mppt vs pwm

Your confusion stems from the fact that solar panels are not voltage sources but current sources. In bulk mode, the panel is directly connected to the battery. The panel voltage is equal to battery voltage. As battery voltage rises, so does the panel voltage. When the battery voltage reaches the absorption set point, pwm action begins.

When using a pwm charge controller, panel voltage is never at 17V. Panel voltage has two states, either Vbat or Voc (panel open circuit voltage).

MrWizard wrote:
you seem to be under the assumption that panel output is 14v instead of 17v ?
and doesn't get altered and processed to become 14+ charging volts
try measuring the panel voltage at the input of the controller