Drop in volts when connecting additional panel in parallel to series circuit.

Hey I´m very new to the solar panel world and I have 4 panels the same as the details shown in the picture below. I want to connect 3 in series and the other in parallel. When I connect the 1 panel in parallel to the other 3 in series the voltage is 73V roughly however when I only have 3 connect in series, I get 240V roughly. I don´t understand why the voltage doesn´t stay the same with the 4th panel connected in parallel. Is there a fault with the panels. I have tried different configurations of the ones in series and the one in parallel. I have also tried with 2 in series and 1 in parallel, but it always reads around 73V. I don´t have a multimeter that can measure DC amps at this current time just DC volts.



relle

Parallel strings must be the same voltage. Your only valid combinations are 4S, 2S2P, 4P, and this depends on your charge controller.

The single panel is forcing the other three panels to operate at its voltage. If you measure current, you may discover the 3S panels are actually discharging into the single panel.

You wouldn't consider putting a 24V battery in parallel with a 12V battery - you've done the equivalent with PV.

When you connect strings in parallel, the lowest voltage string will control the voltage of the circuit.
In your case one string is 3 panels and the other is 1 panel.

sunshine_eggo said:

Parallel strings must be the same voltage. Your only valid combinations are 4S, 2S2P, 4S, and this depends on your charge controller.

The single panel is forcing the other three panels to operate at its voltage. If you measure current, you may discover the 3S panels are actually discharging into the single panel.

You wouldn't consider putting a 24V battery in parallel with a 12V battery - you've done the equivalent with PV.

Click to expand...

Agree.

Typo should be: - "Your only valid combinations are 4S, 2S2P, 4P"