Key without relay with automatic shutdown for battery charging

Powerful key without relay with automatic shut-off

A simple automatic key, in addition to the main function: automatic shutdown when fully charged, also has the function of starting and stopping the cycle using clock buttons.

The circuit is connected between the charger and the battery. Can be easily adjusted to any control voltage between 6-24 V.

Will need

Stabilizer TL431 - http://alii.pub/5mclsi
Transistor IRFZ44N - http://alii.pub/5ct567
Multi-turn potentiometer 10 kOhm - http://alii.pub/5o27v2
Tact buttons - http://alii.pub/5nnu8o
LEDs - http://alii.pub/5lag4f
Resistors 1.5 kOhm; 1 kOhm; 15 kOhm - http://alii.pub/5h6ouv

Scheme

Key without relay with automatic shutdown for battery charging

The circuit consists of two main components: the first is an adjustable threshold stabilizer assembled on a TL431 chip and the second is a switch on an IRFZ44N transistor.

The principle of operation is simple: as soon as the voltage reaches the set value, the stabilizer will close the switch and the flow of charging current will stop.

Making a key for charging batteries

The automatic key circuit will be assembled using a hinged installation. Thick strands of copper wire are used as power buses.We fix one wire and begin the assembly by soldering a 1 kOhm resistor. We first trim the long output elements.

Solder the stabilizer chip. Pinout in the photo.

Solder the adjustable divider circuit.

Add a “negative” power bus.

Solder Light-emitting diode and a resistor.

Next button and more Light-emitting diode with resistor.

Solder the transistor. Pinout in the photo.

All that remains is to solder the button and a powerful diode.

The circuit is ready for use.

Turning on and testing the charger

Instead of a battery, temporarily connect an incandescent lamp to the output. By rotating the variable resistor slider, we will ensure that the lamp goes out when the voltage exceeds 14.3 - 14.4 V (Full charge voltage for acid batteries).