Soapbox on regenerative braking

Post by **Squiggles** » Fri, 29 May 2009, 23:18

My little comment on gear changes.
In an ICEage car the synchros work hardest on down changes where the rotating mass has to increase in speed, they work less on an up change as the rotating mass has a natural tendancy to slow down.
So will that be the same in an EVolved car? ON a down change still have to spin the motor up, more mass more effort more wear most likely.
On an up change, will the motor slow sufficiently, not likely as there is a higher inertia so more wear I guess so.

I suspect there is going to very few gear changes in the EV once one gets used to driving so it is very likely to balance out the issues.

Lastly, how much easier is it to remove/replace the transmission in an EV? You won't even get your hands dirty

Post by **Nevilleh** » Mon, 15 Jun 2009, 14:37

Series dc motors don't do regen! Is that true, or is it just a bit hard? It seems to me that a dc motor should act as a generator if you can get some current into the field winding, but how to do that?
Maybe an extra "motor" such as a BLDC might be a useful addition. It could be configured as a generator when braking is required and add a bit of power when not. But where do you get a BLDC with enough grunt to be useful and not cost more than the battery pack?
I know, I know, just use ac in the first place and the problem goes away!

Post by **coulomb** » Mon, 15 Jun 2009, 15:12

Nevilleh wrote: Series dc motors don't do regen! Is that true, or is it just a bit hard?

It has been done, and it's not all that hard, but clunky. (Edit: plus, there is the possibility of reducing the life of your motor through increased commutator arcing.) You need at least a contactor, so it won't be silent and smooth as it is for AC or sepex DC with the appropriate controller.

This very old article by the designer of the Zilla controllers is arguably the best summary of the state of play:

http://evcl.com/regen/

So he did get it to work, but decided it's not worth the effort.

However, separately excited ("sepex") DC motors are much easier to work with for regen. To minimise commutator arcing, however, your controller needs to know your motor pretty well. Goombi's range of Chinese-made DC systems are now available with regen.

Post by **Goombi** » Mon, 15 Jun 2009, 17:53

Hi Regen motor are of a different winding and are available freely from me from Chine for 48- 144 volt and 4.5 kw to 11 kw
ipMCSep Separately Excited Electronic Motor Speed Controller

Description ipMCSep series programmable controllers provide smooth and seamless regenerative control of separately excited motors. An advanced MOSFET power section, combined with a sophisticated microprocessor provides very high efficiency, quiet operation and reduces motor and battery losses, ipMCSep series controllers are designed for wide application
8.5KW/96V/2800RPM MOTOR（Separately）
8.5KW/ 96V CONTROLLER(Separately)
96V WATERPROOF CHARGER
DC-DC CONVERTER
PROGRAMMER
COUPLER
Sea Freight
Total value: $2.217.00 USD

Post by **acmotor** » Mon, 15 Jun 2009, 18:40

Nevilleh wrote: Series dc motors don't do regen! Is that true, or is it just a bit hard? It seems to me that a dc motor should act as a generator if you can get some current into the field winding, but how to do that?
........
I know, I know, just use ac in the first place and the problem goes away!

Yes, series motors don't do regen.
They can be made to do some regen by making them shunt wound on the fly (also known as separately excited, i.e. armature and field placed in parallel) This can be by re-arranging the fields or having an additional winding.

So DC regen can and is done.

The difference between AC and DC regen comes in 3 factors.

1) efficiency of the regen action. In AC the regen is same efficiency as motoring. No power is used in exciting the field and AC motor is likely more efficient in the first place. (it would be interesting to see a graph of regen torque and efficiency vs RPM for a DC motor)

2) The available regen torque goes down to nearly zero RPM in an AC motor. In a DC motor, regen is OK when the RPM is high enough to generate enough voltage to feed current back to the battery pack.
Re-arranged fields means the armature voltage is quite low wrt battery voltage so regens OK at higher revs but not enough volts at low revs.

3) rotational friction of the motor shaft. Brushes cause drag in a brushed DC motor.

All this is without entering the topic of Permanent Magnets and BLDC motors (AC anyway).

Hey, I'm biased AC is king !

Post by **Goombi** » Tue, 16 Jun 2009, 00:21

My reply to King of the AC Motors .

Promote EV. in any form the easier to make the better
The cheaper to make the better still.
promote 2 cars in a family-- One electric
As i said to acmotor sometime back. If i would find AC Conversion to be
Cheaper
Easier to make
Safer
then i would make one. AC conversions are purely for AC specialists It is not that they are better then DC its just that people like to show off saying seeee i can make AC ---- They say I am smart but i don't travel further ot faster and it cost me more then 7K but i am cleaver making or trying to make AC,
I keep promoting DC series or regen types and thare are more the 2 doz in production as we speak others already on the road..
Amazingly not much came from memebers here. This is a Transit area for information and often not very smart..... lots of Blah Blah not much conversion. How many AC cars are been built and registered and running without touching for 6 month.??? Give me the ststistics
AC motor
More write up in my website about Regen

Post by **acmotor** » Tue, 16 Jun 2009, 01:36

Be patient ! All good things will come to pass.

I promote the 2 car family. 1 x DC, 1 x AC !

I am not negative about DC, just positive about AC advantages !

Here me yet again....
What I have said for many years...
If you want low cost, simple conversion go DC. If you want the best, go AC. I can't be fairer than that.

Looked at a tesla motor lately ?

Post by **Squiggles** » Tue, 16 Jun 2009, 01:57

Looked at the Tesla price lately?

Post by **Squiggles** » Tue, 16 Jun 2009, 02:00

Goombi, let the AC fans have their dream, just don't mention that what they are really playing with is Alternating DC!!

Oh and considerable weight.

Actually it is all good, the experimentation, the building and testing is all adding to the general body of knowledge. In the end that is what will push the movement forward.

Post by **Goombi** » Tue, 16 Jun 2009, 02:16

What makes AC to be the best. Are you on c---BIS?
Please explain how AC will outdo DC make comparisons---

Post by **Richo** » Tue, 16 Jun 2009, 02:47

Even a hippy on c---BIS would understand the benefits of AC.

Post by **a4x4kiwi** » Tue, 16 Jun 2009, 02:52

LOL "...playing with is Alternating DC"

You bet, all the way to 132Hz (or 200Hz for acmotor's experiments)

Post by **Hemonster** » Tue, 16 Jun 2009, 02:54

Squiggles wrote: Goombi, let the AC fans have their dream, just don't mention that what they are really playing with is Alternating DC!! Oh and considerable weight.

you do realise how silly this sounds don't you, this means that all DC motors are in effect AC motors!!! the direction of DC current changes as it "mechanically" commutates whereas AC motors "electrically" commutate ... but I have to take it that you weren't being all that serious anyway.

As for weight, I think AC conversions need to be distinguished from AC "industrial" conversions, that's where there could be a power to weight difference significant enough to argue merit - there are plenty of examples of super light weight AC motors/controllers that outperform DC, tesla being one of them.

Goombi, you have a point about affordability to Joe average converter - and yes most converters have chosen the path of DC because it has been done before, and it works, and it is cheaper.

AC can be expensive, but it doesn't have to be REALLY expensive especially if you go the AC industrial route, but that road is paved with challanges. However by far the bigger cost in dollars and weight in ANY conversion is the battery pack. 50-80kgs difference in motor weight is small compared to the 300kgs of batteries you have to lug around to get decent range, or pay for more exotic sorts. The argument very quickly shifts to Lithium or AGMs!

But like anything there are pros and cons which can be argued for any motor choice. I think AC or DC is more about the personal choice, technical abilities and what challenges the individual. I would say that Sepex is a bit of an oddity, and in the same sort of predicament as AC in terms of adoption, nothing beats the series DC for adoption (there are already 3-4 in little old Christchurch NZ alone). Like many in this thread has said already, sepex may not be worth it if all you're getting is regen capability (at the cost of lower power and increased controller complexity/cost) ... but this comes at the cost of additional/constant losses in the field, and also limitations on the size of the motor to deal with those losses. I like the idea of sepex, but AC is just really elegant and its my personal choice.

(I sound like a panadol advert ... "it's my choice" ...)

Post by **Goombi** » Tue, 16 Jun 2009, 04:14

So now AC is really elegant hee haa

Sorry Kiwi i didn't know you were in fashion business

Post by **acmotor** » Tue, 16 Jun 2009, 04:51

Squiggles wrote: Looked at the Tesla price lately?

But there you go.... If I actually had a choice between a getz with series DC and lead acid or a tesla with lithium (I don't $$$) I know which on I would go for.
Please, that is not meant to be derogatory, just honest.
Surely I can say that without be accused of being anti EV ?

As far a statistics go, does over 1,000,000 priuses count ?
Ok, only hybrids but man that emotor is a technical masterpiece that we should all strive for. (and AC)

The AEVA represents all electric vehicles. Hybrids, trains, planes? and boats etc included.

Again, if you want simple low cost go series DC. (for now at least)

BTW, Check out evcomponets.com AC55 motors.
http://www.evcomponents.com/ProductDeta ... Code=H4820

IMHO

Post by **Richo** » Tue, 16 Jun 2009, 05:13

----------DC System--------
Motor 8.5 Kw
DC-2800 rpm
F series
$669.00 USD
Sea $40
air $706
WEIGHT 80 KG

CONTROLLER 300a for/rev contactor fuses wired complete
$575.00 USD
Air $180
WEIGHT 12 KG
-----------------------------

-----------AC SYSTEM---------
AC Induction motor 7.5kW
0-4500 RPM
AUD $653.40 INC GST **
No sea
Freight $Local pickup
WEIGHT 52kg

CONTROLLER 1238-75 96V 550A
USD$1000
Air $180
WEIGHT $? Prob around 12kg or less as well.

**Motor requires additional rewind for 96-110V AUD$800.

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

So DC USD$2130. (~AUD$2660) Air freight
And AC AUD$2930

DC system all imported.
AC system motor available throughout Australia.

DC system likely no local support for motor repairs.
AC system motor rebuilt in most light industrial areas in Australia.

DC old style mechanical commutation with brushes
AC Electrical commutation with no brushes

DC meets no known local regulations
AC meets CE and MEPS standards

DC inefficent
AC efficent according to MEPS regulations

DC Heavy 80kg
AC light 52kg

DC exposed internal current with possible shorts
AC Totally enclosed shorts not possible

DC 4-wire connection
AC 3-wire connection

DC limited/no regen possible
AC full regen possible

DC motor output limited to initial design.
AC same motor can output 90kW with a controller change/upgrade.

Yeah AC will never beat DC.
Please let us all bury our heads in the sand

Post by **Goombi** » Tue, 16 Jun 2009, 05:38

You keep on Churning -- and i keep on building and selling DC-EV components. People with interest and with large workshops in 4 states going for building small Barinas/ Suzuki type EV cars and specials on order.. for the metropolitan travels. While you admire the fashionable AC.

.Richo. Taking the truth out of concept is not smart

Post by **Squiggles** » Tue, 16 Jun 2009, 05:43

Guys don't get me wrong here, I personally like the idea of AC motors. Even studied them 30+ years ago while I did my electrical trades training so I am at least familiar with them. I am fully supportive of you guys experimenting with wiring changes and over driving industrial motors, totally agree that these things are possible because of the different application and work duty cycle.

The only problem I have is that some people get a bit carried away.
I mean you do have to consider the down side of the story like more complex control technology, much higher battery voltages, higher skills required to implement.

I can remember back to the days when we first moved from carburetors to fuel injection, no dispute that FI was superior but every mechanic could fix a carburetor. In the same vane DC systems are relatively simple compared to AC systems. I reckon there would be plenty of auto electricians out there that could have a reasonable shot at fixing a DC motor after all most ICEage cars have one on them and they do (or used to) get repaired.

I am sure in the fullness of time, when somebody in the EV world designs and builds a VF drive intended for EV use rather than industrial and a major motor manufacturer starts to manufacture AC motors designed for EV use and releases them to the wider market..... AC will become the best option with all things considered. That time has not arrived.

Post by **Squiggles** » Tue, 16 Jun 2009, 05:58

Just for the fun of it

Richo wrote: ----------DC System--------
Motor 8.5 Kw
DC-2800 rpm
F series
$669.00 USD
Sea $40
air $706
WEIGHT 80 KG

CONTROLLER 300a for/rev contactor fuses wired complete
$575.00 USD
Air $180
WEIGHT 12 KG
-----------------------------

-----------AC SYSTEM---------
AC Induction motor 7.5kW
0-4500 RPM
AUD $653.40 INC GST **
No sea
Freight $Local pickup
WEIGHT 52kg

CONTROLLER 1238-75 96V 550A
USD$1000
Air $180
WEIGHT $? Prob around 12kg or less as well.

**Motor requires additional rewind for 96-110V AUD$800.

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

So DC USD$2130. (~AUD$2660) Air freight
And AC AUD$2930

DC system all imported.
AC system motor available throughout Australia. (Mostly Imported)

DC system likely no local support for motor repairs. (Expect better motor repairers can handle them)
AC system motor rebuilt in most light industrial areas in Australia. (Bit exaggerated but I get your point)

DC old style mechanical commutation with brushes
AC Electrical commutation with no brushes

DC meets no known local regulations
AC meets CE and MEPS standards (That is until you rewire them)

DC inefficent
AC efficent according to MEPS regulations ( in comparison to ICE efficiency is this significant??)

DC Heavy 80kg (check you figures 14kW Kostov is 43kg)
AC light 52kg

DC exposed internal current with possible shorts
AC Totally enclosed shorts not possible (do you really believe AC motors do not suffer shorts??)

DC 4-wire connection (or maybe 2)
AC 3-wire connection (or maybe 6)

DC limited/no regen possible
AC full regen possible

DC motor output limited to initial design. (true but usually adequate if you buy the right one)
AC same motor can output 90kW with a controller change/upgrade. (Also true but not needed if you buy the right one...oh I forgot you have to modify them...because the right one isn't available)

Yeah AC will never beat DC.
Please let us all bury our heads in the sand

All good fun, lets get more EVs of any flavour on the road

Post by **Goombi** » Tue, 16 Jun 2009, 05:59

Well said Squiggles.Timing is the main factor..
I can get AC- motors --10-18 hp 2940 rpm with controllers( 650 amp)
Matched and synchronised and bench tested No guesswork. all wired Just install and plug it to batteries. how much? send me PM.. You wouldn't want to know

Post by **Richo** » Tue, 16 Jun 2009, 07:07

Squiggles wrote:I mean you do have to consider the down side of the story like more complex control technology, much higher battery voltages, higher skills required to implement.

The controller just has a simple wiring diagram like the DC ones.
The controller example I gave is 96V so no more than Goobi's DC.
Skill level is the same for both.
Seriously why is the example I gave any more complex than a DC system?
The AC controller also adapts to what ever motor you put on it.
So you are not locked into buying any particular brand of motor.
So in all reality if you can wire up a DC controller you can wire up the AC controller.

Squiggles wrote: I am sure in the fullness of time, when somebody in the EV world designs and builds a VF drive intended for EV use rather than industrial...

The controller example I gave is intended for eV use.
Did you read the spec sheet?

CURTIS wrote:"Designed for use as a traction controller for On-road electric and hybrid passenger vehicles"

You can't get much more specific than that!

Goombi wrote:Please explain how AC will outdo DC make comparisons---

Goombi wrote:.Richo. Taking the truth out of concept is not smart

I explained.
I made comparisons.
If you don't like the answer then you shouldn't have asked.

Post by **Squiggles** » Tue, 16 Jun 2009, 13:50

There you go I should have read closer, when I saw Curtis I assumed DC controller

I agree wiring up the controller is no more difficult, but inside them is a different story. VF drives are significantly more complex.
Also judging by the posts on this forum (in relation to industrial drives) setting them up for optimum performance is not a trivial task...apparently some DC controllers are not so easy either.

Actually speaking of skill levels, it just occurred to me that if you are dealing with voltages above 32V you are probably obliged to engage the services of a licenced electrician...that would be worth investigating.

I can just see it, car in accident, the barbecue gas cylinder starts leaking, fireman sprays some form of conductive foam on it, gets electrocuted some how, court says "who did the wiring".....not sure "it was like it when I bought it" will be a good enough answer

Post by **Gow864** » Tue, 16 Jun 2009, 14:06

I suppose that you've all seen these AC induction would the 18hp push a Barina along?

Post by **Nevilleh** » Tue, 16 Jun 2009, 14:55

Hah! ALL EVs are propelled by DC! From the batteries. And ALL motors are AC!
From the VFD or the commutator.
So what are you lot arguing about?

Post by **Hemonster** » Tue, 16 Jun 2009, 15:16

And I thought this thread was about regen ...