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Why convert to electric drive?

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!

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…

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.

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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.

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 max 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.

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

  • Virtually silent – although road and wind noise are the same
  • 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!
  • Very low maintenance costs – no plugs, oil filters, timing belts, exhausts, tappets etc etc.
  • On AC systems, much reduced ware on the braking system by using regen*.
  • Simple motor design – only 1 moving part for AC motor as opposed to hundreds in an ICE
  • Vans don’t require an MOT
  • Road tax (VEL) for EVs is free
  • 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.

 

Why biofuels are a complete white elephant (so far as road transport goes, at least)...

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 - These are 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 Eelectric 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

12/9/2008 - The charger, watthour meter, timer and cable reel installed.

27/9/2008 - The first of the 5 battery sub-packs being assembled.  The black straps tie the pack together and prevent the cells from swelling unacceptably if they get too hot.  This should not happen if they are to last their specified design life.  I hope to avoid having to actively cool them but will not know if this will be necessary until I have tested the system in the real world.

29/9/2008 - A drawing of the battery box showing main power wiring.

29/9/2008 - The battery box showing battery balancing PCBs and associated wiring.

29/9/2008 - The battery box showing battery monitor (PakTrakr) wiring.

29/9/2008 - The first of the 5 battery pack sub-packs with ballancing PCB attached and wiring started.

10/10/2008 - The gearbox/motor adaptor plate fixed to motor.

07/12/2008 - Where I’m at re the system monitoring program I’m writing in VB6 (the data displayed above is mock data).  This displays the data the PacTrakr  battery monitoring device collates.  It will also show data collected from a USB datalogger measuring RPM, vacuum and ‘other things’ - ie things I haven’t thought of yet.  The program can  send an alert via text to my mobile for various alarm situations etc when the van is unattended.

07/12/2008 - The last of the 5 battery pack sub-packs with ballancing PCB attached and wiring completed.

23/02/09 - The motor/transmission coupler...

23/02/09 - The centering tool (above and below) for aligning the transmission adaptor plate with the centre of the gearbox input shaft prior to drilling the attachment holes.  This ensures perfect alignment of the motor and gearbox to prevent noise and wear on bearings etc..

25/05/09 - With the help of friend and colleague Ade Sell - an ex-toolmaker, we have mounted the gearbox on the adaptor plate with centering tool (not visible) in place, ready for marking the fixing holes.  We have already knocked out  the 2 locating dowels from the gearbox bell housing (see below).

25/05/09 - This is one of the dowel holes with a bush inside it ready to poke a drill bit through to mark the hole position.

25/05/09 - The bush mentioned above, from the other side.

25/05/09 - The dowel back in place ready to mate the adptor plate to the gearbox.

25/05/09 - A device for getting an idea as to the speed of rotation of my motor whilst testing it with 12V - using a mains flourescent bulb as a ‘stroboscope’ (courtesy of Sherline Lathes)

25/05/09 - The RPM gauge in action (right click and play).  The motor speeds up too quickly to see the effect but once at max speed you can see 3 darker patches at the innermost ring which, when the power is disconnected, move outwards and increase in number as the motor slows down.  Each ring represents an rough RPM.  In the video the blobs appear at the innermost ring which represents 2400RPM.  Unfortunately this gauge is designed for use in the US where the mains is 60Hz.  Here in the UK it’s 50Hz so I must apply a correction factor - but at least I know I’m not over-revving the motor.  More than 6000RPM and it might explode (mind, it needs to get very hot too for this to happen!).

31/05/09 - A little template to ensure the gearbox goes back in the right position.

31/05/09 - The seats removed and engine exposed.  The carputer touch screen is shown installed top left.

31/05/09 - The van mounted on ramps to give access to the underneath.  This will make getting the redundant bits out much easier (engine, petrol tank, cooling system and exhaust).  The plan is to drop the engine/gearbox down, back-up the van and move the engine/gearbox out the way (and, hopefully, sell it on eBay). Then put the electric motor & gearbox on the ground below, move the van back over and hoist thethem into place.  A bit of welding for the new motor mount and Bob’s your Uncle!  Like I say, that’s the plan...

01/06/09 - The transmision coupling and adapter plate mounted and LocTite’d up....

01/06/09 - The motor mounted to the gearbox ready for installation.  It even goes the right way when energised so no need to reverse the motor rotation.

02/06/09 - A block and tackle and stout bit of 6 x 2 to drop out the engine...  You can see the carputer and other electrics installed above on a hinge down panel...

02/06/09 - The old ICE engine out of the van, complete with wiring loom - note the tublar ‘cradle’ beneath it - this will be re-used to mount to the electric motor with a home made mount.

02/06/09 - All the gubins which is being ditched (except the ICE motor) - left to right...  exhaust and heat shield, radiator and other cooling system parts and fuel system.  I’ve left the cabin heat exchanger in place for the later addition of a hot water heater for de-misting and cabin heat.  The weights are:-

ICE 1300cc alloy engine 107Kg

fuel tank 11kg

cooling system - 11kg

Bits and Bobs - 7kg

exhaust/cat 18kg

08/06/09 - Electric motor/gearbox in place and steel cradle tack-welded ready for full welding on the bench tomorrow..

10/06/09 - Electric motor/gearbox in place and steel cradle welded, painted and installed.

10/06/09 - Same again from below...

10/06/09 - Same again from nearside.

11/06/09 - Main power cables attached to power centre, main contactor, motor and battery pack connector.

11/06/09 - Existing throttle cable to potbox setup...

21/06/09 - Battery box base is in...

21/06/09 - ... and insulated

28/06/09 - Batteries in and BMS wiring underway.

30/06/09 - Wiring complete and ready to rock and roll...

30/06/09 - With the rear wheels up on axle stands - It works! (right click and ‘play’).  Just need to reregister the van as ‘Electric’ class with the DVLA and get some insurance and it’s ready for some road trials.

15/07/09 - New hydraulic crimpers to crimp power cables - just to be sure of a good connection!

17/07/09 - The van in full flow (well, doing about 40MPH, anyway).

03/08/09 - UPDATE - Well I’ve put about 170 miles on the odometer since the conversion and things have gone reasonably smoothly.  The main issues so far are a bit of a break-down due to a sticky main contactor (my fault as I reduced the energising voltage too far in an attempt  to save power) and I lost my brake vacuum pump for reasons yet to be determined - probably due to it being a second hand unit.

In the wider context, as a short range general purpose vehicle, I think the concept is sound.  Thee van is quite capable of keeping up with most traffic and certainly its acceleration is more than adequate.  I think on balance keeping the clutch would have been a better idea mainly because it just makes the driving experience less complicated.  I tend to find the 3 second delay changing from 2nd to 4th - waiting for the motor to wind down so that its speed matches the 4th gear cogs - without a clutch gets in the way of controlling the vehicle - steering, indicators etc.

It would also make for a much less steep learning curve for other drivers.  On top of that, changing up is one thing but trying to match revs to get the gears to mesh when changing down is a lot more complex - and time consuming.  Fortunately, this doesn’t happen much just using the 2 gears but even then you have to remember to slip it into 2nd as you are just coasting to a halt at traffic lights and junctions etc other wise it can be difficult to get it into gear.

I have just sourced a new vacuum pump switch which should make that side of things a much better system and I am waiting for the new charger from the US so I can properly balance all the cells each time they are charged.

On the economy front, each time I use the van to commute to work I save roughly £4 based on using off-peak electricity (5p/kWh) and petrol at £1.05/l.  As I do around 170 commutes a year (soon to increase to somewhat more due to a new shift pattern starting in September) that equates to a saving of £680 per year. No servicing or MOT and zero rated tax round it up to about £1k/year.

27/08/09 - A screen-shot of the latest version of the van’s computer monitor program during a low current, cell balancing charge.  The cells at the upper, 3.8(ish)V level are balanced whilst the others are not.  In due course they will all come up to the 3.8V level.

Below is another screen-shot of the program, this time with radio on and in night mode.

Total electric miles now stands at 400.

 

IMGP1533

01/10/09 - Free Tax arrives!!

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29/08/08 -  Wall footings rebared and ready for concrete.  Looking North.  This will have a brick and concrete block retianing wall on it.  Further up it changes to brick and brick, non-retaining...