regen. I think one feels "normal", i.e. like ICE, and other is only slightly heavier. This is the "B" gear on the auto-transmission-like shift lever. "PRNDB"? I suspect that rather than first part of brake pedal travel it may use low brake system hydraulic pressures to activate more regen. Anyone know?
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Post by acmotor » Sat, 13 Jun 2009, 19:18

The B does not change the emotor regen, it just tells the CVT to drag the atkinson cycle ICE up to higher revs. A bit like changing down a gear on a hill. (limited battery pack size being a factor)

The point is here that you have selected it (and can deselect) and it deselects if you stop so another person who gets in and drives will start from normal vehicle dynamics again (unless they select B)
Whilst it is selected the little punching mill (Ummm, sewing machine motor) makes more noise so you are aware you have B selected. (depending on the sound system level !)

You also cannot select cruise with B selected.

The operation of additional regen from brake pedal on a prius is smooth and subtle. I understand it is hydraulic pressure sensed and there are articles around where people play with the gain of this setting to get more or less regen. (leave it alone, toyota have it right already)

prius regen
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Post by arnolde » Sun, 14 Jun 2009, 00:41

In my Corsa, I want to implement adjustable regen with an additional hand lever near the steering wheel, like they have in passenger busses (retarder). Slight ICE-like regen when coasting, I wont mess with the brake pedal, but I do want a possiblity for the driver to optionally select more braking power if he wants to. Thats the only way to get max regen and min brake pedal usage, even in stop-and-go traffic. Drivers who are not aware of it, simply dont use it, its that simple.
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Post by acmotor » Sun, 14 Jun 2009, 00:49

arnolde wrote: ...... Drivers who are not aware of it, simply dont use it, its that simple.


I like that thinking at this stage until regen is seriously automated.
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Post by coulomb » Sun, 14 Jun 2009, 01:10

acmotor wrote: The B does not change the emotor regen, it just tells the CVT to drag the atkinson cycle ICE up to higher revs. A bit like changing down a gear on a hill.
OMG!    Image How crude is that? !! I suppose it's mainly compressing fuel-less air and tossing it out of the tailpipe. Plus a small amount of piston to cylinder wall (and other) friction.
(limited battery pack size being a factor)
Well, yes, exactly. Also crude. Yet the best that has been available to the mass market to date.

But that doesn't stop us from implementing a "B" gear and doing it right. Image We can say "it's like the 'B' gear in a Prius" and people might say "oh yes a friend had one of those, I know what you mean".
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Post by Simon » Sun, 14 Jun 2009, 03:16

Its not crude at all!
The only reason to even use the B gear in a Prius is on a long descent when you loose regen because of a full battery.

Personally I like the idea of regen being controlled purely by the brake pedal and 0% throttle being equivalent to coasting in Neutral.
The Vectrix has a good regen setup that should become the standard for motorcycles where the throttle controls regen.
Closed throttle is coasting. Twisting throttle forward is regen OR reverse if stopped. Very neat!

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Post by Squiggles » Sun, 14 Jun 2009, 03:43

I would have thought controlling regen with the brake pedal is basically as hard as adding another potbox attached to the brake pedal. A simple PIC based controller could generate any braking profile you like, or a set of selectable profiles for that matter.
As far as coasting is concerned I reckon you would get used to it fairly quickly, I guess it might add half a metre to your emergency stopping distance though.
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Post by Lectrickery » Tue, 16 Jun 2009, 18:25

I dont mind an almost full coast but I think if a vehicle responds more like an ICE car people will be more open to using an EV. The Pot on the brake pedal was exactly what I was thinking too but you would still want a controll circuit as I think I have heard in many cases that more than about 25% regen nearly throws you through the front screen or locks up the back end. I cant see any real case for 100% regen unless its a really large truck but still then I supose it would be a heaftier motor.
Isnt there some way to burn off the regen power even if the bateries are full so it is still used sa a brake support system without killing the batteries?
Ha ha and I dont mean a large row of 240V 100W globes on the back parcel shelf either.... Although would make sure people knew you were stopping (or blind them in the process)

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Post by coulomb » Tue, 16 Jun 2009, 19:04

Lectrickery wrote:Isnt there some way to burn off the regen power even if the bateries are full so it is still used sa a brake support system without killing the batteries?
Ha ha and I dont mean a large row of 240V 100W globes on the back parcel shelf either....

That's the thing about EVs; you are dealing with significant amounts of energy and power. Suppose you are cruising at 80 km/hr, using say 5 kW. So 100% regen isn't the 5 kW what you are using now; that's just what it takes to keep you from slowing down to 79 km/hr. Full regen is like 50 kW, or whatever peak power your controller and motor are capable of. 50 kW is 500 100W bulbs; the guy behind you won't just get blinded, he'll get a sunburn! Image

I've come across a similar problem trying to load my motor at home without too much danger. I thought of lifting 100 kg loads a metre or two, but it's just not enough. I thought of winching White Suzi up my driveway; there is about a metre from the bottom to the top. So the potential energy is m.g.h ~= 1000.10.1 = 10 kJ. Sounds a lot. But just to put a nominal load on my 7.5 kW motor means I'd have to raise the car in 10/7.5 ~= 1.3 seconds. I'd have to profile the acceleration so as not to snap the cable/chain, and to slow the thing to a halt at the end of it. Not sounding very safe, and I'd like to test it at up to 2xovervoltage (possibly 3) and 3x overcurrent. My mains supply is only up for 15A anyway, which is just 3.6 kW.

So maybe I need to put the motor and controller into White Suzi, such that I can still use the ICEage motor, but then I need to bring along a lot of batteries as well...

Significant power and energy levels.

Fortunately, you don't usually need to blow off regen energy due to a full battery for long, so you could maybe get away with a large brake resistor (think coils of glowing wire 6mm thick in the transmission tunnel or in the nose cone, where there is hopefully lots of cooling. But even then, if you happen to opportunity charge at the top of a long hill, you could exceed the capability of your system to dissipate regen energy.

You could say "well only charge to 80% if you happen to live at the top of a big hill", but you may have opportunity charging different to where you live. You might lend the car to your brother, who lives at the top of a hill when you don't. Etc etc.

So I'm thinking if the battery is full and regen is called for, do nothing. The user's foot will sink a few more mm to the mechanical brakes, and they are (pretty much) rated to take the vehicle's energy continuously. (Though some people do have problems with glowing brake components when descending long hills or mountains). But that's not an EV specific problem; you would have had the same problem with an ICEmobile.

For the maximum safety, it would be nice to make the amount of travel of the brake pedal in regen mode (where it could be ineffective if the batteries are full) as short as possible. Yet have a moderate range of regen, from very mild to about half. (Exactly how far depends on the vehicle; rear wheel drive should probably regen less than front wheel drive). And when the foot pressure exceeds that amount, it should "pass on" the pedal travel to the hydraulic system, in such a way that no possible failure could cause that not to happen.

Any mechanical types have a solution for that?

If we can make the regen happen in ~5mm of travel, is that safe enough?
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