A method of controlling a supercapacitor energy storage unit (12), included in a motor vehicle micro-hybrid system, is disclosed. The storage unit is suitable for performing the functions of an alternator, starter and automatic stop-restart of the vehicle heat engine, regenerative braking and torque assistance. The energy storage unit (12) is a plurality of supercapacitor elementary cells connected in series (C1 to C10) and capable of delivering information (Vmax, Temp and DeltaV) on its internal status. The method includes various stages of: comparing a temperature (Temp) with at least one temperature threshold (ST1=55° C., ST2=65° C. and ST3=70° C.); and, deciding on limitations of the availability of functions of the unit when the (Temp) information reaches the temperature threshold (ST1=55° C., ST2=65° C. and ST3=70° C.).