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From basic power equations, the MPPT's output current should be a 1/x function of its required output voltage. Physically, the boost converter on the MPPT will try its hardest to fill the output capacitor until the pack draws the same amount of current that the boost converter is able to provide (itself being limited by the input side PV cells), at which point equilibrium is reached. We assume the MPPT is never capable of supplying enough current to causing cause overcurrent.
This, of course, results in issues when the battery pack is nearing full charge and is drawing a low current from the MPPT. If the MPPT were to continue to try to maintain the same output power, its output voltage would increase without bound and eventually cause a battery overvoltage. The Nomura MPPT thus implements a voltage limiting function, tuned via potentiometers, which prevents the boost converter from continuing to charge up the output capacitor once it has reached a preset limit.
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