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.
Parts
R1
500 Ohm 1/4 W Resistor
R2
3K 1/4 W Resistor
R3
1K 1/4 W Resistor
R4
15 Ohm 1/4 W Resistor
R5
230 Ohm 1/4 W Resistor
R6
15K 1/4 W Resistor
R7
0.2 Ohm 10 W Resistor
C1
0.1uF 25V Ceramic Capacitor
C2
1uF 25V Electrolytic Capacitor
C3
1000pF 25V Ceramic Capacitor
D1
1N457 Diode
Q1
2N2905 PNP Transistor
U1
LM350 Regulator
U2
LM301A Op Amp
S1
Normally Open Push Button Switch
MISC
Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output
Notes
1. 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.
2. A heatsink will be needed for U1.
3. 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.
4. If you want to use the charger without having to provide an external power supply, use the following circuit.
Part
C1
6800uF 25V Electrolytic Capcitor
T1
3A 15V Transformer
BR1
5A 50V Bridge Rectifier
10A 50V Bridge Rectifier
S1
5A SPST Switch
F1
4A 250V Fuse
5. 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.
Source: Electronics Lab
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