Car NiCad Charger

By Tony van Roon

Car NiCad Charger circuit

Table 1

Part	Description	Radio Shack #	DigiKey #	Notes
IC1	TDA2003, Au Amp	n/a		Pwr Amp,10A, lin, 5-pin
Q1	2N3055T, Transistor			NPN, Power
D1/D2	1N4002, Diode	276-1102	1N4002DICT-ND	Gen purp rect diodes
Led1	Red, 5mm	276-033		Light Emitting Diode
R1	390K, resistor	271-	390KQBK-ND	5%, 1/4W, carbon
R2	2.2M, resistor	271-8061	2.2MQBK-ND	5%, 1/4W, carbon
R3	2.2K, resistor	271-1325	2.2KQBK-ND	5%, 1/4W, carbon
R4	10 Ohm, resistor	271-1301	10QBK-ND	5%, 1/4W, carbon
C1	1µF, Capacitor			25V, electrolytic
C2	220µF, Capacitor	272-1029	P5699-ND	25V, electrolytic
S1	Switch, on-off			SPST, sub-miniature
Fuse	750mA			Slow Blow

IC1 is a Linear, Audio Power Amp (10W) and was orginally designed for car radios by Toshiba. Several replacement types can be used, like the ECG1288, NTE1288 and other substitutes will work fine.
In this circuit, with S1 set in the 'boost' position, IC1 is used to form a squarewave oscillator, and by coupling this square wave to the 13.2V battery supply via D1 and D2 to obtain over 20 vdc. If this is not needed, S1 is left open (normal).

Q1 acts as a current regulator to determine the charge rate of the battery pack. Q1 should be mounted on a sufficient coolrib. R4 is selected from the table below, or it can be adapted and switched with a rotary selector switch (watch current rating!).

R4 can easily be adjusted for any value to suit your needs other than listed here.

 

5220 21 August 2007

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