Performance and cost between DC and AC -EV's

Technical discussion on converting internal combustion to electric
Goombi
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Performance and cost between DC and AC -EV's

Post by Goombi »

Can someone explain the advantage of AC against DC powered EV
What extra power it has --AC
What extra distance can AC travel
What is the advantage cost of building one (AC) as against DC
Which last longer AC or DC?
How safer is AC power.
Are AC components readilly available?
Are AC systems trouble free?
Are AC Regen-- as effective as claimed?

Is the world ready to abandon DC and go for AC?

Please do not answer this subject with possibilities maybe's or
could be's I am looking for truth and correctness I am sure this subject could answer many peoples questions and set them on a correct course to build an EV. May it be DC or AC .


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Post by Electrocycle »

AC does give you higher efficiency, depending on the motor used, and a high voltage AC system reduces the amperage requirement which means you have less loss in the cabling, and can use lower performance batteries with reasonable results.

AC motors have no brushes, which means essentially no maintenance at all - although the usual big DC motor brushes do last a long time.
The wider operating rpm range of most AC motors with VFD means you can more often do away with the gearbox which is better for overall efficiency.

The main problem with AC at the moment, as I see it, is that controllers are much larger, and much more expensive.
At the moment people are buying used industrial motor drives, which are not too expensive (usually slightly cheaper than a new DC controller), but this is not sustainable on a large scale. Once you need to buy new controllers, the cost is more than an expensive complete DC conversion.

The high voltage electronics and wiring is a safety concern for DIY people, but DC drives are already running fairly dangerous voltages.
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Post by woody »

Goombi wrote: Can someone explain the advantage of AC against DC powered EV
Hi Goombi, great question, I will answer as best I can.
Goombi wrote:What extra power it has --AC
There's a range of DC motors available, and a huge range of AC motors. I have seen 13 inch DC motors (Kostov), AC motors go up to massive sizes, much larger than a car. I'm sure DC motors do too.

I think in raw power-to-weight DC motors are ahead, see White Zombie, Killawatt, Current Eliminator.
Goombi wrote:What extra distance can AC travel
You are asking for truth, not maybe and possibly, I will disappoint you here I don't have 2 identical EVs one AC, one DC. That said, I think the AC has higher efficiency (90%+ except when stopped or nearly stopped) compared to DC (85% peak, 80%+ except when stopped or nearly stopped). AC also has regen which would help when you need to brake, maybe 10%.

I would say the AC would go 20% further in city driving, 10% further in flat freeway or economy trial flat circuit.
Goombi wrote:What is the advantage cost of building one (AC) as against DC
I think you have done very well on the DC to keep under $6,000 including the car.
I think Grant's Camry AU$15,000 is pretty usual for a DC lead acid conversion, maybe AU$12,000 is right.

The commercial AC solution, Azure systems from BEV quoted AU$8-AU$10K for an AC24 or AC55 + controller which is almost double the equivalent DC.

Industrial AC cheats a bit by buying second hand parts (usually), e.g. I think a4x4kiwi spent about $500 on the motor (2nd hand dealer) and $1400 (lucky on ebay) on the controller, $3000 on the (new, personally imported) batteries. He's also had to get a battery tray, custom driveshaft + motor mount, coupling and a bunch of contactors, I'm not sure how much all those extras were, a4x4kiwi may reveal the total later :-)

a4x4kiwi's system is approx power equivalent to the AC55.

You can buy the industrial stuff new, I think a4x4kiwi's stuff would be 15kW motor $1500, 30kW High overload drive, $8500?.

I think we can say the up-front costs can be similar.
Goombi wrote:Which last longer AC or DC?
The AC industrial stuff is designed to last for a long time, 20 years+. There are no brushes to wear out, the bearings need grease or replacement I'd assume roughly the same for both AC + DC.

The DC brushes aren't expensive to replace.

The DC stuff is also mostly industrial design, or a development of, I think, so unless the manufacturer is cutting corners to save money, the difference should not be that great.

I'd say there is no clear leader here.
Goombi wrote:How safer is AC power.
AC systems run off DC batteries, the commercial about 350V, the industrial about 600V.

I think there is an advantage for AC as people respect 600 volts, take it seriously, break up the pack into 48V safe chunks. You should do the same with DC, but many kid themselves and think it's "only" 100V.

The AC cables are smaller, less current this is less of a fire risk maybe?

Another advantage is that if a DC controller "hangs" at full throttle, it stays at full throttle, is an AC controller "hangs" the magnetic field stops rotating and the motor has a pretty strong braking effect.
Goombi wrote:Are AC components readilly available?
If you want new, then yes, if you want 2nd hand, you need to be patient on ebay :-)
Goombi wrote:Are AC systems trouble free?
I haven't heard of problems with either, except zeva's blown DC controller which I can't blame the controller for :-).

The AC industrial setup I think is very well tested in thousands of factories, the common DC stuff (Curtis) too, I can't see any difference here.
Goombi wrote:Are AC Regen-- as effective as claimed?
I think in stop/start or hilly terrain, yes effective. In the country on the flat, probably not a big help. acmotor will probably have some hard numbers for you from his sierra.

If you drive like a Hypermiler, then regen is not as big a help either.
Goombi wrote:Is the world ready to abandon DC and go for AC?
My little part of the world is :-)
Goombi wrote:Please do not answer this subject with possibilities maybe's or
could be's I am looking for truth and correctness I am sure this subject could answer many peoples questions and set them on a correct course to build an EV. May it be DC or AC .
I have tried to stick to this request as much as possible, apologies for any transgressions.

cheers,
Woody
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack
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Performance and cost between DC and AC -EV's

Post by Goombi »

Thank you Woody for comprehensice answer to my questions.
I feel that the conclusion and the choice beween AC and DC can only be depending on individual selection.
Personally i found all DC components at ready and the info on this chat room helped me to decide to go DC. My major item was the cost after doing stringent calculations (For Both Systems)I decided to DC
easy to obtain parts
Good info on chat
been done before
It matters NOT if its AC or DC the main factor is speed of completing one conversion and have it registered and on the road. Plus deprive the gov. to make money from us because we know how to use our money better then they can waste True?

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Post by acmotor »

Sorry, it is an old debate and will fade into history.
A bit like film vs digital cameras.

Goombi is correct, DC series motors suit many home conversions now but..
Cost is the only defendable case for DC at present. On all other fronts the AC (and brushless DC) is superior.

Build a DC conversion if that suits you. You will have an EV on the road and that is the important thing. But don't knock the superior technology of AC.
Goombi is on the road, with DC - get on with it everyone else !

Show me one commerical / potential commercial vehicle manufacturer who is going DC - and you will have found a loser. (or an old golf cart)

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Post by woody »

I think the reason that AC is the future is:

1) I think DC voltage is limited by the brush technology - more voltage -> arcing etc, whereas with AC everything is insulated.
This means DC will be low voltage -> high current -> more copper in cables + more losses (I^2xR)

2) AC induction is more efficient, approx half the losses (80% vs 90%). AC permanent magnet (DC brushless) is even more efficient.

3) The older technological problems facing AC technology have had better solutions in the last 10 years (solid state relays / IGBTs / mosfets / cheap, fast, reliable processors for sine wave approximation etc.)
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Post by Gow864 »

Woody Excellent posts. Goombi great questions.

Gow.
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Post by Gow864 »

Woody you said that BLDC is more efficient than AC Induction, do you see BLDC becoming more popular? Are there any BLDC motors around big enough for a small car?
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Performance and cost between DC and AC -EV's

Post by AMPrentice »

I see DC as a winner for 3rd world countries where contactor controllers can be repaired on the side of the road.

I see DC as a cheap and quick solution to getting on the road

I see AC as the ultimate running gear for an EV especially as prices drop or production rises. Yet still for the moment and most people its out of reach.
Its a matter of DC around 12,000AUD vs AC around 25,000AUD.

Yet one Jp man has been at it with a permanent magnet motor that is simpler than available and supposedly a proven performer and has 40,000 unit order finally after years of investor setbacks.


Minato Motor
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Post by Johny »

Of the Minato Motor:
"With the help of magnetic propulsion, it is feasible to attach a generator to the motor and produce more electric power than was put into the device. Minato says that average efficiency on his motors is about 330 percent."

Oh dear...the laws of physics get ignored again.
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Post by acmotor »

Come on guys ! Image

At least Mr Minato is not claiming perpetual motion, he goes one step further and claims power for nothing !
Cleaver man. He will scam a lot of people - and banks ! Image

He would be better off just producing a 100kW, 1kg, 99.99% efficient motor. That WOULD be an invention.

Angled rotor magnets have been a common design feature of BLDC servo motors (correctly known as synchronous 3 phase AC) for 30 years or more to reduce cogging.
Manufactureres such as Parker (US) have produced some quite free wheeling motors (almost as good as AC induction - the most free wheeling of motors).
    
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Post by woody »

Gow864 wrote: Woody you said that BLDC is more efficient than AC Induction, do you see BLDC becoming more popular? Are there any BLDC motors around big enough for a small car?
These brits have some. Small enough to run two in a small car.

I also heard at the Sydney AEVA meeting that Mars is just about to release a "double-pancake" motor which is two of their largest BLDC motors on the same shaft.

I'm not sure if BLDCs are heavier than the equivalent ACIM. I also haven't seen a pancake ACIM (until I found Raser on google).

ABB makes larger PM AC motors (frame sizes 280 + ? - I.E. huge 2 foot diameter!)

cheers,
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Post by acmotor »

Nice links.
What more can one say ?

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Post by Goombi »

This article will prove that i am not biased

http://www.metricmind.com/
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Post by antiscab »

Goombi wrote: This article will prove that i am not biased

http://www.metricmind.com/


Goombi, how does that prove you arent biased?
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Post by Goombi »

Why don't you read the article about AC power very interesting reading.

I have said here that If i could afford to convert AC I would do it. There is a lots of unknowns here The Manufacturing people that are making AC EV's have the resources to research. What is available to us is the leftovers. Most AC conversions are not matching Lot of conversion is a quesswork and I will rather wait another year or two. The unknown is really for people that have true experience here. There are few and they are proving it. For layman like me I am not good enough. and i don't like to wenture into unknown expensive areas.
I made the right decision. The ac converters have also made the right decision. As woody said we are here as one but we are all different.

There are definitely two lines of tought between AC and DC.

So long as we don't make them a battleground.....
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Post by Rob M »

"So long as we don't make them a battleground..... "
Well said Goombi!
This forum is part of the AEVA and as our constitution clearly implies, we should all be encouraging ALL types of electric vehicles, from golf carts to racers.
This is no place for negative comments like "Show me one commerical / potential commercial vehicle manufacturer who is going DC - and you will have found a loser. (or an old golf cart)", particularly if they make someone feel even slightly discouraged from venturing into something electric just because it is not the ultimate.
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Post by Electrocycle »

There are a lot of commercial electric motorcycles using DC motors.
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Post by Gow864 »

An EV is an EV. what reasons do we have for not celebrating another EV hitting the road. AC-DC WHO CARES! It's an EV. I really think that the AC nuts here need to pull their heads in a little! Unless they are chasing some form of elitism.

Rob M your "loser" statement say more about you than anything else. I'm guessing that you are happy to see a car stay ICE rather than go DC.

Another point. As far as I can see most of the AC nuts are still "Planning", spewing out equations and spreadsheets like crazy, but doing nothing. PUT UP OR SHUT UP!

Goombi Be proud! you have an EV, registered and in daily use. Something most of the AC nuts here dont!

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Post by antiscab »

Gow864 wrote: Rob M your "loser" statement say more about you than anything else. I'm guessing that you are happy to see a car stay ICE rather than go DC.


Im pretty sure u mis-read robs statement. didnt read that way to me.
Rob has put (and owns) more EVs on the road than anyone else i know of.
All of them DC.

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Post by tassie_tiger »

Gow864 wrote: Goombi Be proud! you have an EV, registered and in daily use. Something most of the AC nuts here dont!



Something most of us don't, whether AC or DC... well done Goombi.
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Post by Rob M »

Gow864 wrote: An EV is an EV. what reasons do we have for not celebrating another EV hitting the road. AC-DC WHO CARES! It's an EV. I really think that the AC nuts here need to pull their heads in a little! Unless they are chasing some form of elitism.

Rob M your "loser" statement say more about you than anything else. I'm guessing that you are happy to see a car stay ICE rather than go DC.

Another point. As far as I can see most of the AC nuts are still "Planning", spewing out equations and spreadsheets like crazy, but doing nothing. PUT UP OR SHUT UP!

Goombi Be proud! you have an EV, registered and in daily use. Something most of the AC nuts here dont!
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Post by Rob M »

Woops clicked on the wrong tab!
Gow864, I was actually quoting AC Motor's "loser" statement
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Post by Gow864 »

Hey Guys, I'm not trying to get into anyone. Really An EV IS an EV. realistically it doesn't matter how it's done. I am VERY anti Elitism! In any form. Maybe I got hold of the wrong end of the stick. If I've upset anyone, then I am sorry, it certainly wasn't the intention.

I think that an interesting excersise for someone it to turn the benefits of AC into $'s Over say a ten year period of operation (average suburban commuting) how much better off (financially) would you be using an AC setup as opposed to a DC? Woody Interested?

Apologies again.
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Post by acmotor »

Come on guys, actually READ the posts. Image

I wave the flag for ALL EVs. (almost) Image

I congradulate all - you search my posts. Image

I suggest to plenty of people - go DC for 1st up, low cost, simplicity.
Fair but honest.

But if I am asked which I consider is the best system AC or DC I will say
and justify
and explain
and challenge you if you think otherwise !

My question stands re finding a commercial vehicle manufacturer who is going DC. (not just BLDC if that clarifies) Any takers ?
This is not meant as a treat or insult, just a sign of advancing technology.
The point is that if the commerical world, with far more skills and knowledge than us has gone AC, then we will be left behind.

Some people insist that lead acid is better than lithium.
Others insist that DC is better than AC.
They all have their place, however, if EVs are to rule the world they won't be lead acid DC !

From an AEVA point of view, I would also hope for us all to strive for the best technology, budget always being a limit.

How many times must I repeat, all EVs are better than a hummers !

Rob, check out some of the links in this thread, you may be inspired.
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