Batteries are used to power GMDSS equipment. They are very important because in case they are discharged, GMDSS equipment won't serve us as it should. This could be extremely dangerous in the distress situation. So, the batteries should be maintained in good condition.
Batteries store electrical energy in the form of chemical energy. When electricity is drawn from a battery, a chemical reaction occurs inside the battery. The battery will continue to produce electricity until all the chemicals have been used.
Most batteries are made from individual cells. Every battery, and indeed every cell making up a battery, has a positive (marked +) and a negative (marked -) terminal and each cell has a nominal voltage. The units are V (Volts). The nominal voltage of a cell or battery is its average operating voltage. The voltage can be much higher when the battery is being charged and considerably lower than the nominal voltage when the battery is almost discharged. How many volts the nominal voltage is depends on the chemical composition of the cell, for example a lead/acid cell will always have a nominal voltage of 2 V.
How much power a battery can store is called the capacity of the battery. The capacity of a battery is measured by how much current, measured in A (Amperes), it can supply for how many hours. The units are Ah (Ampere hours). For example, a fully charged battery rated at 50 Ah could power a 50A equipment for 1 hour. All batteries will lose part of their capacity to produce electricity while they are waiting to be used. They suffer a chemical process other than the main electricity-producing reaction. This is a self-destructive reaction which slowly uses the chemicals which are needed for the electricity-producing reaction. This results in a steady loss of capacity or loss of charge. How much energy is lost per year varies with the type of cell that is used in the battery.
Batteries are usually joined together in series and/or in parallel to achieve needed characteristics of the battery as a whole.
Batteries are connected in series to achieve needed nominal voltage of the battery as a whole. The voltage of the battery as a whole is the sum of the voltage of the individual batteries.
Batteries connected in series
In the above picture four 1,2 V 1000 mA batteries are connected in series. That is, they are joined together in a string, the positive terminal of one battery connected to the negative terminal of the next and so on. This results in the battery as a whole having a nominal voltage of 4,8 V (1,2 V + 1,2 V + 1,2 V + 1,2 V) and current of 1000mA.
Batteries are connected in parallel to achieve needed current of the battery as a whole. The current of the battery as a whole is the sum of the current of the individual batteries.
Batteries connected in parallel
In the above picture four 1,2 V 1000 mA batteries are connected in parallel. That is, the positive terminals of all batteries are connected together and the same stands for negative terminals. This results in the battery as a whole having a nominal voltage of 1,2 V and current of 4000 mA (1000 mA + 1000 mA + 1000 mA + 1000 mA).
Serial and parallel connection is combined to achieve needed nominal voltage and current of the battery as a whole.
Batteries connected in parallel
In the above picture two 1,2 V 1000 mA batteries are connected in series twice and both series are connected in parallel. This results in the battery as a whole having a nominal voltage of 2,4 V (1,2 V + 1,2 V) and current of 2000 mA (1000 mA + 1000 mA).
Connecting batteries in the circuit
Batteries have to be correctly connected into the circuit due to the terminals having either positive or negative polarity. Positive terminals should be connected to positive equipment connections and negative terminals should be connected to negative equipment connections.
Connecting the wrong way round is likely to damage both the battery and the equipment.