> Wouldn't they interact?

I assume that relates to using many MPPT controllers to 
drive a single battery.

I'd hazard:    To some extent, but as a battery tends to be 
a low impedance source for small delta I_chg the 
interactions probably don't produce a wrong result - just 
lots of work for the trackers. And, as individual panels may 
produce different source impedances at any selected moment 
it's probably somewhat unavoidable.

Panel shadowing which is something which should be avoided 
at all costs, causes a dramatic change in cell output. Even 
partially shadow part of a single cell and a raw panel's 
output will plummet as the resistance of the shadowed cell 
rises and affects the whole panel. Up market modern panels 
now often have FORWARD diodes across each cell. As long as 
cell resistance is low the diode does not conduct as Vcell < 
V_diode_forward. If a cell is shadowed or faulty the forward 
current from the other cells is conducted via the diode.

A partially shadowed panel would lose voltage and MPPT would 
adjust its effective source impedance to match.



            Russell

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