The MKRWAN 1310 now includes a secondary lithium battery charger circuit. Secondary lithium batteries are "rechargeable". Secondary batteries are commonly referred to as "Lithium Ion" or "Lithium Polymer".Lithium primary cells, such as Lithium Thionyl chloride batteries, are not rechargeable. Primary batteries are sometimes referred to as "Lithium Metal" batteries. 1. If you attach a lithium primary cell to the charging port of the MKRWAN 1310 and the MKRWAN is connected to an external power source such as USB or a power adapter, the battery could catch fire or explode.2. To use a lithium primary cell with the MKRWAN 1310, you should use a regulator to regulate the battery voltage to the voltage level of the MKRWAN. Typically, this is 3.3V. (I have operated the MKRWAN at 2.7V). The regulated voltage can be applied to the +3.3V input of the MKRWAN.