I have a 24 V 100 W solar panel and a 24 V DC 50 W pump, which has a resistance of 2 Ω while at 0 rpm. The solar panel is directly connected to the pump motor.
The problem is: While the solar panel can drive the motor when it is running, it mostly fails to provide the break-away current the pump requires, so its motor more often than not fails to start turning.
Therefore I thought of a starter circuit, which stores charge in large caps and and fires (drives the pump) as soon as the voltage over the caps has reached a certain limit. Then the caps would provide more current and help starting the motor. When the sun is blocked by clouds etc., the pump stops and the circuit should "reset", so that the caps can be charged again.
I thought of triggering a thyristor at a certain voltage, but I fear it would only reset back to non-conduction at night, since the solar panel will provide some current even in low-sun conditions, but not enough to keep the pump running.
So, I think I need kind of a custom starter circuit that "fires" when a certain voltage has accumulated across some caps, and stops conducting when the current falls under a certain limit afterwards, so that the caps can be charged again.
Starting voltage and stopping current limits would need to be adjustable, because I have no means to really measure the minimum voltage/current behavior of the pump.
How do I get a solar powered DC pump motor to start reliably?