A1 - Summary
(1) The intent of this Annex is to provide guidance on best practice to facilitate
safe solutions for vessels utilising batteries used for propulsion and/or electric
power supply purposes during ship operations.
A2 - Introduction
(1) This guidance has been developed to identify industry best practice, however it
is recognised that this guidance shall not cover every eventuality in design,
installation, operation, etc, and each case shall be considered separately. There
are several areas within a design where the use of risk assessments or hazard
identification techniques (such as Failure Modes Effects Analysis (FMEA)) shall be
performed to understand the potential safety issues for personnel, the environment,
the vessel and the vessel’s operations.
(2) This guidance does not supersede any other guidance or statutory instruction and
shall be taken into account when developing designs for battery power systems. This
guidance does not replace the need for sound engineering practice nor seamanlike
precautions.
A3 - Definitions
(1) A cell is a single electrochemical unit in its simplest form, typically
packaged in: metal cylinders; or flat, rectangular metal or plastic cases
(“prismatic cells”); or heat-sealed foil pouches.
(2) A battery is an assembly of two or more cells that are electrically
connected together and fitted in a case with devices as terminals, markings and
protective devices that it needs to function properly and safely.
(3) Thermal runaway is when a cell enters a self-heating state (exothermic
reaction) where the heat generated is greater than the heat dissipated. (Note:
thermal runaway can begin at temperatures as low as 120°C depending on the cell
size, design and chemistry, and from the initiation of thermal runaway, a cell’s
temperature can rise to a maximum in under 2 minutes.)
(4) State of charge is the available capacity in a battery expressed as a
percentage of rated capacity.
(5) State of health reflects the general condition of a battery and its
ability to deliver the specified performance compared with a new battery.
(6) A battery management system (BMS) is an electronic device that controls,
manages, detects or calculates electric and thermal functions of the battery system
and provides communication between the battery system and upper level control
systems.
A4 - General Overview
(1) The contents of this guidance shall not cover every eventuality in design,
installation, operation, etc, and each case shall be considered separately. The use
of risk assessments or hazard identification techniques shall be performed to
understand the potential safety issues for personnel, the environment, the vessel
and the vessel’s operations caused by the incorporation of a battery. Suitable
mitigations or safeguards shall be implemented to reduce risks to an acceptable
level. In general, amendments to operational methods or procedures shall not be
accepted as an alternative to the safe design of a battery system and its
installation in a vessel, whether this be regarding location, materials, equipment,
auxiliaries, construction method, etc.
(2) The design of a battery system within a vessel shall anticipate future changes.
These changes might relate to the operational tasking of the vessel, modifications
to the electrical equipment, upgrades to the battery cell chemistry (and energy
density) or caused by obsolescence of equipment. It shall be highlighted that any
modification which changes the requirements upon an existing battery system shall be
thoroughly assessed against the original requirements of the battery and its current
state of health.
A5 - Battery Installation in a Vessel
(1) This section provides guidance to ensure that the hazards associated with
installing and operating a battery on a vessel do not lead to unacceptable risks to
persons, the vessel, the environment, or the vessel’s operations. SOLAS II-1 Part D Electrical Installations shall take
precedence over the following paragraphs however their content shall be considered.
(2) The role of the battery shall be clearly defined for its intended use in a
vessel; for example, the battery may be a small part of a hybrid system, or it may
be the sole source of propulsive power. A risk assessment method such as an FMEA
shall be performed to assess the effects of a battery system failure upon the vessel
and its operations. These assessments shall consider the vessel’s different
operating modes and the state of health of the battery through its intended design
life.
(3) The vessel shall employ its own electrical protective devices (e.g. fuses or
circuit breakers) to protect the battery and personnel but also to prevent damage to
ships equipment caused by battery defects. A positive lockable means of isolating
the battery shall be provided to allow maintenance.
(4) The location of the battery compartment shall take into account the operational
role of the battery (e.g. whether the battery is used for emergency power during an
engine room fire) as well as the effects that a battery fire would have on the
vessel. Consideration shall be given for avoiding adjacent compartments containing
sources of heat or significant fire loads as increases in battery compartment
temperature could affect battery operations or lead to thermal runaway. It is
expected that further considerations would be necessary for vessel not built of
steel or equivalent material. A full assessment shall be made for the routing of
cables and pipework through the battery compartment, and the routing of cables from
the battery in order to maintain essential services during an incident.
(5) It is strongly recommended that the temperature of the battery space/compartment
is given strong consideration for all installations. To ensure that the batteries
are kept within their thermal operating limits, temperature control systems like
water cooling systems or heating, ventilation and air conditioning (HVAC) systems
shall be employed with levels of redundancy to ensure that localised cell
temperatures remain within manufacturers guidelines in the most onerous heating
condition (e.g. high external atmospheric temperatures with all equipment operating
at maximum load). The failure of such temperature control systems shall produce
alarms for the battery system. Temperature monitoring of the battery compartment is
also recommended and this may be linked to early warning alarms as well as fixed
fire suppression systems.
(6) All ventilation and electrical systems within the battery compartment shall be
capable of being isolated from a safe location outside of the battery compartment.
Ventilation systems shall safely expel toxic or flammable gases to a safe location.
(7) The battery and battery systems shall be fixed within the battery compartment
such that they can endure the maximum predicted vessel motions. Heavy items or items
which could cause physical damage to the battery shall not be co-located with the
battery unless these are retained within the same parameters. Consideration shall be
given to fixing the battery adjacent to any potential heat source which could result
in inadvertent heating of the battery, e.g. exhaust, heavily loaded electrical
cabling and direct sunlight.
(8) The battery location and fixings shall ensure that standing water and residues
are removed from around the battery and fire-fighting mediums can adequately
penetrate the battery casings to extinguish and/or quench a potential fire.
(9) Consideration shall be given to the reduction of combustible materials within a
battery compartment, especially those which produce smoke or toxic products in a
fire. For certain types of vessel the use of combustible materials within the
battery compartment may be prohibited. Dangerous goods shall not be stored in a
battery compartment.
(10) The boundaries of the battery compartment shall have fire protection to contain
a fire in the space of origin and it shall be appropriate for the cumulative fire
loads within the compartment and the type of vessel (e.g. an A-60 class division).
Penetrations through these boundaries shall be protected to the same fire protection
standard. For domestic vessels, the required fire protection may be defined in the
applicable vessel regulations.
(11) Early identification of a potential battery fire and automated actions prior to
an incident are key to preventing thermal runaway and a possible chain reaction
between adjacent cells. The battery compartment shall be fitted with detectors in
accordance with manufacturer’s recommendations which are capable of providing early
identification of a fire. Possible early identification could involve the monitoring
of local cell temperatures or detection of electrolyte solvent vapours. When
activated the detectors shall initiate appropriate alarms and may automatically
isolate electrical systems and ventilation, or activate fixed fire-fighting
systems.
(12) An assessment shall be conducted to identify the most appropriate fire-fighting
equipment and procedures for the types of fire within the battery space/compartment
- such an assessment may consider at what point fire fighting using portable
equipment may no longer be appropriate. Both extinguishment and heat removal are
fundamental to fire-fighting efforts and many of the common firefighting mediums can
be utilised once the relevant isolations are made (e.g. electrical or ventilation).
It is strongly recommended that one or more fixed fire-fighting systems are designed
and installed so that these can be operated from a safe location with feedback
provided to confirm proper activation. In addition, portable fire extinguishers
shall be provided to address the potential classes of fire within the battery
compartment and the fire loads that they present. For certain vessel types a fire
hydrant, hose and suitable nozzle shall also be available to access all parts of the
battery compartment.
A6 - Battery Management System
(1) The battery management system is required to maintain the condition of the cells
and battery and protect them from unsafe situations such as internal battery
defects, excessive external demands (e.g. a high current demand) and overcharging.
It shall be ensured that the battery management system is compatible with the
requirements of the battery system, the other battery components and the vessels
electrical equipment. The use of risk assessment methods are important to ensure
that all of the potential failures in the battery (and in the vessel, see paragraph
9.2) have been appropriately considered with mitigations adopted according to the
severity of risk.
(2) Abnormal temperature rise can be considered the first warning of thermal
degradation of cells and shall be continuously monitored. Out of tolerance readings
shall initiate an automatic response such as shut-down of a group of cells. It is
recommended that temperature monitoring is provided at the cell level, especially if
the batteries experience high charge or discharge rates. The battery management
system may actively manage battery operations with respect to the temperature of the
battery to improve efficiencies and to further reduce the risk of high temperature
incidents. Due to the importance of temperature on batteries, continuous temperature
monitoring may also be linked to responses external to the battery (e.g. isolation
of the battery, early warning alarms and fixed fire suppression systems).
(3) The battery management system shall limit currents to ensure the battery remains
in a safe condition. Permitted currents may be controlled relative to the state of
charge and shall take account of the battery’s state of health through-life.
(4) Lithium-ion cells, unlike other conventional battery technologies, shall not be
charged in excess of 100% state of charge as this may cause rapid failure of the
electrodes and possible thermal runaway. Discharging below the minimum safe voltage
can also cause cell damage. Unlike other battery technologies, it is therefore not
possible to balance the state of charge of several lithium-ion cells using top-off
or trickle charging of the battery, and it is vital that charging is stopped
immediately if there is an unacceptable temperature rise - battery management
systems shall only be employed if they are compatible with lithium ion batteries and
are suitable for the application.
(5) The battery management system shall be capable of monitoring cell voltages and
currents to a high resolution in order to ensure that the voltage of each cell
remains within the range specified by the manufacturer. Cell voltages shall be
continuously monitored with an automatic alarm if these voltages exceed or fall
below set limits, and a cell or battery shutdown shall occur automatically if any
voltage approaches the cell-damage threshold.
A7 - Battery Operations and Procedures
(1) Labels and signs - batteries, high voltage equipment, battery systems and
compartments shall be adequately labelled using internationally agreed symbols where
available. Emergency systems shall be appropriately labelled and be clearly visible.
(2) Logbooks and configuration - it is recommended that a battery logbook is held
onboard to record the status of the battery and its equipment. The logbook may
include: equipment serial numbers and dates of
manufacture/installation/testing/expiry, maintenance records, test results, defects,
a summary of the battery charge/discharge cycles, etc. Software used for control,
monitoring, data logging, alarm and safety systems, which may be part of the battery
management system, shall be developed using robust and auditable processes. All
software within such systems shall be version controlled and recorded.
(3) Operational procedures – it shall be ensured that the battery system is never
operated outside of its designed scope of assumptions and limitations. Therefore,
although a battery system shall contain many cascading levels of protective devices,
the vessel shall not employ operational procedures that rely on these protective
devices for a safe condition.
(4) For vessels utilising electrical power from the battery system for propulsive
power or dynamic positioning, operational procedures are considered of prime
important to both protect the battery system whilst ensuring that loss of a battery
system does not affect the safety of the vessel or its operations. Formal operating
procedures shall be developed for the operating scenarios expected of the battery,
considerations might include failure scenarios (e.g. loss of a cooling system) to
ensure that the battery is not inadvertently operated outside of safe parameters –
it is expected that consideration of such scenarios may lead to further safety
mitigations in the design of the battery system.
(5) Inspections and maintenance – all inspections and maintenance shall be in
accordance with manufacturer’s recommendations but shall include the testing of all
sensors, assessment of the state of health of each cell, recording of the
environmental conditions in the battery compartment and assessment of any other
relevant factors. Routine inspections may check for physical damage, cleanliness,
signs of arcing or increased temperature, correct operation of ventilation and
battery protection systems, etc. Maintenance activities shall be planned in a
vessel’s maintenance schedule. Procedures shall be held onboard to detail the
necessary actions if the battery is at risk of being operated outside of its normal
operating envelope (e.g. during extended refit periods, following limited charge
periods or following identification of a defect).
(6) Emergency procedures shall be developed for the actions to be taken in all likely
emergency scenarios; these may require consultation with an independent body such as
a Recognised Organisation. Scenarios may include a battery localised high
temperature, activation of a fire detection device, identification of a fire in the
battery compartment (a battery fire or another combustible), a medical incident,
flooding, violent cell venting, etc. Emergency procedures shall be held onboard and
shall include actions to be taken by all stakeholders, including emergency services
and salvage teams, to create a safe condition. Emergency drills and training shall
be routinely conducted for all of the main emergency scenarios.
(7) An assessment shall be made of the possible medical scenarios related to the
battery and suitable mitigations shall be actioned whether these be pre-emptive
(e.g. provision of personal protective equipment) or remedial (e.g. installation of
an eye-wash station).
(8) Crew Training - it is recommended that at no time shall there be less than two
persons on the vessel who are adequately trained and experienced in all battery
equipment and procedures. In addition, all crew shall have an awareness of the
vessel’s emergency procedures regarding the battery.
A8 - Further Information
MGN 550 (M+F) Electrical Installations - Guidance for Safe Design, Installation and
Operation of Lithium-ion Batteries
BS EN 62281 Safety of primary and secondary lithium cells and batteries during
transport
BS EN 62619 Safety requirements for secondary lithium cells and batteries for use in
industrial applications
BS EN 62620 Secondary lithium cells and batteries for use in industrial applications
IEC 60529 - Specification for classification of degrees of protection provided by
enclosures
UN DOT 38.3 Recommendations on the transport of dangerous goods, manual of tests and
criteria