Autonomous power systems based on a car battery and an auto-inverter are suitable for those who cannot afford ready-made solutions in the manner of a portable charging station. They also fit perfectly into the concept of apartment housing stock, where there is usually no way to install a smoking generator.

Automotive inverters work on the principle of converting an input DC voltage of 12 or 24 V into an AC voltage of 230 V at a frequency of 50 Hz. You can use them both on long trips behind the wheel, charging portable electronics right on the go of the car, and outside the vehicle. As a rule, the first option involves connecting the inverter to the car's on-board network through the cigarette lighter socket. In the second case, the converter is connected to the battery terminals by means of power wires of the "crocodile" type.

The most important parameter when choosing a suitable autoinverter is the rated power of the connected load.

Inverter Rated Power

First of all, it is necessary to clearly define which devices will be powered by a car inverter, after which it is necessary to calculate the total power of all electrical appliances planned for simultaneous connection. Power consumption data is usually recorded in the passport characteristics of a particular device, sometimes they are indicated on the case or power adapter.

To the obtained value of the total load power, it is desirable to add 15-20% in reserve. The reserve will serve as a guarantee of stable operation of the auto-inverter without overloads.

Inverters are often rated for peak or maximum power. You should not strictly focus on them when choosing, because on an ongoing basis the car inverter cannot cope with maximum loads. This parameter is important in another way - it determines the efficiency of the inverter when working with high starting currents. Say, when starting a refrigerator compressor or a power tool engine, peak power can exceed the nominal power by about 2-2.5 times. But only for a very short period of time (within a few seconds) necessary for the power unit to enter normal operating mode.

The rated load power is one of the fundamental parameters when choosing an auto-inverter.

An example of calculating the total load power. Let's assume that it is supposed to power two working laptops (≈150 W each), a router (≈15 W), an ONU terminal for fiber optic cable from an Internet provider (≈15 W), several light bulbs (≈10 W each) from a car inverter.

150 + 150 + 15 + 15 + 10 + 10 = 350 (W).

For autonomous power supply of such a load, an auto-inverter with a rated power of about 400 watts is suitable. Almost 15% remains in reserve. By adding other electrical appliances to the circuit, we also make calculations for them, not forgetting to leave 15-20% of the power in excess of the result.

Popular car inverters

sinusoid

An important criterion when choosing a car inverter is the shape of the output signal. The quality of the power provided by the device directly depends on it.

In models with a pure sine wave, the voltage on the graph is plotted as a smooth line. At the output there is a signal identical in form to the network one (in ordinary household sockets) with a high accuracy of voltage maintenance. Converters with a pure AC sine wave at the output are expensive, but you can’t do without them if gas boilers, circulation pumps for heating systems and sensitive electronics are introduced into the autonomous power supply circuit.

The modified or approximated sine wave has a stepped shape on the graph and a simplified conversion circuit, which reduces the cost of the autoinverter. The lion's share of household and computer equipment, as well as electronics with switching power supplies, can withstand the use of simplified AC voltage without consequences. So in the absence of sensitive devices in the backup power circuit, you can safely choose a car inverter with a modified sine.

Visual waveform graphs with pure and modified sine wave.

Another important character trait of a high-quality auto-inverter is the stability of the output voltage. It is desirable to give preference to converters with a voltage stabilization function. When the inverter is connected, the battery is gradually discharged, which leads to a drop in the level of generated voltage. Household appliances do not like voltage fluctuations and are often able to withstand only up to 10% of such fluctuations. Sudden sags and power surges can disable electrical appliances.

Charging stations

Connection

There is nothing difficult in deploying autonomous power supply systems from an auto-inverter and a car battery. With each other, they keep the relationship with the help of terminal clamps (in common "crocodiles"). The main thing is not to reverse the polarity - otherwise the protection system will work and you will need to change the fuse in the converter. The red crocodile clip corresponds to the positive terminal of the battery, the black one corresponds to the negative terminal.

Be sure to turn on the inverter first, and only then connect all the necessary equipment to it. The number of sockets in the design of the converter does not play a significant role, because the power supply of several electrical appliances can be established through an extension cord. But one or two USB ports on board the car inverter will come in handy for charging mobile gadgets.

Scheme of connecting a car battery and an auto-inverter. The charger is connected to the battery separately from the inverter terminals.

The approximate operating time of the connected load from the inverter and batteries of different capacities is given in a visual table:

Approximate operating time of the connected load from a battery of a certain capacity
Battery capacity> Rated load
100 W 300 W 500 W 1 kW 2 kW
60 Ah 6 hours 2 hours 40 minutes 15 minutes 2-3 minutes
85 Ah 10 hours 3 hours 1.5 hours 30 minutes 10 minutes
190 Ah 22 hours 6 hours 4 hours 1.5 hours 30 minutes

There are more complex schemes for building autonomous power systems using several car batteries. In particular, the serial connection of two batteries makes it possible to double the operating voltage (from 12 to 24 V), which reduces energy losses during voltage conversion. The 24V battery function must be supported by the inverter. Well, the parallel connection of batteries increases the total capacity of the assembly.

Pulse (inverter) chargers

Accumulator charging

Any battery needs regular replenishment of energy reserves. To do this, you need to get a suitable charger. And preferably - pulsed (inverter). The vast majority of these chargers work with automatic parameter control, they are multifunctional, informative, visualize battery parameters on the display.

The charger is connected to the car battery using the same alligator clips. During battery charging, the inverter must be disconnected from the circuit. The correct charging current for the battery is considered to be 10% of the battery capacity. For example, for a 65Ah battery, the charging current should not exceed 6.5A.

Maintaining the charge of the battery "afloat" is carried out by specialized battery chargers.

You can also monitor the battery charge level according to the data on the inverter info screen. As a rule, the display in the design of the converter is used to display information about the incoming voltage, the power of the connected load, and warning of malfunctions with error codes. Some models of auto inverters, when the voltage at the battery terminals drops to a critical minimum, beep, indicating that the battery is low.

Of course, you can charge the battery in the old fashioned way - just install the battery in the car and drive around the neighborhood, or stand at idle for a long time. However, a heavy battery will need to be dragged to the car and back, and we also do not forget about the expense of expensive fuel. It is much easier to introduce a specialized battery charger into the autonomous power supply circuit.

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The car inverter must be selected strictly for your needs, not forgetting to leave some power in reserve. In the best way, such autonomous power supply schemes are revealed in conjunction with strong traction batteries. But starter batteries are also suitable for the role of an energy source. The main thing is not to discharge those “to zero”. Assemblies from an auto-inverter and a car battery allow you to wait out power outages with minimal discomfort.