Uninterruptible power supply (UPS) and battery systems explained…

Most of the emergency power requirements are supplied by the emergency 24V system which consists of a battery distribution board backed up by a separate 24V battery. This provides a smooth changeover to a constant power source upon loss of the ship’s main or emergency power.

When the emergency source of electrical power is an accumulator battery, this must be capable of:

  1. carrying the emergency electrical load without recharging while maintaining the voltage of the battery throughout the discharge period within 12 % above or below its nominal voltage;
  2. automatically connecting to the emergency switchboard in the event of failure of the main source of electrical power; and
  3. immediately supplying at least the following services:
  • for a period of not less than three hours, emergency lighting at every lifeboat preparation station, muster and embarkation station and over the sides.
  • for a period of not less than 18 hours, emergency lighting as detailed below unless alternative arrangements are provided by lamps having accumulator batteries within the lighting unit that are continuously charged:
  1. in all service and accommodation alleyways, stairways and exits, personnel lift cars and personnel lift trunks;
  2. in the machinery spaces and main generating stations including their control positions;
  3. in all control stations, machinery control rooms, and at each main and emergency switchboard;
  4. at all stowage positions for firemen’s outfits;
  5. at the steering gear; and
  6. at the emergency fire pump, at the sprinkler pump, if any, and at the emergency bilge pump, if any, and at the starting positions of their motors.

– for a period of not less than 18 hours:

  1. the navigation lights and other lights required by the International Regulations for Preventing Collisions at Sea in force; and
  2. The radiocommunications, as required by Amendments to SOLAS 1974, Chapter IV – Radiocommunications.

– for a period of not less than 18 hours:

  1. all internal communication equipment as required in an emergency;
  2. the navigational aids;
  3. the fire detection and fire-alarm system; and
  4. intermittent operation of the daylight signaling lamp, the ship’s whistle, the manually operated call points and all internal signals that are required in an emergency, unless such services have an independent supply for the period of not less than 18 hours from an accumulator battery, suitably located for use in an emergency;

A separate 24V battery and charger system is provided for the emergency generator starting arrangements and the controls for this system are mounted on a dedicated section of the emergency 24V switchboard.

Example of UPS and battery system diagram

The battery charger has one 220V supply from the emergency switchboard 220V section and another supply from the main light switchboard.

Example of a battery charger

The board contains the following equipment:
• Voltmeters for rectifier and bus voltage monitoring
• Ammeters for charger, bus and battery monitoring
• Earth leakage monitoring indication lamps and switches
• Protected outputs via miniature circuit breakers (MCBs)
• Charging source power indicator lamps
• Charger failure indicator lamps
• Battery test facility
• Charger selection/parallel switch

Some of the new chargers are fitted with a battery voltage monitoring facility which will raise an alarm if the battery voltage moves above or below a preset level or the battery current rises above a preset level. The unit is also fitted with charger failure, overcurrent, input mains failure and earth leakage alarms. These alarms will raise a common output alarm which will raise an alarm on the main alarm and monitoring system.
When an earth is present on an outgoing circuit, the earth leakage alarm will sound. Operation of the earth test pushbutton will cause one earth lamp to glow bright and the other earth lamp to dim. Careful isolation of the outgoing circuits (mindful of essential consumers), will locate the faulty circuit, the lamps returning to equal brilliance and the alarm clearing once the faulty circuit is isolated. Some of the switchboards are also fitted with a battery test facility which will test the back-up battery for correct condition and this will raise an alarm if incorrect.

The 24V battery system is located in the battery room in an elevated position in the ship and as close to the radio equipment as possible (usually on the bridge level), is normally on a floating charge with the rectifier supplying the load. The room is properly ventilated with supply from the accommodation system and exhaust directly outside and the temperature range of the battery should be wider than the expected temperature range of the location where the battery is installed. Caution should be done as batteries of different types and different cell construction should not be installed in the same location as they might affect each other.

Example of ship’s battery room. Source and credit: Mariners Planet

The radio/GMDSS equipment is backed up by a separate battery/UPS system.

The battery charger is a fully automatic charging device which automatically charges the 24V storage battery. The charger OFF/AUTO switches should therefore be left in the AUTO position.
Some of the charger has a facility to adjust the charging voltage, however, this should not be altered once the charger has been commissioned.
While the storage batteries are fully charged, they are subjected to a floating charge and in this condition, the charger supplies the 24V system with power. The charger will automatically set this mode when initially connected to the switchboard. In the event of a blackout, the batteries will provide power to emergency consumers. If the charging power is recovered while the batteries are discharging, the battery charger will return to floating mode.

A constant voltage is applied to the battery, regardless of any load, power or temperature variation and the charging current varies according to charged state thus maintaining the battery in a fully charged condition. An AVR is fitted to keep the loads voltage constant.

During a failure of the main and emergency power supplies, the battery system will take over.

If the battery has been subjected to a period of duty due to power failure, the battery charger is automatically transferred to an equalizing charge on restoration of the power supply and this rapidly charges the battery. As soon as the battery becomes fully charged, it reverts to a floating charge. The charge performed after the recovery from a power interruption is controlled by the
control system, which protects the battery and charging circuits from excess current.

On new vessels with modern systems the 24V battery charger and discharge system consist of two battery chargers and the discharge distribution board, backed-up by a battery system. These
provide a smooth changeover to a constant power source upon loss of the ship’s main or emergency power. The panel consists of three parts; the two battery chargers and the distribution board. The use of dual chargers means that in the event of failure of one charger, the second charger can be used, thus maintaining essential supplies. The unit is supplied with dual 440V feeds; a main source and an emergency source. In the event of loss of the main source, the system automatically changes over to the emergency source. In the event of loss of both the main and emergency source, the battery system will continue to supply the essential consumers served by the distribution board. In this way the essential consumers are maintained for as long as possible.

The emergency generator starting section of the 24V emergency switchboard houses the ammeters and voltmeters and control equipment for the emergency generator starting batteries and chargers. On some systems, there are two systems with a manual changeover switch.
The switchboard is also fitted with a battery test facility which will test the batteries for correct condition and an alarm is raised is this is incorrect.
The section is also fitted with battery and charger failure alarms which will raise an alarm via the main alarm and monitoring system in the event of any abnormal conditions.

The boards and chargers are designed for continuous operation and are practically maintenance-free. However, the units should be kept clean and dry, and a visual inspection of connection integrity, cable condition etc, made once a year. At this time, the charging voltages should be checked using a high quality digital voltmeter.

Every fixed radio installation onboard vessels are provided with reliable, permanently arranged electrical lighting, independent of the main and emergency sources of electrical power, for the adequate illumination of the radio controls for operating the radio installation. A reserve source or sources of energy (UPS or separate battery bank) is provided, for the purpose of conducting distress and safety radiocommunications, in the event of failure of the ship’s main and emergency sources of electrical power. The reserve source or sources of energy is capable of simultaneously operating the VHF radio installation and, as appropriate for the sea or sea area for which the ship is equipped, either the MF radio installation, the MF/HF radio installation, or the INMARSAT ship earth station and any of the additional loads for a period of at least one hour. On modern sophisticated vessels uninterrupted input of information from the ship’s navigational or other equipment to a radio installation is needed to ensure its proper performance, therefore means are provided (UPS) to ensure the continuous supply of such information in the event of failure of the ship’s main or emergency source of electrical power.

All batteries should be kept clean and dry. The battery poles and connections must be kept covered with acid-free vaseline.

The cell voltages should be checked and logged once a month, and the connection terminals checked for tightness once a year.

The emergency generator duty battery set should be changed over once a month.

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