It has done it again. Autotrail 740SE with EC325 PSU, two 110 amp batteries and 100w SP. When not in use the vehicle sits on the drive with EHU connected but PSU charging switched off. Sargent control unit switched off also, i.e. in theory nothing using 12v. The batteries are normally easily kept up by the SP. Went to the van this a.m. to do a small job. Outside air temperature about 3 deg C. Activated the 12v with the intention of firing up the heating but was met with the unit flashing the message “leisure battery voltage dangerously low”. According to the Sargent book this message only appears if the leisure battery(s) gets to 6v or below. Vehicle battery okay and showing 12.4v. Fired up the PSU charger and the batteries seem to be taking a charge. This is the second time this has happened and I cannot find a reason; so over to the brains of the motorhoming world. Any suggestions?