Questions and Answers
Q- What is the basic cost of converting a vehicle to electric power?
A- There are many variables that could affect the answer to such a general question, so let's just hit on the basics.
The power package or drivetrain package consists of a motor, an inverter and a proper gearbox. There is a big range here; basically, the more performance, the more durability and the more range you desire the higher the costs. The range of a proper street legal drivetrain package will run between about $5k and $30k depending. The first or in some cases the second most expensive item is a proper (safe) battery pack. Different end users and certainly different climates and terrains are big factors in both what cell chemistry is right and how big the pack must be. In general, pack cost, not cell cost, will run between $300 and $400 per kWh. Range from a kWh depends on many factors like vehicle weight, climate and driving speed. A small car may get as high as 3 miles per kWh while a class three or four vehicle with a load or towing might be lucky to get 1 mile per kWh and everyone else is somewhere in between. Easy to see that a pack capable of a 100-mile range could cost between $10k and $40k depending on the factors already mentioned.
There are many more components to a complete conversion and then there is the design, CAD, parts fabrication, and maybe powder coating of mounting pieces for all the components. By the time you add everything together along with massive amounts of labor a typical and proper vehicle conversion will cost between $25k and $45k.
Q- What is the best motor for my application?
A- Application is the key word above. Many low dollar and a few high dollar conversions of been done with DC motors. Usually, a DC motor is less expensive than an AC motor. Drag race only cars benefit from the awesome low-end torque found with DC motors, some even run multiple motors, however DC motors are usually considered rpm limited and not capable of hitting high track speed. This can be overcome with an overdrive or two from someone like Gear Vendors.
Note: all OE car manufacturers making electric vehicles today use high quality liquid cooled motors and inverters. Some motors come with a matched inverter/controller and others leave you to find your own compatible inverter.
Next you need to consider the quality and durability you are looking for. Are you just looking to drive very short distances so you can say "look Ma I made an electric car" or are you looking for OE quality, a vehicle you can drive anywhere, including highway driving and maybe even light towing or weight hauling applications. Suffice it to say there are many variables to choosing the correct motor and inverter for your needs. Learn from others that have gone before you and, in some cases, changed motors multiple times before finding the package that works for them. The next big decision will be are you building a low voltage or high voltage system. Many of the DIY level packages will be air cooled and run at lower voltages like 72v to 96v. Most OE quality conversions use high voltage (275 to 800v) and these are always liquid cooled. Typically, the higher the voltage, the fewer amps are required to do the same work. High voltage is usually more energy efficient.
Note: Every motor has a minimum and maximum voltage that the motor manufacturer recommends.
Torque Trends is an authorized distributor/installer of the UQM/Danfoss motor line. For most applications we recommend the PP-High Speed 160 kW liquid cooled motor which comes with a liquid cooled and matched inverter. For short range light duty DIY projects on a tight budget, we recommend the low voltage Net Gain Hyper-9 air cooled motor. TTI fits many motor packages with our TorqueBox brand reduction gearbox.
Q- What is the best gearbox for my application?
A- A reduction gearbox multiplies the torque of the motor by its ratio and reduces the output shaft rpm also by its gear ratio. For example, a motor that makes a maximum of 330 Newton Meters (Nm) or 243 lb ft of torque when coupled to one of our 1.90 to 1 reduction boxes now produces 627 Nm or 462 lb ft of output shaft torque. Without the TorqueBox, often called direct drive, one would need to run a much larger motor and larger motors cost much more and are, in many cases, rpm limited meaning less road speed capable.
Really low budget and most all of the early gas to ev conversions just made an adapter and coupler to bolt the electric motor to the existing "gas appropriate" multiple speed manual transmission. Then they would typically run in either second or third gear. This is very energy inefficient. A proper reduction gearbox saves weight and reduces frictional losses which extends the vehicles operating range. A reverse gear is not needed as most electric motors can simply be run backwards for reverse.
Q- I see you offer an optional ParkLock system for your gearbox, do I need it and if so, why?
A- Our ParkLock is a system for locking the gearbox and thus the driveline to prevent the vehicle from rolling away when parked. According to DOT for a vehicle to be road legal it must have a positive locking system to prevent rollaway other than the vehicles e-brake. The DOT goes on to say the locking mechanism must be applied as one in the same function as placing the vehicle in the park position, it should not be a separate function. Setting an e-brake when parking even with a transmission lock is accepted and recommended by most car manufacturers. The ev world is rapidly changing but at the time of our ParkLock system development and at the time of this writing, the ParkLock system is a sound investment in safety. We have all heard horror stories about cars and especially ev conversions rolling away. I know of one that ended up in a neighbors swimming pool at the bottom of the hill. ParkLock would have prevented this.
Q- Why do you not offer a yoke automatically with every gearbox?
A- TTI makes ev gearboxes with 27 spline shafts, same as GM PG and Turbo 350 transmissions so many conversions can use their existing yoke, if it is in good condition. We also make a bolt on (fixed) yoke with 32 splines similar to a GM Th400 output spline, in this case the yoke is modified with our sealing system so the yoke usually needs to be supplied by us. Call (623 755 8214) or email (firstname.lastname@example.org) our tech department with any yoke questions.
Q- What is the best battery chemistry and pack size to run for my application?
A- Now here is a subject that was easier to answer a couple years ago than it is today and yes there are many variables here as well. We will try to keep the answer informative and concise.
To start with there are three basic physical battery types used in conversions:
All three physical types are available with several popular chemistries. Most, but not all, Prismatic cells are described as a Lithium Iron Phosphate chemistry. They are considered the safest chemistry. Typically, Prismatic cells have a 3.2v nominal voltage and are what we call "a little sleepy", meaning they don't accept or release electrons quickly. This is an OK battery for most DIY builds and less than high performance vehicles.
Other popular chemistries are Lithium Polymer, Lithium Nickle Manganese Cobalt Oxide, Sodium, Nickle Silicon Aluminum and Sulfur. Some of these performance cells offer 3.7v or slightly higher nominal voltage. All of these have a lithium solution and the other words found in the cells name generally describe the material or coatings used in construction of the cell and primarily the anode and cathode (positive and negative polls) within the cell.
Billions of dollars have been spent on battery improvements over just the last few years and even more will be spent over the next few years to maximize the energy density, longevity and charge cycle capability. The next great gain in battery cell technology will be the solid-state battery offering many advantages over today's liquid lithium solution cells.
Which is best for you is a complex subject. Many of the converters today are using used Tesla modules from salvaged vehicles. A typical Tesla module holds 444 individual cylindrical cells and can be used in both series and parallel configurations or combinations thereof to create the max voltage and amperage desired. Tesla uses 6000 to 7000 cells or around 16 of these modules in a single car. Last I looked the aftermarket was asking between $1200 and $1400 per module. Because these modules are becoming increasingly popular the prices are continually climbing.
There are of course many other options available. Most lithium-based batteries are made in either China, Japan or Korea and most have distributors in the US and Europe. If you are doing your own conversion and building your own packs then hit the Internet hard, see what others are currently doing and find your best deal. Ideally though, you will want to deal with a company who has experience designing and building battery packs. Safety and battery life come through proper battery management, so unless you have done this successfully, lean on others with a good reputation.
Prismatic cells (built like a brick with ridged exterior dimensions);
Pouch cells (soft and flexible like the name implies); and,
Tesla popular cylindrical cell, similar to an AA battery, only larger.
Q- What other components besides a motor, inverter, gearbox and battery pack will be needed to complete my conversion?
A- Not all conversions are the same, but here is a very basic list of items in addition to those listed above.
VCU- Vehicle Control Unit, this is a master controller to manage all components in your EV.
BMS - Battery Management System. Most Original Equipment packs incorporate all or at least most of the management within the pack itself. However, in most DIY projects, the BMS is a separate component.
PDU - Power Distribution Unit comes in many shapes and sizes but usually takes the battery high voltage and breaks it down and re distributes it to the various components as needed.
Coolant pump(s) on liquid cooled systems. If only running a single pump get the coolest fluid to the temperature sensitive invertor first and to the more heat tolerant motor last.
Power Steering - If needed must be addressed. Some later model vehicles already have electronic assist steering and you can easily communicate and manipulate what is already there. On older vehicles that need power steering you may need to add an additional electric motor dedicated to power a conventional hydraulic pump. In lighter vehicles you may be able to just eliminate the power assist all together. We had power steering on our 1999 Miata and just eliminated it when converting to electric.
AC Compressor - There are a number of small but very capable ac compressors on the market that can be tied into the vehicles ac system to keep the driving compartment cool. This can also be used to chill water for component or battery box cooling. Most ac compressors are of the high voltage variety and draw from the battery pack via the PDU.
Cab/ Battery heating - On our very first conversion we ran all liquid cooled components and just a single coolant pump. We plumbed the hottest coolant coming from the motor directly to the vehicles existing heater core and quickly found this was a very inadequate source of cab heat, the electric drive train components just do not make enough heat to heat the average vehicle, especially in a cold climate. There are high voltage electric heaters available and properly sized they can work very well. However, they do reduce range if you need to use them very much. Another option, all though more expensive, is to design or better yet use a good heat pump system from a late model ev.
DC to DC Convertor - Needed to drop pack voltage down to approximately 13.5 volts to run all the cars 12v systems like wipers, interior and exterior lights heater fan and your stereo. These come in various capacities and either liquid or air cooled with fans. A 1kW unit will more than suffice for the basic conversion if not running extra electronic equipment. Liquid cooled is nice but for the more basic conversions air cooled systems can work.
On Board Battery Charger - They come in different capacities and in either air or liquid cooled. Most DIY conversions will have 6.6kW or lower, chargers. Actually 3.3 kW is popular. There are many options available, even combo units with charger and DC to DC combined. Most DIY conversions use level one (household 115v current) or level two charging (can be 115v or 230v but higher amperage than a level one). Then there is DC fast charging which is only found in a few of the high dollar conversions and many, but not all OE electric vehicles. Dealing with high voltage charging is expensive and must be handled with a safety-first approach. Battery pack cooling becomes very necessary when using DC fast charging.
There are many smaller items like gauges, throttles, shift module with buttons and lights, mounting for motor, gearbox and all other components. BTW- it is important to isolate all electronic components from road vibrations. This also leads to quieter vehicle operation. Then there is all the needed hardware and wiring including the dual insulated high voltage (hv) ev cables. Welding cable use is a thing of the past. You want to use a safety approved hv cable and can expect to spend $10 to $13 a foot depending on diameter. Low voltage systems can run smaller cables but high voltage systems usually run 2/0 cable and some as much as 4/0 cable. Always try to find double insulated cables in either red or orange color and always keep the cable lengths as short as practical.