Unlike many units, this battery charger continuously charges at maximum current, tapering off only near full battery voltage. In this unit, the full load current of the supply transformer/rectifier section was 4.4A. It tapers off to 4A at 13.5V, 3A at 14.0V, 2A at 14.5V and 0A at 15.0V.
Circuit operation:
Transistor Q1, diodes D1-D3 and resistor R1 form a simple constant current source. R1 effectively sets the current through Q1 - the voltage across this resistor plus Q1's emitter-base voltage is equal to the voltage across D1-D3. Assuming 0.7V across each diode and across Q1's base-emitter junction, the current through R1 is approximately 1.4/0.34 = 4.1A. IC ensures that Q1 (and thus the constant current source) is turned on.
When the battery has fully charged, the current through IC drops to a very low value and so Q1 turns off (since there is no longer any base-emitter current). R2 limits the current through IC. It allows enough current to flow through the regulator so that Q1 is fully on for battery voltages up to about 13.5V. Decreasing the value of R2 effectively increases the final battery voltage by raising the current cutoff point. Conversely, a diode in series with one of the battery leads will reduce the fully-charged voltage by about 0.7V.
Circuit diagram:
Parts:
Resistors
R1 = 0.32R
R2 = 8.2R
Capacitors
C1 = 10,000uF - 63V
Semiconductors
D1 = 1N4004
D2 = 1N4004
D3 = 1N4004
Q1 = MJ1504
IC = 7815 REG
BR1 = 1N4004x4
Miscellaneous
B1 = 12 Volt Battery
Notes:
- Charger's input voltages are 20 volt AC
- R1 and R2 are high wattage resistor like 2W, 3W, 5W and could be above. Select wattage on your choice.
- Q1 and IC requires a good heatsink. If they are mounted on the same heatsink and will throttle the circuit back if Q1 gets too hot.
18 comments:
car battery should not be charged this way! these batteries should be charged under constant voltage BUT NOT CONSTANT CURRENT!
@Jyoitrmoy
Please open your eyes and look at the diagram, the circuit uses "IC" (7815) for constant voltage.
i cannot find the transistor Q1 = MJ1504, do u have any solution for this Q1.
Hi.
May I answer for Anonymous said...??
I guess that it is replace with MJ15004G or similar. The MJ15004 TR is "POWER PNP TR 20A 140V TO3 type.
Thanks.
hi,
good day...
I'm Jesse Salcedo from Cagayan de Oro City, Phils.
Is there anyone who can give me a circuit diagram of a battery charger that can charge up 15 or 20 amperes.
thank you...
Jesse
how could you add led's to see what stage of charging the battery has reached ?
how could you add led's to see what stage of charging the battery has reached ?
Hello!
Can anybody tell me the input value of current?
Regards
Hasnain Raza
here is my build of this project:
http://buju357.blogspot.com/2010/12/battery-charger-charges-at-maximum.html
I am confused? my transformer puts out 13.9 after the rectifier is this acceptable? also please give me the color for the resistors? Is R1 330ohm? and R2 8.2 ohm?
@Dave
I can't understand your question? Please explain briefly. By the way here are the colors for 330 and 8.2 ohms resistors.
330 OHMS = Orange - Orange - Brown
8.2 OHMS = Grey - Red - Gold
@Dave:
It should be 0,34 ohms, not 330 ohms.
@all:
still searching for an MJ1504
alternative. Tryed a BD250 with no success.
@Dave: It's 0,32 ohms. Not 330 ohms.
@All: Stil searching for an MJ 1405 alternative. Tryed A BD250 with no success.
U can use the following transistors replacing the MJ1404 (in this project only):
NTE 30
MJ 2955A
hi guys can help me to a charger diagram from solar to car battery
hi
Hi all.......
Anyone know which software is used to draw the schematic diagram?......i try to find this too......but not success....please help me
my mail ID : msnoj2madhav@gmail.com
Thanks in Advance
Can I add a charging indicator LED to this Circuit ?
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