An Introduction To Electric Vehicles

by Ian Hooper, June 2010

 

The Conversion Process:

Electric Vehicle Components:

  1. Electric Motor
  2. Battery Pack
  3. Motor Controller
  4. Contactor
  5. Fuse
  6. Vacuum Pump
  7. DC/DC Converter
  8. Instrumentation
  9. Power Steering Pump
  10. Battery Charger

Introduction

We Australians love our cars. We can't live without them. Unfortunately our cars are doing a lot of damage – to the environment, our climate, and to our hip pocket every time we fill up with fuel! But you do have a choice. You can own an electric car – today. While there are no electric production cars currently for sale in Australia (as of 2010), you can convert your existing vehicle to zero emission electric. Never pay another cent for petrol, and know that you're doing your bit to minimise air pollution and climate change*.

This article contains some introductory information about the process of converting your car to electric, and an overview of the components involved. Many people with mechanical and electrical experience choose to undertake a conversion themself, and it is a very rewarding project. But if you don't have the time, space or expertise to tackle an EV conversion yourself, there are professional workshops around the country who can do the conversion for you.

 

The Conversion Process

 

Step 1: Research!

Converting your car to electric is a big decision, and you want to make the right choices. Fortunately there is a wealth of information available on the internet (such as this website!), as well as knowledgeable experts around the country. For Australian residents, AEVA is a great resource, and meetings are held regularly in most states. You may also wish to sign up for the EVDL mailing list.

Step 2: Select your donor vehicle

Any vehicle can be converted to electric. Generally small and light vehicles will give you the best performance for your money, but you should always choose a vehicle you like to own and enjoy driving.

Step 3: Remove engine and related parts

Electric cars are actually much simpler than petrol vehicles, with far fewer moving parts, so a lot comes out. The main components are the engine, fuel tank & lines, radiator and cooling system, exhaust, and sometimes the gearbox.

Step 4: Install electric components

A small, quiet and efficient electric motor goes where the engine was, and batteries are installed in the remaining space – usually half where the fuel tank was, and half under the bonnet – and a variety of other components. The second half of this article describes most of the components you will encounter in an EV. Installation of electric components should be performed in accordance with the National Code of Practice for EVs.

Step 5: Relicense your vehicle

Now that your electric vehicle is complete, you should relicense it as an EV to make the conversion official. You may need engineering signoff if any major modifications were performed (such as chassis changes), or if the weight has changed appreciably. For comprehensive insurance you may need to go to a specialist company, such as Shannon's.

 

Electric Vehicle Components

 

(1) Electric Motor

This is what makes the car move, instead of the petrol engine. Electric motors are very efficient, up to around 95% instead of around 25% for a petrol engine! There are various types available, with Series DC being the most popular and cost-effective. We recommend the Kostov 17R or NetGain Impulse 9 for small cars, the NetGain Warp 9 for medium vehicles, or the Warp 11 for larger vehicles. For motorbikes, we recommend the Mars motors.

 
   

(2) Battery Pack

 

This is what stores the energy for powering the motor. We recommend Lithium Iron Phosphate (LiFePO4) chemistry cells such as those from ThunderSky or Sky Energy. For most cars we recommend 144V battery packs, comprised of 45 cells in series. Motorbikes will usually use 48V-72V battery packs (16-24 cells in series). For small cars we recommend 90-100Ah size cells, for medium cars use the130-160Ah cells, or large cars 200Ah cells. Typical driving range is 80-160km, depending on battery pack size and vehicle efficiency. Our Physics Theory page describes how to predict range based on your vehicle and battery.

Lithium battery packs also require a battery management system, which monitors all the batteries to ensure they remain in a good state of charge and health.

 
   

(3) Motor Controller

 

This little box does all the hard work, electrically speaking, controlling the flow of electricity from your battery pack to your motor as you press the accelerator. For the more common Series DC motors, there are a variety of motor controllers available. A good economical option for small cars is our ZEVA MC600C (~90kW max), or for larger vehicles and sports car conversions there's the MC1000C, handling up to 150kW. For even higher performance, take a look at the Manzanita Micro Zilla controllers. For motorbikes and other low voltage conversions, Alltrax provide a range of suitable controllers.

 
   

(4) Contactor

 

This is like a big ON switch, powering up your drive circuit when you turn the key. The Nanfeng ZJW400A is an economical option, or the Gigavac GX14 and Kilovac EV200 are hermetically sealed, higher powered options.

 
   

(5) Fuse or Circuit Breaker

 

Every EV will have a fuse in its power circuit to ensure that the vehicle will shut down safely in the event of a fault in the traction circuit. The ideal fuse depends on the power rating of your batteries, controller and motor. With ThunderSky batteries we generally recommend a fuse with a rating 4x the capacity of your battery pack, e.g with 100Ah batteries use a 400A fuse. (Circuit breakers for EVs are rare due to their prohibitively high cost.)

 
   

(6) Vacuum Pump

 

Petrol vehicles use vacuum pressure from the engine's intake manifold to for vacuum-assisted braking. With no petrol engine, electric vehicles require a small electric vacuum pump to provide this vacuum.

 
   

(7) DC/DC Converter

 

To keep your car's 12V systems running you can retain the vehicle's original alternator, driven off the auxillary shaft of your motor. However alternators are only about 50% efficient, so many people opt to install a DC/DC converter instead, which recharges the 12V battery directly from your traction battery. The Iota DLS-55 is a common option.

 
   

(8) Instrumentation

 

An electric car usually has some specialised instrumentation on the dash to help the driver monitor the state of the battery (the equivalent of your fuel gauge) and the operation of various electrical components. The simplest option for monitoring your battery's charge is the Fuel Gauge Driver, which uses the vehicle's original fuel gauge in the dash. Devices such as the EVMS can supply extra information such as pack voltage, power, etc.

 
   

(9) Power Steering Pump

 

If your vehicle originally featured power steering, you will probably wish to retain this feature. Most petrol-powered vehicles use a hydraulic circuit for power assisted steering, with a hydraulic pump driven off the fan belt. Some people choose to run this original power steering pump off a small dedicated electric motor, but a more elegant option is to use an integrated electric power steering pump. Some more modern vehicles use electric power steering systems already, which will need no modification to work in your electric conversion.

 
   

(10) Battery Charger

 

Every EV needs a charger to recharge its battery pack after use. Most run off single phase power (in Australia, normal 240VAC household sockets), using either a common 10A or a more powerful 15A socket. Some good brands to consider include Zivan and TC Charger.

 
     

(11) Other components

Emergency Stop Button: There are two main variants, the larger type breaks the traction circuit directly, or the smaller type interrupt the power to your contactors. These were once a legal requirement for EVs in Australia but are now just a recommended option.

Inertia Switches: These switches will trip in the event of a vehicle collision, interrupting the power to your contactor(s) to shut down the traction circuit. These are now a legal requirement for EVs in Australia.

Cabling and Lugs: For most EVs we recommend 50mm² cable for most of the traction circuit with 95mm² cable between the controller and motor. All high voltage wiring in EVs must be double insulated with the outer layer orange. You will also need a range of lugs to suit.

Tools: Working with heavy power cable needs some specialised tools, in particular a large cable cutter and hydraulic crimping tool. AEVA branches in most states have loaner sets of these tools available, or you can purchase your own set from vendors such as EV Works.

Precharger: To avoid excessive inrush currents to the controller when your main contactor closes, you should always run a precharge circuit. This article from our tech library discusses their use and offers one simple solution: Contactor Jewelry

 

* Electric cars are only as clean as the energy used to recharge them! I highly recommend signing up for Green Power, a federally regulated scheme available throughout Australia which ensures that the electricity you use is generated from renewable sources. Installing solar panels on your roof is another great way to "clean up" your electricity.


 
 

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