The traditional solution is the direct battery connection solution, like Figure 2-1. The communication model such as NB-IoT is connected with the LiSOCl₂ and HLC package directly. The voltage of the LiSOCl₂ and HLC package is about 3.6 V at room temperature. When the smart meter does the transmission, the HLC supports the high pulse current for the NB-IoT. During sleep mode, the LiSOCl₂ charges the HLC and supports the whole system consumption.

The disadvantage of the direct battery connection solution is customers must choose HLC1550 instead of HLC1520. Because the LiSOCl₂ and HLC package has the poor performance at cold temperature (-25 degC or -40 degC) , like in Figure 2-2 and Figure 2-3. Figure 2-2 is the performance of ER26500 and HLC1520 at high pulse current (250 mA / 250 ms). In the waveform, the voltage of the battery package is down to 3.4 V at high pulse current. It is too little margin to power the whole system. Figure 2-3 is the performance of ER26500 and HLC1550, because HLC1550 has a bigger size and higher current capability, the voltage is down to 3.6 V, and it can support the whole system and do the transmission. But HLC1550 has bigger size and higher cost.

Another disadvantage of this solution is the discharge current of LiSOCl₂ is uncontrolled. In the Figure 2-2 and Figure 2-3, the discharge current of LiSOCl₂ is up to 15 mA and 5 mA, respectively. The LiSOCl₂ cannot achieve the maximum capacity, referring Figure 1-2.