The use of water as an extinguishing agent on a lithium fire is flawed. Lithium is extremely reactive with water and does nothing but accelerate the reaction. If you expose enough to water it will cause an explosion. Lithium also burns so hot that it will strip the water molecules appart adding oxygen and hydrogen to the fire. The best thing a hobbiest can do is allow the fire to burn itself out and hopefully in a safe location away from anything else flammable. DRY sand can also be used to smother the fire and limit the amount of oxygen that can reach the metal, slowing the reaction. The sand also acts as a medium to remove heat.