The main characteristics of a maintenance free (MF) battery is that

a maintenance free battery requires little maintenance during normal use and it is sufficient to add water instead of an electrolyte containing sulphuric acid

a maintenance free battery has a relatively short shelf life when compared with standard batteries

since it is sealed, the water in a maintenance free battery is not lost through evaporation thus accordingly it is not necessary to top up the cells with water

recharging of a maintenance free battery is neither required nor possible

has lead antimony plate grid

has lead calcium plate grid

does not contain acid

does not contain water

supply electric power

convert mechanical energy into electrical energy

continually recharge the battery

partly convert engine power into electric power

magneto system

battery system

electronic control unit system

magneto and electronic system

sharp edged fragments

small particles

big particles

none of the above