Monoblock Management Module (MMM)

Size: px

Start display at page:

Download "Monoblock Management Module (MMM)"

Augusta Shepherd
5 years ago
Views:

Monoblock Management Module (MMM) 6V MMM and 12V MMM versions Monitoring every 2 seconds of monoblock voltage & temperature 3W of passive balancing configurable for desired float Amount of balancing

1 Monoblock Management Module (MMM) 6V MMM and 12V MMM versions Monitoring every 2 seconds of monoblock voltage & temperature 3W of passive balancing configurable for desired float Amount of balancing coulombs recorded and reported Operates from 4V to 18.6V (both 6V and 12V versions) Measures directly across monoblock terminals to avoid voltage drops due to monoblock interconnects Oscilloscope mode facilitates monoblock impedance analysis Tolerant of overvoltage up to 43V and to reverse polarity connection Works on any pack up to 128 monoblocks LED indicators for balancing, warnings and status Communications over a single signal wire that is fully isolated High noise immunity communication using RF Modulated signalling Low power as typically uses 0.12mA at 12V (<1.4mW) Autonomous operation in a stand-alone configuration External thermistor option for temperature measurement Fully over-molded, insulated, shockproof (IK05), waterproof (IP67A) and sulphuric acid proof Description The Monoblock Management Module (MMM) is a per-monoblock device, with one MMM connected to each monoblock of a battery pack. Used in conjunction with a single Battery Energy Meter (BEM), a complete Battery Management System (BMS) can be implemented. The BEM acts as a central management unit to collect information from the individual MMMs and distribute commands to them. The MMM is designed to operate on any monoblock within an operating voltage range of 4V to 18.6V. Two versions with different balancing resistor values are available being a 6V version and a 12V version. The two versions only have different balancing resistors. The MMM performs three main functions: continuous monitoring of monoblock voltage and temperature, measuring and reporting monoblock voltage, temperature and balancing current and passive balancing of a monoblock. The MMM is designed to be used in any pack configuration with any number of monoblocks in series and/or parallel combinations from 2 to 128, and bigger banks can have a split BMS s sections. The MMM can capture and report an oscillogram waveform, with a 1k sample length at a variable sample rate from 20sps to 96ksps. This is carried out synchronously with all the MMM s throughout the pack, together with the BEM, which captures the battery pack voltage and current. This allows detailed monoblock impedance analysis to be performed using anything from a DC step, to the 50/60 Hz ripple from the charger, to a 1 khz injected signal. By default the temperature measured and reported is the temperature inside the MMM itself. As the MMM is on top of the monoblock this internal temperature is a fair indication of actual monoblock temperature, provided it is not balancing. An optional external thermistor can be factory fitted to the MMM if required, and would then be reported additionally. June,

2 The MMM provides up to 3W of passive balancing on any chemistry. The voltage set-points at which passive balancing occur can be fully configured. This function can also be enabled or disabled as required. The module is fully over-molded and made to meet the very harshest environmental conditions, being completely insulated, mechanically robust, flame retardant, waterproof and acid proof. It can survive complete submersion in concentrated sulphuric acid. This allows its use in most environments including flooded lead acid monoblocks in motive applications. The communication between a MMM and BEM is carried out over a fully isolated (1500V) and floating single wire. An RF modulated signal is sent over this wire using a proprietary communication protocol with multiple levels of redundancy and error checking. This was designed to deal with the high levels of electrical noise present on large battery packs used by industrial equipment. Large monoblocks have low impedances, however, the cell to cell interconnects and physical battery layout add inductance to the battery pack. Hence noisy industrial equipment with very high current transients will cause the battery terminal voltage to exhibit significant transient voltage spikes. This necessitated the use of an RF modulated protocol by the MMM so that it can communicate through the noise in these environments. The MMM offers continuous monitoring, performed every 2 seconds, for limit conditions on both monoblock voltage and temperature. These limit conditions are fully configurable and if exceeded are reported to the BEM as well as being visibly indicated on the MMM via the on-board LEDs. This enables immediate visual identification of any monoblock at fault. The three limits that are user configurable are over-temperature, overvoltage and under-voltage. The MMM module in monitoring mode consumes very little power, since it is in sleep much of the time between the one minute reporting and two second monitoring operations. The power and current requirements are given in the typical performance curves section (e.g. 0.12mA on a 12V monoblock). If monoblock voltage is below 3V then the MMM shuts down, where it draws less than 0.1µA. The MMMs also offer a failsafe feature, as they continue to operate in a stand-alone manner even if the BEM fails. In this case the balancing of the pack continues to be performed and the LEDs illuminate when limits are exceeded allowing visual identification of monoblocks at fault. Putting an intelligent MMM on each monoblock, creates a more resilient battery bank made up of smart monoblocks. The distributed nature of implementing a module per-monoblock means that failure of individual MMM s will not interfere with the operation of rest of the system, making the BMS more robust. Replacement of a single MMM is an easy and cost effective fix, compared to the replacement or repair of an entire BMS. The complete isolation of each module also means that the battery stack can be broken or disconnected to replace monoblocks with no damaging effects on the rest of the BMS. CE certification for electrostatic discharge, radiated emissions and radiated susceptibility has been obtained for the MMMs. CISPR22 (2008) / SANS 222 (2009) IEC (2008) / SANS (2009) IEC (2010) / SANS (2008) June,

3 Electrical Specifications Operating voltage range Valid monoblock voltage readings region 4V to 18.6V Maximum overvoltage 43V Reverse polarity voltage (6V MMM) -8V Reverse polarity voltage (12V MMM) -16V Operating temperature range Operating temperature range -25 C to 80 C Default monoblock over temperature warning 50 C Balancing Balancing Power Maximum (6V And 12V MMM) 3W Balancing resistor (6V MMM) 22Ω Balancing resistor (12V MMM) 82Ω Balancing stops When monoblock voltage >18V Balancing stops When MMM temp >85 C Balancing resumes When MMM temp <70 C Relative voltage measurement (MMM to MMM) Typically at 30 C, Max range -25 C to 80 C Measurement time < 200us Measurement synchronization between monoblocks < 200us 12 Bit ADC, Quantization of ADC 4.5mV/bit Relative measurement accuracy Typ = +/-9mV Max = +/- 27mV Absolute voltage measurement accuracy Typically at 30 C, Max range -25 C to 80 C Monoblock voltage from 4V to 18.6V Typ = +/-18mV Max = +/- 36mV Oscilloscope voltage measurement Typically at 30 C, Max range -25 C to 80 C Sample memory, 12 bit, same range as above 1000 samples Synchronization between all monoblocks < 4us Sample rate 20sps to 96ksps Total sample period (of whole oscillogram) 10ms to 50 seconds Temperature Measurement Reported 8 bit value range (Internal, Chip level:) -128 C to 127 C Accuracy Typ = +/- 1 C Max = +/- 3 C External, 10k thermistor: 12 Bit ADC, quantization of ADC TBD implementation specific Total accuracy TBD implementation specific Certifications CE CISPR 22, IEC , IEC SABS SANS 222, SANS , SANS Environmental IP67A, IK05 (only module, not battery connections) June,

4 Operation Limits: Over voltage, over temperature and under voltage limits can be set on MMM s. The flashing pattern is given in the table below. The temperature is based on the MMM s estimate via its connection leads. The estimate of monoblock temperature is adjusted to compensate for any heat generated by balancing. RED LED Flashing pattern Condition Default 50ms on / 450ms off = Short pulse twice a second Over-temperature 50 C 450ms on / 50ms off = Long pulse twice a second Over-voltage 15V Fully on 50ms on / 3000ms off = Short pulse once every 3 seconds Over-voltage and over-temperature Under-voltage 15V 50 C 5V 50ms on/ 200ms off/ 50ms on / 3000ms off = two short pulses once every 3 seconds Under-voltage and over-temperature 5V 50 C BLUE LED Flashing pattern On power up, the BLUE LED will come on once only for 3 seconds. NOTE: This is used to show correct polarity connection. Its absence indicates that the device has been connected incorrectly. Condition Correct Initial connection 50ms on/ 200ms off/ 50ms on/ 200ms off/ 50ms on/3000ms off = three short pulses once every 3 seconds Un-configured 50ms on/ 200ms off/ 50ms on/ 200ms off/ 50ms on/30000ms off = three short pulses once every 30 seconds Lost communication Whenever a message for itself is received correctly, the MMM will flash its BLUE LED once for 50ms = short pulse. Received Message Correctly Note on un-configured state: If the MMM has not been configured it will flash its BLUE LED for three short pulses, every three seconds. This is to indicate that a MMM has not yet been addressed by the BEM. June,

5 Note on lost communication: If the MMM has not received any communications from the BEM to itself for more than 90 seconds it will flash its BLUE LED for three short pulses, once every 30 seconds. This is used to indicate either a bad communication connection to the MMM itself, or that the BEM has stopped communicating. YELLOW LED Flashing Pattern Always on, but brightness is proportional to the duty cycle of balancing resistor. Brighter indicates higher balancing current. Condition Balancing Reverse Polarity Connection The MMM can handle a reverse polarity connection provided it is within the nominal monoblock voltage region. This is -8V for a 6V MMM and -16V for a 12V MMM. Passive balancing Passive balancing is also called dissipative or resistive balancing and is carried out by drawing some current/charge/energy off a monoblock and dissipating it as heat in a resistor. Passive balancing is only able to sink current from a monoblock, which is a negative monoblock current and reported as such. The MMM can perform up to 3W of passive balancing. This function can be enabled or disabled, and a variety of algorithm approaches can be used. These approaches include a simple on/off balancing around a single level, to proportional, to proportional integral, to scaling all balancers according to highest monoblock, or maximum temperature etc. VRIP balancing algorithm The default algorithm used by the MMM's is termed the VRIP algorithm and this is an acronym for Constant Voltage, V, Constant Resistance, R, Constant Current, I, Constant Power, P = VRIP. The MMM is set with a balancing level and a maximum balancing level from the configuration tool. The maximum balancing level must be in the region of 10-20% higher than the balancing level. When a Monoblock reaches the balancing level the MMM will then start to perform integral control of the balancing current to keep monoblock voltage constant. In other words, the balancing current will be adjusted up or down to keep the monoblock voltage at exactly the balancing level. If a charger is set correctly then at top of charge the current will be reduced to something that will not over power the balancing. If this is the case then, as a monoblock reaches the balancing level, the balancing current will progressively increase, and hence the monoblocks will receive progressively less charge current until it has truly reached the balance level. The second region is constant resistance which appears as a pure resistance connected permanently across a monoblock, and as monoblock voltage increases the current increases. The third region is the constant current region, meaning a constant current is drawn from the monoblock as voltage increases further. However in practice this region does have a small positive slope, so higher voltages will draw slightly higher current. Thus if the charger current is too high, then the monoblocks will go into the constant resistance or constant current region, but the system will still have a balancing effect as higher monoblocks will have more balancing current drawn off them. To explain it in converse, if this was not the case and higher monoblock voltages drew less current once they are over the balancing level, they are then in danger of going even higher than the other monoblocks and the system becomes unstable. Provided the monoblock voltages never exceed the maximum balancing level, the system will remain June,

6 stable as higher monoblock voltages will always have more current being drawn off them. The maximum balancing level is the point where maximum monoblock balancing current and power will occur. It is the point that the monoblock voltage should never exceed. If the monoblock voltage goes even higher than the maximum balancing level and goes into the fourth region of constant power dissipation. In this region the MMM will go into a constant power mode to prevent itself from overheating, and current will decrease with increasing voltages. This is simply a protection mechanism and in theory the monoblock voltage should never be in this region. However, even if it does end up in this region, the design philosophy is that the MMM should and will continue to draw power from the monoblock in an effort to bring its voltage down again. Graphs below show typical balancing levels for 6V and 12V monoblock. More balancing examples can be found by downloading spreadsheet to calculate balancing currents from website. June,

7 0,14mA MMM normal current and power consumption vs cell voltage 2,8mW 0,12mA 2,4mW 0,10mA 2,0mW Current 0,08mA 0,06mA 0,04mA 1,6mW 1,2mW 0,8mW Power 0,02mA 0,4mW 0,00mA 0,0mW 0,0V 2,0V 4,0V 6,0V 8,0V 10,0V 12,0V 14,0V 16,0V 18,0V 20,0V Current Power Cell Voltage Typical Current and Power consumption Of MMM with no LEDs on and not balancing. June,

8 MMM Installation The MMM can have customer specified connector lugs and lengths of connecting leads. Current default standard is a M6 Lug, and wire lengths so that it is 300mm from lug to lug. It connects to a monoblock at the normal positive and negative terminals. It is good practise to fist connect the monoblock interconnects and then connect the MMM s. Communications wire Installation The communications is done using a single wire that is fully capacitively isolated at all connection points and hence is capable of floating at any DC voltage level. It uses the actual battery pack as a return path. Hence to minimise noise and pick up interference the communications wire and the monoblock and monoblock interconnects should make a twisted pair, or the area between them should be minimised. Please see communications wire installation guide and video. 6V MMM and 12V MMM These are identical except for their balancing resistor values, being 22Ω for 6V and 82Ω for the 12V. They can be identified on the underside of the MMM by an arrow pointing towards the numbers 6 or 12, as shown in mechanical drawings 12V MMM 6V MMM June,

9 Mechanical Layout Dimensions in (mm) typical lead length of 300mm. Lead length can be specified for orders (>3k). Alternative connection lugs and wiring lengths are available in OEM quantities June,

Cell Management Module (CMM)

Cell Management Module (CMM) 2V CMM and 4V CMM versions Monitoring every 2 seconds of cell voltage & temperature 3W of passive balancing configurable for any cell chemistry Amount of balancing coulombs