The cycle life of a battery refers to how many times it can be fully charged and discharged before its capacity is significantly reduced. A battery with a longer cycle life will last longer. Lithium batteries have longer cycles and are considered to be more affordable on the long run. At Energy of Africa we do not recommend gel batteries as they have a shorter cycle.
The voltage of a battery should match the voltage of the solar panels and inverter in your system.
Some batteries are more sensitive to temperature than others. Make sure to choose a battery that can operate in the temperature range of your location.