Car Battery Charger

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This charger will quickly and easily charge most any lead acid battery. The charger delivers full current until the current drawn by the battery falls to 150 mA. At this time, a lower voltage is applied to finish off and keep from over charging. When the battery is fully charged, the circuit switches off and lights a LED, telling you that the cycle has finished.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
R1	1	500 Ohm 1/4 W Resistor
R2	1	3K 1/4 W Resistor
R3	1	1K 1/4 W Resistor
R4	1	15 Ohm 1/4 W Resistor
R5	1	230 Ohm 1/4 W Resistor
R6	1	15K 1/4 W Resistor
R7	1	0.2 Ohm 10 W Resistor
C1	1	0.1uF 25V Ceramic Capacitor
C2	1	1uF 25V Electrolytic Capacitor
C3	1	1000pF 25V Ceramic Capacitor
D1	1	1N457 Diode
Q1	1	2N2905 PNP Transistor
U1	1	LM350 Regulator
U2	1	LM301A Op Amp
S1	1	Normally Open Push Button Switch
MISC	1	Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output

Notes

The circuit was meant to be powered by a power supply, which is why there is no transformer, rectifier, or filter capacitors on the schematic. There is no reason why you cannot add these.

A heatsink will be needed for U1.

To use the circuit, hook it up to a power supply/plug it in. Then, connect the battery to be charged to the output terminals. All you have to do now is push S1 (the "Start" switch), and wait for the circuit to finish.

If you want to use the charger without having to provide an external power supply, use the following circuit.

This is the schematic of the Car Battery Charger Power Supply

Part Total Qty. Description Substitutions

C1 1 6800uF 25V Electrolytic Capcitor

T1 1 3A 15V Transformer

BR1 1 5A 50V Bridge Rectifier 10A 50V Bridge Rectifier

S1 1 5A SPST Switch

F1 1 4A 250V Fuse

The first time you use the circuit, you should check up on it every once and a while to make sure that it is working properly and the battery is not being over charged.

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Comments

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anonymous Car Battery Charger Sunday, April 12, 2015 11:03:44 AM

I am a novice but I built this charger and it works just like it's supposed to. I am going to hook this up to a table fan that I converted to a generator and charge the battery on windy days. Great site.

richard Car Battery Charger Friday, October 21, 2011 8:11:48 AM

from the power supply the positive and negative of the supply connects to where in the charger? it only has one "IN" where does the negative of the supply go? the ground goes to the transformer right?

leochbattery Car Battery Charger Friday, September 16, 2011 5:10:16 AM

I just know more about car battery. Don't over charge the battery or it will damage it.

anonymous Car Battery Charger Thursday, September 01, 2011 6:59:10 AM

Can i use a 8amp 13.8V voltage regulator as an input supply for the car battery charger?

Lee Car Battery Charger Wednesday, February 09, 2011 3:17:59 PM

what should the output voltage of the charger be? i got around 15 V according to multisim. thanks

anonymous Car Battery Charger Thursday, October 28, 2010 8:41:28 AM

hi, when saying "most any lead acid battery" do you mean it will charge a 6 Volter too?

shoaib Car Battery Charger Sunday, October 10, 2010 7:04:10 AM

can i use any other diode instead of D1 IN457?help me plz....

Max Car Battery Charger Friday, June 25, 2010 1:15:25 PM

Thats a great circuit ! I am gonna use it as a storage battery charger. Thank You

siamak Car Battery Charger Sunday, June 20, 2010 11:41:25 PM

the circuit that u suggested has 18v input i think it should be DC voltage and as you know a 12v AC transformer after passing throgh a diode bridge give 18v DC( 12x2 root squire). so i think a 12vAC transformer with 3 amp current are enough for this circuit, is it ok?

Spooge Car Battery Charger Friday, May 28, 2010 8:38:17 AM

Nice circuit. what needs to be changed if i want to make it charge a 140 amp battery quckly. I need a 10A to 20Amps charger at least, For my ups, we get 4-5hrs blackout here every day.

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anonymous	Car Battery Charger	Sunday, April 12, 2015 11:03:44 AM
I am a novice but I built this charger and it works just like it's supposed to. I am going to hook this up to a table fan that I converted to a generator and charge the battery on windy days. Great site.
richard	Car Battery Charger	Friday, October 21, 2011 8:11:48 AM
from the power supply the positive and negative of the supply connects to where in the charger? it only has one "IN" where does the negative of the supply go? the ground goes to the transformer right?
leochbattery	Car Battery Charger	Friday, September 16, 2011 5:10:16 AM
I just know more about car battery. Don't over charge the battery or it will damage it.
anonymous	Car Battery Charger	Thursday, September 01, 2011 6:59:10 AM
Can i use a 8amp 13.8V voltage regulator as an input supply for the car battery charger?
Lee	Car Battery Charger	Wednesday, February 09, 2011 3:17:59 PM
what should the output voltage of the charger be? i got around 15 V according to multisim. thanks
anonymous	Car Battery Charger	Thursday, October 28, 2010 8:41:28 AM
hi, when saying "most any lead acid battery" do you mean it will charge a 6 Volter too?
shoaib	Car Battery Charger	Sunday, October 10, 2010 7:04:10 AM
can i use any other diode instead of D1 IN457?help me plz....
Max	Car Battery Charger	Friday, June 25, 2010 1:15:25 PM
Thats a great circuit ! I am gonna use it as a storage battery charger. Thank You
siamak	Car Battery Charger	Sunday, June 20, 2010 11:41:25 PM
the circuit that u suggested has 18v input i think it should be DC voltage and as you know a 12v AC transformer after passing throgh a diode bridge give 18v DC( 12x2 root squire). so i think a 12vAC transformer with 3 amp current are enough for this circuit, is it ok?
Spooge	Car Battery Charger	Friday, May 28, 2010 8:38:17 AM
Nice circuit. what needs to be changed if i want to make it charge a 140 amp battery quckly. I need a 10A to 20Amps charger at least, For my ups, we get 4-5hrs blackout here every day.