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GMDSS reserve sources of power

Why reserve power?

In early 2001, an 80 foot crabber with fiver persons on board lost electrical power and steering and was disabled and adrift in the Bering Sea after heavy seas knocked out their pilothouse windows.� Radio equipment which could have been used to make an emergency call to the Coast Guard and other nearby fishing vessels was rendered useless by the loss electrical power.� The only effective communications the ship had was their 406 MHz EPIRB.� During the same month, another fishing vessel, also in the Bering Sea, also lost power and steering, and also had to rely on their EPIRB to communicate with the Coast Guard.� That vessel's crew, unable to communicate on any of their radio equipment, were in the pilot house with exposure suits on, with life raft standing by.

The Global Maritime Distress & Safety System took this problem into account, requiring a reserve source of electrical power, to supply radio installations for the purpose of conduction distress and safety radiocommunications, in the event of failure of the ship's main and emergency sources of electrical power.� This reserve source of power is capable of simultaneously operating both the VHF radio, and the HF or Inmarsat satellite equipment.

Guidelines on the configuration of the reserve source or sources of energy used to supply radio installations on GMDSS ships


The radio reserve source(s) of energy should meet the requirements set out in regulation IV/13 of SOLAS 1974, as amended and in IMO resolutions A.694(17) and A.7202(17), as applicable, and should also comply with the following requirements.

47 CFR Part 80.1099.(b)//80.1105(h) (Excerpts).� A reserve source(s) of energy to supply radio installations must be provided on every ship for the purposes of conducting distress and safety radio communications in the event of failure of the ship's main emergency sources of power. The reserve source of energy must be capable of simultaneously operating the VHF radio installations, and either the MF/HF radio installation OR the INMARSAT ship's earth station (as appropriate for ship's sea area operation).

How long should it last?

  • Ships constructed after 1 February 1995 are required to have a reserve source(s) of energy that lasts for at least one hour.
  • Ships constructed before 1 February 1995 and on cargo ships of less than 500 tons gross tonnage will provide six hours of reserve source(s) of energy if the ship does not have emergency generators.

80.1105(h). The capacity of the reserve source of energy should be sufficient to operate the particular installation with the highest power consumption for the appropriate period specified.

  • Ships with emergency generators: 1 Hour
  • Ships without emergency generators: 6 Hours

What equipment does the reserve source of energy have to supply?

80.1099(1)(3) The reserve source of energy need not supply the HF and MF radio installations at the same time. When, in addition to the VHF radio installation, two or more of the other radio installations can be connected to the reserve sources of energy, they must be capable of simultaneously supplying, for one hour:

  • All other radio installations which can be connected to the reserve sources of energy at the same time, or:
  • Whichever of the other HF/MF radio installations will consume the most power

What are the battery and charging requirements when batteries are used solely in the absence of ship's supply?

80.1099(f)(1).� The capacity of the battery must be checked "Using an appropriate method, at intervals not to exceed 12 months".

NOTE: An instruction manual that contains all necessary specifications of the batteries should be available on board. The information should include at least:

1. Capacity and temperature range within which the stated capacity is maintained for the specified period;

2. Charging voltage and current limits in order to keep batteries fully charged while preventing overcharging;

Actual specific gravity of the electrolyte and/or cell voltages or the voltage of the fully charged battery;

3. Guidelines on how to carry out a controlled discharge test. Since these tests result in the batteries being substantially discharged, this must not be done at sea.

4. Methods of determining the condition of charge of the battery; e.g. check of specific gravity of electrolyte (acid density) or check of battery cell voltages/battery voltages by using an accurate measuring instrument in accordance with the battery manufacturer's specifications.

5. Requirement for ventilation;

6. Requirement for maintenance.


How long should it take to recharge the batteries?

80.1099(F)(1).� The batteries must be recharged to required minimums within a 10-hour period.

NOTE: The changeover between the ship's supply and the radio reserve source of energy should not require any of the equipment connected to it to be re-initialized manually and should not result in loss of data stored in memory. Any fault in the battery or battery charger should not impair or reduce the functional availability of any GMDSS equipment while energized from the ship's supply. �

What are the requirements for an Uninterruptible Power Supply (UPS)?

80.1099. (b).(I).� The UPS must insure a continuous supply of electrical power to communications equipment in the event of a ship's main or emergency-sourced power failure.

NOTE: The UPS should be operational within 5 seconds of switching on. To provide for failure of the single UPS, a second UPS or means for directly supplying the radio installation from ship's main or emergency supply should be installed and be available permanently. The changeover to the second UPS or ship's supplies may be manual or automatic. . The changeover should not require any of the equipment connected to it to be re-initialized manually and should not result in loss of data stored in memory. The UPS must be able to service the load requirements determined in SOLAS 1974 IV/13.2, 13.4 and 13.6 taking into consideration duplication equipment when provided. The capacity of the battery charger(s) used in the UPS should be sufficient to comply with regulation IV/13.6/1 �

How do I know when there has been an interruption of ship's power?

Provisions should be made for an aural alarm and visual indication at the position from which the ship is normally navigated, indicating an interruption of the ship's supply. It should not be possible to disable the alarm and indication. It should only be possible to acknowledge and silence the alarm manually. Both the alarm condition and indication should reset automatically when the ship's supply has been restored

What entries am I required to make in the GMDSS logbook with respect to reserve sources(s) of power?

80.409(e)(8),(9)� The times when the batteries are placed on charge and taken off charge. The results of required equipment tests, including specific gravity of lead-acid storage batteries and voltage reading of other types of batteries provided as a part of the compulsory installation.

NOTE:� When fully automatic charging systems are used, it is not possible to know the times to enter in the log. In lieu of the time entries, a statement detailing the use of a fully automatic charging system will suffice. The requirement for checking the specific gravity or battery voltage and entering this into the log remains.

This is meant to be an overview of the subject.� Some material has been left out.� For brevity and clarity, please refer to 47 CFR 80 Subpart W, and SOLAS Chapter IV for accurate and more complete sources of information.

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