I wonder what is a better solution for a 24v marine system: 1 one larger panel or 2 smaller panels. 1 Big panel delivers more current but 2 smaller panels have a higher voltage so will deliver easier when there is not that much sun.
The one or two panel debate is more about
- making sure you have enough voltage to start the controller, you need 5V higher than the battery to start charging, so your panels have to be as an absolute minimum 33V for a lithium system (batteries at 27.0V before charging starts).
- If there is shade then 2 smaller panels in parallel may be more effective than one large panel as long as point 1 is achieved.
Surprisingly, the brightness of the sunlight makes very little difference to the voltage at the maximum power point and to a first approximation, the maximum power voltage is constant. See graph below for varying light intensity, green line showing maximum power point voltage vs light intensity. Therefore, higher voltage / lower current or lower voltage / higher current makes very little difference as long as points 1 and 2 are met.
Thanks for your reply.
My idea was to use 2 smaller panels serial so the starting voltage is reached easier but from the graphic is see that isn’t necessary.