Lithium Battery Fires. Although lithium is a metal, do not treat a fire involving a small number of lithium batteries as a Class D fire. Halon, Halon replacement and/or water fire extinguishers can be used to control fires involving a small number of lithium batteries, such as found in common portable electronic devices (PED) or a laptop computer. Lithium batteries are capable of ignition and subsequent explosion due to overheating. Overheating may be caused by shorting, rapid discharge or overcharging. Overheating results in thermal runaway, which is a chemical reaction within the battery causing the internal temperature and pressure to rise.