# Car Battery 6V or 12V charger

## Circuit Description

Always we needed a charger with which we can charge the car battery.
This circuit can charge automatically, fast and rightly, batteries 6V
and 12V. A basic factor in the success in the circuit operation is the
use of transformer [T1] of good quality with very good insulation and
resistance in the short circuits. The Q1 via divider R1-2, the TR1 and
the R4, functions as regulated current source. The current via the R9
drives the power transistors Q5 -6, where is strengthened X2000 times
roughly. In a car battery charger the voltage is roughly 6V until 8V.
With these conditions the charge current is roughly 1.2A [is regulated
by TR1]. When the battery charge slowly, is increased her voltage in
across. In the 7V it begins conduct the D1. As long as its increased
the battery voltage is decreased the voltage in across the R3 making Q1
conductible. This continued as far the current reaches the 6A roughly.
Then via the fall of tendency in utmost the R10, becomes driver the Q4.
The current that in excess in base of Q5 grounded, confecting the
current charge constant. When the battery charger [14.4V] is completely,
activated the parallel to the battery circuit that is constituted by
the R6, D8, and D2 until D6. Simultaneously turns on the D8 that shows
that battery charged completely. Simultaneously Q2 turn on from cause of
voltage fall in the R6. The Q3 becomes conductible and grounding some
of current in the Q5 base. When the voltage across the battery reaches
roughly in the 15V the current in the Q5 base is very small, so that
stops the battery charging. Diodes D5-6 protect the circuit from error
placement of battery or from short-circuit of big duration. Diode D4
protects the circuit from error placement of poles of battery. Then Led
D9 turns on shows the connection ERROR. Closing switch S2 short the
diode D2 [6.8V], now we can charge a battery 6V.

The inceptive charge current should be adjusted via the TR1 in
1.2A. Adjust can become with a battery 6V. Connect in cascade with the
battery a ampere meter [biggest 10A]. If does not exist battery 6V,
sorted output charger via their ampere meter and we adjust with the TR1
the current in 1.2A. At the regulation switch S2 it should they are in
the 12V place, that is to say open. Attention should be given in the
diodes D2 and D3 precision because these protect the battery from
overcharge. If the voltage deviation is up to 100mV we believe to
consider as acceptable. If you meet difficulties in the current
adjustment and TR1 is not enough, you can change the resistance R4
value, until you measure charge current become 1.2A. The two parallel
resistors that constitute the R10, it should they are placed in distance
by printed board and Q5-6, because they are heated. Bridge B1 and Q5-6
should be placed on heatsink after isolate electric from this with
suitable silicone mica. Bridge B1 and the PCB where it will be placed
circuit should connected with near and fat cables, special there that
the current are big. Also the lines in PCB should have proportional
width [in the drawing they appear with far line]. The manufacture should
become in a good metal box, suitable dimensions so that exists good
ventilation. The all manufacture requires the proportional experience.
The WORK WITH BATTERIES REQUIRES VERY BIG ATTENTION IN the HANDLING,
BECAUSE EXIST ALWAYS the DANGER of EXPLOSION.

## Part List

• R1-11=1K ohm 0.5W 5%
• R2=22K ohm 0.5W 5%
• R3-5-8=10K ohm 0.5W 5%
• R4=2.2K ohm 0.5W 5%
• R6=100 ohm 0.5W 5%
• R7=100K ohm 0.5W 5%
• R9=470 ohm 0.5W 5%
• R10=0.08 ohm 10W [2X0.18 ohm parallel] 5W
• B1=Bridge Rectifier 25A/40V
• D1-2=6.8V 0.4W Zener
• D3=4.7V 0.4W Zener
• D4-6-7=1N4148
• D5=18V 0.4W Zener
• D8=LED 5mm Yellow
• D9=LED 5mm Red
• Q1-2=BC557
• Q3-4=BC547
• Q5=BD139 [On Heatsink]
• Q6=2N3055 [On Heatsink]
• TR1=4.7K Trimmer Pot.
• C1=4700uF 40V
• C2=1uF 25V
• T1=230Vac//15V 10A Transf. [See Text]
• F1=Fuse 1A Slo Blo [5X20mm]
• S1=2X2 Switch 10A per contact
• S2=1X2 step mini switch
• J1…4=Flat Pin Connector
• J5=6pin Connector 2.54mm pin step
• A=0-10A Ampere meter
• Batt=12V or 6V Battery