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220 volts from a 3.7 V battery

220 volts from a 3.7 V battery

In everyday life, we are most often faced with power supplies that lower the high voltage in the network to several volts, which are necessary for connecting different devices. However, you can do the reverse transformation. And the scheme is completely uncomplicated.
It can be useful in two cases:


  • In order to connect the equipment and devices that are powered from only 220 volts in the field.
  • In case of a power failure.


Well, we do not forget that experimenting is always entertaining. For example, I collected this design simply out of interest, without an eye for practical application.
True, it should be noted that the presented converter is of low power and will not withstand a large load, for example, a TV. However, as will be seen from the example, an energy-saving light bulb works from it.

Manufacture of a converter

We need only a few details:

  • Transformer from the old charger for the phone.
  • Transistor 882P or its domestic analogues KT815, KT817.
  • Diode IN5398, analog KD226 or any other designed for reverse current up to 10 volts medium or high power.
  • Resistor (resistance) at 1 kΩ.
  • A small breadboard.


Another naturally need a soldering iron with solder and flux, pliers, wires and a multimeter (tester). You can of course make a printed circuit board, but for a scheme of several parts, you do not need to spend time designing the tracks for their drawing and etching foil-shaped textolite or getinax. We check the transformer. The old charger board.

220 volts from a 3.7 V battery

Soldered transformer.

220 volts from a 3.7 V battery

Next, we need to check the transformer and find the conclusions of its windings. Take the multimeter, switch it to the ohmmeter mode. In turn, we check all the conclusions, we find those that pair “call” and record their resistance.
1. The first 0.7 Ohm.

220 volts from a 3.7 V battery

2. The second 1.3 Ohm.

220 volts from a 3.7 V battery

3. The third 6.2 Ohms.

220 volts from a 3.7 V battery

That winding, in which the greatest resistance was primary, it was supplied with 220 V. In our device, it will be secondary, that is, output. The lower voltage was removed from the rest. At us they will serve as the primary (one that has a resistance of 0.7 ohms) and a part of the generator (with a resistance of 1.3). The results of measurements for different transformers may differ, you need to focus on their relationship among themselves.

Device Diagram

220 volts from a 3.7 V battery

As you can see, it is the simplest. For convenience, we marked the resistance of the windings. The transformer can not convert direct current. Therefore, on the transistor and one of its windings, a generator is assembled. It supplies a pulsating voltage from the input (battery) to the primary winding, the voltage of about 220 volts is removed from the secondary.

We collect the converter

We take the breadboard.

220 volts from a 3.7 V battery

We install the transformer on it. Choose a resistor in 1 kilo. We insert it into the holes of the board, next to the transformer. We bend the resistor terminals so that they are connected to the corresponding contacts of the transformer. Solder it. It is convenient at the same time to fix the board in whatever clamp, as in the photo, so that there is no problem with the missing “third hand”. Soldered resistor. Extra bite the length of the output. A board with bitten resistor leads. Then we take the transistor. We install it on the board on the other side of the transformer, as in the screenshot (I selected the location of the parts so that it would be more convenient to connect them according to the circuit diagram). We bend the terminals of the transistor. Solder them. Fixed transistor. We take the diode. We install it on the board in parallel with the transistor. Soldered. Our scheme is ready.

220 volts from a 3.7 V battery

220 volts from a 3.7 V battery

Solder the wires to connect the DC voltage (DC input). And wires for removing the pulsating high voltage (AC output).

220 volts from a 3.7 V battery

For the convenience of wire for 220 volts we take with “crocodiles”.

220 volts from a 3.7 V battery

Our device is ready.

We test the converter

In order to apply voltage select the battery for 3-4 volts. Although you can use any other power source.

220 volts from a 3.7 V battery

We solder the low voltage input wires to it, observing the polarity. We measure the voltage at the output of our device. It turns out 215 volts.

220 volts from a 3.7 V battery

Attention. It is not desirable to touch the parts when the power is connected. It’s not so dangerous if you do not have health problems, especially with the heart (although two hundred volts, but the current is weak), but it’s unpleasant to “pinch” it.
We finish testing by connecting a fluorescent energy-saving lamp to 220 volts. Thanks to the “crocodiles” it’s easy to do without a soldering iron. As you can see, the lamp burns.

220 volts from a 3.7 V battery

Our device is ready.
Council. You can increase the converter power by installing a transistor on the radiator.
True battery capacity is not enough for a long time. If you are going to constantly use the converter, then choose a more capacious battery and make a case for it.

Watch the video

220 volts from a 3.7 V battery


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