Battery Monitoring Why Technology Matters Mats Karlstrom V.P. Sales & Marketing, Alber 1
Agenda Introduction Why is battery monitoring needed? Example of battery failure Why are resistance measurements important? Doing it right Why Alber s resistance measurement technology will help customers while others fail Monitoring advantages Optimizing useful battery life Reliable test data Safety Alber products and their application 2
Who is Alber? Established 1972 Based in Boca Raton Florida We manufacture battery test equipment based on extensive experience in and knowledge about Battery design and Battery aging characteristics. We are the Battery Test Experts! 3
Capacity vs. Resistance Test What s the difference? 4 Battery Capacity Testing. Off-line discharge test using load bank with constant current capability while continuously monitoring each individual battery cell voltage to identify the bad cells. Time consuming (1 to 10 hours plus re-charge time) Requires external load bank and sometimes backup battery + Reliable. Only way to truly assess the battery s absolute capacity Resistance Test. On-line test measuring the internal resistance of each battery cell. As battery condition declines, the resistance increases. Increased internal resistance indicates aging or pre-mature failure before the cell cause critical failure to the battery + On-line, non-invasive test that can be performed manually or automatically - Does not provide an absolute capacity value and chemical problems are more difficult to detect in an early stage.
5
6
What do we learn from this example? Increased resistance revealed the weakest link ~ 25% increased resistance in one module is enough to fail a complete battery string Monitoring overall voltage is not enough Monitoring cell voltage will not detect a bad cell Partial discharge tests will not detect all faults Individual cell voltage monitoring is important during discharge tests This is why it is important to DO IT RIGHT! 7
Why monitor? Because Batteries Fail! Batteries are like humans. Sooner or later the battery will reach end of life. It can happen through Normal aging Positive Grid Corrosion Pre-mature failure Manufacturing defects Battery abuse High temperature Excessive charge current Defective chargers Damaged battery jars 8
Cell Resistance Capacity 80% capacity Resistance Safety zone 25% increased resistance 9
Internal resistance Why is internal resistance related to battery capacity? Positive plate Negative plate Separator material 10 New Grid
Internal resistance Lead Paste Grid Structure Active Material Expanding Cracks Corrosion Fully Charged During Discharge Aged Plate 11
Internal resistance 12 New Grid Aged Grid
Ohmic measurements The following terms are used, in the battery industry, to describe internal ohmic measurements : AC Impedance (Z) (B-tech, MEGGER, Polytronics, Enersafe ) AC Conductance (Siemens) (Midtronic) Resistance (NDSL/Cellwatch) DC Resistance (Alber) But this is only the presentation of the data. It is the way the measurement is made that dictates the accuracy and bearing of the test 13
Obtained from Johnson Control application note Metallic Resistance 14 Electro Chemical Resistance Capacitor
Why is internal ohmic measurements tricky? ~ 40 % of resistance is in parallel with a capacitor 15
Normal battery operation When load is applied, DC current is generated 16
AC testing AC testing is an abnormal battery condition. When AC load is applied, most of the current will pass through the capacitor. Test frequency and size of capacitor will define the amount of current passing through the capacitor instead of plates. 17
How are Alber resistance measurements made? Voltage Ω V Open Circuit Voltage Current V 2 - R int = I V 1 18 Test current is disconnected before the battery voltage reaches the open circuit voltage level. No electro chemical reaction and no loss of capacity.
Non-Technical Explanation Normal Operation Aged Condition 19 AC Testing Alber Test Method
Test Current The resistance difference between a good and bad battery is 25% Example: A 1000Ah battery has 200µΩ resistance. 25% = 50µΩ In order to accurately measure this difference the resolution of the test equipment should be 10% of the critical value Required resolution Difference between good and bad 50µΩ New Battery 200µΩ 20
Test Current/ Measurement Resolution Ohms law: R = V/I 50µΩ difference from previous example. 1A test current requires 5µV resolution 10A test current requires 50µV resolution 30A test current requires 150µV resolution Most competitors use test currents below 1A. Alber use a 30A resistive load! 21
Noise Typical ripple 40mV (40.000µV) Low AC test signal will disappear in UPS noise, Trending data will typically change when noise change due to load or failing capacitors on UPS. The Alber DC test method is not affected by ripple 22
Trending difference between AC and DC Nominal Load Considerable ripple Partial Load Some ripple AC based readings, (Impedance) Continuous variations due to noise 50 % increase (~25% - 50% capacity) 25% increase (~70% - 90% capacity) No Load No ripple DC resistance Time 23
Trending difference between AC and DC Mondays Discharge April 4 th True DC resistance? Screen dump from AC based trend report 24
Doing it right 25 Alber s technology is developed based on experience and knowledge about how batteries fail Always comparing capacity tests with resistance tests Alber s technology addresses the three most important battery testing obstacles The capacitor effect The noise problem Resolution requirements
Increase Reliability What is needed to make sure that current can be supplied to the critical load? We have to detect problems in the complete conduction path Internal to the cells (to secure capacity) Inter-cell and Inter-tier connections Increased resistance = Increased temperature = Increased resistance = Increased temperature Catastrophic failure 26
Modular approach???? 27
Cost savings Optimize battery life 28 Monitor critical parameters and take appropriate action Internal resistance Replace bad cells before they affect other cells Maintain a balanced resistance level in all redundant strings Temperature Temperature has a direct influence on battery life Uneven temperature over the string cause cells to float differently Voltage Charge voltage should be adjusted to ambient temperature Float current Improper ripple affects the battery life
29 Recommended Task FLOODED IEEE 450 VRLA IEEE 1188 Monthly Quarterly Annually Monthly Quarterly Bi-Annually Annually Battery system voltage X X Charger current and X X voltage Ambient temperature X X Visual inspection X X Electrolyte levels X Pilot cell voltage and specific gravity IEEE 450 / 1188 Task Matrix Specific gravity all cells X X All cell voltages X X All cell temperatures X 10% Only Cell internal ohmic values Intercell connection resistance Detailed internal visual inspection X X X X X UPS X AC ripple current and X X voltage Capacity test 5 Years X Can be monitored X Equivalent data provided
Man-hour savings vs. IEEE based service contract Battery application. Cost basis Cost per routine test No of visits per year Test savings per year UPS 4 Strings of forty 12V modules $15 per module $2,400 4 $9,600 UPS 2 Strings of $6 per cell $1440 2 $2880 240 cells 30 Substation 1 string of 60 cells 4 Hours @ $80/hr (test time, travel, test report) $320 4 $1,280
Safety 31 Detect problems before they cause a catastrophic system failure!
Why Alber? Repeatable readings Test result shows actual battery condition Correlates with Capacity tests Takes the capacitor effect out of play Tests the complete conduction path All cells and connections are included in test results Separate sense leads for Inter-tier connections Monitors all critical parameters Monitors voltage real time during discharge Easy to interpret test results Can work stand alone without PC Well proven in all standby battery applications Intel, Nasdaq, Verizon, BankOne, Visa, Sun Micro system, HP, UPS 32
Battery Monitors BDS-256 Battery Diagnostic System Monitor any battery system up to 600 volts DC UPS systems Generating stations Industrial UL Certified CE Approved 33
BDS Controller The Brain that control the system. Collects and stores data from the DCMs Microprocessor driven Stand alone No on site PC required. 8 strings of 256 cells per Controller 34
Data Collection Module (DCM) The Data Collection Module acquires all readings from the battery 48 cells or modules 2 temperatures Discharge current Charger float current 35
External Load Module Supports proactive DC internal resistance testing One ELM for each string Tests battery in 10% increments Test current approximately 30 amps 36
Configuration examples 2 strings, 240 jars, 2V per jar 1 controller Fiber optics for data transfer and 24VAC power supply between DCM and Controller String 1 5 DCM s and 1 ELM per string 1 CT and at least 2 temperature probes per string 37 String 2
Configuration examples 3 strings, 120 jars, 4V per jar 3 DCM and 1 ELM per string 1 controller String 1 1 CT and at least 2 temperature probes per string String 2 String 3 38
Configuration examples 1 strings, 240, 2V jars 1 strings, 120, 4V jars 5 DCM s and 1 ELM per string 1 controller String 1 Fiber optics for data transfer and 24VAC power supply between DCM and Controller 39 1 CT and at least 2 temperature probes per string 3 DCM s and 1 ELM per string 1 CT and at least 2 temperature probes per string String 2
Parameters Monitored Overall voltage Discharge current Charger float current (optional) 2v cells, NiCad cells, 4v, 6v, 8v and 12v modules Temperature Resistance of all cell/jars, inter-cells, and intertiers 40
System Level I/O System inputs Remote alarm reset 16 digital inputs System outputs (form C contacts) Maintenance alarm Critical alarm 8 programmable control outputs(bds- 256) 41
Communication Two RS-232 for local computer RJ-11 for telco dial up RJ-45 for Ethernet connection Standard Modbus protocol OPC Compliant 42
The NEW optimized UPS cabinet monitor The BDS-40 Battery Cabinet Monitor 43
Designed for battery cabinets Optimized monitor All-in-one enclosure Pre-manufactured cables Tests the complete conduction path Individual leads for inter-tier Easy install and setup Setup Wizard Built-in decision support Identifies issues and suggests corrective maintenance procedure 44
BDS-40 BDS-40 Base unit All-in-one controller, Data Collection Module and Load Module One per system. Can power up 5 Plus units 2 temperatures, 1 current transducer / string Customized harness for easy install Simplified setup 4 U high, 16 deep, 19 wide to be mounted on top of cabinet 45
BDS-40 BDS-40 Plus unit All-in-one Data Collection Module and Load Module Connects to Base unit via fiber optic cable One unit for cabinets 2-6 2 temperatures, 1 current transducer Customized harness for easy install Simplified setup 3 U high, 16 deep, 19 wide to be mounted on top of cabinet 46
47 BEFORE
AFTER BDS-40 Plus Units BDS-40 Base Unit 48
Monitoring via Web-browser Real time string status Executive summary and detailed reports 49 Pop-up screens with real time data
50 Email alert
Decision support reporting Automatic data analysis with explanations of abnormal data Suggests appropriate maintenance activities Zip & sends test data for expert analysis 51
MPM-100 Designed for applications below 130VDC UL and CE approved More than 100 battery configurations available Monitors 1 string of 120VDC or up to 4 strings of 12, 24 or 48VDC Modbus protocol Powered from DC bus or 115VAC Network, Serial, Modem connection options 52
53 Alber the total solution