> 5.3 | Effects of Temperature

> The temperature has the biggest influence on the available capacity. Figure 11 illustrates the dramatic difference of the available capacity at three different temperatures.
> The measurement has been taken under realistic conditions, assuming battery discharge due to 10mA current consumption in idle mode and a 1-minute GSM call made every hour at PCL5 with a current profile 2A / 200mA, until the battery is empty.
> Figure 11: Voltage of a typical 1000mAh Li battery measured at different temperatures
> As you can see, the capacity decreases at lower temperatures. This is caused by significant rise of the internal resistance and the recovery voltage. The spikes in Figure 11 represent a 1-minute call, not only a sending burst. Table 5 shows the measured values in detail.

> Table 5: | Parameters of a typical 1000mAh Li battery measured at different temperatures

> Temperature | Relative capacity | Internal resistance | Recovery voltage
> -10°C | 54% | 115m Ω | 490mV
> 10°C | 92% | 95m Ω | 330mV
> 30°C | 100% | 85m Ω | 140mV

> To operate the mobile equipment at low temperatures, design engineers are advised to choose a battery with the lowest recovery voltage to achieve maximum capacity. Even a battery with a lower nominal capacity and low recovery voltage may be much more suitable than a battery with higher nominal capacity and higher recovery voltage.
> The described effects are accounted for through the sophisticated software and battery parameters of the Siemens GSM module.