The calculator calculates the battery's working time based on battery capacity and load. 
 among them：
 IBAT (Maximum) is the maximum battery current, which is given in the RTC data sheet. 
 IBAT (Typical) is a typical battery current defined at +25 ° C and nominal supply voltage, which is given in the RTC data sheet. 
 The operating time (days and years) of the backup battery is estimated using the formula Ah/A, where Ah is the battery capacity expressed in ampere-hours, and A is the load current expressed in amps.
 According to the Arrhenius model calculation, consider the backup battery working time under the condition of self-discharge of the battery:
 The life-acceleration test estimates the hours before the 1% failure (TTF) and the activation energy (EA). As the operating temperature increases, the self-discharge of the battery will significantly affect the overall operating life of the battery.
 In any case, assuming an activation energy of 1 eV, the TTF for several common batteries is given in the table below. In the calculation, the stress temperature (T2) is assumed to be +110 ° C (+383 ° K). Note that different manufacturers, different battery model serial numbers, may have different 1% TTFs, depending on manufacturing tolerances. Contact the battery manufacturer for reliability data of the actual model.