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Servato - Battery Power 2016


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A modified version of the one presented by Alex Rawitz at Battery Power 2016, this presentation describes Servato's Adaptive Charging, a new development in battery management. This methodology is designed for telecom batteries used in standby systems for Outside Plant and wireless towers. Servato's unique battery management system extends battery life, lowers costs for battery maintenance, and helps improve network reliability. Learn more at

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Servato - Battery Power 2016

  1. 1. Steven A. Mulawski, Dorion Carr, David P. Boden and Alex Rawitz Presented by Alex Rawitz Servato Corp Adaptive Charging: A Further Development of Intermittent Float for Charge Maintenance of VRLA Batteries in Telecommunications Standby Systems
  2. 2. Issues with Continuous Float Charging of VRLA Batteries Shortcomings of Intermittent/Periodic Charging as Improvements to Continuous Float Adaptive Charging ► Overview ► Principles Case Studies: Examples of Adaptive Charging’s Ability to Enable Battery Life Extension, the Identification of Bad Batteries, and other Equipment Issues Conclusions SERVATO – CONFIDENTIAL/PROPRIETARY Outline
  3. 3. IoT applications will require investment in network reliability ► As more devices connect to the Internet – not just cellphones and PCs but cars, residential and industrial appliances, other personal devices – downtime is more impactful The foundation of network reliability are VRLA batteries that today are almost exclusively continuously float charged ► Worse, they are subject to inadequate maintenance cycles. Millions of essential batteries right now, constantly charging SERVATO – CONFIDENTIAL/PROPRIETARY The Internet of Things (IoT) An example of VRLA Batteries for a standby system in a telecommunications deployment
  4. 4. VRLAs have been successful in reducing maintenance costs by elimination of watering, they have shorter life than the flooded type ► They incorporate a gas recombination mechanism that is exothermic (generating heat inside them) Heat trapped inside the battery and can only be removed by transmission through the container walls ► Batteries are usually closely packed in telecom installations exacerbating heat removal issues Higher temperatures accelerate failure ► A cabinet like the one on the right could routinely see temperatures in excess of 45C during the summer SERVATO – CONFIDENTIAL/PROPRIETARY Problems of Float Charging VRLA Batteries in a small Outside Plant Cabinet
  5. 5. Accumulation of heat from oxygen recombination drives the primary drawbacks of continuous float charging Increased battery temperature from gas recombination accelerates: ► Grid corrosion ► Dehydration ► Dry-out Active material degradation and capacity loss take place as a result of: ► Plate softening ► Loss of cohesion SERVATO – CONFIDENTIAL/PROPRIETARY Problems of Float Charging
  6. 6. Telcos rely on manual, cyclical maintenance that may involve checks as frequently as every few months, but usually happen once a year or less Inadequate maintenance exacerbates battery decline ► Long periods of time without a site check mean that battery health readings provide limited insight into true State of Health ► Without data it’s impossible to take proactive actions to protect reliability ► Equipment failures of other kinds such as fans or heat exchangers can end up damaging batteries in other ways not directly related to charging Maintenance protocols and performance are linked, and we need to treat them that way SERVATO – CONFIDENTIAL/PROPRIETARY Reliability Impacted by Maintenance
  7. 7. Battery companies are reluctant to require frequent in-situ equalizing ► VRLA batteries are starved of electrolyte and equalizing would cause even more overcharge and the associated gassing and corrosion ► Repeated equalizing of continuously floated batteries will accelerate dry-out The status quo is inefficient: ► Battery companies do not require in-situ equalizing ► Ineffective manual maintenance inhibits proactive battery improvement ► Continuous float charging reduces battery life If these destructive processes can be eliminated, battery life can be greatly increased ► Intermittent, or periodic, charging has been proposed as a solution to these problems SERVATO – CONFIDENTIAL/PROPRIETARY Status Quo vs. Effective Charging
  8. 8. “Intermittent” or “periodic” charging describe a strategy for float charging for a specific period of time, and then placing the batteries on open circuit for some period of time after ► Importantly, in “intermittent” or “periodic” charging, the ratio of float time to open circuit time is fixed ► No matter what the battery or environmental conditions are, the cycle proceeds at fixed intervals Reduces time on float and thus overcharging, but still has shortcomings: ► Correct ratio of float to open circuit time is a moving target dependent on temperature and battery condition ► An incorrect ratio can result in overcharging or undercharging SERVATO – CONFIDENTIAL/PROPRIETARY Intermittent or Periodic Charging
  9. 9. A float to open circuit ratio that might be adequate at 40°C will not be satisfactory at higher or lower temperatures because of different rates of corrosion and dry out ► The rate of self-discharge is temperature dependent and the amount of charge required to maintain 100% state of charge at 40°C will be considerably greater than at 25°C ► These magnitudes of temperature fluctuations are common, especially in outdoor cabinets, and with a fixed charge to rest ratio it is impossible to continually adjust float voltages and currents to maintain an optimum charge A further weakness is that a fixed ratio may not be capable of compensating for power outages ► In cases where numerous short power outages occur, the charge period must also be long enough to restore the battery to full charge A fixed ratio does not meaningfully improve upon standard float charging ► To compensate for varying rates of self-discharge at different temperatures and ensure maximum battery charge for use, the ratio of open circuit to float needs to adapt SERVATO – CONFIDENTIAL/PROPRIETARY Temperature Dependency
  10. 10. A methodology that uses battery data to determine and administer battery charging needs on an ever- changing basis ► Batteries are only ever charged exactly as much as is necessary and otherwise remain in an isolated state ► Using a unique hardware appliance capable of automated testing and charge control, data is automatically collected on pertinent battery parameters many times per day to ensure that batteries end each day fully charged The practice also allows the identification of other potentially negative events SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging
  11. 11. Servato’s adaptive charging regimen uses a dv/dt charge termination to ensure that charging stops immediately when the battery is fully charged, thereby preventing continuous overcharge and overheating ► It adapts to the depth of discharge of the preceding discharge and compensates for the effect of temperature ► That is, dv/dt=0 indicates that the battery is charged whether it is at 25°C or 40°C, and whether it has experienced a recent discharge or simply been isolated at rest This eliminates/reduces the need for temperature compensation of the rectifier SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging
  12. 12. Certain measurements collected by the appliance, such as open circuit voltage, internal resistance and voltage under load give a good indication of whether a battery needs to be charged or replaced ► OCV is an indication of Electrolyte Specific Gravity, State of Charge, Short Circuits ► Internal Resistance indicates Active Material Sulfation, Dry Out, and Grid Corrosion ► Voltage Under Load can tell us about increased Internal Resistance and Active Material Degradation Monitoring these signatures coupled with data trending gives us useful information regarding when the battery needs to be charged or changed out SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging
  13. 13. Servato has developed a line of hardware appliances – the Smart Power System (SPS) Appliances – that allow for automated adaptive charging in situ ► These unique appliances utilize proprietary technology that allows them to inhibit battery charging when it is unnecessary ► These are the only systems that can “virtually disconnect” the batteries from the bus SERVATO – CONFIDENTIAL/PROPRIETARY Achieving Adaptive Charging SPS-148 (1 String) SPS-48 (4 Strings) ActiView
  14. 14. In addition to the SPS appliances, there is a user-focused enterprise class software component, ActiView, that is used for visualizing battery data and advanced analysis of battery signatures to detect harmful trends ► The data can be accessed from anywhere in the world via an Internet connected device such as a computer or smart phone ► Every individual battery in the network can be accessed The link between maintenance and performance is strong, and a tool that provides monitoring and management capabilities is a major asset to battery managers in telecommunications and other industries SERVATO – CONFIDENTIAL/PROPRIETARY Achieving Adaptive Charging SPS-148 (1 String) SPS-48 (4 Strings) ActiView
  15. 15. SERVATO – CONFIDENTIAL/PROPRIETARY Principles of Adaptive Charging Adaptive charging is a simple cycle The principle is to minimize the amount of time batteries spend on float while maintaining full charge for backup applications
  16. 16. Batteries are maintained in a standby (off charge) mode by isolating them from the rectifier bus via Servato’s proprietary technology ► Batteries end up charged about 20% of the time and at rest about 80% and are still kept at full capacity Life is significantly increased by reducing internal temperature and all the associated adverse affects through a limited oxygen recombination ► Reduced grid corrosion ► Reduced dehydration ► Reduced need for cooling Since temperature increase is greatly reduced, thermal runaway is virtually eliminated and the need for cooling is reduced In this standby mode, batteries are still available for instantaneous discharge in case of a power outage SERVATO – CONFIDENTIAL/PROPRIETARY Principles of Adaptive Charging Batteries Off Charge
  17. 17. Periodic Measurement s While the batteries are at rest they are monitored at periodic intervals multiple times per day ► Servato uses OCV and Temperature to indicate state of charge ► State of Health is determined by evaluating several parameters including DC Resistance, charge efficiency, and self-discharge rates, among others ► All battery data is parsed for any trends that may indicate existing or developing battery issues SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging Protocol
  18. 18. Data Analysis The measurements are collected and analyzed automatically by the SPS appliance ► Servato owns a library of battery data accumulated through more than 5 million battery operating hours ► If stable , the batteries are allowed to remain in the standby mode for a period of time when they will be tested again ► If the data show changes greater than embedded set points a charge is initiated SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging Protocol
  19. 19. Charge Batteries If and only if charging is necessary, the batteries are put on the rectifier bus until they are fully charged ► dv/dt charge termination This replaces energy lost through self-discharge and any short term discharges that may have occurred ► As soon as the full charge criteria are satisfied the batteries are again isolated from the rectifier ► If the batteries have been discharged for more than a preset time during the standby period they are immediately connected to the rectifier for charging to eliminate any possibility of standing in a partially discharged condition SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging Protocol
  20. 20. In a multistring application, the strings are charged sequentially to assure string-to-string equalization ► Each string is brought to full charge independent of the other strings in the system ► This significantly reduces the adverse affects caused by random inter-string variation SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging Protocol Charge Batteries
  21. 21. Batteries Off Charge Following any charge event the battery strings are given a state-of-health test ► A short discharge is applied to the batteries ► Voltage/Time characteristics are recorded and used to calculate the internal resistance ► Batteries isolated again at rest SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging Protocol Charge Batteries
  22. 22. SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging • Standby, available for backup • Battery life extension • OCV • Internal Resistance • Discharge test • Library of battery data • Charging decision • If charge is required, SPS places batteries on rectifier • Strings charged individually • Batteries are again isolated from the rectifier Batteries Off Charge Periodic Measurements Data Analysis Charge Batteries
  23. 23. This sequence assures that the batteries are charged whenever the data trends indicate that a charge is necessary and not anymore ► Automatically compensates for normal temperature-dependent phenomena such as self-discharge ► The accumulation of data means Servato can detect many other issues (see Case Studies)SERVATO – CONFIDENTIAL/PROPRIETARY Adaptive Charging Overview
  24. 24. SERVATO – CONFIDENTIAL/PROPRIETARY Life Testing An independent test laboratory was used to compare the capacities of VRLA batteries over time when they were on continuous float and when managed by the Adaptive Charge Management (ACM) of the SPS system ► Tests were carried out at 40ᵒC (104ᵒF) to simulate hot weather conditions ► Four strings of batteries were tested, battery capacities were measured at approximately three-month intervals and averaged and charted as shown This predicts that the life of batteries operated by the ACM regimen will be twice as long as batteries on continuous float Expected failure for the continuously floated string = 39 months Expected failure for the adaptively charged string = 79.5 months
  25. 25. Field applications of the adaptive charge management system have been underway in locations throughout the USA for over four years ► The examples cited below are intended to show typical examples where an adaptive charging regimen has increased battery performance, detected deteriorated batteries, or found other equipment issues ► Only a system capable of adaptively charging and automated tests enables such a wide range of benefits so cost-effectively Evidence of battery life extension has been expanded Proven ability to detect and predict battery issues as well as other equipment problems SERVATO – CONFIDENTIAL/PROPRIETARY Field Testing Overview
  26. 26. 75 80 85 90 95 100 1 2 3 4 Percentnominalcapacity Battery Number Float ACM Case Study A: SERVATO – CONFIDENTIAL/PROPRIETARY Battery Capacities from Outside Plant Installations After 18 Months At an installation in Arizona after 18 months of testing, a string of adaptively charged batteries shows higher capacity than a control string on float (data at right) ► The data reflects that found in the independent trial In another trial in Colorado, the SPS-48 device was placed on a battery string approximately 5 years old next to a 2-year old string being floated ► After 18 months (total battery life = 3.5 and 6.5 years) both strings showed 96% nominal capacity ► It would be expected that the capacity of the 6.5-year-old batteries would be lower
  27. 27. Case Study B: SERVATO – CONFIDENTIAL/PROPRIETARY Detection of Aging Battery by DC Resistance Trending The importance of an adaptive management system that will report on battery issues rather than try to compensate for them improperly cannot be understated The graph at the right shows an example of increasing internal resistance of a deteriorating battery in a telecom network ► This was from an aging battery in a string in which the other batteries in the same string were showing a constant resistance and were operating properly ► This allowed timely changing of the battery to prevent deterioration of other batteries
  28. 28. Case Study C: SERVATO – CONFIDENTIAL/PROPRIETARY Trend in Open Circuit Voltage In this graph the OCV of a string of 12-Volt VRLA batteries is shown ► ActiView was able to detect that Battery A3 had a declining OCV before the battery ultimately failed and it was replaced ► The battery was shipped to the manufacturer and an autopsy revealed a manufacturing defect that caused a short circuit ► OCV cannot be used as an indicator of battery condition if the batteries are on float since they are always polarized Periodic scheduled maintenance and spot- checking would be unlike to reveal this issue
  29. 29. Case Study D: SERVATO – CONFIDENTIAL/PROPRIETARY Detection of Faulty Rectifiers With Servato appliances this company discovered several sites experiencing what appeared to be brief power outages, sometimes multiple times per day (see graph at left) It had been assumed that the rectifiers were working normally despite the fact batteries were dying very quickly at these sites ► ActiView showed healthy batteries ruling out faults or issues the batteries ► As the batteries were charged with the Servato appliance, the rectifier voltage would drop ► When the rectifiers were examined bad blades were discovered and as the company replaced the rectifiers the outages ceased ► Had they not been replaced the batteries would have been damaged
  30. 30. Continuous charging as a method of maintaining standby batteries at 100% state of charge has been standard for many years but has serious negative consequences that can add significant cost to battery management budgets ► Float accelerates battery failure due to increased temperature, grid corrosion, plate degradation and dry-out resulting in high replacement costs ► Battery life can be increased by removing these harmful failure mechanisms and by charging only when necessary and only for as long as necessary Adaptive Charge Management combines an automated battery management process and an enterprise class remote monitoring solution to maximize visibility into backup batteries SERVATO – CONFIDENTIAL/PROPRIETARY Conclusions
  31. 31. Servato’s Adaptive Charge Management delivers meaningful and measurable benefits in four strategically important areas: ► Battery Life Extension: Adaptive Charging improves battery life ► Site Insight: Using the remote monitoring software we make it easier to detect battery and equipment issues by looking at the data of rested batteries ► Optimized Maintenance: Better insight means better maintenance, reducing costs and improving reliability ► Other Reduced Costs: Battery life extension and optimized maintenance are key pieces, but the business case has many other cost savings associated with Adaptive Charging SERVATO – CONFIDENTIAL/PROPRIETARY Conclusions
  32. 32. Thank you Alex Rawitz | 504-655-2733 1441 Canal Street, Suite 221 New Orleans, LA 70112