The request
“Draw a solar battery overcharge protection circuit with an 18 V solar panel, blocking diode, 12 V battery, capacitor, adjustable resistor divider and shunt transistor.”
Then tryChange the battery to 24 V.Add a fuse between the panel and diode.
What is in this drawing
Read the decisions behind it.
01
Use an NPN transistor across the solar panel output to shunt excess current when overvoltage is detected.
02
A resistor divider from battery positive sets the threshold, with values chosen so the transistor base reaches ~0.7V at the maximum safe battery voltage.
03
A blocking diode prevents battery backfeed through the shunt transistor during normal charging.
Small off-grid solar battery chargers where a simple discrete shunt regulator is sufficient and adjustable threshold is preferred over fixed IC solutions.
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