How To

  • SEVA member Deb Seymour wiring battery packs for Charlie Tsai's 1996 BMW Z3 conversion as part of the South Seattle Community College Electric Vehicle Conversion Class.

Recycle Your Old Gas Car!

There are no limits to what you can convert to electric power!

Furthermore, electric vehicles are really quite simple and you do not have to be an electrical engineer, an auto mechanic or a genius to convert one. Many people have converted a vehicle to electric power without having any previous experience, so if you have the desire, YOU CAN TOO! The conversion process can be broken down into 5 steps:

Step 1. Determine your budget
Step 2. Research
Step 3. Acquire a vehicle and parts
Step 4. Start building
Step 5. Finish and test

NOTE: All of the material contained on the SEVA Website is intended for educational purposes only and is NO SUBSTITUTE for real world experience and knowledge! Many components and voltages in electric vehicles and other vehicles can cause personal injury or death if proper precautions are not taken. Never work alone and when in doubt, always assume high voltage is present and do not proceed of you feel uncertain or unqualified! By reading the information contained in SEVA’s website, you are agreeing to hold SEVA (The Seattle Electric Vehicle Association) and any of its members, contributors and affiliates harmless in the event that you suffer any losses or injuries due to any of your own projects.

STEP 1: DETERMINE YOUR BUDGET – The first step is to figure out how much you are willing to spend to convert a vehicle. Converting a vehicle to electric used to be one of the only ways to get an electric vehicle at all. Today there are a number of factory-built electric vehicles ranging from motorcycles, to luxury sedans to delivery trucks. It might be better for some people to simply purchase a new factory-built electric vehicle instead of taking the time and expense to convert something. Although driving an electric vehicle may save you a lot of money in the long run, the resale value of conversions (like any used car) is typically much lower than what the owner payed to convert the vehicle. If you are planning to convert a vehicle you can use this to your advantage and pick up a used EV either to drive or simply for its parts.

Because of the availability of factory-built EVs, it is prudent to choose a candidate vehicle for conversion which is a vehicle that you really like and want to spend a lot of money on. Bicycles, motorcycles, ATVs and other small vehicles usually require fewer parts, less powerful motors and smaller battery packs; therefore they can be converted for less money. The larger or heavier the vehicle, or the faster, or farther you want it to go, the more expensive it will be.

As of 2014, typical costs for converting various vehicles to electric power are as follows:

Bicycle………………………………………$150 – $3,000
Motorcycle………………………………….$500 – $10,000
Full-size car or truck……………………..$3,000 – $40,000
High performance race vehicle……….>$10,000

Note: The figures above are generalizations and there will always be exceptions, but if you have $20,000 to spend, you should be able to get a fairly decent full-size conversion. It is also important to note that the more work you can perform yourself, the cheaper your conversion will cost (assuming you don’t assign a dollar value to your own time).

STEP 2: RESEARCH – It’s okay if you know nothing about converting an electric vehicle, all you need is the desire to learn. Start attending the monthly SEVA meetings to see real conversions and connect with local builders. There is also the SEVA email list and the worldwide EVDL (Electric Vehicle Discussion List) as well as various books and online resources which are listed below. Be sure to check out the Events Calendar on our SEVA website to find out about upcoming events. SEVA members sometimes offer electric vehicle classes through South Seattle Community College.

During the research phase of your electric vehicle conversion project it is wise to start a project binder where you can store all of the information you gather. This is the time to figure out the whole list of what components you will need in order to make your specific vehicle conversion live up to your expectations and match your budget. This is also a good time to assess what additional tools or skills you may need to acquire in order to convert your desired vehicle. It is highly recommended that you talk to multiple people and consult various resources so that you can begin to separate the many opinions from the facts and decide for yourself what will work best for your project. Often the greatest learning comes from real-world experience, so attend meetings and events and then start actually building and testing things yourself!


Two good books on converting a vehicle to electric power are:

There are a number of web resources available for those researching or already converting a vehicle:
The EV Album is a website which allows people to submit detailed information on electric vehicles (mostly conversions) which they own. This is a very useful resource which allows users to sort vehicles by such things as make, components used, or vehicle location. You may be able to get in touch with a number of other people who have already converted the type of vehicle you were thinking of converting.
The Electric Vehicle Discussion List has been an email-based electric vehicle information resource with an extensive archive dating back to the early 1990s.
The DIY or Do It Yourself Electric Car Forum is an online EV conversion information forum which has many users from all over the world is a forum specifically geared toward electric motorcycle conversions
The Endless-Sphere forum is specifically geared toward electric bicycle conversions
The National Electric Drag Racing Association is a place to learn about EV racing and they also have their own NEDRA email list
The EV Tradin Post is a widely used classified ad website for people interested in purchasing or selling electric vehicle components and services. This is an excellent website to visit for finding deals on electric vehicle components.
EV Finder is another good resource with a popular electric vehicle and EV parts classifieds section.
Home of Jack Rickard’s highly opinionated but popular weekly Electric Vehicle TV show. The folks at EVTV also put on the yearly EVCCON – Electric Vehicle Conversion Convention. The weekly videos are usually well over an hour long and although some of the show is taken up sharing opinions on random electric vehicle news items, there is almost always a portion of the show with information specific to converting a vehicle to electric power.

STEP 3: ACQUIRE A VEHICLE & PARTS – Many great ideas and plans, remain great ideas and plans in people’s heads and never actually materialize. Don’t be one of those people who sits around talking about converting a vehicle for years and never gets around to it. Think about how good it will feel when you can zoom around exhaust-free on a few cents worth of electricity and proudly tell people, “I built that!” Another reason to actually purchase things and get started is that most EV projects take people much longer than they initially anticipate. Even though it may seem intimidating, if you purchase the vehicle and components and get going, you’ll gain motivation and even if you don’t think you have it all figured out, you can learn as you go. The learning process frequently entails trial and error and so the sooner you actually start, the further along on the curve you will be and the sooner you will be able to enjoy your EV.

By now you should have come up with a budget, done some research and set aside some money for your EV conversion project, so it is time to actually buy the parts. The electric vehicle conversion market it not as mature or large as the general automotive aftermarket and as a result, EV conversion components may have very long lead-times so you want to get things ordered sooner than later. Even in this day of CAD (computer aided design) modelling, when it comes to figuring out how things will fit into your vehicle, nothing is better than having the real parts and the actual vehicle.

Whether you are converting a lawn mower, a bicycle, a motorcycle, a sports car,  a boat or a bus, your electric vehicle should have these 4 main components:

  1. At least one electric motor – this is what replaces that stinky, loud, oily, exhaust-producing infernal combustion engine.
  2. A battery pack – this is what provides the energy required to move your vehicle and it is usually made up of Lithium-ion or Lead-acid batteries.
  3. A controller – this is what regulates the power from your battery pack to your motor.
  4. A safety disconnect system – This may be a main contactor (large on/off relay), a fuse, a circuit breaker or switch, a physical electrical disconnect or a combination of these things.

In addition to the aforementioned basic electric vehicle components many electric vehicles also have the following:

  1. A throttle control – this tells the motor controller how much power you want.
  2. At least one main contactor – this is part of your safety system and is usually a large relay with a 12V control side that is tied to an ignition switch. The high voltage / high current side of the main contactor usually goes between the most positive battery and the appropriate connection on your motor controller. When the ignition switch is turned on, 12V is applied to the main contactor and it closes thereby allowing the electricity stored in the battery pack, to flow through to the controller and ultimately to the electric motor.
  3. A DC/DC converter – this device is what replaces the alternator in order to keep your 12 volt auxiliary battery charged so that your vehicle’s 12V system (stereo, lights, power windows etc.) can continue to function. One side is connected to your main high voltage motive battery pack and the other side has a 12 volt output. The DC/DC converter must be sized appropriately
  4. A 12V battery – this may be the original 12V battery that came with your vehicle or you may be able to use something smaller. Most EVs still use an auxiliary 12V battery because then critical items such as headlights and power brakes may still function in the event of a DC/DC converter failure or in the event that something happens inside the main motive battery pack so that it cannot provide the DC/DC converter with power.
  5. A 12V vacuum pump – this is a small vacuum pump which runs on 12VDC and provides a vacuum source for your vehicle’s power brakes (if so equipped).
  6. A power steering pump – Some people choose to convert to a manual steering rack, or have no power steering at all, but if your vehicle originally had power steering the most common way to retain that option is by adding an auxiliary power steering fluid pump. Like the brake vacuum pump, power steering pumps used in conversions usually run on just 12 volts.
  7. An adapter plate or coupler – this provides a means of connecting your new electric motor to your vehicle’s existing transmission, gearbox or drive shaft. This may have to be custom made or there may already be options built specifically for your vehicle.
  8. A battery charger – this charges your electric vehicle’s main motive pack. Having a charger on-board your vehicle, will allow you to plug in nearly anywhere that electricity is available. Some chargers can only plug in to 120 volt electrical outlets but others can accept 120-240VAC (volts alternating current). Chargers usually have rated maximum power levels of between 1,500 watts and 18,000 watts. The higher the wattage rating, the faster you can charge (assuming you can plug into a wall outlet capable of providing that many watts). If you have a full-size road-going EV, it is recommended that you get a charger which can handle both 120 VAC and up to 240VAC. Most EV owners make adapters since there are many different kinds of outlets available to plug into especially at 208 to 240VAC.
  9. Instrumentation – The recommended minimum instrumentation will consist of a motive pack voltage display, a motive pack amperage display and an SOC (State of Charge) display. The SOC display will replace the fuel gauge and let the user know how full the battery pack is. The voltage and amperage displays will show the user what is happening with the battery pack as a whole. Other useful instruments would be something that shows motor amperage and motor voltage. Since the motor side of the controller is often quite different from what is happening on the battery side, being able to watch information such as motor current, can be very useful in determining what gear to be in in order to keep the motor amps at their lowest so that the motor or controller do not overheat.
  10. A battery management system (BMS) – Some folks will tell you that you do not need a battery management system, however there are good reasons why most all of the commercially available EVs built by major manufacturers have battery management systems. Every battery or cell in a battery pack has a given voltage based on it’s particular chemistry. In order to create enough voltage to move an electric vehicle quickly, many cells are hooked together in series so that a larger battery pack is created that has an overall voltage which is much higher than that of the individual cells. Anytime cells are connected in series, the entire pack will be limited by the weakest cell. Most battery management systems have some means of equalizing the cells so that they are all closely matched, but more importantly a proper BMS should give the EV user a means of viewing individual cell or battery module data such as voltage and temperature. Being able to monitor individual cell voltages in real-time will allow you to spot problems (such as weak cells or imbalances) and to see exactly what is happening under various conditions such as when accelerating, going up hills or charging.
  11. A heater – There are commercially available fluid heaters which allow you to use the vehicle’s existing heater core and control systems, or many people also make their own heaters using simple resistive heating elements or even from cannibalizing space heaters or hair dryers. In the Seattle area, we might not have to worry about freezing temperatures very often but we have plenty of moisture and if you cannot defrost your windshield it isn’t very fun driving your EV around with your head out the window like Jim Carrey in Ace Ventura Pet Detective! There are no creature comforts that an EV driver must do without and in fact an advantage of resistive style EV heaters is they usually provide heat immediately instead of having to warm up. Some people may even design cabin pre-heating systems or battery heating systems. Still others use a compressor to create an air conditioning system.

Those are the main components needed to convert a vehicle to electric. Of course there will be a lot of small wires and fuses and larger high current cables needed to provide the paths for the electricity to flow to the various components in your vehicle. Your main motive pack should have one or more safety fuses which can open the circuit in the event that too much power is moving through the circuit (such as an electrical short). Additionally, any other components which are connected across your high voltage battery pack should have their own smaller low amperage yet high voltage fuses. Standard automotive fuses are usually only rated for 12V automotive applications so they must never ever be used on the high voltage side of other components such as your motive pack voltage gauge or DC/DC converter!

Even the wiring and cabling that is used will have specific voltage insulation ratings and again standard 12V automotive wire will likely not be sufficient. Your motive battery pack voltage must not exceed the rated voltage of any of the other components in your system whether it be the fuses, wiring, DC/DC converter, main contact, or even the motor controller. It is very important when choosing electric vehicle components that all of them can safely work together.

It is also important to keep accurate financial records, receipts and serial numbers of every new component you purchase for your EV conversion. In the future, if anything is stolen, or you get into an accident, or if you want to get an appraisal and/or a specific ‘stated value’ style vehicle insurance policy, your detailed records should increase the likelihood that you will be fairly compensated.

A common problem seasoned electric vehicle veterans notice is that many a person who is doing their first EV conversion will choose a vehicle which is in poor condition. Any vehicle can be converted to electric and classic or exotic vehicles are often good choices since they differ from the modern factory-built EVs, but unless a vehicle is so rare that there are no examples in good condition, save yourself the trouble and start with a good quality donor!

Choosing a good donor vehicle means that you don’t start with some car just because your friend gave it to you for free or you found it in your field after finally mowing the lawn. You may find a vehicle which is already missing an engine, but this doesn’t mean it will save you time; in fact if you have to create a custom adapter plate to mate your electric motor to your old transmission, there is critical information you must get from the old engine. It is actually highly recommended that you start with a fully operational and drivable donor vehicle. This way you can make sure the vehicle’s existing 12V electrical system is functioning and you can determine whether other components such as brakes, clutch, transmission, steering etc. are all in good working order. Choose a vehicle that is also in good condition cosmetically or else you may spend far longer on your project because you wind up having to restore the entire vehicle in addition to adding all of the new electric components.

Some final advice is that you start with a donor vehicle that has a manual transmission. Yes, automatic transmissions or direct-drive (no transmission) conversions do exist but the vast majority of conversions use manual transmissions. It is also usually true that the older a vehicle is, the simpler it’s systems will be.  Furthermore, it is highly recommended that you purchase a full set of the factory service manuals for your vehicle as these will be far more detailed than any aftermarket repair manuals and the factory service manuals usually contain more detailed wiring diagrams.

STEP 4: START BUILDING – By now you should have an actual vehicle ready to convert and all or at least most of the components that you will need. Although a heated shop with a vehicle lift would be ideal, most conversions are done in home garages. Some SEVA members have done conversions inside very small garages or even under carports or simply out in a driveway, but whatever your situation, make sure that you choose a spot where your vehicle can sit for an extended period of time. The conversion of a full size vehicle to electric power will likely take between 200 and 800 hours of labor. Yes, there are people who talk of converting a car in a few weekends and SEVA’s own Stephen Johnsen has taught classes where a vehicle is converted in 6 days, but these feats require an extreme amount of work with the right parts, tools and people and are exceptions to the norm. The more automotive experience you already have and the more people you have available to help you the faster you can finish your conversion but most people take many weeks, or even months or years to finish a conversion.

NOTE: Again, all of the material contained on the SEVA Website is intended for educational purposes only and is NO SUBSTITUTE for real world experience and knowledge! Many components and voltages in electric vehicles and other vehicles can cause personal injury or death if proper precautions are not taken. Never work alone and when in doubt, always assume high voltage is present and do not proceed of you feel uncertain or unqualified! By reading the information contained in SEVA’s website, you are agreeing to hold SEVA (The Seattle Electric Vehicle Association) and any of its members, contributors and affiliates harmless in the event that you suffer any losses or injuries due to any of your own projects. SEVA and it’s contributors and members accept no responsibility for any actions taken by others as a result of what they have read on the SEVA website, in this guide or in any SEVA literature.

Hopefully you have heeded the advice of starting with a running, drivable vehicle. If so, now would be the time to test all of the systems and get any drivability issues or electrical system, or instrumentation problems fixed. If you know everything functions when you start, then you’ll know something must have changed if things don’t work once it has been converted to electric power. While the vehicle is drivable, it is also often a good time to take it to a professional car wash where you can have the entire vehicle and underside cleaned. It’s also nice to have the under-hood area steam cleaned. Starting with a clean vehicle is not just more pleasant to work on but in fact, it can be easier when it comes to finding and loosening bolts and other components.

Weigh the vehicle and get individual axle weights – Remove everything which did not originally come with your vehicle and drive your vehicle to a truck stop or other weigh scale, or find someone who has a set of 4 individual wheel scales. It is important to write down the total weight of your actual vehicle, and each axle weight as it was when it was powered with an infernal combustion engine. As you convert your vehicle, you can weigh each item you are planning to put in and try and get the vehicle to have a similar weight and similar front-to-rear weight balance as it was originally designed for. For safety reasons, it is also important that you not exceed the original gross vehicle weight and gross axle weight ratings of the vehicle; these can usually be found on a sticker in the door jam area of the driver’s side door.

If your vehicle has a computer system, you might take it to a shop which can perform a diagnostic check so you can get a report of any error codes that it has prior to your converting it. Remember how it was mentioned that older vehicles are often simpler to convert? One reason is you don’t have to hassle with as many existing electronic modules or on-board computers. As a general rule computers in cars became more complicated throughout the 1980s and then even more advanced around model year 1996 with OBD-II. In more recent vehicles the electronic and CAN control methods have become so widely used that many features of the car may be completely computer controlled. For example the entire instrument panel may not function if a computer module is not happy about what it is seeing from the engine (or lack thereof).

If your vehicle has a working air conditioning system which you will be taking apart, then it is wise to take it to a professional to have the system purged so you do not have to deal with high pressure refrigerant escaping when you are working in your garage. Additionally, if you do not want to hassle with the various fluids such as coolant, oil and transmission fluid, you can drive your vehicle to a repair shop with proper vehicle fluid handling capabilities and disposal methods, have them remove all the fluids and then have your vehicle towed back to your place for you to work on. It is worth noting that another advantage of choosing a running donor vehicle is that you can sell the vehicle’s engine as a running engine; for this reason you might want to take one last video of the engine running before it is disabled.

If you do not already have an engine hoist (cherry picker) or gantry crane for removing your old ICE (internal combustion engine) then you should probably purchase or rent one. Now is the time to remove that dirty old engine. LABEL EVERYTHING BEFORE YOU REMOVE IT! Again, label ABSOLUTELY every wire, connector or sensor that you remove from the engine. You can use a professional label maker or simply tape and a permanent marker. Even if you don’t know what something is, USE A NUMBER OR LETTER to designate that connection as something and LABEL BOTH the part it was plugged into on the engine, and the plug itself. Never try and rely upon your memory or assume you won’t need a part or wire! NEVER EVER, EVER cut your vehicle’s original wiring harness until you have the vehicle running as an electric vehicle (and in that case, only cut wires one at a time while testing in between so that you can easily determine if something was crucial after-all)! Another trick when removing engine components on newer vehicles is to actually remove each sensor from the engine instead of just unplugging it’s wiring harness. Then you can simply tuck the wires (with their original sensors still connected) out of the way until you get the vehicle back on the road driving as an EV at which point you can determine one at a time what is really needed or not.

Once you have removed all of the unnecessary old infernal combustion engine parts and subsystems such as the exhaust system, fuel system etc., then you can finally start determining where you will mount all of the new EV components! Avoid routing high voltage wiring inside the passenger cabin and use common sense when considering placement of various components so as to avoid damage from road debris or during heavy rainfall, snow or while driving through puddles. Visit and find the NEDRA rule book. Although the NEDRA rule book is designed for race vehicles, it includes many prudent safety guidelines and information on properly sizing and constructing battery hold-down means for a given battery pack weight. If you design for the NEDRA specs, not only will you be able to easily pass an inspection if you ever decide to race your car in the future, but you can feel confident driving on the street knowing you designed your car for the even more stringent racing rules.

BE VERY CAREFUL AROUND  VEHICLE BATTERY PACKS! You cannot turn batteries off! Therefore proper safety equipment and procedures must be followed in order to avoid injury. That is beyond the scope of this simple educational guide and IT IS THE SOLE RESPONSIBILITY OF ANY INDIVIDUALS READING THIS TO SEEK PROPER TRAINING OR HAVE WORK PERFORMED BY OTHER QUALIFIED PROFESSIONALS IF THE INDIVIDUAL(S) THEMSELVES ARE NOT QUALIFIED TO WORK WITH HIGH VOLTAGES!

The batteries will need to have proper racks and/or cases built to protect and shield them. While the cases should be designed and built in the early stages of the electric vehicle conversion, the actual hooking up of the batteries should usually be the very last step after everything else is already mounted, figured out and ready to run. It is wise to have multiple mid-pack disconnects so that the overall voltage can be kept to a minimum until the last possible moment. Once everything is installed, it is finally time for Step 5 which is the final finishing and testing phase!

STEP 5: FINISH & TEST – Once all the many hours of hard work have been put in figuring out and mounting and integrating all the various new electric vehicle components, it is finally time to test your new EV conversion! Make sure you have tested and know how to activate your various emergency disconnect measures. Before your first driving test, make sure to fully charge your battery pack. The very first time you turn on your vehicle and close the main contactor, it is wise to have the vehicle on blocks or out in the driveway with ample space around the car in case it takes off, or moves in a direction opposite that which the driver was expecting.

Many EV conversion owners will tell you things like, “Well, my car’s never really finished” and certainly once you get it running there are usually plenty of little things you will find that you want to change or tidy up but keep that EV drivable and enjoy the fruits of your labor and the feeling you get each time you zoom past a gas station.

The more you start to drive your EV, the more you will start to learn what it is capable of and how to drive it. By having a good BMS for monitoring the individual cells or battery modules, you will be able to see how your pack is doing. Usually the pack capacity will increase with regular use, and also with warmer temperatures. You may find it useful to keep a small notepad or journal in your EV so that you can take notes on how far you drive it and what various readings you have on your instrumentation. At some point, it is nice to do a “range run” where you drive your EV a long distance monitoring the SOC and the batteries and ending the ride near to a charging station (such as driving around and around your neighborhood). Make notes on how fast you were going, what the temperature was, which accessories you were using and how much weight the vehicle was carrying and you can start to get a better idea of what your EV is capable of.  Now that it is electric, you can once again take your vehicle and weigh it and both of it’s axles to see how similar it is to what it had been before the conversion.

As of 2014, at the time of this writing, Washinton State does NOT require electric vehicles to be inspected prior to having them registered as an electric vehicle. Assuming you have a vehicle that is already street legal and licensed and titled for Washington State, then all you have to do if you want to avoid getting notices for vehicle emissions tests, is take your ID and vehicle title in to a licensing department and have the DMV employee change the vehicle’s power type to “E” for Electric. Many licensing agencies will not be familiar with the law and may inappropriately tell you that you have to take it somewhere to be inspected. If this occurs, you can politely ask that they check with their supervisor, or that they call their head office in Olympia. Once they talk with someone who is familiar with the rules, they will be able to walk them through the process of changing the indicated power type on your title. It is also worth noting that as of the time of this writing, Washington State imposes a $100 annual flat fee on electric vehicles in order to bring it extra revenue that they will have lost due to your not purchasing gasoline or diesel and paying those fuel taxes.

Once you have a drivable conversion, please bring it to a SEVA meeting and take it to car shows! Give your friends and neighbors rides and you’ll start to witness what has become known as the “EV Grin” – a smile that creeps across the face of anyone who has just started feeling the silent acceleration of an electric vehicle for the first time!


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