Make 12V Car Battary Changer and Circuit

Firstly, the battery is charged, discharged and stored very carefully.
We normally think of batteries can be stored for several months (if not years), and are available for immediate use.
This is not the case with the SLA batteries.
When you save a new, fully charged battery SLA for 6 months or longer, you may find it completely empty.
You may find you can not charge! It may be worthless.
That’s how fragile the SLA batteries.
You must be recharged regularly, so do not take on a very low voltage.
When the terminal voltage of the battery SLA should go into 8V, begins a process called sulfation on the surface of the slab and prevents battery recharge. Battery internal resistance increases, and it will be useless.
More about this at the end of the article. 
    

How does the circuit
Circuit consists of five components:

R1= 1Kohms D1= 1N4001 T1= 220V/17V 4A Transformer
R2= 1.2Kohms D2= 6.8V 0.5W zener LD1= Green LED
R3= 470 ohms TR1= 4.7Kohms  trimmer LD2= Red LED
R4= 470 ohms Q1= BTY79 or similar 6A SCR M1= 0-5A DC Ampere meter
R5= 10Kohms Q2= C106D  SCR S1= 10A D/P On Off Switch
C1= 10uF 25V GR1= 50V 6A Bridge Rectifier F= 5A Fuse

  Circuit does not turn on until the battery is connected to the terminals, as shown in the picture. (Assuming the pressure switch is connected to a circuit where there is a completely discharged battery started.)
This action turns on the PNP transistor in the “Turn On” block. Resistance between the collector-emitter terminals, and LED lights.
Journey to the bottom of the circle passing through the railway signal diode, gate-cathode junction of SCR and two parallel resistors 1R8. Therefore, it shines.

Must use the AC PLUG PACK
Before we go further, working circuit pack into the AC outlet. There must be an AC power supply, as we do not want to be present at all the capacitors on the power flow rail, because it allows a very high charging current and possibly damage the SCR.
DC does not let you turn on the SCR, it will shut off flow through to zero.

Circuit is half-wave rectifier!
Circuit is actually a half-wave rectifier. It only charges the battery in each half cycle. Plug-pack, not the way it leaves a residual flow in the transformer core and leads him overheat. But that is a disadvantage of the circuit.
SCR switches in each half cycle and flows into the battery.
Voltage through two resistors 1R8 (parallel development), and this voltage is fed into the electrolyte-47U. Is charging and turns the BC547 transistor.
Transistor turns off SCR gate voltage and robs the SCR. 47U energy channels of the transistor for a short time, but could not maintain the transistor.
Transistor switches and switch SCR and provides further impetus to the current battery.
Since the battery is charging, the voltage increases and it is followed by “Voltage Monitor Block.
The circuit is very complex and able to look at the operation is to check the top rail as a fixed rail and increasing the battery voltage, rail is the negative battery terminal is connected, pushed down.
So you can see how to “Turn On” transistor is switched on and a “voltage monitor” components to create voltage drops on each of them.
“Voltage Monitor” component consisting of transistors and Zener diode and resistor 8k2, 1k pot 1K5 resistor, 150R resistor and diode signal.
Signal-emitting diode is actually part of the flashing circle and discuss the operation later.
When the battery voltage rises to 13.75 volts, all resistance in “voltage test systems, will have a voltage drop, which corresponds to the resistance of resistance. Diode is a constant 0.7 V above them.
Voltage at the wiper of banks will be about 3.25V and 10V, the voltage across the Zener. This leaves 0.6V between the base and the producer of the transistor voltage monitor.
This voltage is sufficient to turn transistor.
When the monitor voltage transistor switches, it robs the “Turn On” transistor base-emitter voltage and the circuit is turned off.
SCR has only two states: ON and OFF.
By the mid-cycle when it is turned on, battery power and high pulse current is limited to the ability to plug-pack.
There are no capacitors to enable very high current pulses are delivered, and it is fortunate, because the SCR is only 0.8 amps drive, but it will take 10 amps to increase the half-cycle.
Whenever the SCR is in the lead during the mid-cycle operation initiated, remains in heat conduction, the voltage supplied plug pack will drop to zero. That is, when the SCR turns off.
If the plug-pack delivers a negative voltage on the top rail and a positive voltage to the lowest rail, the SCR is triggered into the conduction band and none of the components in the circuit provides power to the battery. SCR provides a couple of Half-stream and then turns to several cycles. This is how the average current supplied by the battery is controlled.
The circuit is designed to deliver approximately 300-400 mA average charging current. The actual value is set resistors 1R8.
If the battery is fully charged, the LED will blink.
Flashing is made of resistance 2K2 and 47U (connected to a voltage monitor section).
That the battery is connected through diode 47U, charging 150R BC557 transistor and a signal diode to the negative terminal of the battery.
If the battery is fully charged, the monitor turns on and turns off the power supply section of “Turn On” section.
This eliminates stress on the positive side of the 47U and the positive side, a negative rail through resistor 2K2. This allows the negative side of 47U and 150R resistor is enabled, distorted, negative despite the presence of light rail, because the diode is reverse-drop.
This keeps the circuit in the “off” state, as part of the voltage monitor provides an additional voltage across the battery and it thinks it is “over-burdened.