Some important rules for selecting a battery:

2.1 The larger the capacity, the smaller the discharge and the longer the life, do not buy battery contact! The battery is preferably more than 50% of the power we need.

2.2 By unloading less than 50% of the capacity, you can shorten the cycle life three times!

2.3 Do not load (100% discharge) below 10.5V unloading

Deep discharge (100% discharged battery)

2.4 Deep cycle 10.5V load, the current in its parameter of the specified battery. For (at 20ST. 100Ah C20 = 5A)

2.5 The engine of the ship does not use the car battery. The starting battery is not suitable for deep discharge.