The name Battery can produce the most varied representations for each person when talking about this topic. There are small batteries, similar to cells, cell phone Battery Systems and of course, automotive batteries. They all refer to the same thing, the accumulation of energy.
We will then segment the battery element in reference to the storage of the energy produced for use on demand, and that is that one of the characteristics of renewable energy is its intermittency. The sun gives us all its power during the day, and the wind depends on the atmospheric pressure factors that can sometimes appear too low or directly without movement. It is then that we must consider the batteries as a repository where to store the production surplus while the system is in operation.
Batteries are electrical and chemical. By changing sulfuric acid and lead into water and lead sulfate, they create electricity. When electricity is forced back into the batteries, the chemical reaction is reversed and the electricity is chemically stored. Basically Battery Systems facilitate a reversible chemical reaction that allows the accumulation or distribution of electrical energy.
Car batteries are called short-cycle because they are designed to deliver their full potential in a short amount of time, approximately 3 to 6 seconds. For example, a vehicle with a 65 amp battery may draw an average of 400 amps for 3 seconds until the engine starts, and then the alternator will take care of recovering that discharge immediately. This discharge-charge cycle is estimated to be around 5% of the battery's capacity, and since the alternator remains active during engine operation, the battery will always be at 100% charge.
In the case of a residential installation or of continuous use, the consumption will be distributed in different devices that will take energy constantly, producing a slight discharge over long periods of time. This is where deep discharge cycle batteries come in, designed to withstand discharges of up to 90%.
In deep cycle Battery Systems, the capacity is determined by the Ampere-Hours, which determine the total amount of energy that a battery can deliver after a 20-hour cycle, at a constant discharge rate, before the battery reaches 10, 5 volts. Other industries use a different period of 20 hours, but 20 hours is an industry standard. This means that a 200 amp-hour battery can run on 10 amp hours for 20 hours, at which point the battery will be dead. This is commonly known as the 8 pm rate.
There is a wide variety of deep cycle Battery Systems, with voltages ranging from 2v to 48v, and a variety of capacity in ah (ampere-hours). Usually the lower voltage ones offer higher amperage capacity . The relation of quality and cost, places 6v batteries as an efficient alternative, with capacities ranging from 150ah to 230ah.
When sizing the power system, all appliances that will draw power from the battery bank must be considered, also calculating a surplus to avoid complete discharge. The less discharge occurs in the battery, the longer its useful life. This is because batteries have a certain number of life cycles, before losing considerable efficiency.