Battery System Requirements
Coastal Profiling Float HD Battery

2021-02-12	ECM	assemble from previous versions

1.	Physical

1.1.	Battery pack plus manage/monitor elex should fit into designated annular volume within Float pressure housing.  Dimensions are approx 2.7” ID x 8.0” OD x 9.2” OAL, with ability to be installed and removed radially (i.e. 2.7” clearance).

1.2.	Ambient temperature limits are 0-50 degC for discharge, 10-40 degC for charge.  Most discharge will take place around 10 degC and most charge around 20 degC.  Actual measured cell temperature must be within these limits for operation. 

1.3.	Pack plus elex should tolerate normal shipboard oceanographic environment:  TBD any axis shock, 20-99% RH, and filtered salt air. 

2.	Electrical

2.1.	Battery pack actual energy capacity will be determined by the designated volume.  Desired capacity is 1.5 kWh at 20 degC.  It is expected that the available volume will accommodate either 3 x 8S4P 21700 cells, or 6 x 8S3P 18650 cells, plus monitor and control elex.

2.2.	Battery pack output bus voltage should be 24-36 V continuous, 29 V nominal, 42 V absolute max.  It is expected this will allow an 8S Li-Ion architecture.

2.3.	Battery pack max discharge current is 11 A .   It is desirable to operate with partial battery complement, e.g. with 2 x 8S4P 21700 decks, or 4 x 8S3P 18650 decks, installed.  (⅔ of full pack.)

2.4.	Typical daily discharge profile is 10 min pumping at 8 A, 1 hr profiling at 0.3 A, and ~23 hr sleeping at 0.004 A.

2.5.	Full pack charge time should be 8 hr.   3 hr charge time is desired.

2.6.	Battery pack internal consumption should be less than 5% per year, not including cell self-discharge.  This implies standby power during Sleep (see Features, below) less than 10 mW.

2.7.	Cell balancing within the pack is desirable, rate need not exceed 0.0025 C.

2.8.	Battery pack discharge and charge current should be integrated by the pack elex, with TBD time resolution and measurement accuracy, to yield total pack charge (coulomb count) in real time, to TBD resolution.  Cycle counting, impedance measurement, and capacity prediction are desirable but not required.

3.	Interfaces to Float system

3.1.	Connection to Motherboard (CPF Microcontroller):  The battery system should present I2C on two signal lines at 100 kbit/s, 29 V battery power output at 3.2 A max, and I2C 5 V logic power input at 100 mA max (for Mobo-related interface circuits in the battery pack)..  It is expected that the I2C connection will provide CPF Micro access to the battery system cell string monitors, fuel gauges, pump power controls, and sleep timer.  A Harwin M80-5100842 connector is desired for compatibility.

3.2.	Connection to Pump Drive: the battery system should present 29V battery power at 8 A max.  A Harwin M80-5000000M3-04-332-00-000 connector is desired for compatibility.

3.3.	Connection to Charger:  The battery system should present 29V battery charge input on TBD circuits at TBD A max, robust serial communications TBD, and deadface relay control TBD.   Deadface relay isolation of the charger connection is desired.  The charger endcap connector should be in the SubConn Micro Circular series; the 8 pin version is desired for compatibility.  It is expected that the serial communication link will provide charger access to the battery system cell string monitors, fuel gauges, and other safety functions TBD.

3.4.	Arbitration of Charger and Mobo/Micro access to battery pack I2C devices is TBD.  Joint access is not required.

4.	Features

4.1.	Battery cycle life of 100 is desirable, at 100% depth of discharge.  Safety, reliability, and capacity (in that order) are higher priorities.

4.2.	Battery pack should include sleep timer logic able to switch the pack outputs off for programmable periods from 1 to 64 minutes.   The sleep function should be armed and triggered over the I2C connection to the Mobo/Micro.  (Existing LHE functionality.)  Standby power in the sleep state should be less than 10 mW.

4.3.	Battery pack outputs should be switched on/off from the endcap by two momentary contact reed switches.  (Existing LHE functionality.)  Power when switched off should be less than 10 mW.

4.4.	Battery pack should include power switching, fault reporting, and energy monitoring for the Pump Drive power output.  The power, fault, and monitor functions should be controlled over the I2C connection to the Mobo/Micro.  (Existing LHE functionality.)

4.4.1.	Pump Drive power switch should include soft start inrush control with a current limit of 10A and be able to charge 1000 uF of downstream capacitance.
4.4.2.	Pump Drive power switch should include Electronic Circuit Breaker function with a trip rating of 10A and trip time of 15 msec.
4.4.3.	Pump Drive power feed should use a large TVS diode(s) for pump regen control.  An active regen control circuit is not required.
4.4.4.	Pump Drive power feed should include an energy monitor circuit.  The energy data should be accessible to the Mobo/Micro over the I2C bus.  The LTC2946 device is desired for compatibility.
4.4.5.	Pump Drive power switch should include a watchdog with TBD functionality.

5.	Safety

5.1.	Cells must be purchased through safe channels from these recognized manufacturers: Panasonic/Sanyo, Sony, Samsung, or LG.  Cells must pass UN 38.3 abuse test.  Cells must incorporate overpressure and overcurrent/overtemperature (PTC) disconnect devices.

5.2.	Battery packs must be assembled with welded tab connections.  No more than TBD cells may be paralleled without protective fusing between them.  Pack design must incorporate TBD radial spacing and TBD axial spacing between cells to reduce propagation in the event of thermal runaway.

5.3.	Every cell in the battery system must have its terminal voltage monitored continuously during operation.  The monitor should be able to cause or request normal termination of charge by the charger, and termination of discharge by the Mobo/Micro, when normal cell operating voltage limits are reached.  The monitor must have the capability to autonomously terminate both charge and discharge current flow through the cell or cell string, if cell safety voltage limits are reached or exceeded.  The operating and safety voltage limits must be as specified by the cell manufacturer.

5.4.	Cell string (series string) overall voltage must be monitored by a redundant circuit able to autonomously terminate both charge and discharge current flow, in abnormal situations and when the primary cell voltage monitor fails to act.

5.5.	The charger must have a CC/CV characteristic suitable for Li-Ion charging.  The CC current must never exceed the charge rate limit for a single string of cells.  The CV voltage must never exceed the voltage limit for a series string of cells.

5.6.	Cell temperature must be monitored at TBD points within the battery pack.  Cell temperature data must be available to the charger at all times during charge, and to the Mobo/Micro during discharge.  The charger must adjust the charge rate according to cell manufacturer specifications, based on measured cell temperature, and stop charging if temperature limits are exceeded. 

5.7.	The charger must have continuous communication with the battery pack during charging, and must terminate charging if communication is lost.  The charger must continuously monitor voltage, temperature, and current in the pack, and must terminate charging if any measurements exceed normal limits TBD.  The charger must be able to alert a responsible party at all times if any measurements exceed safety limits TBD.

5.8.	The Mobo/Micro must have continuous communication with the battery pack during discharge, and should abort the mission if communication is lost.  The Mobo/Micro should continuously monitor voltage, temperature, and current in the pack, when not sleeping, and abort the mission if any measurements exceed safe limits.  Whenever possible and always when in the lab or aboard ship, the Mobo/Micro must be able to alert a responsible party if any measurements exceed safe limits.

5.9.	The pack must be fused at the charge input for the expected charge current, and fused at the discharge outputs for the expected discharge currents.  These fuses protect the pack, and the upstream and downstream wiring, against overcurrent due to catastrophic failure.