Adap%ve Charging: A Further Development of Intermi9ent Float for - - PowerPoint PPT Presentation

Adap%ve Charging:

A Further Development of Intermi9ent Float for Charge Maintenance of VRLA Ba9eries in Telecommunica%ons Standby Systems

By Steven n A. Mula lawski ski, , Dor

• rion
• n Car

Carr, , David d P. Bode

• den and

and Ale lex x Rawitz Prese sented d by Ale lex x Rawitz, , Busi sine ness ss Develop lopme ment Manag anager, , Servato

• Cor
• rp

August st 4th

th,

, 2016 2016 | BaIe aIery Power 2016 2016 | Denver, , CO

Outline

§ Issues with Con0nuous Float Charging of VRLA Ba;eries § Shortcomings of Intermi;ent/Periodic Charging as Improvements to Con0nuous Float § Adap0ve Charging

§ Overview § Principles

§ Case Studies: Examples of Adap0ve Charging’s Ability to Enable Ba;ery Life Extension, the Iden0fica0on of Bad Ba;eries, and other Equipment Issues § Conclusions

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The Internet of Things (IoT)

§ IoT applica0ons will require investment in network reliability

§ As more devices connect to the Internet – not just cellphones and PCs but cars, residen?al and industrial appliances, other personal devices – down?me is more impac@ul

§ The founda0on of network reliability are VRLA ba;eries that today are almost exclusively con0nuously float charged

§ Worse, they are subject to inadequate maintenance cycles. Millions of essen?al baFeries right now, constantly charging

An example of VRLA BaFeries for a standby system in a telecommunica?ons deployment

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Problems of Float Charging VRLA

§ VRLAs have been successful in reducing maintenance costs by elimina0on of watering, they have shorter life than the flooded type

§ They incorporate a gas recombina?on mechanism that is exothermic (genera?ng heat inside them)

§ Heat trapped inside the ba;ery and can only be removed by transmission through the container walls

§ BaFeries are usually closely packed in telecom installa?ons exacerba?ng heat removal issues

§ Higher temperatures accelerate failure

§ A cabinet like the one on the right could rou?nely see temperatures in excess of 45C during the summer

BaFeries in a small Outside Plant Cabinet

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Problems of Float Charging

§ Accumula0on of heat from oxygen recombina0on drives the primary drawbacks of con0nuous float charging § Increased ba;ery temperature from gas recombina0on accelerates:

§ Grid corrosion § Dehydra?on § Dry-out

§ Ac0ve material degrada0on and capacity loss take place as a result of:

§ Plate soVening § Loss of cohesion

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Reliability Impacted by Maintenance

§ 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 ba;ery decline

§ Long periods of ?me without a site check mean that baFery health readings provide limited insight into true State of Health § Without data it’s impossible to take proac?ve ac?ons to protect reliability § Equipment failures of other kinds such as fans or heat exchangers can end up damaging baFeries in other ways not directly related to charging

§ Maintenance protocols and performance are linked, and we need to treat them that way

A technician manually tes?ng baFeries in the field

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Status Quo vs. Effec0ve Charging

§ Ba;ery companies are reluctant to require frequent in-situ equalizing

§ VRLA baFeries are starved of electrolyte and equalizing would cause even more

• vercharge and the associated gassing and corrosion

§ Repeated equalizing of con?nuously floated baFeries will accelerate dry-out

§ The status quo is inefficient:

§ BaFery companies do not require in-situ equalizing § Ineffec?ve manual maintenance inhibits proac?ve baFery improvement § Con?nuous float charging reduces baFery life

§ If these destruc0ve processes can be eliminated, ba;ery life can be greatly increased

§ IntermiFent, or periodic, charging has been proposed as a solu?on to these problems

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Intermi;ent or Periodic Charging

§ “Intermi;ent” or “periodic” charging describe a strategy for float charging for a specific period of 0me, and then placing the ba;eries

• n open circuit for some period of 0me aber

§ Importantly, in “intermiFent” or “periodic” charging, the ra?o of float ?me to

• pen circuit ?me is fixed

§ No maFer what the baFery or environmental condi?ons are, the cycle proceeds at fixed intervals

§ Reduces 0me on float and thus overcharging, but s0ll has shortcomings:

§ Correct ra?o of float to open circuit ?me is a moving target dependent on temperature and baFery condi?on § An incorrect ra?o can result in overcharging or undercharging

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Temperature Dependency

§ A float to open circuit ra0o that might be adequate at 40°C will not be sa0sfactory at higher

• r 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 fluctua?ons are common, especially in outdoor cabinets, and with a fixed charge to rest ra?o it is impossible to con?nually adjust float voltages and currents to maintain an

• p?mum charge

§ A further weakness is that a fixed ra0o may not be capable of compensa0ng for power

• utages

§ In cases where numerous short power outages occur, the charge period must also be long enough to restore the baFery to full charge

§ A fixed ra0o does not meaningfully improve upon standard float charging

§ To compensate for varying rates of self-discharge at different temperatures and ensure maximum baFery charge for use, the ra?o of open circuit to float needs to adapt

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Adap0ve Charging

§ A methodology that uses ba;ery data to determine and administer ba;ery charging needs on an ever-changing basis

§ BaFeries are only ever charged exactly as much as is necessary and

• therwise remain in an isolated state

§ Using a unique hardware appliance capable of automated tes?ng and charge control, data is automa?cally collected on per?nent baFery parameters many ?mes per day to ensure that baFeries end each day fully charged

§ The prac0ce also allows the iden0fica0on of other poten0ally nega0ve events

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Adap0ve Charging

§ Servato’s adap0ve charging regimen uses a dv/dt charge termina0on to ensure that charging stops immediately when the ba;ery is fully charged, thereby preven0ng con0nuous overcharge and overhea0ng

§ 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 baFery 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 compensa0on of the rec0fier

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Adap0ve Charging

§ Certain measurements collected by the appliance, such as open circuit voltage, internal resistance and voltage under load give a good indica0on of whether a ba;ery needs to be charged or replaced

§ OCV is an indica?on of Electrolyte Specific Gravity, State of Charge, Short Circuits § Internal Resistance indicates Ac?ve Material Sulfa?on, Dry Out, and Grid Corrosion § Voltage Under Load can tell us about increased Internal Resistance and Ac?ve Material Degrada?on

§ Monitoring these signatures coupled with data trending gives us useful informa0on regarding when the ba;ery needs to be charged or changed out

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Achieving Adap0ve Charging

§ Servato has developed a line of hardware appliances – the Smart Power System (SPS) Appliances – that allow for automated adap0ve charging in situ

§ These unique appliances u?lize proprietary technology that allows them to inhibit baFery charging when it is unnecessary § These are the only systems that can “virtually disconnect” the baFeries from the bus

SPS-148 (1 String) SPS-48 (4 Strings) Ac?View

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Achieving Adap0ve Charging

§ In addi0on to the SPS appliances, there is a user-focused enterprise class sobware component, Ac0View, that is used for visualizing ba;ery data and advanced analysis of ba;ery 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 baFery in the network can be accessed

§ The link between maintenance and performance is strong, and a tool that provides monitoring and management capabili0es is a major asset to ba;ery managers in telecommunica0ons and other industries

SPS-148 (1 String) SPS-48 (4 Strings) Ac?View

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Principles of Adap0ve Charging

Batteries Off Charge Periodic Measurements Data Analysis Charge Batteries

§

Adap0ve charging is a simple cycle

§

The principle is to minimize the amount of 0me ba;eries spend

• n float while maintaining full

charge for backup applica0ons

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Principles of Adap0ve Charging

§ Ba;eries are maintained in a standby (off charge) mode by isola0ng them from the rec0fier bus via Servato’s proprietary technology

§ BaFeries end up charged about 20% of the ?me and at rest about 80% and are s?ll kept at full capacity

§ Life is significantly increased by reducing internal temperature and all the associated adverse affects through a limited oxygen recombina0on

§ Reduced grid corrosion § Reduced dehydra?on § 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, ba;eries are s0ll available for instantaneous discharge in case of a power outage

Batteries Off Charge

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Periodic Measurements

Adap0ve Charging Protocol

§ While the ba;eries are at rest they are monitored at periodic intervals mul0ple 0mes per day

§ Servato uses OCV and Temperature to indicate state of charge § State of Health is determined by evalua?ng several parameters including DC Resistance, charge efficiency, and self-discharge rates, among others § All baFery data is parsed for any trends that may indicate exis?ng

• r developing baFery issues

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Data Analysis

Adap0ve Charging Protocol

§ The measurements are collected and analyzed automa0cally by the SPS appliance

§ Servato owns a library of baFery data accumulated through more than 5 million baFery opera?ng hours § If stable , the baFeries are allowed to remain in the standby mode for a period of ?me when they will be tested again § If the data show changes greater than embedded set points a charge is ini?ated

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Charge Batteries

Adap0ve Charging Protocol

§ If and only if charging is necessary, the ba;eries are put on the rec0fier bus un0l they are fully charged

§ dv/dt charge termina?on

§ This replaces energy lost through self-discharge and any short term discharges that may have occurred

§ As soon as the full charge criteria are sa?sfied the baFeries are again isolated from the rec?fier § If the baFeries have been discharged for more than a preset ?me during the standby period they are immediately connected to the rec?fier for charging to eliminate any possibility of standing in a par?ally discharged condi?on

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Adap0ve Charging Protocol

§ In a mul0string applica0on, the strings are charged sequen0ally to assure string-to-string equaliza0on

§ 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 varia?on

Charge Batteries

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Batteries Off Charge

Adap0ve Charging Protocol

§ Following any charge event the ba;ery strings are given a state-of- health test

§ A short discharge is applied to the baFeries § Voltage/Time characteris?cs are recorded and used to calculate the internal resistance § BaFeries isolated again at rest

Charge Batteries

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Adap0ve Charging

• Standby, available for backup
• BaFery life extension
• OCV
• Internal

Resistance

• Discharge

test

• Library of baFery data
• Charging decision
• If charge is required,

SPS places baFeries on rec?fier

• Strings charged

individually

• BaFeries are again

isolated from the rec?fier

Batteries Off Charge Periodic Measurements Data Analysis Charge Batteries

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Adap0ve Charging Overview

§ This sequence assures that the ba;eries are charged whenever the data trends indicate that a charge is necessary and not anymore

§ Automa?cally compensates for normal temperature-dependent phenomena such as self-discharge § The accumula?on of data means Servato can detect many other issues (see Case Studies)

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Life Tes0ng

§ An independent test laboratory was used to compare the capaci0es of VRLA ba;eries over 0me when they were on con0nuous float and when managed by the Adap0ve Charge Management (ACM) of the SPS system

§ Tests were carried out at 40ᵒC (104ᵒF) to simulate hot weather condi?ons § Four strings of baFeries were tested, baFery capaci?es were measured at approximately three- month intervals and averaged and charted as shown

§ This predicts that the life of ba;eries operated by the ACM regimen will be twice as long as ba;eries on con0nuous float

Expected failure for the con?nuously floated string = 39 months Expected failure for the adap?vely charged string = 79.5 months Servato Corp. 23

Field Tes0ng Overview

§ Field applica0ons of the adap0ve charge management system have been underway in loca0ons throughout the USA for over four years

§ The examples cited below are intended to show typical examples where an adap?ve charging regimen has increased baFery performance, detected deteriorated baFeries, or found other equipment issues § Only a system capable of adap?vely charging and automated tests enables such a wide range of benefits so cost-effec?vely

§ Evidence of battery life extension has been expanded § Proven ability to detect and predict ba;ery issues as well as other equipment problems

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75 80 85 90 95 100 1 2 3 4 Percent nominal capacity Ba0ery Number Float ACM

Case Study A:

Ba/ery Capaci4es from Outside Plant Installa4ons A=er 18 Months

§

At an installa0on in Arizona aber 18 months of tes0ng, a string of adap0vely charged ba;eries 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 ba;ery string approximately 5 years old next to a 2-year old string being floated

§

AVer 18 months (total baFery 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 baFeries would be lower

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Case Study B:

Detec4on of Aging Ba/ery by DC Resistance Trending

§

The importance of an adap0ve management system that will report on ba;ery 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 deteriora0ng ba;ery in a telecom network

§

This was from an aging baFery in a string in which the other baFeries in the same string were showing a constant resistance and were opera?ng properly

§

This allowed ?mely changing of the baFery to prevent deteriora?on of other baFeries

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Case Study C:

Trend in Open Circuit Voltage

§

In this graph the OCV of a string of 12- Volt VRLA ba;eries is shown

§

Ac?View was able to detect that BaFery A3 had a declining OCV before the baFery ul?mately failed and it was replaced

§

The baFery 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 baFery condi?on if the baFeries are on float since they are always polarized

§

Periodic scheduled maintenance and spot-checking would be unlike to reveal this issue

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Case Study D:

Detec4on of Faulty Rec4fiers

§

With Servato appliances this company discovered several sites experiencing what appeared to be brief power outages, some0mes mul0ple 0mes per day (see graph at leb)

§

It had been assumed that the rec0fiers were working normally despite the fact ba;eries were dying very quickly at these sites

§

Ac?View showed healthy baFeries ruling out faults or issues the baFeries

§

As the baFeries were charged with the Servato appliance, the rec?fier voltage would drop

§

When the rec?fiers were examined bad blades were discovered and as the company replaced the rec?fiers the outages ceased

§

Had they not been replaced the baFeries would have been damaged Servato Corp. 28

Conclusions

§ Con0nuous charging as a method of maintaining standby ba;eries at 100% state of charge has been standard for many years but has serious nega0ve consequences that can add significant cost to ba;ery management budgets

§ Float accelerates baFery failure due to increased temperature, grid corrosion, plate degrada?on and dry-out resul?ng in high replacement costs § BaFery life can be increased by removing these harmful failure mechanisms and by charging only when necessary and only for as long as necessary

§ Adap0ve Charge Management combines an automated ba;ery management process and an enterprise class remote monitoring solu>on to maximize visibility into backup ba;eries

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Conclusions

§ Servato’s Adap0ve Charge Management delivers meaningful and measurable benefits in four strategically important areas:

§ BaFery Life Extension: Adap?ve Charging improves baFery life § Site Insight: Using the remote monitoring soVware we make it easier to detect baFery and equipment issues by looking at the data of rested baFeries § Op?mized Maintenance: BeFer insight means beFer maintenance, reducing costs and improving reliability § Other Reduced Costs: BaFery life extension and op?mized maintenance are key pieces, but the business case has many other cost savings associated with Adap?ve Charging

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Thank you

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