Battery Managment system
The battery is a crucial component of any solar-powered boat. It acts as an energy buffer that stores energy produced by the solar panels and supplies a relative constant voltage for the motor path and peripheral electronics. A solar boat battery is not just a single unit; it is made up of several parts that work together to ensure efficient and safe operation.
Because the BMS is used during the Solar Sport One (SSO) races, they should comply with their regulations (Link)
All specifications of the BMS are summarized below:
- Maximum nominal voltage: 58,8V (14S lithium-ion)
- Maximum capacity: 1,5 kWh (= 5400 MJ)
- All battery cells must be commercially available
- The BMS must monitor the battery voltage and current
- The BMS must be capable of shutting down the system
- The BMS must be able to monitor charge and discharge currents
- The BMS must have a means to limit over-current in charge and discharge paths
- The BMS must monitor all individual cells
- All electrical systems must be provided with a fuse in series connection with the main battery ('Main fuse')
- The battery must be fused
- The BMS must be fused
About the BMS
The main component of a solar boat battery is the battery cells. These cells are responsible for storing energy in the form of chemical potential energy. Lithium-ion batteries are the most commonly used type of batteries in solar boats because of their high discharge capabilities and high energy density. Engineers of Innovation choose for the INR21700-P45B 4500mAh battery cells from Molicell.
The second component of a solar boat battery is the Battery Management System (BMS). The BMS is a device that monitors and manages the battery's health and state of charge. It ensures that the battery cells are not overcharged or over-discharged, which could damage them or create hazardous situations. In addition to monitoring voltage, the BMS also monitors input current, output current and temperature.
The Battery Multi-Function Controller IC from Texas Instruments is an excellent choice for the BMS main board as it is specifically designed for battery management in applications such as solar boats. This IC can measure important battery parameters such as voltage, current, and temperature, and it also has communication protocols that allow it to send this data to other devices such as the boat's monitoring system.
In addition to the Battery Multi-Function Controller IC, the BMS also includes a self-controlled fuse from Eaton. This fuse provides over current and overcharging protection in combination with the BMS, ensuring that the battery is safe from any potential damage.
One of the key challenges in designing the BMS for a solar boat battery is ensuring that the battery can be turned on and off safely. Engineers of Innovation has addressed this challenge by designing the BMS to include multiple states of turning on. They have also made sure that peripheral power is available without any power to the motor path, allowing for a safe working environment while continuing to receive telemetry data.
To ensure the safety of the battery, different user inputs must be applied before the battery is turned on (e.g. dead man’s switch) . This is because the safety of the BMS is quite complex, and any failure could result in serious damage to the battery, the boat or even the pilot.
Overall, the design of the BMS for a solar boat battery is a complex process that requires careful consideration of the different components and their interactions. Engineers of Innovation has chosen the Battery Multi-Function Controller IC and self-controlled fuse from Eaton, along with a carefully designed safety system for turning the battery on and off, to ensure the safe and efficient operation of the battery in their solar boat.
In conclusion, a solar boat battery is an essential component of a solar-powered boat. It stores the energy produced by solar panels and provides a constant voltage for the motor and peripheral electronics. The battery consists of battery cells and a Battery Management System, which work together to ensure safe and efficient operation. Specific technical regulations must be followed for solar boat races, and Engineers of Innovation has chosen the Battery Multi-Function Controller IC from Texas Instruments for their BMS main board.
The full set of schematics for the BMS are made available upon request free of charge, by requesting the CAD files you agree to not use the design files for commercial purposes. Please see a live view of the Altium project below.
The full set of layout for the BMS are made available upon request free of charge, by requesting the CAD files you agree to not use the design files for commercial purposes. Please see a live view of the Altium project below.
The software is available upon request free of charge, by requesting the software files you agree to not use it for commercial purposes and comply with all licences.