EV Conversion - Part 1

 


Why convert to electric drive?

12/9/2008 - Here is the first of a series of pictures of the components which will be used to convert my van, a 2001 Daihatsu HiJet (1300cc petrol), to fully electric drive. This is the van - well, obviously!...

Why aren’t we all driving EVs then?

Historically, mainly because of range and performance.  The only electric vehicle most people will have come across is the milk float.  This job is an ideal one for ‘traditional’ electric drive as the range required is relatively low, the speed required is also low but the load requirement is quite high.  This suits electric drive perfectly - hence the popularity of the electric milk float - in urban areas at least.  Other successful examples of electric drive vehicles are:- forklift trucks, golf carts and campus/airport service vehicles.

The main problem when you start thinking about using electric drive for conventional cars is the fact that the drag on the vehicle (which the power of the motor or engine has to overcome to accelerate or maintain speed) is proportional to 3 main variables:-

 1/ the frontal area of the vehicle (i.e. the cross sectional area of the vehicle at its widest and highest point - and don’t forget the wheels and mirrors,

 2/ the square of the speed of the vehicle,

 3/ the weight or mass of the vehicle.

 Less important is its shape but the coefficient of drag ‘Cd’ is a function of the slipperiness and the frontal area...  Anyway, the faster the car goes the more the drag increases  - exponentially so.  In fact the amount of engine power required to maintain 45MPH doubles in order to maintain 60MPH.

With the above in mind, the problem then is POWER.  The motor generally isn’t an issue.  Either AC or DC motors can be used – both are relatively cheap and easy to use and quite efficient – anywhere from 70-90%+.  The best ICE’s get is maybe 25% (a gas turbine or ‘jet’ engine is around 30%). No, the main problem is batteries and getting enough energy density into them.  Lead-acid (Pb-A) batteries have ruled the roost for ever – indeed one oft-forgotten fact is that at the dawn of the motor carriage age the roads were dominated by electric cars – ICE ones were considered dirty, noisy, smelly, dangerous and difficult to drive.  It was only the invention of the electric starter that started to make ICE cars more appealing especially (dare I say it ) to ladies – otherwise all those wealthy types, the only ones who could afford a car in the first place, would have to get hot, sweaty and dirty hand-cranking the engine.  Oh, the irony.

12/9/2008 - The cells - all 38 of ‘em. 3.2V, 5.6Kg each.  Still in their packing crates just arrived form Hong Kong.

The Pros & The cons…

So, to recap the advantages of electric drive are:-

 More efficient by a factor of at least 3 than the ICE’ed vehicle

  1. Virtually silent – although road and wind noise are the same

  2. Very cheap to run – at today’s prices (£1.10/litre for petrol) you get the equivalent of 150 miles+ per gallon.  Got a PV (photovoltaic) system?  How about free!

  3. Very low maintenance costs – no plugs, oil filters, timing belts, exhausts, tappets etc etc.

  4. On AC systems, much reduced ware on the braking system by using regen*.

  5. Simple motor design – only 1 moving part for AC motor as opposed to hundreds in an ICE

  6. Vans don’t require an MOT

  7. Road tax (VEL) for EVs is free

  8. London congestion charge is free

 ... and the disadvantages:-

Range is the main issue.  But if you need a car for long journeys rarely, then hire one or swap with a friend (and spread the EV word).

 The other main disadvantage may be the fact that you don’t have the ability to get mains power to where your car is parked when you’re at home to charge it.  Not much to be done about that, I’m afraid.  You could charge it at work if that is possible but it’s not an ideal situation. A lot of central London boroughs are able to offer limited EV charging points with free parking (and free charging) – a situation which will hopefully improve as time goes by.

*With AC drive you can take advantage of regenerative braking (regen) where the kinetic energy of the vehicle due to its speed is converted into electricity by the motor which is electronically reversed to act as a generator.  The electricity produced is put back into the batteries. This generally increases range by around 10% - better in the stop-go urban environment.

The Future…

Assuming we are all fortunate enough to have one…

10 years from now we’ll all be driving round in 2 seater EVs made in China.

Lastly (rant warning!), I believe it is way past time that the world stopped wasting finite fossil fuels and started acting a lot more responsibly for the benefit of future generations.  It also sickens me that the worlds politics is fundamentally driven by oil – directly or indirectly and if we could get an EV into every home where there is currently a petrol or diesel driven car and combine that with the reintroduction of an efficient, reliable and cost effective motorail system the world would be an inordinately better place.  (Mr Branson – are you listening??)

Note the absence of reference to global warming – I’m not a de-bunker, just a ‘not entirely convinced it isn’t mostly due to a natural warming cycle’ - er.

The next reason is to try to ‘spread the word’ a bit about EVs in general and the fact that it is one way of drastically reducing our dependence on oil imports.  Which leads on to...

Recently (in the last 20 years or so) advances in battery technology have created many alternatives to Pb-A, eg NiMH (nickel metal hydride) and NiCd (nickel cadmium) but the best currently available (for the money) is Lithium and specifically – in my view, anyway – lithium iron phosphate or LiFePO4. This type of battery has general all round advantages, particularly in terms of safety.  E.g. it won’t burn or explode when punctured or crushed, has a good high current charge/discharge capability (‘3C’ or 3 times its rated capacity continuously, 10C for short bursts) and high cycle life of up 2000 cycles based on 80% depth of discharge (DOD) per cycle – one ‘cycle’ being one full discharge and recharge.

It is the cycle life of LiFePO4 cells that make them so attractive as the best Pb-A cells only give around one tenth the cycle life of LiFePO4 and only then if they are molly-coddled, discharged to 50% DOD maximum and kept at 15 to 40 degrees C.  This makes them less expensive in the long run.  They also have the benefit of one quarter of the weight of the same Pb-A capacity.  This means much better acceleration and hill climbing speed for a given battery pack capacity.  On top of that they only use half the volume of Pb-A.

The chart below shows a comparison of  how far a car can drive based on different source of energy, each  produced from 100m x 100m (2.5 acres) of land (timescale unknown), PV stands for ‘photo voltaic’:

Anyway, back to the conversion...

12/9/2008 - The photo (right, above) contains the main components required for the conversion (along with the batteries, of course).  There are a few bits missing such as the vacuum pump and reservoir (needed as there is no vacuum created in the electric motor as there is in a petrol engine - a diesel powered vehicle has the same problem), the emergency shutoff switch and the diesel water heater (plumbs into the van heater core to provide warmth and windscreen defrost) all of which I forgot to put in the picture.

Also missing is the transmission coupler to connect the output shaft of the electric motor to the input shaft to the gearbox.  This is away being made.  There will be no clutch as its main function - to allow the car to move off from stationary without stalling the engine - is not required in an EV as the electric motor - unlike the ICE - has maximum torque at zero RPM.  It may make changing gears a bit interesting (and relatively slow - this is the clutches next most important function) but I will only need to change gear once over the van’s maximum speed range again due to the electric motors toque characteristics.  2nd gear (0 to 40MPH) and 4th 40MPH +) will be all I need.

The last thing missing are the components which go into the battery box which is going to be insulated and possibly (later) will have heating and cooling added.  Obviously this will increase the complexity (and cost) so I am going to see if the batteries will stay warm enough whilst being charged or discharged to keep them in their happy temperature range.

If needed, heating will be achieved with a modified electric blanket.

Cooling is more likely to be needed - particularly during any 45MPH+ driving when wind induced drag becomes significant - or going up a long, steep hill.  I’ll be leaving the radiator in situ to be used if cooling is needed.




The main specs of the Electric Vehicle (EV) are (subject to change!):-

Vehicle weight unconverted 1000kg - payload 600kg

Vehicle Weight converted 1100kg - payload 500kg

63 HP motor (@ 120V - 435A) (somewhat more at max acceleration)

Motor Torque = 116 Ft. pounds torque (16 kilogram m)

Motor Weight = 133 pounds (60Kg)

Motor Speed = 5500 RPM (max)

Battery pack  = 120V* (nominal) LiFePo4  (38 x 3.2V)

Range = about 60 miles at 55 MPH (100m+ @ 30MPH)

Max speed = around 70 MPH

*The pack voltage will vary between 110V and 160V depending on state of charge - LiFePo4 = Lithium Iron Phosphate

http://www.winlow.co.uk/wychwood.co.uk/EV_Conversion_-_Part_2.html

Next Page...

“Electric vehicles are like heaven. Everyone wants to go there, but no one wants to go now." Victor Juarez



For an up to date insight to the EV market with comparison tool and more, see http://www.electriccarbuyer.com.


My main reason is to investigate the practicalities of using a fully electric vehicle for commuting and general domestic use.  Anything in fact except the ‘long’ trip.  It is for this reason (and the fact that I already have it) that I decided to use my aging van.  Easy to convert.  Later, I may look at putting the bits into something a bit more interesting – after I’ve finished the house!

What about the Hydrogen Fuel Cell?...

Hydrogen (H2) fuel cell powered vehicles are a total white elephant and here's why...


There is a reason why H2 has not taken over as a replacement for fossil fuels, despite the world being told is is going to do so 'soon' for the last 50 years, and that is because it simply does not work.  


It could, I'm sure, be made to work - if billions (more) $ were spent - but why bother when there is a simple, reliable, cheap and home-grown solution here NOW using readily available infrastructure and technology?  I'm talking electric vehicles, here.


So what are the main reasons I don’t think H2 is the answer, for now, at least?


1. The main source of hydrogen currently is from 'cracked' (steam reformed) natural gas - i.e. it is effectively a fossil fuel. The efficiency of the steam reformation process is approximately 70%. Alternatively, electrolysis uses much more electricity to make H2 than just using the electricity in EVs directly would.  Even then, fuel cells require exceptionally pure H2, far purer than typical commercial-grade H2 which contains impurities that would ruin a fuel cell catalyst quickly.


2.  If you plan to use H2 in an ICE, you are still getting dire efficiency - 30% at best and that's on top of the 70% efficiency in making the H2.  If you use a fuel cell it is still only 40% efficient, maximum.  Back to the argument in 1.


3.  To put enough H2 in a package sufficiently practical to put in a car to give it 'adequate' range is enormously expensive due to its lack of compressibility.  It isn't LPG or propane etc which will compress to a liquid with a few atmospheres - standard H2 filling pressures are 350 & 700 BAR (atmospheres or 4900/9800 PSI!) meaning very strong and therefore big, heavy (and VERY expensive) containment vessels.


4.   To store and transport H2 has all the same issues as 3.  For this reason, to build a network of equivalent motorway-style refilling stations would require HUGE sums of money compared to petrol/diesel (or electric) designs and more huge sums of money to service it.


5. Having all that H2 sloshing about everywhere you look would be a recipe for colossal disasters on a daily basis.  It would be much more dangerous than petrol - hence the reason the only London based H2 refueling point was shut during the Olympics causing all London-based trial H2 powered vehicles to either not be used or worse (and don't laugh) truck them all to Swindon and back for refueling!


  1. 6.Fuel cells capable of powering a vehicle are very expensive at US$50-100k and they have not fallen in price much and probably won't for a very long time.


  1. 7.H2 is incredibly dangerous - far more so than petrol or any other common flammable gas.  The main reason for this is because it has a very wide explosive/ignition mix range with air ie when leaking.  Also, if it ignites, its flame is near invisible.  Consequently, a leak is much more likely to lead to an explosion than other fuels.