App description

Input data: battery capacity mAh; °C operating temperature; +110 °C, 1% pre-failure time (hours); I_BAT (maximum); I_BAT (typical)

Usage example

The calculator calculates the battery's operating time based on battery capacity and load.

among them:

I_BAT (maximum) is the maximum battery current, which is given in the RTC data sheet.

I_BAT (typical) is a typical battery current defined at +25°C and nominal supply voltage, which is given in the RTC data sheet.

The working 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.

Note

In any case, assuming an activation energy of 1 eV, the TTFs for several common batteries are 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 numbers, may have different 1% TTFs, depending on manufacturing tolerances. Contact the battery manufacturer for reliability data of the actual model.

Model and capacity of common button lithium batteries <table class="pure-table"> <tbody> <tr> <th width="67">Model</th> <th width="66">Capacity</th> <th width="187">1% TTF below +110°C </th> </tr> <tr> <td height="32">BR1632</td> <td>125mAh</td> <td>1900hrs</td> </tr> <tr> <td height="38">CR1632</td> <td>140mAh</td> <td>1350hrs</td> </tr> <tr> <td height="36">BR1225</td> <td>48mAh</td> <td>1900hrs</td> </tr> </tbody> </table>