Efficacy of Personnalized Transcranial Direct Current Electrical Stimulation (tDCS) in Drug-resistant Epileptic

The goal of this clinical trial is to to obtain a significant decrease in seizure frequency in patients with refractory focal epilepsy after applying treatment of cathodal tDCS, compared to sham stimulation drug-resistant epileptic patient. The main questions it aims to answer are: * Changes in quality of life * Percent of newly reported side effects after the stimulation period * Scores in epilepsy severity. Participants will be randomized in a cross-over, and will receive 10 days of tDCS or Sham. Each day will allow 2 periods of 20 minutes stimulation separated by 20 minutes off (with 40 minutes of cathodal stimulation total).