Question: what is the difference between aa and 18650 batteries?
Answer: The key distinction is that the 18650 is specifically a size for a rechargeable lithium-ion battery while AA can be zinc-carbon, alkaline, nickel-cadmium, nickel-metal hydride (NiMH), or even lithium-ion among others. The 18650 lithium-ion batteries are 18mm x 65mm in size, hence the name.