CellSense Manual 1 st generation
Contents
1. Internal comm port Figure 1 Schematics CellSense User s Manual June 2006 4 15 CVM specifications Parameter Value Supply voltage 20 30 VDC Power consumption 1 W 50 mW cell Measuring range 0 1 1 1V Accuracy 10mV Resolution 2 5 mV Conversion rate 900 cells sec Maximum number of cells 270 Galvanic isolation between cell groups and central unit 300 VDC Galvanic isolation over power supply 1500 VDC Galvanic isolation of the CAN bus 2500 VAC Table 1 Specifications Installation Programming connector Alarm LED CAN bus NO Com NC 24V GND Relay Power spply Figure 2 Connections Assembly The system is delivered in order to be mounted on a fuel cell stack and can be considered as a part of the stack The dimensions of the printed circuit board PCB fit to a stack with 73 76 cells Smaller stacks down to 28 cells can be equipped with the same system cutting off the PCB between two VSU s minimum 7 VSU s have to be kept intact The two long sides of the PCB have a strip 5 mm in order to assemble the PCB on top of the stack The assembly must guarantee protection against CellSense User s Manual June 2006 5 15 radiation reception of EMI also via cables mechanical stress contact or electric shock isolation failure in case of high voltages especially when connecting more stacks in series Connecting the power supply2. at least a suitable resistance 470 Ohm in case of 8 mA The accompanying LabView interface can be used for baptizing the VSU s Baptize tab the progress of the process can be followed interactively Figure 4 Baptizing Connecting the stack stack celll cell2 cell3 cell4 cell5 Figure 5 stack connections The negative terminal of the stack must be connected to the first connection closest to the corner of the print of the first VSU This VSU has 5 connections The remaining four connections are the positive terminals of the first four cells of the stack All following VSU s have four connections for the positive terminal of each of the four cells of a group of cells Connecting the alarm relay The alarm relay switches if the voltage of at least one cell drops below a set value and remains low for several consecutive measurement cycles function code 13 to 15 A NO CellSense User s Manual June 2006 7 15 normally open and NC normally closed contact are available The operating mode of the relay can be programmed to 1 be exited in case a of fault b of no fault 2 change state when a acell voltage becomes low only b a cell voltage becomes low and an internal fault was detected 3 signal a low cell voltage when the lowest cell voltage a drops below a fixed threshold b deviates from the average cell voltage These options allow the user to set up the system and use the relay fo
3. not used bit 4 led on 0 led on if fault 1 led on if no fault bit 5 led fault definition 0 cell voltage only 1 cell voltage and internal function bit 6 led cell voltage fault definition 0 compare to constant 1 compare to average cell voltage bit 7 not used 5 Voftser consists of the sum of two components a common part for all cell groups and an individual part for each cell group Cell group number FFh refers to the common component Cell group number FEh collectively refers to all individual parts Cell group number FDh instructs the CVM to automatically calculate and store the individual offsets CellSense User s Manual June 2006 13 15 Software The CVM contains following software microcontroller firmware on each VSU o converts individual cell voltages o communicates with the main controller e microcontroller firmware on the main controller of the CVM o communicates with de VSUs processes the data of the VSUs into easily interpretable information O o communicates on the CAN bus o holds all measurements e LabView driver example PC Windows LabView 7 1 required o can be used as user interface to the CVM over the CAN bus for starting up commissioning and for adjusting settings o can be used as a driver or as an example for data acquisition code in Labview with the CVM The Labview interface consists of a number of tab sheets interface with the CVM are grouped per sheet functi
4. Power to the system is supplied by a 24 VDC isolated power supply or grid adaptor The connection is on the terminals of the PCB Several CVMs may be connected to one power supply provided isolation limits are not exceeded Connecting the CAN bus The CAN bus is connected by a DB9 oo We n 00 1 connector The connections are 2 CANL according to the recommendations Li 3 CAN_GND CiA DS 102 RE 4 5 CAN_SHLD The power supply of the galvanic 6 GND isolation of the CAN bus can be 7 CAN H passed from an external source over Figure 3 DB9 CAN 8 this connector In this case the jumper bus connector 9 CAN V at the CAN interface should be removed In the other case the galvanic isolation will be powered from the CVM and no supply lines should be connected Allocate Node number The CVM communicates over a CAN bus with its own protocol that can coexist with CANOpen This allows connecting several participants nodes on the bus such as other CVM s invertors PLCs sensors etc Every participant node receives a node number between 1 and 127 In order to adjust the node number of the CVM a point to point CAN connection has to be made and the node number has to be adjusted following the CVM CAN protocol see lower As soon as the CVM has received its node number it can be connected to a CAN bus The supplied LabView interface can be used to adjust the node number Baptizing procedure Befo
5. programmed number of consecutive cycles A relay contact can be e g part of a emergency shut down circuit or can be part of the signal enabling the load Time counters The CVM includes two time counters counting the seconds that the stack is operated under open circuit conditions and under load condition These conditions are recognised by comparing the average cell voltage to two thresholds Ucel_average gt Uopen_circuit_threshold the open circuit counter increments Uoperation_threshold lt Ucel_average lt Uopen_circuit_threshold the in operation counter increments Ucel_average lt Uoperation_threshold no counter increments The counters can be reset or preset via the CAN bus interface The counters are saved in permanent memory every 256 seconds or when Ucel_average drops below Uoperation_threshold Interrupting the power supply to the CVM while the fuels cell stack is in operation may cause loss of maximum 256 seconds Whenever the sum of the counters reaches approximately 5000 hours or any of its multiples an memory refresh procedure should be executed The user should request this procedure by sending an appropriate CAN message function code 21 to the CVM at a convenient moment e g after shutting down the fuel cell stack The procedure needs 1 second to complete While it is running the CVM can not operate normally The accompanying LabView interface can be used to set and read the stack ID Stack ID tab to
6. set an read alarm levels A arms tab and to set and read time counters Hour counter tab CellSense User s Manual June 2006 10 15 CVM CAN protocol The protocol used by the CVM on the CAN bus can coexist with CANOpen With CANOpen each node in the network requires an unique node number NN between 1 and 127 This is also the case for the CVM The message IDs used by a CAN node are derived from the NN see next table In addition one fixed message ID is used to set the NN of anode Therefore this can only be done in a point to point connection CAN ID direction length en frequency Contents 0 Receive 2 bytes Set node number Byte 0 10 hex program node number Byte 1 NN for one CVM 180 NN Send 8 bytes Send summary of cell voltages hex at the end of e cycle Byte 0 cell number met highest voltage Byte 1 2 highest voltage mV Byte 3 cell number met lowest voltage Byte 4 5 lowest voltage mV Byte 6 7 average voltage mV 280 NN Send 8 bytes Send details of all cell voltages hex After reading of one cell Byte 0 cell group to which data belongs group Byte 1 4 cell voltages as 4 x 12 bits mV 2 580 NN Send 8 bytes Send status and settings hex Byte 0 function code Byte 1 7 see next table 600 NN Receive 8 bytes Receive settings hex Byte 0 function code Byte 1 7 see next table Table 4 Different CAN messages The messag
7. version number 11h version reply to Byte 2 minor version nummer function code 16 19 set time counter gt Byte 1 2 Vopen circuit threshold mV 13h thresholds Byte 3 4 Voperation threshold mV 20 request time gt 14h counter thresholds 20 reply time lt Byte 1 2 Vopen circuit threshold mV 14h counter reply to Byte 3 4 Voperation threshold mV thresholds function code 20 CellSense User s Manual June 2006 12 15 21 request time gt Byte 1 counter number 15h counter values 1 open circuit counter 2 operation counter 21 reply time lt Byte 1 counter number 15h counter values reply to Byte 2 5 counter value in seconds function code 20 22 set time counter gt Byte 1 counter number 16h values Byte 2 5 counter value in seconds Table 5 protocol on the CAN bus 2 4x12 bits refers to a compression method in which four 12bit numbers are concatenated into six data bytes 3 Cell groups are numbered between 0 en 220 00h to DCh 4 The alarm operating mode is a byte composed or interpreted as eight bits with these functions bit 0 relay coil excitation 0 relay coil excited if fault 1 relay coil excited if no fault bit 1 relay fault definition 0 cell voltage only 1 cell voltage and internal function bit 2 relay cell voltage fault definition 0 compare to constant 1 compare to average cell voltage bit 3
8. Om Wiel CelliSense User s Manual Cell Voltage Monitor CVM October 2007 Contents Introduction Application Technology CVM schematics CVM specifications Installation Assembly Connecting the powder supply Connecting the CAN bus Allocating a Node number Baptizing procedure Connecting the stack Connecting the alarm relay Connections in case of more stacks Basic settings Advanced settings and possibilities Message type detailed or summary Extra idle time Stack ID Led and relay Time counters CVM CAN protocol Software References CellSense User s Manual June 2006 OO OOO DAAANANHNADID DI DI IL UI Va LU W W 2 15 Introduction Cell Voltage Monitor CVM has been designed to measure all individual cell voltages of a fuel cell stack The measurements are processed into a summarizing message that is sent over a serial connection to a system controller allowing to react on decreasing cell voltages Application This concept is meant to be part of a control and monitoring circuit of a commercial fuel cell stack The accuracy and the rate of the measurements are based upon this target resulting in a significant cost reduction compared to classic cell voltage measuring systems The performance of the system allows to obtain polarisation curves of individual cells or to detect low cell voltages in an early stage Detection of low voltages can be followed by e g increasing gas flows or in worse cases switchi
9. U The common part should be selected in a way that each individual part is between 0 mV and 250 mV CellSense User s Manual June 2006 8 15 The CVM can be instructed to calculate the individual offsets To do this it is required that all cell voltage inputs are at the same potential If the CVM is equipped with cell shunt resistors this can be achieved by leaving the terminals unconnected In the other case all terminals should be shorted to each other It is necessary to wait 10 seconds for the cell voltage inputs to stabilize at OV Then the CAN message can be sent to instruct the CVM to calculate and store the offsets Initially the common part is set to 350 mV and all individual are automatically calculated by sending following two CAN messages to the CVM ID 600 NN func c data 1 data 2 data 3 set 350mV 06h FFh 1 5Eh calculate offsets 06h FDh Table 3 Set offsets via the CAN bus Additional settings are explained in more detail in the description of the protocol The supplied Labview interface can be used to set the number of cells the offsets Setup tab Advanced settings and_possibilities Message type detailed or summary The CVM measures all cell voltages almost simultaneously less than 300 usec The measurements are than read from the VSU s As soon as all measurements have been read one cycle a CAN message is sent with ID 180 node number containing the mi
10. ells data reply to Byte 3 0 send only min max ID 180 NN stream type and function code 1 send each cell data ID 180 NN en additional delay 2 ID 280 NN Byte 4 additional delay after measurement cycle 4 request Vottset gt Byte 1 cell group number 5 5 reply Vottset lt Byte 1 cell group number 5 reply to Byte 2 3 Vottset function code Byte 4 5 Vsuppyy in 0 01V 4 6 set Vottset gt Byte 1 cell group number 5 Byte 2 3 Vofiset in MV 7 baptize VSUs gt Byte 1 0 stop procedure 1 start procedure 8 baptized VSU lt Byte 1 cell group number of baptized VSU at detection of baptizing conditions 9 reset all VSU to gt Byte 1 4 AAh 55h 33h CCh default 10 request stack ID gt OAh 11 reply stack ID lt Byte 1 7 ID in ASCII OBh reply to function code 10 12 set stack_ID gt Byte 1 7 ID in ASCII OCh 13 request alarm gt ODh trip cell voltage 14 reply alarm trip lt Byte 1 2 min cell voltage for LED on mV OEh cell voltage reply to Byte 3 4 min cell voltage for relay on mV function code Byte 5 number of failures before relay switches 13 Byte 6 alarm operating mode 4 15 set alarm trip cell gt Byte 1 2 min cel voltage for LED on mv OFh voltage Byte 3 4 min cell voltage for relay on mv Byte 5 number of failures before relay switches Byte 6 alarm operating mode 4 16 request software gt 10h version 17 reply software lt Byte 1 major
11. es with ID 180 NN and 280 NN can be compared with the PDOs defined in CANOpen The other messages 580 NN and 600 NN are comparable with SDOs In these messages the first byte of the data block is reserved for a function code that determines the contents of the remaining bytes of the data block Next table specifies what function codes are defined and how to interpret the contents of the data block Rows with lt as direction from CVM to PC or PLC are related to messages with ID 580 NN the remaining are related to messages with ID 600 NN Function code gt CVM Contents of van byte 1 7 filled up with 00s Byte 0 PLC lt 0 status message lt Byte 1 failure code spontaneous 0 no failure in case of error 1 no VSU found 2 data line continuously high 3 data line continuously low 4 no data received or failure in data van 1 VSU Byte 2 cell group VSU with last failure Byte 3 number measured cell groups set number of gt Byte 1 2 number of cells in system cells data Byte 3 0 send only min max ID 180 NN stream type and 1 send each cell data ID 180 NN en additional delay ID 280 NN Byte 4 additional delay after measurement cycle CellSense User s Manual June 2006 11 15 2 request number gt of cells data stream type and additional delay 2 reply number of lt Byte 1 2 number of cells in system c
12. lly in the case that several CVMSs are connected to the same bus The large amount of data will inevitable lead to overloading the CAN bus References 1 NI CAN Hardware and Software Manual National Instruments Using CAN in LabView 2 http www can cia org Official CANOpen standards 3 http atlas web cern ch Atlas GROUPS DAQTRIG DCS CANINFO canproto html Practical CANOpen standards 4 Controller Area Network a Serial Bus System Not Just for Vehicles ESD gmbh CAN bus documentation principle and operation CellSense User s Manual June 2006 15 15
13. ng off the load Possible advantages e lower gas stochiometry lower e higher availability better quality of electric power e less chance of damage e increased life expectancy e fast diagnosis in case of damage Technology A detailed description of the technology can be found in the patent text The system consist of two components the voltage scanning unit and the central unit The voltage scanning unit VSU measures the voltages of 4 cells Any number of VSUs are connected through a galvanic isolation to a common data bus and a voltage supply line The central unit takes care of the data communication with the VSUs the power supply to the VSUs and the communication to the outside world e g via CAN bus The central unit can pre process the measured data so that only relevant data will be sent limiting the data stream on the communication bus and by that also the work load on the receivers of the data The pre processing is completely implemented in software and therefore it can be adapted according to the application The pre processing sends a CAN message with the maximum the minimum and the average cell voltage and the corresponding numbers of the cells where the maximum and minimum voltage occur and it controls two digital outputs pointing out an alarm status CellSense User s Manual June 2006 3 15 CVM schematics Data Power bus bus ae VSU
14. nimum maximum and average cell voltage and the cells in which the minimum and maximum voltages occurred It is also possible to obtain a detailed picture of all cell voltages by programming the CVM to send a message with all individual cell voltages after reading each VSU function code 1 These messages have a lower priority ID 280 node number Retrieving these details significantly slows down the system and generates a lot of data traffic on the CAN bus Extra idle time In order to limit CAN bus traffic or to slow down the conversion rate of the CVM an additional delay of 2 to 425ms can be programmed after each conversion The CVM will not perform any action during this delay Stack ID Each CVM belongs to a stack An individual identification of the stack and CVM can be stored in the CVM function code 12 and can be read function code 11 The maximum length of this identification is 7 characters Led and relay A red LED and a relay are provided for detecting low cell voltages The operation mode and the cell voltage for switching the LED and the cell voltage for switching the relay can be set each function code 15 or read function code 13 and 14 The LED operation is similar to the relay operation as explained in connecting the stack except that it CellSense User s Manual June 2006 9 15 changes state after only one error was detected On the other hand the relay switches only if and error condition persists during a
15. ons and possibilities is unambiguous The diagram source code can be used as is or can serve as inspiration to build if desired your own interface or data acquisition Moreover the interface is an illustration of the protocol description that can be useful when programming of an interface for other hardware e g a PLC The functionalities of the The relation to the earlier described In order to communicate via the LabView interface with the CVM first the node number of the CVM to which we want to connect has to be set on the main screen In this way one can communicate with one single CVM even though several CVMSs are connected to the same CAN bus As soon as the node number has been set the functions on the sheets can be used and they relate only to the selected CVM Selecting the nod number CellSense User s Manual E ont Pa Ele Edt Operate Tools Browse Window Help e D 1a 139 Aopicaion Fork e STOP EEE Celspenningen StackID Status Alarmen Celi jo mv Cerco caz ow Je cals o w o wv Celspanning per celgroep colt 100 4 Offsets Node nummer Dopen Ruwe Data Umax Umin sparing ca gemiddeld fo mh hoogste 0 laagste fo W my fo mv fo al Figure 6 LabView interface example June 2006 14 15 It is recommended not to set the CVM to sending individual cell voltages detailed data stream type for general use especia
16. r fail safe operation Connections in case of more stacks If several stacks are connected in series and each stack has its own CVM differences in potential occur over the different CVM s The magnitude of these potential differences is a function of the number of stacks in series and can be present over the isolation of the power supply the CAN bus and potentially the alarm relay The user should take care of the fact that the different CVMs should not have the same potential via the power supply In this case each CVM needs its own galvanic isolated power supply An individual adaptor with the corresponding isolation potential will be sufficient Basic settings Before doing the first test at least the number of cells for a stack function code 1 and the offset voltage of the A D converters in the VSU s function code 6 have to be set In case of a stack with 50 cells one has to send following CAN message to the CVM ID 600 NN func c data 1 data 2 data 3 set 50 cells 01h 0 32h 0 Table 2 set the number of cells via the CAN bus Each A D converter has an offset voltage that allows measuring negative voltages This voltage is in principle 400 mV but can vary slightly between different VSU s Therefore this offset can be individually programmed It consists of the sum of two parts a common part e g 350 mV and an individual part e g 47 mV 50 mV 49 mV for each VS
17. re connecting a stack every VSU has to receive an unique within one CVM address This address is an increasing number between 0 and 220 The VSU of the first cell group cell 1 to cell 4 receives the address 0 the VSU of cells 5 to 8 receive address 1 etc Adjusting the addresses is called baptizing and is necessary to be able to make the correct link between each VSU and its physical connection to the stack CAN communication has to be active Clear all existing addresses in the VSU s function code 9 and start the baptizing procedure function code 7 Supply a voltage of 2 2 4 5 V between two terminals of the first VSU As soon as this voltage has been measured by CellSense User s Manual June 2006 6 15 the VSU this VSU receives address 0 This is reported over the CAN bus function code 8 and the first VSU has been baptized Move the voltage supply to the following VSU for baptizing After each confirmation over the CAN bus the supply voltage can be moved to the next VSU Scrupulously respect the physical sequence of the i VSUs If the last VSU has been baptized the baptizing procedure should be stopped function code 7 and one can start connecting the stack In the CVM every cell has a suit resistance of 100 Ohm In the worst case the supply voltage has to have the capacity to deliver 45 mA 4 5 V 100 Ohm in the best case 8 mA 2 2 V 300 Ohm need to be delivered The voltage source can be a 9V battery with
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