The MACH2 is a Pilot's Watch Chronograph with a rugged, bold, yet detailed style that is more youthful and technological. Solar Cell Description This watch is equipped with a storage battery (ML2016) can use light energy to convert electricity and can be generated into the built-in battery, usually the battery does not need to be replaced, but after a few years of use, its charging capacity will gradually reduce and can not be charged, if you find that after charging the pointer can not be walked, that is, the battery has been aging, please replace the battery model for maxell (ML2016);