Input data: battery capacity mAh; °C operating temperature; +110 °C, 1% pre-failure time (hours); IBAT (maximum); IBAT (typical)
The calculator calculates the battery's operating 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 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.
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
| Model | Capacity | 1% TTF below +110°C |
|---|---|---|
| BR1632 | 125mAh | 1900hrs |
| CR1632 | 140mAh | 1350hrs |
| BR1225 | 48mAh | 1900hrs |
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