Simple universal automatic charger

I tried to insert into the title of this article all the advantages of this scheme, which we will consider, and naturally I did not quite succeed. So let's now look at all the advantages in order.

The main advantage of the charger is that it is fully automatic. The circuit controls and stabilizes the required battery charging current, monitors the battery voltage and when it reaches the desired level, it reduces the current to zero.

What batteries can be charged?

Almost everything: lithium-ion, nickel-cadmium, lead and others. The scope of application is limited only by the charge current and voltage.

This will be enough for all household needs. For example, if your built-in charge controller is broken, you can replace it with this circuit. Cordless screwdrivers, vacuum cleaners, flashlights and other devices can be charged with this automatic charger, even car and motorcycle batteries.

Where else can the scheme be applied?

In addition to the charger, this circuit can be used as a charging controller for alternative energy sources, such as a solar battery.

The circuit can also be used as a regulated power supply for laboratory purposes with short circuit protection.

Main advantages:

• - Simplicity: the circuit contains only 4 fairly common components.
• - Full autonomy: control of current and voltage.
• - LM317 chips have built-in protection against short circuits and overheating.
• - Small dimensions of the final device.
• - Large operating voltage range 1.2-37 V.

Flaws:

• - Charging current up to 1.5 A. This is most likely not a drawback, but a characteristic, but I will define this parameter here.
• - For currents greater than 0.5 A, it requires installation on a radiator. You should also consider the difference between input and output voltage. The greater this difference is, the more the microcircuits will heat up.

Automatic charger circuit

The diagram does not show the power source, but only the control unit. The power source can be a transformer with a rectifier bridge, a power supply from a laptop (19 V), or a power supply from a telephone (5 V). It all depends on what goals you are pursuing.

The circuit can be divided into two parts, each of them functions separately. The first LM317 contains a current stabilizer. The resistor for stabilization is calculated simply: “1.25 / 1 = 1.25 Ohm”, where 1.25 is a constant that is always the same for everyone and “1” is the stabilization current you need. We calculate, then select the closest resistor from the line. The higher the current, the more power the resistor needs to take. For current from 1 A – minimum 5 W.

The second half is a voltage stabilizer.Everything is simple here, use a variable resistor to set the voltage of the charged battery. For example, for car batteries it is somewhere around 14.2-14.4. To configure, connect a 1 kOhm load resistor to the input and measure the voltage with a multimeter. We set the substring resistor to the desired voltage and that’s it. As soon as the battery is charged and the voltage reaches the set value, the microcircuit will reduce the current to zero and charging will stop.

I personally used such a device to charge lithium-ion batteries. It's no secret that they need to be charged correctly and if you make a mistake, they can even explode. This charger copes with all tasks.

To control the presence of charge, you can use the circuit described in this article - Current presence indicator.

There is also a scheme for incorporating this microcircuit into one: both current and voltage stabilization. But in this option, the operation is not entirely linear, but in some cases it may work.

Informative video, just not in Russian, but you can understand the calculation formulas.