Hi Bayo, thanks for your question on batteries. Like you rightly said, starting or starter batteries are used to start machines by ignition. They are different form deep cycle batteries in technical design. Deep cycle batteries like the name implies is designed to sustain deep use and recharging. So for example with a starter battery, you can start your engine which requires large burst of current on start up but you can not use this same battery to continuously power an electrical appliance. Doing this will permanently damage the battery.
But you can deeply discharge a deep cycle battery up to 80% and it will still retain its ability to be recharged and reused.
Hope this helps? Feel free to ask any other question.