Battery

This page contains the information about the EoI battery development, everything from the requirements to the implementation can be found here.

What is the battery?

The battery is the energy buffer of the boat, it stores the energy coming in from the solar panels and provides a constant voltage for the motor path and peripheral electronics. The battery consists of multiple parts:

• Battery cells
• Battery management system (BMS)

The BMS makes sure that the battery cells can't be overcharged or over-discharged, as this might damage them and present dangerous situations. Besides monitoring the voltage a BMS usually monitors the current and temperature as well.

Technical regulations (as per September 2022)

• 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

Specifications

Functional requirements

ID	Specifiction	Value	Pass/Fail
	Nominal pack voltage	<= 58,8V
	Maximum capacity	1,5 kWh
	Monitor (pack) voltage
	Monitor (pack) current
	Monitor (pack) temperature	>> 1 sensor (8)
	Limit overcurrent in (dis)charge path
	Capable of shutting down the whole system
	CAN-bus communication	5V / 1 Mbit
	Internal cell balancing
	Charge and discharge paths can be operated simultaneously
	Motor and MPPT should be enabled independently
	The battery should be enabled with a N.O. contact	open = off closed = on
	Separate enable contact for Motor path (output) (Optional: Software disable only)
	Battery should be fully disabled (all outputs disabled) by emergency switch
	Shelve life (Save battery mode)	>= 1 year (2.8mA max)
	Humidity sensor
	Galvanic separation of safety path (bilge and horn)
	(Optional) I.M.U.
	(Optional) Phase change cooling hardware

Electrical requirements

ID	Specification	Value	Pass/Fail
0	Motor path (output)	60V / 300A
1	Charge path (input)	60V / 50A
2	Peri path (output)	24V / 2.5A
3	Safety path (output) (bilge and horn)	24V / 4A

Environmental requirements

ID	Specification	Value	Pass/Fail
0	Ambient operating temperature	0 - 50 °C
1	Ingress protection	IP67 or better

Open questions

• Do the MPPTs have to be modified for the 14S battery?
• Integrated or seperate charge/discharge paths? (I've got a slight preference for seperate pcb's)