Batteries
A battery is an electrochemical device that stores electrical power through chemical reactions that are electrically driven. Battery systems can provide the flexibility and freedom to store electrical energy and utilize the energy when it is most beneficial for system operation.
Batteries on ships can be used for energy storage for hybrid marine power (HMP) & electrical propulsion systems, emergency back-up power or as part of a renewable energy solution. Batteries are also used to start motors for lifeboats, rescue boats & to start emergency generators.
Essential routine power supplies, eg. for radio equipment, telephone exchange, fire detection, general alarm circuits, etc, are often supplied from а set of batteries worked оn а regular charge/discharge cycle.
Emergency battery supplies, eg. for emergency generator start up and emergency lighting, are used in а standby role to give power when the main supply fails. Ships' batteries are usually rated at а nominal voltage of 24 V DC.
Figure 37. Batteries
The two main types of rechargeable battery cell are:
- Lead-acid
- Alkaline.
Battery installations for both types of battery are similar in that the battery room should be well ventilated, clean and dry. Both types generate hydrogen gas during charging, so smoking and naked flames must be prohibited in the vicinity of the batteries.
Battery charging equipment uses а transformer/rectifier arrangement to supply the required DC voltage to the cells. The size of voltage depends on the battery type (lead-acid or alkaline) and the mode of charging, eg. charge/discharge cycle, boost charge, trickle or float charge.
Оn all ships and also on offshore vessels, there are essential services that are vital during а complete loss of main power. Such services include switchgear operation, navigation lights, foghorns, fire and gas detection, internal communications, some radio communications and alarm systems. To avoid the loss of essential services, they are supported by an uninterruptible power supply or UPS. These can be for battery-supported DC supplies or АС supplies, both of which can be configured as continuous UPS or standby UPS. On figure shows an AC-supported UPS arrangement.
Figure 38. UPS systems
The arrangement shown on figure is typical of а continuous UPS DC-supported supply system. The essential DC services are normally supplied from the 440 V main power system through charger. №1 which continuously trickle charges its battery. During а loss of main power, battery №1 maintains а transitional supply while the emergency generator restores power to the emergency board and so to charger №2. Either battery is available for а few hours if both main and emergency generators are unavailable.
Some critical emergency lights have an internal battery-supported UPS within the luminaire, where its battery charge is continuously maintained during non-emergency conditions.
