Great post! I wil delete this reply when you modify two things at the very end:
Quote:
Originally Posted by scrubjaysnest
.... Note the use of 12 volts since we are drawing off the battery.
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When calculating demand at the battery, perhaps use battery voltage ~ 12.4V. (A battery running at only 12.0 is pretty severely discharged, and being damaged.) For SLA, 50% SOC is about 12.2V (standard conditions).
Quote:
Originally Posted by scrubjaysnest
A pair of 120 to 150 watt panels on the front shell along with a pair of 100 watt panels on the rear shell will get you a nice solar array for use with MPPT. Keep Voc of all panels within 10% of each other.
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Right! With Panels in Parallel (for PWM) the lowest voltage among the multiple panels "on the string" will determine the Operating Voltage of the "Parallel String", while the
Current of all the panels is combined at that Voltage.
But with Panels in Series, (for MPPT), you want to keep the Imp
Current values close: The Voltages simply add together, and widely differing voltage values do not cost power on the "Series String" as whole. But the lowest Current among the panels on the "Series String" determines the performance of the String as a whole, limiting the higher-current panels to the current value of the lowest panel. (That is why a shaded panel degrades a Series String so badly).
My own configuration is now a very good example of "mismatched panels". I've got two 'Renogy' Panels at 5.29 Amds (Imp), 18.9 Volts (Vmp) for 100 watts each. My 3rd panel is rated at 135 Watts, but runs at much higher Voltage: 5.45 (Imp) and 24.9 Volts (Vmp). If I connected all the panels in parallel, the 3rd Panel would only run at 18.9 Volts, for maximum output of just 103 Watts. In Series, as I'm going to use it, it will run at the full 24.9 Volts - but the maximum amps (standard conditions) will be limited to just 5.29, matching the Renogy panels. In standard conditions, 5.29A * 24.9V = 131 Watts, a negligible drop from its "stand-alone" rating.