Our current battery system consists of battery packs from Akasol and a rack system from LG Chem.
Akasol battery packs
The battery pack is a maritime version of a pack that Akasol in Germany has developed for the bus and train industry. Akasol has signed delivery contracts for their bus battery pack with among others Volvo Trucks in Gothenburg. A dedicated battery assembly factory located outside Frankfurt has been in operation since November 2017. The battery pack has gone through extensive testing by the bus companies and is certified for use in the automotive and train industry. Module Propagation tests according to DNV-GL and NMA regulations have been passed. The battery system has achieved DNV-GL Type Approval.
One benefit of using a standard pack from the bus industry is that spare parts and replacement packs will be available for many years. A requirement in the automotive industry is that spare parts shall be available 10 years after the last unit has left the production line.
The battery packs are based on cells and sub-modules from Samsung SDI in Korea. Samsung is one of the world’s leading suppliers of li-ion battery cells. The battery cell is an automotive graded cell and is also used in BMW and VW electric and hybrid cars. The main cell specifications are shown below:
The cell is of a prismatic aluminium can type and contains a number of safety mechanisms as shown in the illustration below. Among these are both an internal fuse, an Overcharge Safety Device (OSD) and a Ventilation Device.
12 cells are coupled together in series and forms a sub-module. 15 sub-modules makes a battery pack. The pack is a self-contained unit with system voltage of 540 – 756 V, its own BMS (Battery Management System) and control electronics with contactors, fuses, pre-charge circuits, voltage and current measurements. The pack has IP 67 rating and the outer shell is a sandwich structure made of stainless steel with an isolating core material. A Gore-Tex membrane in the outer shell secures that inside pressure in the pack equals the outside pressure.
The pack has dimensions 1700 x 700 x 150 mm, the weight is 253 kg and each pack have a rated capacity of 24.4 kWh (33,3 kWh from 2021). A number of these packs can be coupled in parallel to form the energy storage system.
The integrated BMS in the battery packs communicates with a Master BMS unit. The main function of the Master BMS is to monitor cell voltage and temperatures, measure the current and system voltage, balance the packs and transfer all relevant battery parameters to the automation and control system.
The Master BMS communicates with the PLC based Vessel Controller and will together with the controller be installed in a separate Control cabinet. Internal communication in the battery system and between the battery system and the vessel controller is CAN 2.0B.
For more information about Akasols batteries: https://www.akasol.com/en/battery-systems
LG Chem Rack system
With 22 years of experience in successfully delivering products and solutions to customers in the global energy sector, LG Chem is recognized as the industry leader in Lithium-ion battery manufacturing.
LG Chem’s L&S (Lamination & Stacking) process minimizes dead space, enables higher energy density, and enhances the sustainability of cell structures
LG Chem’s SRS® (Safety Reinforced Separator) increases the mechanical and thermal stability of battery cells.
The battery system is built up of cells, modules, racks, Battery Protection Unit (BPU) and a Battery Bank Controller.
The cell used for the battery system is a 65 Ah NMC cathode and graphite anode pouch power cell with specifications as given below.
The cells are built into modules in a 2 parallel and 14 series configuration. The modules are
air-cooled with one fan located at the front of each module providing a uniform airflow
through the module. All interfaces such as power and communication terminals are mounted at the front for easy installation and maintenance. The table below describes the module specifications.
17 modules are coupled in series forming the system voltage and located in a rack. The rack
is enclosed in a cabinet.
The battery cabinets are installed in the battery rooms in such a way that the airflow from
the cooling system forms a loop were chilled air is provided in the front of the cabinets and
blown through the modules. Each module is equipped with a cooling fan. The air in the loop
is cooled by a water to air heat exchanger using water as the cooling medium.
The vertical distance between each module is 12.6 mm. This gap is filled with an aerogel mat
which provides very efficient thermal insulation.
Battery Protection Unit (BPU)
The BPU includes electric circuitry and components which monitor the status of the battery
modules and communicate with the Battery Section Controller. The main components are
rack BMS, contactors, relay, voltage sensor and current sensor.
For more information about LG Chems batteries: https://www.lgessbattery.com