If you need 220 volts in your car: expertise of inverters
To power a laptop or power tool designed for 220 V in the car, you need a voltage converter. The experts of “Za Rulem” tested six samples, powerful – from 1 kW, and weaker – about 200 W.
It is often remembered about the converters capable to transform on-board 12 V into desirable 220 V. Judging by the inscriptions on the packages, they are capable of any power. A grinder, an electric drill, a computer, a microwave oven, plug it into a car socket and be at home…
Alas, it will not work that way. And here is why.
Wishes and possibilities
In electrical engineering an inverter (from Latin Inverto – “flip, change”) is a device for converting direct current into alternating current of desired value. Technically it is not very difficult. However, it is necessary to understand that all the necessary energy for powering bolsters, refrigerators and other things will be taken by the inverter from the battery and the generator. And if the power of such load, for example, 2 kW (electric kettle), then even without taking into account the efficiency the current consumption will be about 150 A! No passenger car will endure this. Even if the load will be much smaller – say, 250 W, even in this case you will have to drive the motor all the time: otherwise the battery will be discharged in a couple of hours.
Sometimes 220V inverters are built in the car from the factory – but even in this case their power usually does not exceed 150-200W.
INVERTER NUMBER ONE
Curiously enough, devices for converting DC to AC have at all times been an integral part of any car with a gasoline engine. We’re not talking about inverters, we’re talking about… the ignition system! In order to produce high-voltage pulses on the ignition coil, the DC voltage of the onboard network is interrupted synchronously with the crankshaft speed. The resulting intermittent current can be called alternating current, even if it does not change direction, as in a domestic circuit.
What inverter do you need?
The weakest inverters are rated at about 200 watts and plugged into a 12V socket. You can use them to recharge your smartphone, power your laptop, heat up your soldering iron, etc. But no serious tool like a jigsaw will be able to work from such a device.
Powerful inverters – from 1 kW – connect directly to the terminals of the battery. If you want to use a grinder or a drill with power under 800 watts, don’t forget to start the motor of the machine. Otherwise, the battery will not last even an hour.
We have divided purchased for our expertise invertors (they are voltage converters, too) into these two groups – weak and powerful.
How we tested them
We decided to carry out the tests in the battle mode. For the serious adapters we have prepared an electric drill with power of 800 W and a grinder with 880 W. The drill was equipped with soft start system, but the grinder was not.
Power was carried out from the battery at 70 Ah with permanently connected starter, working in the “Start” and giving a current of about 100 A, thus simulating the work of the engine at high speed. The drill was to drill a 10 mm diameter hole in a 6 mm thick steel plate. The grinder was forced to cut a steel angle #4 (40×40×5)
A 100-watt soldering iron and a 60-watt incandescent lamp were found for the low-power adapters-they were powered from a laboratory power supply. The soldering iron had to heat up to operating temperature in the light of the lamp and solder the twist of two copper stranded wires with a cross section of 1.5 mm².
Battery-powered inverters
| Approximate price of 7500 ₽ Declared power 1500W USB port output 1A Cute soft-start device easily verified the claimed power characteristics, providing simultaneous operation of a grinder and an electric drill. It has protection against overload, short circuits, overheating, etc. The disadvantages are unstable digital display, which at the maximum load occasionally showed a voltage of 350 V, although our test equipment (voltmeter and oscilloscope) did not fix anything like that. The price is high but worth it. It is highly recommended. |
| Approximate price 4500 ₽ Claimed power 1500 W USB port output 1 A According to the description, this device has a soft start. However, when I tried to plug in a grinder, it immediately got cranky, going into buzzer mode. There were no problems with the electric drill, but the converter turned out to be incapable of more. I don’t recommend it. |
| Approximate price 6300 ₽ Declared power 1000 W USB port output 0,5 A The declared power is not the highest in our sample, however the converter confidently coped with the paired work of an electric drill and a grinder. It can be connected to the 12 V socket inside the cabin, but don’t count on high power. There is protection against overload and faulty connection. It was upset by some technical mistakes in the description (e.g. wrong spelling of “ah”), but overall it worked better than we expected. Recommended. |
| Approximate price 5500 ₽ Claimed power 700W USB port output 1A The device disappointed: the packaging indicates the power of 1500W, but a careful reading of the instructions told us that it will not produce more than 700W of constant power. The same instruction said that the device is not intended for persons with “reduced physical, sensual or mental abilities”. And another pearl: they say that the inverter has protection against overheating, overloads and abnormal input voltage, but if the latter turns out to be too high, it will break anyway. In practice the inverter could not handle the offered load. We do not recommend it. |
12-volt socket inverters
| Approximate price 850 ₽ Declared power 75W USB port output 0,5A Weak converter, connected to the passenger compartment 12V socket, did not like it from the first seconds: the standard euro-plug did not fit the diameter of the pins. Somehow I managed to plug it in, but at the same time the flimsy case cracked at the seams and finally disassembled itself. The output voltage was already 250 V, and the signal shape was more like a meander (steps) than a smooth sine wave. The conclusion is obvious: do not buy! |
| Approximate price 1900 ₽ Claimed power 200 W USB port output 2,1 A Protection against overload and abnormal input voltage is provided. But on the whole, the capabilities of the device are very limited: the manual does not recommend connecting consumers with more than 170 W of power. The only tools you can connect are a soldering iron, a glue gun or an electric graver. In fact, it is a toy, though the price is not a toy anymore. Not recommended. |
FLEXIBLE PUSH
If the real power of the inverter and the tool are close, the probability that the tool will spin up and be able to do the job is higher with a speed control or soft start system. Without such a system, when the tool receives power, it starts to jerk: the current consumption rises and the inverter immediately goes into protection. It is not possible to work properly in such conditions.
Results
From powerful devices we would definitely single out Airline API-1500-08 as well as Telefunken TF-P103. They coped with the task even when two power tools are working simultaneously. But their low-powered colleagues did not like them: such devices are of little use. Recall that they are plugged into a 12 V socket, protected by a fuse (usually rated about 15 A), which has the right to burn out even with the claimed 200 W.
Sine and quasi-sine wave
The output signal of most inverters differs markedly from a normal sine wave: it has a stepped shape. For heating devices, incandescent lamps, as well as equipment with switching power supplies such power supply is fine, but the sound equipment begins to hum. Devices with transformer power supplies can overheat and even fail.
As the load grew, the PN-90 converter began to produce this “something” instead of a sine wave. No wonder that neither a drill nor a grinder wanted to use it.
As the load grew, the PN-90 converter began to produce this “something” instead of a sine wave. No wonder that neither a drill nor a grinder wanted to use it.
The Neo Maverick’s sine voltage looks a lot more like a meander, a rectangular graph.
The Neo Maverick’s sine voltage looks a lot more like a meander, a rectangular graph.
POSSIBLE PORTS.
For solid devices, having USB ports with currents less than 1A is not serious. Modern phones and tablets need chargers with an output current from 2A.
Gembird 400 W auto inverter (Gembird I-400U) overview
A car inverter is a voltage converter from 12 volts DC to 220 volts AC (the same that in conventional sockets). Thus it becomes possible to use conventional devices in the car, designed to work “from the socket”. What you may need to connect in the car? 1. Cell phone chargers. 2. Camera chargers, video camera chargers, AA / AAA battery chargers. 3. Laptop.
In general, quite a useful thing, and I decided to get it. What are the parameters to choose from? First of all, the power. We will proceed from the power of those devices that we are going to connect: 1. Cell phone chargers – up to 10 watts. 2. Netbook – about 40 W (look at the charger or multiply its output voltage by the output current and a safety factor of about 1.2, since the efficiency of switching power supplies is usually 90% or higher) 3. A 15″ laptop is 90 … 120 W (I haven’t seen any more). If you read the manuals of some autoinverters, you will notice that the power numbers in the name are often “short-term allowable load”. The real power, under which the inverter can work for a long time, is a bit less, e.g. 50 watts. Therefore, if we are not going to connect anything more powerful than a 90 watt laptop, a 150 watt inverter is fine. However, if the firm autoinverter is not well established, it is better to take more stock, based on the analogy with the Chinese power supplies for system devices. Cooling. When the auto inverter works, its internal elements get hot, and the heat must be removed from them effectively. If the heat is poorly dissipated, the inverter may fail. Therefore, active cooling (fan) and a metal case (usually a heat sink for some internal elements) are highly desirable requirements for the inverter. Also necessary functions: – short-circuit and overload protection – disconnection when the car battery voltage is low (so as not to discharge it completely). And a handy trick is the presence of a USB port (you can charge phones, players, etc.).
Near work is a convenience store, so I chose it. After reading reviews chose the following inverter: Gembird I-400U (400W) which cost 1020 rubles. Why 400W? The difference with the 250W model is only about 100 rubles, it would be better to have a margin.
Characteristics: Output rated power, W … 350 Maximum output power, W … 400 Output voltage, V … 220 ± 10% Output frequency, Hz … 50 ± 2 Output voltage for USB port, V … 5 Output current for USB port, mA … 500
Overload protection Short-circuit protection Low voltage protection Overvoltage protection
Threshold at low input voltage: 10 V ± 0.5 V Material – aluminum-magnesium alloy operating temperature -5°C to + 50°C
Dimensions (L x W x H): 122 x 89 x 47 mm Weight: 350 g
Supplied with: Cables for cigarette lighter socket, cables with clips for battery connection, Allen key for the bolts on the inverter (these are used to clamp the wires when connected to the inverter)
The first test was on the road. Literally the night before we decided that tomorrow we were going to drive. Charging the battery in the camera was lazy, too, to read about the alleged objects of visit. I put the charger and the netbook in the bag, and tomorrow on the way quietly charged everything, and the people in the meantime was preparing an “excursion program” by the downloaded guidebooks.
So far I have no complaints, the netbook is calm and cool, but slightly warm. When the computer is switched on (there is a power button on the end where the fan is) the fan is always on, but this can hardly be attributed to the minus, let it cool down, as long as it works. An interesting point: the USB port is active even if it is turned off, i.e. if you want only USB to work, you can not turn the inverter on, then the fan will not work, no noise.
For now I am satisfied, let’s see what will happen next, I will add information here as I use this inverter.
P.S. The important thing that I forgot to mention is the connection of powerful devices to the inverter. If you do not connect anything more powerful than a laptop to the inverter, you can plug the inverter directly into the cigarette lighter socket, the current will be small, the car wiring will not hurt. A small calculation. Let’s assume that the car wiring is able to pass a current of 20A without any consequences. Let’s calculate the power: P = U*I = 12 V * 20 A = 240 W. Taking into account the efficiency of the inverter is about 90%, it turns out that if the inverter is plugged into the cigarette lighter it is impossible to connect anything more powerful than 240 W * 0.9 = 216 W. If you want to connect a more powerful device to the inverter, the inverter itself must be connected directly to the battery terminals!
