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Can anyone provide a schematic/s for a battery charger for at least 6 ampere or more current out and with an indicator if it is already full
charge and for 12 volts system and any info on any adjustment necessary.
For up to 6A, you can do as I mentioned above - parallel 2 LM350's. Or you can add a pass transistor as shown - I haven't drawn the whole circuit, just the first bit:
(For the transistor, I would use a 2N2955 or similar, mounted on a generous heatsink)
Also, I can't see the purpose of R1 - I would delete it.
Phasor Is there an error on your diagram that if the load takes 1/2 amp the pass transistor will turn hard on allowing the 18v input through to the battery (which will not rise to this voltage).
The circuit will latch up with no voltage regulation.
I think the linked circuit has to have R1 to start the circuit up - providing some signal through to the control circuitry, otherwise I think the regulator would remain 'shut down' as if the battery was fully charged.
I didn't think of that...
A little research shows that this circuit was actually copied directly from the National Semiconductor LM350 datasheet. (NB - It does include R1 on the datasheet, so I guess it should be there after all...)
R1 along with R2 sets the output voltage.......R1 is nominally 240 ohms....making R2 adjustable sets the output..........
The purpose of the 2R2 resistor is as follows :
Consider the output voltage as 13.8v, as the load current increases, the o/p volts drop, the reg makes up the difference in v out, the circuit then becomes stable. Now as the load current increases the voltage across the 2R2 resistor (R3 for arguments sake) rises, as V=I*R,
Now Vbe of Tr1 is ~ 0.6v, so if R3 is 2R2 and the load current rises such that it develops a voltage across it of 2R2*I volts, then as it approaches Vbe of Tr1, Tr1 will start to conduct, causing a rise in o/p volts, the reg cuts back its o/p and so the current falls, eventually the system restabilises.......
The value of R3 isnt critical it sets the point of operation of Tr1, the higher the value of R1 the more current is passed by the regulator until Tr1 turns......the ideal situation would be to allow a nominal current through the regulator to enable it to perform, and the remainder of the current supplied by Tr1........