Another newbie joining the EV enthusiasts ranks

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priit
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Post by priit » Sun, 01 Jun 2008, 00:11

Hello,
First to introduce myself, My name is Priit and I come from Estonia. I moved to Brisbane about 2 months ago with my wife and we are still trying to settle here and see how it goes. Currently we are on a 3 year student visa and if things work out we will apply for permanent residence Image

OK on to the EV enthusiasm now. While I lived in Estonia I looked into converting a car there to electrical for a little while, but since we have like 3-4 months below 0 temperature there and it occasionally got to below -20 it seams alot of hassle to keep the batteries heated to keep them alive. I do know there were couple of people who actually still ocnverted their cars there, but the batteries were a major problem and seam to die very often still. So I kind of shelved the idea for a couple of years.
Now that I moved to a place where sun always shines and heating in the car is only needed to keep the windows dry occasionally, I figured I would resurrect the idea.
Now the hard part is that I am somewhat Mercedes fan. I have owned 3 old Mercedeses so far and I have loved the way they drive and the comfort of driving them, so I want to convert a merc to electric. I know they are not the most suitable because of their heavy weight and being mostly automatic and lots of electonics and electrical stuff in them. But from my perspective, I will not start to work on the project if I would not love to drive the car in its current state, so the project is only to improve it.
So I have been reading alot on the web and doing some calculations to determine what would fulfill my needs and wants from the car.
I can not start working on the project before I get a job here, so I have plenty of time to work on the planning now until I find a place to work.
From my current plans, I would like to convert a Mercedes 300CE, it is a very beautiful coupe that was made from 1988 to 1996 on a W124C body and is a thrill to drive.
I would like to do a direct drive and dump both the engine and transmition. I would need to swap the differential to something with about 8 or 9 to 1 ratio for that. I want to go for AC motor but have not yet decided on the batteries. There are some more rough edges to work out on the paper still and then when I start to put money on the table for it I will definitely ask for alot of advice from all of you here.
I have looked but have not found any that type of Mercedes-s converted so I am really not sure who to ask advice from ot to take as a good example, so I will try to figure most stuff out and ask if I am not sure.

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Post by acmotor » Mon, 02 Jun 2008, 07:10

Hi Priit, Image

At last, somebody with class in their vehicle choice !
Not a charade or a getz but a 300CE !

Just means a bigger motor and more batteries.
Electric heated leather seats takes on a whole new meaning !!!!

BTW, why are you thinking of such a high diff ratio?
What is the normal ratio ?

iMiEV MY12     105,131km in pure Electric and loving it !

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Post by priit » Mon, 02 Jun 2008, 17:04

acmotor wrote: Hi Priit, Image

BTW, why are you thinking of such a high diff ratio?
What is the normal ratio ?


With direct drive the higher ratio will mean that the electric motor will be able to run at higher RPM for the most of the time. From what I understand at lower RPM the motor will draw more current to get the torque. And I will need a bigger motor if I want to get any acceleration with so low RPM? I may be mistaken there so correct me if im wrong.
From what I gather it will help reduce the current draw and since the AC motors love a little higher RPM for optimal. With 8-1 ratio in the differential, driving at regurlar city speeds would keep the RPM of the motor at a little over 4000. and for Highway speeds if the motor can go up to 9000 RPM-s, then the car would move at 130km/h which is More then I need. I figured if I want to drive from Brisbane to Gold Coast, I will need to be able to go up to 110 km/h on the Motorway.

Mercedes made 6 different differential ratios for 124 body line.
2.24
2.56
2.82
2.87
3.07
3.27
In the 300CE models they used 2.87 and 3.07 mostly, though all those have same outside parameters so you can just pop one out and put another in there.
I figured if I put the 3.27 (mostly was used in 124 stationwagon models) one in there. The motor would only get up to 1500 RPM in city driving and 3700 RPM for going 130 km/h.
There are also differentials made for Mercedes rally cars that have 5-1 ratio Those would get 2500 RPM for city speeds and little over 5600 RPM for 130 km/h

I use 130 km/h as a marker so that I leave over 10% buffer at the end of what I need as not to run the motor at its limit.

So swaping the differential to ratio 8-1 would be probably close to like leaving the gearbox in there with only second gear or so. However will make things easyer, since I will not have to worry about the auto gearbox or look for one of those rare manual gearboxes and then end up with alot of extra weight in there and still checking the gearbox oils. Looking at the size of the Mercedes gearbox, I might be able to put the motor at the place where the current gearbox is leaving me more room for the batteries under the hood.

So if any of this does not make sence or I have understood something completely wrong please let me know.

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Post by antiscab » Mon, 02 Jun 2008, 20:14

Hi Priit,

The warp9 motors aren't meant to be run at 9000rpm. from what i read 6000rpm is about their safe continuous limit.
However, with that kind of setup, you wont be able to get to 130kmh anyway.
The max voltage you can put across the armature windings without causing significant arcing is 170v.
to maintain 110kmh on a vehicle of that size requires 15kw mechanical.
With the 170v limit at 6000 rpm you will be able to apply 200A and only have a max power of 27kw.
at 9000 rpm max current would be 128A, power available would be approx 18kw.
so with the 5:1 ratio, your conversion is still doable, but high end acceleration will still be very lethargic, though possible.

paradoxically, if you used a warp 11, the available power at 6000rpm would be even less.

you will also need to run a high voltage battery pack (which means a high voltage controller) to get 170v under load.

of course if you weaken the field (by reducing the current flowing through the field windings) you can improve the amount of high end power available.

The continuous current rating of both the warp 9 and warp 11 is 200A. So you will need to ratio so you don't need more than this continuously.

just a few things to consider.

Matt

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Post by priit » Mon, 02 Jun 2008, 20:50

Ok, I think I did not make myself that clear but currently I'm not considering a DC motor for conversion so Warp9 and Warp11 are both DC motors. I am going for the AC motor which have higher RPM and use over 300 volt batterie pack. I know the AC motors and controllers are more costly but I believe this is the way to go and I will get regenerative braking without extra hardware. I know the building costs will be higher.
Currently I have been looking at about 5 different AC motors that have been used for EV-s, I am really interested in AC-150 Gen-2, since it appears to be better then my requirements except for the price. according to its specs it could run 50 kW continuous at 8,000 rpm and Efficiency: 91% peak (50 kW, 9000 rpm), so for the Motorway speed limit being 110km/h with 8-1 differential my motor would be doing 7,850 RPM at that speed.
I also have been looking at the Siemens 1PV5135-4WS14 motor, which has max RPM at 10,000 and seams to be all I need, I have not got any idea of its price though. Rest of the motors on my list have a little less power. My concern also is that it would still accelerate reasonably from the standstill. I dont need the 7-8 sec acceleration that the 3 liter ICE engine provides, but I would like to get it below 16sec from 0-100km/h
However if you can point out some flaws in that plan, please do.

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Post by antiscab » Tue, 03 Jun 2008, 00:09

ah, yes for that, a higher ratio would be better.
looks like a good conversion.
your 0-100 in 16sec target is very achievable.
btw, what kind of budget are you looking at?
what kind of batteries were you thinking of using?
your conversion is starting to sound better and better.

Matt

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Post by priit » Tue, 03 Jun 2008, 01:19

I was hopeing to keep the budget below 25,000 AUD, but looking at the prices of most components, this does not sound very realistic, so unless I get some major discounts or the prices take a major fall by the time I start buying things, I am afraid I will go over the budget or have to compromise on some stuff. I still believe I will get a great car out of it :)

For the batteries, I have not yet made any decisions. I have like 15 different batterie options on the table here.
On one end, I figured that if I take really good motor and controller and spend most of my budget there I will have very little left for batteries and charger, so I will get a set of deep cycle led batteries probably gel ones and drive with them until they die and by that time can replace them with Lithium ones.
On the other end, I could try to get everything else a little cheaper and maybe afford a set of Lithium batteries, but that would mean that the batteries would take over half my budget :(
Looking at my current state and the amount of numbers and drawings in my scetchbook, I think I will not make the decision on that until I actually order the motor and controller.
From what I figure, the motor and controller are pretty much permanent and never to be replaced on the car, so once the car dies they can be moved on to the next car project, so I would want the best I can get there. However batteries are like the maintenance part of the car, that you need to change after couple of years, so if I cant afford the best at the first build, I can rectify the problem in couple of years since I will need to repalce them anyways.

However I will need to get good enough batteries that I can do at least 80-100km on a charge. The regenerative breaking will help a little but the weight of the car will work against me there. The drag coefficient on 300CE is about 0.29 and frontal area is 16700 cm².
Since I hear that batterie prices drop over time I only try to make calculations based on what I need and what I would want and try to mach the results to available batteries.
The ideal solution would be to get Lithium batteries that would take me 170 km on a charge. This way I may sometimes take longer trips and do couple of trips without need for recharge in between, but those batteries would cost a fortune. So realistically I would need 80 km and a little over that would be just great :)

Priit

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Post by antiscab » Tue, 03 Jun 2008, 01:46

yes, staying below $25k will be a challenge, and impossible if this includes the cost of the donor vehicle.

to get 100km range you will need around 20kwh of battery capacity for a car of that size.
have a look at http://www.waeva.asn.au/batrun_tutorial.htm
in particular, look for a link "spreadsheet - batteries"
that spreadsheet is up to date from an engineering standpoint, but the prices are way way way off:p

for some of the batteries the capacities are corrected for peurkert effect.

im not 100% on the prices for lead, maybe someone who uses them can pipe in, but i recently bought a 22kwh (288v@90AH) lithium battery pack and it cost me about $13k, plus another $3k for BMS and charger. it weighs 270kg, and has a max power of 63kw if you keep cell voltages above 2.5vpc, or 110kw if you push them as hard as they will go.

since it will be a while before you get to the stage of buying batteries, you could probably wait for the next big group buy. hopefully prices would have come down a bit by then, even if just due to increased order size.

I would agree that ordering your drivetrain first, batteries second is the way to go. Batteries don't like sitting around for months on end.

Matt

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Post by priit » Tue, 03 Jun 2008, 03:59

I know it is a challenge, but I also know that if the project will not fit in the budget, it will still be done, just will take a little longer time and maybe couple of compromises. The donor car is not in that budget so the 25,000 is for the parts and modification costs.
I do plan to do most of the work myself, but there will probably be some things that I cant do so will need to pay to get those done.

To get 100km range according to my calculations I will need 22.5kwh, so you are correct there. 270kg is very light for this kind of battery. By the time I get to the point where I will need to decide on the battery, I might need to make an extra budget and try to go for the Lithium ones still, since with so light battery pack I will not increase my car weight almost at all over its factory empty weight, since the 3 liter engine and automatic 4-speed transmition weigh about 290kg and with the rest of the stuff I can through out and the electric motor and controller weighing about then 80-100 kg together it would add less then 80kg to the car weight or even less depending on the stuff that I can through out without compromising comfort or safety.

If I need to keep to the original budget at that point and go for cheaper batteries, then the weight would increase and I might need to throw out the rear seats to register it as 2 persons car, so the extra weight from led batteries would not overload the cars max factory weight. The car weighs 1420kg and max weight is 1920kg so I do have some room to play but the ~85kg reserve per person in car limits it still. According to factory papers the car has 4 seats.

Priit

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Post by antiscab » Tue, 03 Jun 2008, 04:40

yes i had (have) a similar experience with my budget, i too started with $25k, but now ive had to push that out to $33k.

at least if you start out with lead, you will know what the car will handle like with lots of weight, and how usable it will be with just 2 seats. lol you could probably then upgrade to the same battery weight in lithium and have the highest range ev in Aust:p

at least with the 160kg weight you can add, you have some breathing space.

btw, how did you estimate the 22.5kwh/100km?
i estimated it by taking the L/100km and multiplying by 1.875 to get kwh/100km. i cant remember where i got that ratio from, ive been using it for quite some time.

Sounds like youve thought this conversion through.
do keep us posted.

Matt

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Post by acmotor » Tue, 03 Jun 2008, 06:03

Acpropulsions don't return my emails (they did last year). Has anyone heard from them lately ? I nearly bought an AC-150 last year until the problem of diff ratio came up. There was no way I was going the waste $25k on sending it through a standard gearbox just to match the revs and drive around in first gear !

The 300CE drag co-efficient of 0.29 sounds very low. Is this correct ? I like it.
Priit, will you actually be able to get an 8:1 diff ?

Why are people prepared to spend 15 to 20k on good batteries and just connect up a basic DC motor ?
Ok, Ok, budget.
I still prefer the idea of spending more on the motor/drive, losing the gearbox and get best range for your kWh (read efficiency) including real regen braking.
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Post by acmotor » Tue, 03 Jun 2008, 06:13

The other way to go is with a lower revving AC motor to match the existing diff ratio.
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Post by MikeD » Tue, 03 Jun 2008, 14:34

In 2007 I visited ACP in an effort to create a personal relationship with people in the company. At the time they were very friendly, took me around the facility and even let me drive an E-box, and when I asked about purchasing a motor the advice was to wait a few months and try again (production issues).

A few months latter and my emails were ignored?

I ended up purchasing an MES-DEA from Victor at Metric Mind.
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Post by priit » Wed, 04 Jun 2008, 01:59

antiscab wrote:
btw, how did you estimate the 22.5kwh/100km?
i estimated it by taking the L/100km and multiplying by 1.875 to get kwh/100km. i cant remember where i got that ratio from, ive been using it for quite some time.


The estimation actually did not come from me, I used the table here:
http://www.waeva.asn.au/docs/spreadshee ... 20calc.xls
and added the parameters for the Mercedes leaving all the formulas so got the result.
acmotor wrote: The 300CE drag co-efficient of 0.29 sounds very low. Is this correct ? I like it.
Priit, will you actually be able to get an 8:1 diff ?


The drag co-efficient is according to factory specs and since I still belong to a Mercedes fan club my buddies there confirm that.

About geting the 8:1 differential I am not relly sure yet. I have found couple of companies over the internet that claim they make customdifferentials, so I will have to get some replies from them first before I can confirm that. If I cant then I might have to start looking for other options to make it most efficiently work.
acmotor wrote: The other way to go is with a lower revving AC motor to match the existing diff ratio.


Can you recommend any good AC motors that would be suitable with say 3.27 differential? I would need the regurlar city speeds to rev then at 1400-1500 RPM and the highway speeds up to 3700 RPM, with possibility to run on Motorway at 3500 RPM constant.
According to the AC150 efficiency curve the revving below 2000 RPM seams to not be very efficient for the motor?
http://www.acpropulsion.com/technology/ ... ciency.gif
I have been looking at this motor with controller as an alternative that would be revving at somewhat lower speeds and might work with the 3:27 differential or probably better with the rally 5:1 diffrential.
http://www.azuredynamics.com/products/f ... tSheet.pdf
MikeD wrote: A few months latter and my emails were ignored?

I ended up purchasing an MES-DEA from Victor at Metric Mind.


How powerful MES-DEA motor did you get? I have been looking at Metric Mind page aswell and have considered buying a motor through him if the AC150 appears to not be available. I even contacted the Siemens and Evilsol, who are the Siemens motor distributors in Europe, but they said they dont do business with individuals, so only mass orders from partners work for them. Then Metric Mind might be the best option there unless there are some Australian companies selling good AC motors that would work?

Priit
Last edited by priit on Tue, 03 Jun 2008, 16:33, edited 1 time in total.

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Post by MikeD » Wed, 04 Jun 2008, 14:57

Priit
I when thru the same process, ACP, Siemens, Evisol all to no avail and then approached Azure Dynamics and Metric Mind. Both were happy to deal but in the end I went with MM (Victor) who was very easy to do business with. I have an MES-DEA 200-250 which is a 30kW 3 phase AC motor.

It is expensive to import from the US. When calculating your costs look at the US price, factor in exchange rates and then add about $4k to your budget for taxes and duties and freight to Australia.

MikeD

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Post by MikeG » Thu, 12 Mar 2009, 20:48

How much did the AC-150 cost? I'm looking at one of these also...
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