September, 2007
E-Loremo debate hots up
- but only in Germany
Diesel - Nein Danke! Vorsprung durch Elektro-Technik - Ja, bitte !
"Time for evolution" reads the new strapline at Loremo.com - well ..
"Time for EVolution" has been our clarion call for nearly a decade - ah, yes..what a difference a couple of capitals could make..
Click for new official Blog and NOW ...watch latest video(Sept 8) of Loremo L1 'spied' on the open road..
In just a few days a working prototype of the 11,000 euro, 117 mpg(24% less than the original 157 mpg) (bio-)diesel Loremo L1 is scheduled to appear at the
Frankfurt Motor Show(13-23 Sept) and EVeryone - well everyone at the newly revamped official Loremo Forum(English version) and sadly nowhere else - is talking and fantasizing expertly - and almost exclusively in German - about the potential for a long-range, low-cost, fast all-electric Loremo - or E-Loremo.
Click for English Loremo Forum
Many highly-informed and articulate advocates of an electrified Loremo have emerged at the Loremo Forum over the past year or so but none of them can quite match the technical expertise, caustic wit and all-round EV-worldly wisdom of Forum contributor "FourofFour" (don't ask!) whose 300+ km/charge, 200 km/h, quick-charge dream Loremo - battery-life 300,000+ km - would likely cost less than €30,000 Euros(£23,000 ) to put together - even less of course if Loremo could be persuaded to sell donor
vehicles minus diesel engine and Heath Robinson ICE-support system(click on artist's impression, right, for details).
But precisely how many man hours it would require to build the Loremo dream and exactly what price "4of4"'s family might have to pay along the way is pretty much anyone's guess at this stage...
But what better time, anyway, to share that realisable dream with a global English-speaking audience - just a few days before Europe's hard core of diesel die-hards and crank'n'piston fundamentalists(and that's just the journalists...) gather for this month's electric v. ICE showdown in Frankfurt - surely the last-chance saloon for what remains of the head-in-the-sand, fossil fuel brigade...
So we contacted "FourofFour" - aka "Dr. Martin Schulz - to ask if he'd object to our translating his extremely green dream into English. Within two days he'd done the job - the translation not the conversion - for us.
Speculative aside: We believe that an Anglo-German Dream Team consisting , say, of Dr. Dennis Doerffel(REAP Systems/magazine), Cedric Lynch(of Agni Motor and Lynch Motor fame) and Dr. Schulz himself could probably translate this particular dream Loremo into reality in a frantic fortnight - once the (often) nightmarish task of getting batteries , BMS and motor delivered in mint condition had been completed of course.
Click image for all Youtube'd Loremo clips - most recent first. So far only one is in English...
My E-Loremo dream - by Dr. Martin Schulz
...in his own words(with the odd Editorial aside..)
To start with I've been an EV-driver for quite some time now. I own a VW-Golf-CityStromer(built by Siemens-VW in 1995, click inset for details)
and as I use the car for my daily commute, I'm totally satisfied with it.
(Ed. see also: 1994 CityStromer for sale, just 2000 miles on clock: http://www.elektroauto-forum.de
I live in Erwitte in the middle of the so called "Sauerland", This is a rather large region in North Rhine Westphalia. I have a Dr. degree which was achieved at the Institute of Power Electronics and Electric Drives, University of Siegen (Germany). I know one or two things about electric drives and my favorite subjects are renewable energies, power semiconductors and inverter technology.
As a technician, technophile, "Ingenieur" etc. I'm constantly thinking that my 62 mph /100km/h VW EV with its range of around 70km(44 miles) really performs very poorly in view of what could be achieved today. Two things are particularly problematic about the Golf of course: weight(1500kg !) and battery technology.
So my thinking is: could I convert a road vehicle available on the market to be a better EV than this?
And would I be a megalomaniac to think that I - as a one-man enterprise - could do better than a whole host of VW-Engineers and Siemens system designers?
The drawback most EV enterprises suffer from was easily identified ie. they reconstruct cars by simply replacing the ICE with an electric motor, throw in batteries and keep the comfort to what "the customer" demands.(Ed: or "what the carmakers et al want the customer to want")
Then I stumbled upon the Loremo. Planned to be highly efficient, low in weight, low on energy consumption with its designers claiming the 450kg car would cover 100km on just 1.7L of Diesel. With almost all of the gadgets gone that make a car fat(not 'phat'...just overweight!)
Fingers to Wikipedia and calculator:
1.7L of Diesel equates to approx. 17kWh of energy. With an efficiency of the diesel engine being not much more than 30% I ended up with about 5-6kWh/100km if driven by batteries - so around 300Km range with the capacity installed into my own car.
Click for English Loremo Forum
From this moment on I couldn't resist contemplating what potential this car would have as an EV and so here's a summary of what eventually became my dream Loremo:
I want this car to go as fast as 200km/h (I live in Germany!) And anyway what is a Porsche-like looking car good for if not for a little hunting and chasing - a little hot pursuit if you will ?(Ed: most of us would be quite happy with 130 km/h / 81mph of course...)
Also, I'm a biker. I'm an acceleration junky and I want the car to reach 100km/h in less than 10 seconds. The more acceleration the better.And I want at least 300km/charge.
So - could I do it? Could anyone do it? Would the laws of physics allow it? And most importantly of all - could I afford it?
I'll divide my dream into four parts:
Batteries, Motor,Thermal design, Semiconductors & heat.
Firstly the battery mystery...
Here are my favourites - to date:
Nanosafes by Altairnano
Great on paper and already being used by Phoenix Motorcars of course.
Extraordinary lifetime and cycling capabilities. Price unknown.
One drawback of these is energy density. 1.2kWh in 17kg is very low.
The 15kWh I'd like to have would be 13 pieces with a weight of 221kg.
Despite their impressive capabilities, this is a knock-out criteria.
Li-Tecs
This is a German company building Li-Ion batteries using a ceramic separator.
Their Li-BP-3-0400-24 provides 24V/40Ah, so 0.96kWh per battery at
8.2kg of weight and 5.82L in volume. The 15kWh I want would be 16 of these arranged in a 4x4 array. 96V 160Ah.
Li-Tec states the price for 1kWh would be about 700€ but there is no reassurance that this is a valid price if you try to buy these batteries.
Battery cost estimates are about €200. Ouch!!!
With 16*8.2kg the battery weight is "down" to 131kg and volume would be 94L. But the batteries come with one more advantage. A BMS, Battery Management System, is included in each battery so charging can be done with a rather simple charger and I wouldn't have to build the BMS on my own.
The batteries are supposed to reach at least 1k cycles so where would I end up?
If I were to charge 1000 times, every 300km let's say, the battery would last for 300,000km(187,500 miles) still giving me 240km/150 miles per charge. I decided this should be good enough.
A123Systems
This company, up to now, has no large capacity packs but only single cells of small capacities. These are for the reasons given above, not an option for a private conversion. Simply too many cells here.
Still: Their ANR26650M1 has 7.6Wh at 70g of weight. Roughly 2000 Cells would be needed adding up to 140kg of weight and 15.2kWh. Not a big gain towards the Li-Tecs here, right? And imagine the wiring of 2000 cells.....
One more to go:
Kokam - see full Kokam datasheet pdf
This is a Chinese battery manufacturer offering cells with 240Ah at nominal voltage 3.7V. A single cell comes with 0.88kWh of stored energy at 5kg in weight and 2.4 Liters in volume.
I prefer 100V-Systems in an EV, so I would like 27 of these in series.
135kg of batteries giving me 24kWh in just 64 Liters – oh my goodness!!
This could do far more than I expected!
24kWh would be enough to easily go 400km/charge. And just one hour to recharge.
240A nominal current at 100Vdc is almost the 27kW I want but I suppose the batterries do not suffer too much from 300A being drained now and then as the company claims the cell can provide 480A peak current.
Or maybe I could reduce the target top speed down to 180 km/h - still good enough to do at least some hunting(German: "jagen") .
With the datasheet stating only a cycle life of ">800" this would get me 400km/charge when new and 320km after the battery is down to 80%.
Up to this point the car would have 320.000km(200,000 miles) on the meter.
Again: good enough - and a BMS for 27 cells should not be too difficult
to build.
Postscript: I just got the price quote for Kokam's 240Ah cell.
590€ per piece at 1k pieces. Tough - given the fact that I would like 27 of these, ending up with more than 15k€ for the battery pack alone.
Of course by 2010 there may be even more Li-ion options to choose from given all the increasing Li-ion dependent EV/plug-in promises that are being made for 2009/10.
The mysterious Fortu-Batteries for instance - and maybe Gaia will get cheaper (Actually about 2k€/kWh) Who knows?
next...
Motor
The first, most innovative idea of course: in-wheel motors!
And at least two of them – perhaps four. In-wheel motors are not a new invention of course: in 1899 Ferdinand Porsche built his racing car based on this technology.
But in Germany at least you face one major obstacle when you make modifications to a car. I'm referring to the TüV(MOT in UK) and it can be a real pain in the rear-end.
TüV in German means "Technischer Überwachungsverein". Every two years you have to pay an (expensive) visit here to get your car checked. If they find something they don't like you get the number-plates removed and have to get your car back by trailer.
You change the tailpipe – TüV has to be consulted. You want different tyres? Chip tuning? Different seat belts? Oh boy – you're in trouble.
I talked to one engineer at the local TüV-station for quite some time
and surprise, surprise:
If you convert your car to electric drive all they calculate is whether or not the energy stored at maximum speed can be handled by the brakes.
Of course this means the brakes as they were in the car before the conversion. So changing brakes in size or geometry is simply not an option After this information, in-wheel motors were no longer in the discussion.
So I'll go for a centrally mounted machine to replace the ICE.
So how much torque do I need?
Here we go: If you sit in the car, the weight to be accelerated is
about 550kg (give or take a few).
To reach 100km/h or 27.77m/s in less than 10s you need a driving force
of F=m*a. So 550kg*2.77m/s² would be necessary – roughly 1525N.
The car is equipped with tyres 105/70/14 that have a diameter of about
20 inches or 50cm.
I prefer MKS-systems and staying with cms.
The torque at the wheel would have to be M=F*r where „r“ is the wheels radius. So you end up with 380N being just good enough.
I'm not a mechanic and as nobody knows what gearbox the Loremo will get, I'd have to make a guess. All they tell us is that it will have a 5-gear manual transmission. Searching for one, I came accros the AudiA6 gearbox . It simply was the first I found in google and I discovered this:
5. Gear: 2.6:1 (Rotation Motor : Rotation wheel including axle
transmission)
4. Gear: 3.3:1
3. Gear: 4.8:1
2. Gear: 7.7:1
1. Gear: 14:1
In first gear, you need a machine capable of delivering "only" 27Nm.
As I know what a 20kW permanent magnet synchronous machine does to my
1500kg Golf-EV, I decided that 27kW would be enough for a car with a quarter of that weight.
It turns out that some machines are available. And as synchronous machines are expensive, I would like the Brusa ASM .
This pretty little thing will do 65Nm at rated current. More than enough reserve for some extra speed.
But what could you expect from 27kW in 550kg weight? The drag coefficient of the Loremo is about cwA=0.22. The power to drive the car with 200km/h has to be sufficient to overcome friction and aerodynamic drag.
Friction is linear with speed and of minor impact. The aerodynamic drag, however, is a cubic function of speed.
The motor can be driven up to 10.000rpm, but I keep it below that.
Changing gears at 40km/h, 75km/h, 120km/h and >170km/h would mean that up to 200km/h I will not need 5th gear.(Ed: ..but who needs all that tribal speed machismo - all that Freudian yanking of knobs & sticks ?)
So back to calculating with the result: 200km/h needs 23kW for moving air and almost exactly 6kW for friction. So 27kW is not enough.
But don't despair – the machine can provide up to 192Nm – so the few extra Nm to do 200km should not drive it to thermal death – but that topic is covered later.
So how will the car perform?
See the graph and be astonished:
Zero to 100km/h in 8.4s without giving more than rated current to the machine.
Thermal design
Ok – I now know the machine can drive the car fast enough and will provide the torque I want. But can I really give some more than rated current to the machine later? Usually, EV-ers remove the liquid cooling system from their conversion but I think I would keep it. Here is the reason why:
It comes for free if I buy a Diesel-Loremo. The Loremo engine provides 36kW mechanical power. Diesel enginges, however, have an efficiency of only approx. 30% so about 70kW of thermal energy needs to be dissipated. Assuming that the car has to work with ambient temperatures of up to 50°C while the coolant may not exceed 120°C you end up with a thermal resistance Rth of ?T/?P=70K/40kW=1.75K/kW. In this assumption a lot of heat is dissipated through the tailpipe but 40kW remain for the liquid cooling system.
1.75K/kW means, a heat source reaches 1.75K above the ambient temperature when 1kW of thermal power is dissipated.
Back to the maths :
The Brusa-motor has a rated efficiency of 94%. You won't get that all the time, but from their diagram I take it 80-85% can be fairly assumed. I'm conservative and will assume 80%. With this and 27kW of mechanical power, the losses in the motor are about 6.75kW but they are not the only losses. An inverter needed to drive the machine also has an efficiency less than 1. As the inverter needs to supply the motor with its mechanical power and losses it needs to provide 33.75kW of output power. Given an efficiency of 90% r - but knowing it will be far better than this - adds another 3.75kW of losses.
You should have noticed that the calculation really is conservative!
With now 10,5kW of losses an the Rth calculated – what happens?
Motor and inverter will reach a temperature level of about 21K above ambient temperature.
Semiconductors and heat
Semiconductors can be destroyed by a variety of influences - the most important ones being overvoltage and overcurrent. Both can be prevented by porperly choosing components and designing the system carefully. Two more effects exist. Cosmic radiation is the one I'm not going to focus upon – too spooky...
What remains is – again – temperature.
High power semiconductors are stressed by two thermal mechanisms.
Power Cycling is when short bursts of power need to be handled periodically. This poses a threat to the internal connections, the bond wires. This effect is in a range of seconds or less. Thermal cycling, on the other hand occurs when semiconductors start operating at low temperatures and get hot during operation. This would happen if the power electronics have to drive a car in winter starting at e.g. -20°C and then reaching their rated maximum temperature of 125°C a few minutes later.
If the destination is reached and the car is turned off, the semiconductors again cool down to -20°C.
One thermal cycle complete.
Thermal cycling stresses all components including case, silicon and especially the solder layers below the chips that degrade over time.
Both effects get worse if:
a) the temperature swing increases, so cycling from 20-80°C is less stress than from 20-120°C but also
b) if the temperature levels increase. Cycling 20-80°C is less stress
than from 60-120°C though the temperature swing is the same.
An increase by 25°C upwards will halve the lifetime of any given semiconductor.
It can be concluded that lower temperature levels are always fine so that's the reason for me to keep the liquid cooling system.
Additionally, the Brusa will tolerate larger currents than the rated current as long as the winding temperature is not exceeding 150°C.
You can see what happens? I'll get the few extra Nm without getting into thermal trouble.
So what?
The machine can drive and accelerate the car, there is no thermal problem, and the TüV is not a problem.
But could I store enough energy to get the 300km/charge?
More long days of surfing, searching, calculating go by.....
So my E-Loremo dream is complete:
27kW electric machine instead of ICE, proper inverter as an "off the shelf" component, Li-Tecs or Kokams, depending on the price.
This leaves me with one choice that is not jet decided:
When my Golf-Battery is dead and needs replacement in a few years – would I go for the Loremo and convert it or would I rather spend the money upgrading the Golf to Li-Ion?
I think this depends on how pregnant my wife is by then.(Ed: so E-Loremo fate is in your....hands?)
After all a Golf - yes, even an electric one - is a fine family car.(Ed: and so far you are a "fine family", right?)
Forum - to find all recent & archived electric Loremo threads: first register/log in, then Search Forum on keywords:
E-Loremo EV
August, 2007
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