Many truck drivers, agricultural machinery or owners of specialized equipment face the need to install a powerful radio station, winch or inverter in a passenger car. The standard on-board passenger transport network is designed for 12 volts.Professional equipment often requires 24 volts.. Attempting to connect 24-volt equipment directly to the onboard network will lead to the device inoperability or its instant failure.
The solution to the problem lies in the plane of competent voltage conversion or change in the configuration of power. There are proven methods to obtain the necessary current parameters without risk to the electrical equipment of the car. It is important to understand that a simple wire twisting here will not help – you need the use of specialized electronic devices or change the scheme of connecting batteries.
In this article, we will discuss in detail two main ways to increase voltage: DC-DC Converters and the series connection of batteries. You will learn about the benefits and risks of each method, learn how to select the right equipment and safely mount the system. It is critical to remember that improper connection of 24-volt load to 12-volt network without converter is guaranteed to bring the equipment out of order.
Why you need 24 volts in a car
The standard voltage on-board passenger car network was established decades ago and is 12 volts. This is enough for the starter, ignition system, lighting devices and multimedia. However, with the development of technology and the emergence of powerful additional equipment, the requirements for the power system are growing. Professional CB radios, powerful sound amplifiers, winches and compressors for air suspension are often designed to the standard. 24Vaccepted in cargo and special equipment.
Using 24-volt equipment in a 12-volt network is impossible without prior preparation. When trying to connect directly, the device simply won’t start, as the voltage will be half the required threshold for activation of the electronics. Moreover, some devices may try to consume double current at low voltage, which will lead to overheating of the wiring and a fire hazard situation.
The main consumers requiring increased voltage are:
- 📡 Powerful radio stations (e.g., President, Alan professionally Motorola), which at 24 volts give a higher power output and have better efficiency.
- 🔋 Chargers portable battery tools that only run on 24V.
- ⚙️ Pneumatic compressors and tire pumping systems designed for high voltage for fast operation.
- 🔊 Audio systems professional level, where high voltage power allows you to get more power without huge currents.
⚠️ Attention: Never try to power a 24-volt device from a 12-volt network “directly”, hoping that it will work half-heartedly. The electronics will either not turn on or burn up due to incorrect operation of the internal transistors.
Method One: Using a DC-DC Converter
The safest, most modern and most common way to get 24 volts out of 12 is to use a pulsed voltage converter type. Step-Up (boosting). These compact devices, often called boosters, take the input unstable voltage on the onboard network (which can range from 11 to 15 volts) and give a stable 24 volts.
The main advantage of DC-DC converters is their high efficiency (efficiency), which in high-quality models reaches 90-95%. This means that the energy loss is minimal and the device does not require giant currents from the generator. Modern converters are equipped with built-in protection against overheating, short circuit and overloading current, which makes their use as safe as possible for the regular wiring of the car.
When choosing a converter, you need to pay attention to the following parameters:
- 🔌 Maximum output current: It should exceed your device consumption with a margin of 20-30%.
- ❄️ Cooling system: for heavy loads (more than 150 W) an active cooler is required, for small capacities an aluminum radiator is enough.
- 📉 Stability of output voltage: High-quality models hold 24V even when the on-board network drawdowns up to 10V.
It is important to calculate the power correctly. If your device consumes 120 watts at 24 volts, the output current will be 5 Amps. Given the efficiency of the converter (take 0.9), the current at the input (from the 12-volt network) will be much higher. Formula of calculation: I input = (P in/U input) / efficiency. In our case: (120 / 12) / 0.9 ≈ 11 Amps. This means that the wiring and safety lock on the side of 12 volts should be designed for a minimum of 15 Amps.
Method two: serial connection of batteries
The second method, often used by truck or motorhome owners, is to install a second battery and connect them in series. In this scheme, the plus of the first battery is connected to the minus of the second, and the total voltage at the free terminals is 24 volts. This method allows for greater capacity and current output, but has serious limitations for passenger cars.
The main problem is charging. The standard generator of a passenger car produces 13.8-14.4 volts. For full charging of two series-connected 12-volt batteries, a voltage of about 28-29 volts is necessary. If you connect such a bundle to a regular generator, the batteries will not be charged, and when working from them, the load will quickly land one of the batteries, causing a deep discharge.
Additional components are required to implement this scheme:
- 🔋 Two identical batteries: The same capacity, age and technology (AGM, GEL, WET) are required.
- 🔌 Charger separator (ROM): A smart relay that allows batteries to be charged in parallel from the generator (14V), but switches them to a serial circuit (24V) when consumers are working.
- ⚖️ Balancing: device for equalizing the charge between banks, preventing stress skewing.
Why can’t two squats be connected in series?
If you simply connect two batteries in series and charge them from a 12-volt generator, the voltage at the terminals of the bundle will grow very slowly or not at all. The generator will think the battery is charged when the voltage reaches 14 volts, but each battery will only have 7 volts, which will lead to sulfation and death of the batteries in a few months.
Implementing a dual-battery scheme in a passenger car requires a lot of space, which is often impossible in the conditions of limited under-hood space. In addition, the weight of two full-fledged batteries will significantly increase the load on the suspension and body. Therefore, this method is recommended only for off-road expedition vehicles or cars where a powerful winch is installed, requiring huge starting currents that are not available for a single DC-DC converter.
Comparison of voltage conversion methods
The choice between a converter and a second battery depends on your goals, budget and free space. For most users who want to install a radio station or charge a tool, the best solution is a DC-DC converter. It's cheap, compact and safe. The scheme with two batteries is the lot of professionals who need autonomy and huge power.
Below is a comparative table that helps to determine the choice of equipment:
| Parameter | DC-DC Converter (Step-Up) | Two AKS in succession | Inverter 12-220 + 24V power supply |
|---|---|---|---|
| Efficiency | High (90-95%) | Medium (depending on the switching scheme) | Low (Losses on Double Transformation) |
| Difficulty of installation | Low. | Tall. | Medium |
| Cost | Low/Mediocre | High (requires 2nd battery + relay) | Tall. |
| Reliability | Tall. | Medium (deep discharge risk) | Medium |
| Dimensions | Compact | It takes a lot of space. | Overall |
The third option, indicated in the table - the use of an inverter (12V -> 220V) and the subsequent connection of the standard power supply of the device (220V -> 24V) - is the most inefficient. Double energy conversion results in large losses in the form of heat and requires equipment with a power reserve. This method makes sense to use only temporarily, if there is no specialized car converter at hand.
For 95% of the cases where additional equipment is installed in a DC-DC passenger car, the converter is the only rational and safe choice.
Instructions for installation of DC-DC converter
Installation of the booster converter requires care and compliance with electrical safety rules. Before starting work, be sure to remove the minus terminal from the main battery of the car. This will prevent accidental short circuit and sparking at the time of connection of the wires.
The installation process consists of the following steps:
- Selection of location: Place the converter in a dry place, away from heat sources (muffler, exhaust manifold) and water. Ensure free air circulation around the radiator of the device.
- Wire laying: Use the copper wire with a cross section corresponding to the load current. For currents up to 10A, a section of 1.5 mm2 is suitable, for 20A - 2.5-4 mm2. Lay the wires away from high-voltage ignition wires to avoid interference.
- Installation of the safety lock: In the break of the plus wire going from the battery to the converter, install a fuse. The nominal value of the fuse is selected with a margin of 20-30% of the maximum current of consumption.
- Connection: Connect the input of the converter (
Input 12V) to the on-board network and the exit (Output 24V) to the consumer. Observe polarity!
☑️ Pre-launch checks
After assembling the circuit, but before connecting the consumer himself (for example, a radio station), it is recommended to check the output voltage with a multimeter. Turn on the ignition of the car and measure the voltage at the output terminals of the converter. It should be stable and in the range of 23.5-24.5 volts. If the voltage is "floating" or different from the nominal, check the reliability of the contacts and the cross-section of the wires.
⚠️ Attention: Do not use the regular thin wires of the car to connect powerful consumers. The wiring of a cigarette lighter or tape recorder often has a cross section of less than 1 mm2 and is designed for currents up to 5-10 Amps. Direct connection of a powerful load through such chains will cause insulation melting and fire.
Typical errors and security measures
The most common mistake is to ignore the quality of the connections. The twists in the electric car are unacceptable – they are oxidized, warmed and become a source of resistance. All connections must be made using soldering, high-quality sleeve squeezing or reliable terminal pads. Poor contact at the 12 volt inlet will cause the voltage to drop and the connection site to heat up, which can melt the plastic.
Another mistake is choosing a converter without a power reserve. Electronics are running at the limit of capabilities, which reduces the life of the device. If your winch consumes 200 watts, the converter should be designed for a minimum of 250-300 watts. Work at the limit of nominal value causes overheating and operation of thermal protection at the most inopportune moment.
Basic safety rules:
- 🔥 Fire protection: All power wires must be laid in corrugated or cable channel, especially in places of passage through metal partitions of the body.
- 💧 Moisture protection: If the equipment is installed in the trunk or outside, make sure that the body of the converter is protected from moisture (minimum IP54) or additionally protected by a box.
- 🔋 Charge control: When using powerful consumers, watch the voltage on the main battery. A deep discharge of the starting battery below 11.5 volts can lead to the inability to start the engine.
Use the multimeter to periodically check the voltage at the battery terminals with the engine running and the consumers on. This will help to notice the fault of the generator or drawdown of the network in time.
Remember that the electrical system of a car is a complex organism. The changes must be justified. If you are not confident in your abilities, it is better to entrust the installation of complex equipment to professional auto electricians. Errors in the electrician can cost not only the burnt fuse, but also the failure of an expensive electronic control unit (ECU) of the engine.
Frequently Asked Questions (FAQ)
Can I charge a 24-volt battery from the 12V onboard network?
Directly, no. To charge a 24-volt battery from a 12-volt network, a special charger with a voltage increase function (Step-Up) or a DC-DC converter sharpened for charging the battery is necessary. A conventional 12-24V converter may not have the necessary charging algorithms (CC/CV) and may damage the battery.
Will a 24-volt light bulb burn if you plug it into 12 volts?
No, it will not burn, but it will not shine (or it will be barely noticeable). The incandescent lamp at half voltage consumes approximately 1/4 of the rated power. However, LED devices with drivers may simply not turn on, as the input voltage is below the electronics trigger threshold.
What wire is needed to connect the winch 24B through the converter?
The wire cross section depends on the current. For a winch with a capacity of 1000 W, the current at the 12V input will be about 90-100 Amps (taking into account efficiency). For such a current, a wire with a cross section of at least 25-35 mm2 (copper) will be required. Be sure to use copper tips and reliable insulation.
Does the DC-DC converter heat up when working?
Yes, heating is normal, as some of the energy is lost as heat. When the load is more than 50% of the nominal value, the body can be heated to 60-70 degrees. That is why it is important to ensure good ventilation and not cover the working converter.
Can I use a 12-24 converter for a laptop in a car?
Yes, if the output voltage of the converter corresponds to the required laptop (usually 19V or 20V, but there are also 24V models). It is important to check the exact voltage on the label of the laptop power supply. If a laptop needs a 19V and you file a 24V, it will burn. There are universal car adapters with adjustable output.