This is perhaps the easiest battery charger you can think of. Such a charge more than once helped me out in difficult situations. It is quite simple to assemble on your own in the absence of a soldering iron and other radio elements. Such a charger can charge the battery of a motorcycle or car in various difficult situations.
Of course, I do not recommend using such a device in everyday life, because all its parts, including the battery, are under a voltage of 220 volts that are life-threatening, and for a single use it will completely disappear, naturally, subject to elementary electrical safety rules. Its biggest plus is the obvious simplicity of the design that does not require much knowledge in radio electronics and scarce parts. A big minus is the low efficiency. Let's get acquainted with the charger circuit:
It has only two parts: an incandescent lamp and a diode. When using an incandescent lamp with a power of 100 watts, the battery charging current is about 0.25 Amperes, which is enough to charge a motorcycle battery. You can also hang another lamp and get about 0.5 amperes. Details: any standard incandescent lamp, voltage of 250 volts; any diode - voltage of 250 volts and current not lower than 0.5 A.
Here is an even more complicated diagram of this charger.
It already has four diodes or one diode bridge. Here, from one 100 Watt lamp, the current is about 0.5 Amperes. But of course, you can increase it by hanging another incandescent lamp in parallel at the rate of 1 lamp = 0.5 A. Calculate the power of the diodes yourself, depending on the number of lamps and a voltage of at least 250 volts.
In general, the battery should be charged 0.1 of its capacity. That is, if a rechargeable battery with a capacity of 90 amperes / hour, then the current through it should be 9 amperes. The time from full discharge to full charge will be about 10-12 hours. But usually, few people charge with such current and usually take two times less and more time. I tell you this so that you yourself would calculate your charge time.
Personally, I had such a case. Once I arrived at the cottage and, out of awkwardness, forgot to turn off the dimensions. After several hours of work in the country, before driving, I inserted the key into the ignition switch and realized that the battery was discharged to zero. Nearby it’s not like cars, no people to ask for help. The benefit in the country was electricity. I quickly rummaged in the barn and found a Soviet board from a lamp TV. I pulled out a rectifier board with diodes from there. Well, finding a light bulb is not a problem. Gathered all twenty minutes. He removed the battery, connected everything, turned it on. (you will do this - do not mix up the sequence of actions!). I went and drank some seagull. After two or three hours, I decided to try to start it, the battery was not new, but not old. Turned off, put the battery, started. The car started up without unnecessary difficulties. Well, then let the car charging system work. And I got home without any problems.
PS: I want to once again draw your attention to compliance with electrical safety rules! Before all work, turn off the power! A voltage of 220 volts is life threatening!
Be especially careful!