# Characteristic Resistance

The characteristic resistance of a solar cell is the inverse of the slope of the line, shown in the figure above, which, after Green 1, can be given as VMP divided by IMP for most cells it can be approximated by VOC divided by ISC:

## Characteristic Resistance

${R}_{CH}=\frac{{V}_{MP}}{{I}_{MP}}\approx \frac{{V}_{OC}}{{I}_{SC}}$

Commercial silicon solar cells are typically very high current and low voltage. A 156 mm (6 inch) square solar cell has a current of almost 9 amps and a maximum power point voltage of 0.6 volts giving a characteristic resistance of around 0.067 Ω. As a consequence, connections to a single cell require resistances in the milliohm range.