converting a w124 petrol to electric power?

Page may contain affiliate links. Please see terms for details.
The Boss

The Boss

MB Enthusiast
Joined
Dec 10, 2008
Messages
3,537
Location
private!
Car
private!
Folks, hope you are all well.

Does anyone have any knowledge on electirc powered mercedes?

I am thinkin of purchasing a older high mileage 200ce/230ce and converting it to electric powered. Not hybrid, just pure electric.

whats the scope or possibilities?

With the govt as is, they will potentially create a huge tax for cars over 10 years with engines larger than 3 litres (similar to congestion charging for hi co2 vehicles ie - 300 and upwards that may have come out last year had Boris not got into the office) which would have been ridiculous.

I would love to see the feasibilites of an alternative fuel for a w124.

thanks
 
I would guess that weight will be the problem with a W124, it may be possible but not at any sort of reasonable cost. No doubt at some stage battery technology will catch up and make it possible and even do-able, but not right now. Nice idea though!
 
I think even V7 kicks up a fuss when opening https pages

FYI here's the page:
You need about 100 Amperes at nominal 60 volts DC to move a 1 ton vehicle on level roads at a constant speed of around 20 / 25 mph.

100 Amperes x 60 Volts DC = 6 kW, or about 8 BHP.

You need about 250 Amperes at nominal 60 Volts DC to accelerate a 1 ton vehicle on level roads up to chosen cruising speed.

250 Amperes x 60 Volts DC = 15 kW, or about 20 BHP.

If you want 100 miles range we have to make some assumptions.

Assumption #1, speed = resistance, doubling speed will more than double rolling resistance and air drag, so maximum range is going to be attained at a lower speed, so our chosen 25 mph is good for a top speed. Picking 40 or 50 mph for a top speed is going to kill us in the power stakes.

Assumption #2, acceleration = wasted energy, every time we have to accelerate we are consuming power that is no longer available for propulsion at steady speeds, regenerative braking can help, but realistically we can't expect more than 10% of the vehicle's kinetic energy to make it back into the batteries as available charge.

Assumption #3, gradients = acceleration, we will only get 10% of the energy we expend climbing a hill back into the battery bank using regenerative braking on the downhill side of the hill.

Assumption #4, we are describing a vehicle that makes a laden diesel truck look sprightly, so it isn't going to appeal to those who want to burn rubber away from the lights or overtake everything in the fast lane, we are looking at a vehicle that is quiet and CHEAP and sedate.

Assumption #5, we can assume that average urban driving 50% of our energy will be expended on acceleration or climbing inclines, and 50% on cruising at fairly steady speeds.

A 100 mile range at 25 mph = 4 hours endurance, or 4 hours at 6 kW, or 24 kWh, and real urban driving from assumption #5 will double this, to 48 kWh.

A 500 Ah 60 VDC battery bank will, on a ten hour cycle, put out 50 Amperes for 10 hours, so 50 Amperes x 60 Volts DC = 3 kW, for 10 hours = 30 kWh.

We are going to be drawing current faster than that, so we'll get maybe 20 kWh out of a 500 Ah @ 60 VDC bank, so we need a bigger battery bank.

A 600 Ah 96 Volt DC battery bank, on a ten hour cycle, will put out 60 Amperes @ 96 V DC, so 60 x 96 = 5.76 kW, for 10 hours = 57.6 kWh, we're getting close, and we haven't done anything clever with regenerative braking.

So.............

So far we have worked out that we can build a useful electric vehicle with moderate performance and a 100 mile range on an energy budget of about 50 kWh.

1 kWh = 3,412 Btu, so 50 kWh = 170 thousand Btu, approx. which is roughly equivalent to a gallon and a quarter of diesel in Btu terms.

So our 100 mile range over 4 hours equates to just over a gallon of diesel, which is about right, I have an old Lister CS 6/1 diesel engine that burns a quarter of a gallon of fuel an hour to produce 6 BHP @ 650 RPM, and 6 BHP is 4.5 kW, which is in the ballpark of our 6 kW while cruising electric vehicle motor.

So it comes right back in a circle, we can run a 1 ton vehicle on as little as 0.25 gallons of diesel (maybe 0.4 gallons of petrol, as petrol has lower Btu per gallon than diesel) per hour, provided we are happy with electric milk float performance, e.g slow acceleration and 25 mph top speed.

My diesel Peugeot 405 will do 60 mpg @ 60 mph on the level, that's one gallon of diesel per hour, for four times our electric vehicle speed.

So all these numbers work out and agree with each other.

100 mile range is pathetic compared to my Peugeot, which will do 600+ on a tank full, but compares well with the average motorbike.

So.............

How do we buy energy?

My motorbike burns petrol, 95 pence per litre (currently that works out about US$1.90c per litre) and at 125,000 Btu per gallon that makes about 27,700 Btu per litre, and that makes 291 Btu per penny.

My car burns diesel, 98 pence per litre, and at 139,000 Btu per gallon that makes about 30,900 Btu per litre, and that makes 315 Btu per penny.

My imaginary electric vehicle would get charged up overnight from the mains, so 4.3 pence per kWh for off peak Economy 7 power, and at 3,412 Btu to the kWh that works out at 793 Btu per penny. ("normal" electricity is 9 pence per kWh, at 3,412 Btu to the kWh that works out at 349 Btu per penny, surprise surprise, same ballpark as diesel (315) or petrol (291), just different ways to buy the same product, which is energy...)

Right away, we can see that even if we allow for 14% losses in charging our batteries, we are getting twice as many Btu per penny charging an electric vehicle, compared to filling a petrol or diesel vehicle at the pumps.

The other "efficiencies" of electric vehicles are mainly down to low speed and low acceleration, that is what makes them more economical in energy usage than say average family saloon cars.

So....................

1/ Electric vehicles, such as milk floats, are economical in energy terms because they are slow, make then perform the same as an internal combustion powered vehicle and they burn energy at the same rate, surprise surprise.

2/ Electric vehicles, such as milk floats, are economical in cost per unit of energy terms because they can take advantage of discounted overnight electricity generation spooling capacity to "refill the tank". Electricity companies have to generate this energy, and if it isn't sold it is simply wasted, hence them offering Economy 7 tariff.

3/ Electric vehicles charged overnight on an Economy 7 tariff are very eco friendly, the energy used to charge them would otherwise simply go to waste, instead of doing useful work, however, this scenario only works as long as electric vehicles are the rare oddity.

4/ Electric vehicles have a range problem, you aren't going to recharge them in 5 minutes and have another 600 miles range, which I can do by filling my Peugeot with diesel. Plus, I can fill up with diesel anywhere, not many people have an Economy 7 plug that I can pull 5 kW from overnight. Electric vehicles require 8 hours to recharge, unless you return to base and hot plug / swap a battery bank...

5/ Generating my own electricity from a petrol or diesel generator doesn't make sense, running my old Lister Start-o-matic on "free" waste vegetable oil, lube oil, hydraulic oil or whatever makes more sense, but only if my time is worthless or the Economy 7 is down for good.

6/ Solar doesn't cut it, I need 5 kW for 8 hours to fully charge my electric vehicle and get another 100 miles range, if I cover its roof with high quality solar I may get 500 watts, so I'll be driving 100 miles then waiting a fortnight to recharge.

7/ Generating my electricity from eco stuff like bio-diesel doesn't cut it either, easier and cheaper and more efficient to burn it in my Peugeot.

8/ The Electric vehicle only wins if used for short range, low speed, charge overnight from cheap Economy 7 power. Longer range, higher speed, or other power sources all negate the very few advantages electric vehicles have.

9/ A standard petrol station pump transfers energy at a rate of about 10 MW, a domestic Economy 7 power outlet is going to have a hard time going much over 5 kW, this is 2,000 times slower, 8 hours divided by 2,000 = 14.4 seconds.

10/ Other, non-technical benefits may apply, such as financial incentives for the "non polluting" electric vehicle not paying Road Tax, cheaper insurance, and so on, may well apply and tip the scales, but this will still only really influence those who are already attracted to electric cars for urban travel because of economy, silence and just plain being different, people who may only do 20 urban miles per day, people quite happy with a top speed of 25 mph.

11/ A 125cc motorcycle is going to work out cheaper to run than an electric vehicle, a lot cheaper. A hybrid "tik-tok" with an efficient small diesel engine and diesel electric drive system with only 100 Ah of 24 V DC battery and electric traction is likely to be the all round winner for practicality and economy. GM won't be making it.

12/ The "performance" electric cars don't use cheap and heavy lead acid batteries, so they are ridiculously expensive, the "cheap" electric cars like the Riva of India are still expensive, and trade battery weight and capacity for performance, 60 Km/h is good, 60 Km range is useless. The Riva will have worn out its batteries long before its sticker price runs out of pump diesel for my old £199 Peugeot which gives 60 mpg @ 60 mph and 600 miles range.

13/ The serious electric vehicle makers, such as Smiths who have been making them for nearly 100 years non stop, know all this, so stick exclusively to mudane commercial vehicles such as milk floats, baggage tractors and fork lifts.

The bottom line.

A gallon of diesel is about 41 kWh in energy terms.

Electric cars are not going to come of age until the battery bank can hold at least 0.2 MWh of energy per 500 kilo of battery, which is orders of magnitude away from where we are now, and this same battery bank needs to be rechargeable in 15 minutes tops, so room temperature superconductors are another pre-requisite.

It is, as always, all about energy requirements, and there is nothing about using a different form of energy to power a vehicle that suddenly voids friction, drag coefficients or energy to climb an incline or carry and accelerate passengers and load, and even if we had the installed electrical generation capacity, which we don't, unless and until electrical generation offers a source of energy vastly cheaper per kWh than any other form of energy such a hydrocarbons, which ain't gonna happen thanks to the fixed free market and profit motive, the electric car as a replacement for the IC car is both impractical in technical terms, and infeasibly expensive to run in financial terms.

Now, about my Moller Skycar....
Click to expand...
 
Last edited:
I think you would struggle to get a diferential to fit in a 124 floor pan that is big enough for all the torque.

So your idea maybe dead in the water.
 
vincenz said:
I think you would struggle to get a diferential to fit in a 124 floor pan that is big enough for all the torque.

So your idea maybe dead in the water.
Click to expand...

Possibly.. who knows... you are probably right, but its an avenue i must look into as w124 is my favorite car!
 
It would be my first port of call, anything can be done with enough money (as i found out) but if you never design your underbody to accomodate an electric diff (that handles much bigger torque than incomparison to an IC engine output) you are seriouslly screwed!
 
vincenz said:
It would be my first port of call, anything can be done with enough money (as i found out) but if you never design your underbody to accomodate an electric diff (that handles much bigger torque than incomparison to an IC engine output) you are seriouslly screwed!
Click to expand...

I appreciate your thoughts, but i dont understand the various terminologies you use :(
 
I think this graph explains it better:

http://www.teslamotors.com/performance/acceleration_and_torque.php

Without getting bogged down in how an electric motor works, maximum torque is avaible from the moment you put your foot down (see the flat red line) whereas an internal combustion engine (IC) is shown in the black line and this behaves differently.

From owning a 124 coupe i'm pretty sure the differential housing won't accomodate the type of differential required.

The obvious way round it would be to make the housing bigger, but then you end up butchering the floorpan and more importantly compromise the strength of the body.
 
Electric motors generate maximum torque at zero rpm so they will stress the differential much more than an IC (internal combustion) engine

You'd either need a tough diff or some electronic means of limiting torque

Nick Froome
www.w124.co.uk
 
You must log in or register to reply here.

Users who are viewing this thread

Total: 2 (members: 0, guests: 2)
Back
Top Bottom