2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.
With a MPPT charge controller, array current and load current should not be compared. But as long as battery terminal voltage is at or above float voltage, the array/charge controller is supplying the entire inverter load. Anything not used by batteries or loads ends up as heat in the panels.
Will an MPPT charge controller supply power to the battery based inverter when the batteries are fully charge and there is plenty sun.
The energy from the sun that hits the panel always goes somewhere. If it isn't turned into electricity and removed by the electrical wire, where else would it go? But we agree that a MPPT controller can (and typically does) provide energy to a load (instead of to a battery).
First, if no current is passing through the panels (i.e., the charge controller isn't consuming any of the power to charge batteries), the panels only have a Potential. That is what the open circuit voltage Voc is. There is no current, so electrically, there is nothing that is converted to heat.Second, sunlight hitting any surface does convert to a varying degree into thermal energy, and moreso with darker objects (like a solar panel). But this is independent of electrical potential that is generated by the photons knocking loose electrons in the cells.All in all, the amount of heat generated when the sun hits a solar panel is not affected much by whether or not current is flowing through the panels.At least, that's how I have digested the physics.