[Ovmsdev] Save Status

I would like to implement Save status to save / load value when module crash. I copy kia_common.h/cpp and remove all code not relevant, added code to vehicle_mitsubishi.h/cpp same as kia, but not restore the soc value. If i check the saved file at web interface / editor has size 4, and if i open it is empty. Last time i saw the Trip power plugin do the same at my module, if module restart no data in web interface. I think Trip power chart plugin overwrite the datafile after reboot. Save data to SD card. Any idea?