Onboard merchant ships an annual battery capacity test has to be conducted on the GMDSS batteries, according to SOLAS. During my sixth semester I was onboard a tanker and was asked to perform the test. No proper guidance was available onboard, and nobody seemed to know how to carry out the test. The lack of knowledge and the ad-hoc approach to testing prompted this report, which includes Lead-acid batteries and similar types
The problem statement focues on the requirements of a proper capacity test. Details which influence the test must be known before testing can commence. Without knowing the characteristics of battery capacity calculation, mistakes can easily be made. The problem is divided into two segments; one concerns the written legislation and recommendations, the second concerns the influence of physical specification such as temperature and discharge current. Furthermore, the Danish Maritime Authority was asked about their knowledge regarding the test. Two Recognised Organisations were asked to contribute their knowledge as well. Finally, companies with expert knowledge in GMDSS equipment were asked about how they interpret the legislation. The actual written requirement of the test is simply that the method has to be “appropriate”. This vague statement is clearly open to interpretation by any party.
SOLAS is translated into Danish legislation (Meddelser B). Because any Danish flagged vessel must obey the legislation , the requirements from SOLAS are effectively brought into force.. During the project a circular ( COMSAR/Circ.32) was discovered and was found to be very informative.
The lack of proper documentation onboard the vessel lead to current and voltage measurements on the GMDSS radio batteries. It was however desirable to know the actual consumption of all the radio equipment because these readings might influence the capacity. An old article written by W. Peukert in 1897 was discovered and based on his theory and experiences it is possible to calculate and predict time and capacity. Vessels are moving around the world, and they have to face the weather, pleasant or not. Lead-acid batteries are sensitive to variations in temperature. The temperature must therefore be considered when performing a capacity test, together with other appropriate precautions.
The report draws the knowledge from physical specifications, legislation, recommendations, and practical advices from the expert companies. Based on this a solution is constructed in an Excel spreadsheet (Battery capacity calculation & v0erification model). The main core of the solution is to construct a statement which forms the foundation for a capacity test. On this basis it is possible to determine whether or not a test is passed.
Title: Kapacitetskontrol af radiobatterier
Author: Søren Viisholm Trankjær
Year: December 2012
School: Aarhus School of Marine and Technical Engineering
Education: Bachelor of Technology Management and Marine Engineering.