Building your own electric vehicle has ceased to be the preserve of a select few engineers and has become an accessible hobby for enthusiasts. The modern market offers ready-made kits for building an electric car, which allow you to assemble a full-fledged vehicle even with basic technical skills. This is not just a constructor, but a complex engineering project that requires an understanding of the operating principles electric drive and energy storage systems.
Unlike re-equipping an internal combustion engine, where you have to deal with the inertia of old systems, assembling from scratch gives you the freedom to choose the architecture. You decide where to place the battery, which motor to choose and how to organize the controls. However, despite the apparent simplicity of purchasing components, the process requires careful preparation and understanding physical processesoccurring in a high voltage circuit.
Before starting work, you need to realize that safety comes first here. Working with lithium batteries and high currents carries real risks if installation rules are neglected. In this article we will analyze all the stages of creating your first electric car, from choosing a donor to the first launch.
Choice of base: donor or frame from scratch
The first step is always to choose a base for the future vehicle. Many enthusiasts choose to take a lightweight ICE car and remove the engine and transmission to make room for a new powertrain. This approach allows you to use a ready-made body, suspension and braking system, which significantly speeds up the process. However, it is important to consider that body weight should be minimal to ensure good dynamics.
An alternative way is to use specialized frames or create a spatial structure from scratch. This option requires deep knowledge in the field of strength materials and welding. When choosing a donor, pay attention to the condition chassis and lack of corrosion, since the weight of the battery pack is significantly higher than the weight of the gas tank.
⚠️ Attention: When using an old donor car, be sure to carry out a complete inspection of the suspension. The increased mass of an electric vehicle will quickly damage worn silent blocks and shock absorbers.
If you're planning on building a lightweight urban vehicle, consider ATVs or even motorcycle frames. There are compact kits for them that include everything you need. The main thing is to ensure sufficient rigidity of the structure to withstand vibrations and loads during movement.
Heart of the system: electric motor and controller
The key element of any electric vehicle is the combination of the engine and the controller. For DIY projects, direct current (DC) motors or modern brushless (AC) motors are most often used. DC motors are easier to control and cheaper, but require brush maintenance. In turn, AC motors have higher efficiency and do not require regular maintenance.
The controller (inverter) is the brain of the system, which converts direct current from the battery into alternating current for the motor (in the case of AC) or regulates the voltage (for DC). When choosing a controller, its characteristics with motor parameters are critical. An incorrectly selected controller may burn out under peak loads or not produce the declared power.
Difference between series and parallel connection of motors
With a series connection, the voltage increases, but the current remains the same. A parallel connection doubles the current while leaving the voltage unchanged. For home-made cars, a parallel circuit for two motors is often used.
Many modern kits are equipped with motor wheels that are integrated directly into the hub. This solution eliminates the need for a transmission, differential and driveshaft. However, installing motor wheels requires strengthening the pendulum or forks, since the torque is transmitted directly to the axle.
- 🔌 Current type: Decide whether the system will operate on direct (DC) or alternating (AC) current.
- 📉 System efficiency: Modern AC controllers provide energy recovery during braking.
- 🌡️ Cooling: Powerful controllers require active liquid or air cooling.
Power plant: battery calculation and assembly
The battery is the most expensive and complex component of an electric vehicle. Lithium iron phosphate (LiFePO4) or lithium polymer (Li-Po) cells are used for assembly. LiFePO4 is considered safer and more durable, although it has a slightly lower energy density. The capacity is calculated based on the desired power reserve and motor power consumption.
The process of assembling a battery is called packaging. It involves connecting cells into series-parallel groups to achieve the required voltage and capacitance. The critical element here is the BMS (Battery Management System). This system monitors cell balance, temperature and currents, preventing overcharge or deep discharge, which can lead to fire.
When designing the battery compartment, it is necessary to provide reliable protection from moisture and mechanical damage. The battery case must be sealed, but have a ventilation or thermoregulation system. Keep in mind that when charging or discharging quickly, the cells can become hot and heat dissipation becomes a priority.
☑️ Check before assembling the battery
Transmission and chassis
In the classic design with a central engine, the transmission plays the role of a gearbox, reducing high engine speeds to wheel speeds. A standard gearbox from a donor car is often used, but without higher gears, since the electric motor has a wide range of operating speeds. Some builders leave the box in for use as neutral and reverse if the controller doesn't support reverse.
If you choose a scheme with motor-wheels, then there is no traditional transmission. In this case, the entire load falls on the wheel bearings and pendulum mounts. Make sure the axles can handle the torque, especially when starting from a standstill. For front-wheel drive designs, ready-made axle shafts from compact cars are often used.
| Component | Function | Features for EV |
|---|---|---|
| Gearbox | Reduced speed | Often replaced by chain/gear drive |
| Differential | Torque distribution | Mandatory for central motor |
| Suspension | Depreciation | Requires spring reinforcement |
| Brakes | Stop | Used with recovery |
The braking system of an electric vehicle works in conjunction with electric braking. When you release the gas pedal, the engine goes into generator mode, slowing the car and charging the battery. Mechanical brakes are only activated during a full stop or emergency braking, which increases the life of the pads and discs.
Tooling and Build Security
Assembling an electric car is impossible without specialized tools. You will need not only a standard auto mechanic kit, but also equipment for working with electricians. The key device is a multimeter with the ability to measure high currents and resistances. To work with batteries you need spot welding machine or a powerful soldering iron with low resistance.
Assembly safety is more than just words. Working with voltages above 60 Volts is considered life-threatening. All connections must be reliably insulated, and high-voltage circuits must be laid in corrugated sleeves away from metal parts of the body. Use dielectric gloves and tools with insulated handles.
⚠️ Attention: Never short-circuit the positive and negative contacts of the battery directly. This will lead to an instant release of enormous energy, melting the metal and a possible explosion.
Use adhesive-backed heat shrink tubing to insulate battery connections. Regular electrical tape can slip over time due to vibration and heat.
It is also worth getting a thermal imager or pyrometer to monitor temperature conditions during the first launches. Overheating of contacts or controller is a common problem when wire cross-sections are incorrectly calculated. The cross-section of the power cables must correspond to the current flowing through the system, with a margin of 20-30%.
Setup and first launch
The final stage is setting up the control system. Most modern controllers have an interface for connecting to a computer or smartphone. Through special software, you can configure the power output curve, current limits, regeneration parameters and BMS operation. This allows you to adapt the behavior of the car to your preferences.
It is better to carry out the first launch on a stand when the drive wheels are off the ground. This will allow you to check the operation of the motor, the absence of beats and the correct rotation without the risk of driving away or damaging something. Listen carefully to the operation of the gearbox and motor: extraneous sounds will indicate problems with the bearings or the rotor getting caught.
The first 100 km are considered break-in. Do not load the system with maximum currents and regularly check the temperature of all connections and fastenings.
After successful on-site tests, you can hit the road. Start at low speeds, checking the brakes and steering. Remember that the inertia of an electric vehicle may differ from usual due to a different mass distribution. Gradually increase the load, monitoring the condition of the battery and electronics.
Do I need to register a homemade electric car?
Yes, any vehicle driving on public roads must be registered. However, the procedure for electric vehicles may differ depending on the country. Structural and electrical safety certification is often required. Registration is not required for race tracks or private property.
How much range is realistic for a DIY project?
The actual range depends on the battery capacity and the weight of the car. For a light city electric car with a 10-15 kWh battery, it is realistic to travel 80-120 km. Increasing capacity leads to increased weight and cost, so balance is important. Using recuperation in the city can add up to 15-20% to your mileage.
Is it difficult to find spare parts for such projects?
The main components (motors, controllers, BMS) are widely available on specialized sites and from manufacturers such as Golden Motor, Kelly Controls or Chinese OEM suppliers. Mechanical parts are often taken from production cars (VAZ, Oka, minicars), and problems usually do not arise with them.