Last year, the US state of Texas was hit by a snow storm that disrupted power grids. The residents left without electricity were forced to put up tents right in their houses to keep warm, and local supermarkets ran out of firewood and coal. The owners of the Ford F-150 hybrid pickups with the Pro Power Onboard power system found a way out. They connected refrigerators, heaters, small appliances and even televisions to their cars. Moreover, it is relatively budgetary: for 12 hours of continuous operation of the F-150 engine, it burned only about 15 liters of gasoline.
Ford’s Pro Power Onboard system is a station for charging electrical devices from the car’s on-board electrical network and provides power from 2 to 7.2 kilowatts. This is a record, because the on-board inverters that are on some cars – usually SUVs – can provide much less output, but they can power a laptop or charge a smartphone from them quite successfully. Manufacturers usually install the inverter in the trunk and bring the outlet to the trim. And if this option is not available in your car, you will need a separate voltage converter to power external electrical devices.
What is an inverter
In electrical engineering, an inverter (inverto in Latin – “turn over”) is a device for converting direct current into an alternating current of the desired value. From a technical point of view, this is a simple device, but it must be understood that the inverter will take energy from the car battery and generator to power electrical appliances. If you need to power a powerful device like an electric kettle, then you can’t do without a running engine, otherwise there is a chance to quickly discharge the battery. The inverter converts the direct current of the car’s on-board network with a voltage of 12 volts into an alternating voltage of 220 volts and is equipped with a traditional socket for connecting a conventional plug.
What are inverters
Converters differ in power and, as a result, in the shape of the case.
- Low-power inverters can be made as an adapter that plugs directly into the cigarette lighter socket, or as a cylinder the size of a can of soda so that you can put it in a cup holder and connect it to the cigarette lighter with a cable. This is convenient, but due to the compact case and the lack of a cooling system, the power of such inverters is significantly limited and usually does not exceed 70-100 watts for the first option and 100-150 watts for the second.
- More powerful inverters are available in rectangular aluminum cases with radiators on the outside and fans inside. Models with a power of up to 200 watts are usually equipped with a cable for connecting to the cigarette lighter, and more powerful ones are equipped with alligator clips for connecting to battery terminals under the hood. This is because the fuse in the cigarette lighter circuit on most cars is typically less than 15 amps, and with that current, the inverter will not be able to provide more than 200 watts.
From compact devices with a power of less than 100 watts, you can power, say, a charger for a laptop or tablet, an electric razor, and similar small appliances. A 100-200 watt converter will slightly expand the range of “compatible” devices, but not that much. For example, a 220-volt power tool like a “grinder” will not be able to work from a cigarette lighter – this will require at least 400 watts of power, for a drill – more than 300. But the simplest eccentric polisher should have enough power.
Inverters of 400-500 watts and above will greatly expand the possibilities. With their help, it is already possible to power a relatively powerful power tool – the main thing is not to forget to start the car engine in order to avoid a quick battery landing. And one more important point – for many powerful electrical appliances, the short-term starting current exceeds the operating current by one and a half to two times, so the converter must be designed for this.
Where is the limit?
Inverters with a capacity of more than a kilowatt allow you to connect even more powerful gadgets, but in this case, the possibilities are limited by the car’s generator. A kilowatt converter at full load will require about 70-80 amperes from the vehicle’s on-board network. Such a high current cannot be safely and permanently transmitted through point contact through the terminals, and many generators with such a load will literally work at the limit. This applies not only to generators with a maximum output current of 90 amperes, but also to more powerful ones. Over the years, rectifier diodes pressed into the bridge deteriorate heat transfer and increase resistance at the contact point, which potentially threatens the generator with failure.
The power of the consumer connected to any inverter must be selected at least 25% less than the limit value in watts written on the converter case. Thus, it is possible to power from a kilowatt inverter connected to a car battery, at best, devices with a power of no more than 600-700 watts – taking into account the starting current.
An important characteristic of any inverter is the presence of overload protection at the output. Connecting a load with a starting current higher than the rated operating current can damage both the converter itself and at least the fuse in the on-board circuit. Budget inverters to protect against connecting too powerful a load are equipped with a simple fuse in the cigarette lighter plug. Protection should be more thorough – for example, so that when overloaded, the converter turns off and then automatically turns on again. And do not forget about elementary safety – 220 volts in the inverter is just as dangerous as in a home outlet.
By the way, do you know why the voltage in Russian power networks is 220 V, while in the States and many other countries it is 110 V? Read about it in our article.