the voltage of a 12 v battery in a deep discharged condition will be around 10 to 11.4 v. When a deeply discharged 12 v. battery at say 13.8 v. it will initially draw avery large current. as the battery capacity is restored , the battery voltage increases to around 13.8 v when fully charged and the current drawn by the reduces a few hundred mA
if a deeply discharged battery is directly charged by SEC-1235 / SEC-1235M the battery will initially draw avery large current and thus will force the power supple into current limit mode for prolonged period of time . this is harmful for the power supply as operating under prolonged periods under current limit conditions is an abnormal operating condition. SEC may be used for battery charging and battery back up application only when he battery is charged through a suitable external isolating diode will ensure that the battery does not feed power back into the power supply and the series connected charge limiting resistor will limit the maximum charging current to a value less than the current limit