Method for controlling an electrochromic device and an electrochromic device

An electrochromic device, comprising:

• an electrochromic film comprising two electrodes;
• said electrochromic film presenting a transmittance being dependent on a charge of said electrochromic film;
• and
• a charge control arrangement configured to control a voltage applied between said electrodes;
• said charge control arrangement having an input configured for obtaining a target colouring level, a voltage meter configured to measure an open circuit voltage between said electrodes, and a current meter configured to measure a charging current, charging said electrochromic film through said electrodes;
• said charge control arrangement being configured for obtaining a measure of an initial colouring level and for obtaining a measure of an initial open circuit voltage between said electrodes of said electrochromic device;
• said charge control arrangement being configured for causing a calibration ramping of a voltage applied between said electrodes of said electrochromic device;
• said charge control arrangement being configured for measuring a calibration charging current during said calibration ramping of said voltage;
• said charge control arrangement being configured for interrupting, intermittently and temporarily, said calibration ramping of said voltage;
• said charge control arrangement being configured for measuring a calibration open circuit voltage between said electrodes during said interrupting of said calibration ramping;
• said charge control arrangement being configured for stopping said calibration ramping of said voltage when a calibration condition based on said calibration charging current and/or said calibration open circuit voltage is met;
• said charge control arrangement being configured for applying a constant main charging/discharging voltage between said electrodes of said electrochromic device;
• whereby said charging/discharging voltage is selected in dependence of said ramped voltage when stopped;
• and
• said charge control arrangement being configured for removing any application of a voltage between said electrodes of said electrochromic device when said target colouring level is reached.