ML18101A228

Provides Recent Ltr from Charter Power Sys Battery Div Supporting Values of Specific Gravity & Float Charging Current Incorporated in Request for Amend

ML18101A228
Person / Time
Site:	Salem
Issue date:	09/13/1994
From:	HAGAN J J Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NLR-N94169, NUDOCS 9409220259
Download: ML18101A228 (24)

Text

, ** **** ... * ' Public Service Electric and Gas -*-Company Joseph J. Hagan Public Service Electric and Gas Company P.O. Box 236, Hancocks Bridge, NJ 08038 609-339-1200 Vice President

-Nuclear Operations SEP 13 1994 NLR-N94169 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:

SUPPLEMENTAL INFORMATION REQUEST FOR AMENDMENT SALEM GENERATING STATION, UNIT NOS. 1 AND 2 DOCKET NOS. 50-272 AND 50-311

Reference:

LCR 93-27 By letter dated January 21, 1994 (NLR-N93196) and a supplement dated June 25, 1994 (NLR-N94108)

Public Service Electric and Gas Company (PSE&G) submitted a request for amendment to Appendices A of Facility Operating Licenses DPR-70 and DPR-75 for Salem Generating Station (SGS) Unit Nos. 1 and 2. This amendment request would revise the 125 VDC Distribution sections of the SGS Technical Specifications.

• Pursuant to telephone conversations with Messrs. Jim Stone and Peter Kang of the USNRC staff, we hereby provide a more recent letter from the C&D Battery Division supporting the values of specific gravity and float charging current incorporated in our request for amendment.

Additionally, PSE&G confirms that the subject 125VDC batteries have sufficient capacity margins, which take into consideration IEEE 485 factors for aging (1.25) and temperature (60°F minimum @ 1.11) to meet their required duty cycles. Should you have any questions or comments on this transmittal, we will be pleased to discuss them with you. Sincerely, Attachment

---

*------------------\ ( 9409220259 940913 * . PDR ADOCK 05000272 I p PDR f\OD' I I

,

• Document Control Desk NLR-N94169

• c Mr. T. T. Martin, Administrator

-Region I u. s. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. J. c. stone, Licensing Project Manager u. s. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. c. Marschall (S05) USNRC Senior Resident Inspector Mr. K. Tosch, Manager, IV NJ Department of Environmental Protection Division of Environmental Quality Bureau of Nuclear Engineering CN 415 Trenton, NJ 08625 SEP 13 1994

• STATE OF NEW JERSEY ) )SS. COUNTY OF SALEM )

• REF: NLR-N94169 LCR 93-27 Joseph J. Hagan, being duly sworn according to law deposes and says: I am Vice President Nuclear Operations of Public Service Electric and Gas Company, and as such, I find the matters set forth in the above referenced letter, concerning the Salem Generating Station, are true to the best of my knowledge, information and belief.

and me .... this /3th day , 1994 Pllblic Jersey My Commission expires on April 21, 1998

Reference:

NLR-N94169 ATTACHMENT 1 LETTER FROM C & D BATTERY DIVISION

• • • • -----P.2 AUG 17 '94 17:50 C&D PLY MTG 'C::l:t

• I>> CHARTER POWER IYITEMB 3043 Wallen Road -Plymcu1h Meeting, PA 19482 Telephone (2iS) 828-9000 FAX (215) 834*7308 16 August 1994 Public Service Electric & Gas Co. Nuclear Department P.O. Bcx238 Hancocka Bridge, NJ 08038 Attn: Tim Johnson Subj9ct: Gentlemen:

Salem Nucl*ar Generating Station, Units 1 and 2 125 Volt Safety R81ated Ba*rllls Model LC ind LCR*33 tor Batteries A, e. and c The fol/owing diacuaslon describes battery conditions with raga.rd to Its state of charge and operability status, From an operability perspective, the battery state of charge is defined as th* charged condition that will allow the battery to nave sufficient capacity to supply design loads for the specified period of time, to minimum terminal voltage, while experiencing specified environments.

The discussion will be limited to charging current and electrolyte strength as they relate in determining battery operability as described in the proposed Standard Technical Specification (STS) for the Salem Plant. The state of charge of a battery can be determined In either one of two methods provided in IEEE-450 and the STS. Ons method uses specific gravity. corrected for level ancJ temperature; and the other uses a stabilized float charging current. Some characteristics and limitations of each method are given below. Stablllpd Roat Chtcqlna CWr!nt When fully charged at a stabilized voltage and temperature, the LC/LCR*33 battery cell, depending on age, should require between 250 and 500 milliamperes of charging current to maintain nteammended float voltage; and between 700 and 1800 milliamperes of charging current to maintain recommended equallze vcltage. Stabilization, however. Is often difficult to achieve be.cause charger output voltage fluctuations, occasional short duration power failures, or periodic transfers between redundant chargers, resutt in a brief discharge/Charge cycle on the battery; and although the capacity removed from the battery is quickly replaced, the charging current for many days thereafter ls often much greater than the "stabilized float eurrenr. Since It require* approximately the same a.mount of time far a lead calcium battery to achieve charging currant stabilization, reg.rd less of the depth of discharge,

• • • -*-*----***--*--*

--AUG 17 '94 17:50 C&D PLY MTG P.3 . C:l:I

• RS*89a " CHAATIR POWER SYSTEMS 16 August 1994 Page2 3043 Walton Road Plymouth Meeting, PA 19462 Telephone (215) 828-9000 FAX (215) 834-7308 the battery would be considered fully charged long before the charging current reached a stabilized minimum value. The charging characteristics of lead calcium batteries are well known. Basically, after a discharge of any length, the Initial charging current is high (up to the llmfts of the battery charger)for the duration is takes for the battery to reach Its float voltage, then declines, rapidly at first, but very slcwly c.nce the current falls toward milliamp values. In batteries or the LC/LCR .. 33 capacity range, the charging current will be well above nominal float values when the battery has 100% of the amount of the discharged ampere hours rel)lac:ed (Reference 1). Lead calcium batteries have recharge efficiencies in the 98 to 99 percent range, therefore It Is easy to conclude that onca 100% of the ampere hours removed by a discharge have bHn replaced, the battery will have 1ufflci1nt eapadty to meet design loads at that moment, even though the charging current ii well above the nominal float value. For L.C/LCR-33 battery calls, a charging current of 3 amp1 or lass would be indicative of a battery in an operable state of charge. The limltatlons cf this surveillance method is that a meter capable of reading small currents on the order of 5 amperes or less is necessary, and a specific charging (floilt) current limit be established for each partic:ufar battery size. This value will vary scml\'Vhat with age, voltage, and temperature, and these variations must be factored into the use of this method. Sptcfflc Graylty, Cort19f!d for Lent and Teazpt11ture For constant potential, current limited charging methods which prevail in standby battery applicatlons, there Is practically no ga11ing In lead calcium calls to mix the electrolyte, so specific gravity readings are unreliable for determining operability unless there has been a very long period of st.abiJized float. (It should be noted that STS's originated at a time when both lead antimony and lead calcium batteries were employed in safety related systems in almost equal proportions.

For lead antimony cells, voltage and specific gravity are batter indicators of state of charge than charging current. But today, the vast majority, if not all, of 1E batteries are of the lead calclum type.}

RS-8915 . . AUG 1 7 "94 1 7 : 51 C&D. Y MTG C::l:I

• P.4

• CHAATl'R POWER 8YSTEM8 3043 Waiton Read 18 August 1 '994 Page3 Plymouth Meeting, PA 19482 Telephone (215) 828-QOOO FAX (215) 834-7306 This surveillance method presumes that all cells, once received and fully charged 1 will have an electrolyte level at the high level Indicator, and have been equalized to not less than the nominal 1peclflc gravity strength of 1.215 at 7"fOF. It also a11um11 that no electrolyte stratification

(*pecltlc gravity gradient) exists, or that multiple readings have been taken to mitigate this condition.

For lead calcium cells, specific gravity of the electrolyte,-without correlating the values 'l.lith voltage and charging current and existing performance margins, should not be used as the sole criteria for determining battery operability.

Since they are however, we recommend STS Category A, B, and C surveillance requirements for minimum specific gravity be 0.005 sp.gr. leas the values currently established by the NRC. This would make the limits 1.195 sp.gr. for r.11t"(1ory A; 1.1;o Ip.gr. (cell) and 1.:200 ep.gr. (battory)

'ofl Catqery D: and 1.1QO sp.gr. (battery) for Category C. These racommendatfons are based on several factors: (1) A fully charged battery with all cells having a measured specific gravity of 1.190 (due to over watenng 1 for example) wHI have approxlmateiy 93% of the performance capability of the same cells with 1..215 specific gravity. Thi* reduced J)9rformance would not lmp1ct operabllJty*unleu m1rgins for temperature and aging are exceed1d.

Note that a fully charged battery with 1 .195 spec:ific gr.vity in all cells will have approximately 94% Of the capacity of an identical battery with 1.215 *peaflc gravity. Sizing calculation*

would demonltrata hew much margin actually exist1. (2) A nominal 1.215 sp.gr. battery with electrolyte of 1.1 EIO in all cells, but with nominal float voltages and a charging current lesa than 3 amps would indicate the battery i* l'GCharglng from a discharge, and the electrolyte has yet to fully diffuse. In thia sJtuttfon, the voltage and ch1rging current would Indicate the battely has sufficient capaeity ,(a11umlng temperatura and aging margins have not been comprcmlMd}

to meet d*lign loads. Thus, if a battery meets our reccmmendad Category C parameters, and hlstorical data demonstratea that there i1 sufficient capacity margin, then adequate assurance exists that the battery will meet its de1ign loads during the time corrective action occurs.

RUG 17 '94 17:52 C&D PLY MTG P.5 **c:.1:1 e

• RS-896 CHART!R POWER SYSTEMS 16 August 1994 Page4 e 3049 Walton Road Plymo1Jth Meeting, PA 19482 Telephone (215) 828-9000 FAX (215) 834-7308 By way of historical note, the IEEE Battery Working Group (BWG) recommendations to the NCR relative the STS surveillance category limits for spacirlc gravity were as follows: CateporvA

• minimum value to be determined by the user and the battery manufacturer

• level correction unnecessary If no specific gravity gradient exists and charging current Is less than ( ) amps

• for parameters outside the llmlts, the battery Is operable If within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, Category C values are measured and are within the limits; and all Category A and Category S parameters are within their limits within 30 days C1teqory B

• minimum values for cell and battery limits to be determined by the user and the battery manufacturer

• no more than 10% of the c:ella can be at the minimum limit (i.e., one cell with a low specific gravity does not render a battery inoperable, nor does it significantly reduce the capability of the battery to perform Its design function)

• for parameters outside the limits, the battery is operable if Category C values and the Charging current are within their limits within 7 days, and Category 8 parameters are restored within 30 day1. Category C

• minimum values to be determined by the user and the battery manufacturer In summary. for lead calcium batteries the specific gravity of the electrolyte is important when these readlngi are used as indicators cf the state of charge and/or the need for an equalizing charge. But there are several limitations to their accuracy.

and there are ether indicators that must also be applied when determining battery operability.

It is important that knowledgeable personnel are involved in the surveillance, maintenance, inspection, and auditing of the batteries.

It is equally important that experienced battery personnel select the beat indicatcrs for their lnstallatlcn to determine battery condition and/or ccrrectrve actions n1quired.

....

RS-896 AUG 17 '94 17: 52 C&D PLY lTG e

• P.6 3043 Walton Road

• CHARTER POWER SYSTEMS Plymouth Meeting, PA 19462 Telephone (215) s2s-sooo FAX 834-7308 1e August 1994 Page 5 I trust the above is clear and concise. If you have any questions, please call me. Very truly yours, Granam Walker Manager, Applications Engineering

References:

1. C&D Laboratory Report No. 1430, 6 July 1970, Charge Characl$ristics of LCU*23 Cells on a 100 Ampere Current Limited, 2.22 Volts/Ce//

Rschat;s Following Dlacharges of 200 1 300, 400 and 500 Ampere Hours Attachments:

• Reference 1

• 5 Aug 94 Kyle Floyd Memo to IEEE BWG ** STS Topics

• Technical Paper fer Publication, Assessment of Lead Acid Battery State of Charge by Monitoring Float Charping Current Rs-e&a AUG 17 '94 17:55 C&D PLY MTG e P.1

• Ill CHARTl!Fll POWIR SYSTEMS 3043 Walton Road 16 August 1 994 Pages Plymouth Meeting, FIA 19462 Telaphone (215) 828-9000 FAX (215) 834-7306 I trust tne above is clear and concise. If you have any q'-Jestiona1 please call me. Very truly yours, Graham Walker Manager, Applications Engineering

References:

1. C&D Laboratory Report No. 14SO, 6July1970, Chatpe Characteri11tica of LCU-23 Cells on a 100 Ampere Currant Umited, 2.22 Volta/Cell Recharge Following of 200, 300, 400 and 500 Am,,_,.. HOUf'$ Attachments:

• Reference 1

• 5 Aug 94 Kyle Floyd Memo tc IEEE BWG --STS Topics

• Technical Paper for Publication, Assessment of Lead Acid Battery State of Charg* by Monitoring Float Charping Current

.

• AUG 17 '94 17:57 C&D PLY MTG P.2 . a ::** . M-43 REPORT NO. 1430 C&D BATTERIES DIVISION OF ------EL'rRA CORPORATION . DA'rE 7-6-70 LABORATORY REPORT TITLE: Charge Characte1*istics of LCU-23 Cells on *a 1.00 .Ampe1*e Hour Cui*i-ent Limited .2. 22 Volts/Cell Chargcn-Following Discharges of 200, 300 1 400 and 500 Aiu1,ere Hours " H. J. Schaetzle

.. REPORTED BY: .APPROVED BY: *DISTRIBUTION:

Messrs. Clqssey, JensenJ Stove1*., and Zachau OBJECT: To deter2nine the tion in gravitl of the etectro1J1L.

as mc:'asured in the vent well and at the bottom. of "the gravJtv tube *dw*hJrt 2. 20

-ctu*rent limited recharges.

ABSTRACT:

Three fully conditioned LCU-23 cells were given four carefully measured one hour chages at rates of 200,,

• 300, 400 and 500 amperes. Followi.ng each discharge the cells were fully *recharged on a 2. 20 volt/cell bus with a *maximum available current ouiput of 100 amperes. The speci!ic gravity of the cells was monito1*ed throughot1t the recharges by n1easuring the specific gravity of the electrolyte at two points, at the. top of through the vent well, and at the bottom of the gravity reading tube located in diagonally opposed corners of the cell cova1* a11d eA'ieitding approximately 7 inches below the-? liquid surface. The difference in electrolyte concentration (expi*essed tn* apecifto gravity tmits) between the top of the cell and the bottom oi the gravity l*eatling tube is shown in ihe f'ollowi ng table: ico a I 2. t

_. "'\::l

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NO. ::l*lnA-;20 01ET2Lii:.N f'APl.H: 20 ){ 20 INC:H 2 4 to !i;Ula::o; Dlt:TZOEN co. ,,.,ADC t.N U... J\. 50 90 130 f70 .

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1ri:l 1 .......... .,...., IEEE BATTERY WORKING< DATI: bOMs TOI IOb .. Wl'I Del IWG llllllllcn e Poat-It'" FP Nata Al we dflcwlRd b1 plaont 11rUer, I *m n1quOllln1 a rpot on the lepttmbu S'llMthal

• pad& to dl1&11111 IM!l'll luuu related co tuMlll*RCG pr11tlcu, upeclaJJ7 pel11lnln1 io audear appllc1doa1.

lmral 1ucl11r plant* art now eomplet1a1 their tru1Hlo1 to new ..,.IMI .,.Clfltatlcm1(TI) baled on 1'H 1&1nd1rdlled TNJaaJcll lpecfftHtlOlil(S'i1) the IWG re¥fewed and tomm1nted on IMl'll )'lln qo, nJt actMC7 bu pnorated I lot of qucu.kHll oa aumlllance

• ethOcll *d pl'IC'dcea.

WbUe wa m11 aot bl able tD addll'UI *JMClftc Tl llmla1,

• dllcuulcaa ot tht buf1 tor .tetet11f11l*1 certal* llnaltl 111)' b1 verr helpftal.

Dr'. liba of 1ht NRC b** badlc1Md dl11t &omeDDI from ellt TS ,,... ot th* NllC m11 be 1bl1 Co Jola ut for Chi* dllcu11fon.

Tbt tollowlac q111nlon1 Jn*1 be ultflll to *" the di.ICuaaton.

J, 'Whit r:nterla waurd be 1111d to d1termin1 th.t.t 1 battory 11 tuU1 cap*bll ot pertonnlq ltt f11tendeC1 tunctlanf Whit 111nmoitr1 would bt ..,.ntlal 10 makln1 tilt* cltiermhl*tlonf Dacri!M a pntral criterfa te* 1ettln1 the llmlta o* euh of dltN para11neten1' Would dlf1 N a pd ICNltfoa to l111450f 1. Wllat 11 tlal llult for .. "NIHl'*thumb" tll1t 1 IO*polnt(0,010) drop In 1ptelnc 11"1\11U Hl'l'tlpOlldl NMtloa fft battol")'

l!AplCltr(from UllSllO Jl:Ht 1o lohD Kno1)f Haw 11 'tltll nlatea to Tl 11 ... 1raramc11b that 1 value oto.011 b1Jaw th* mariufactunr'r fully cb1,...d IOftdlal apedftc 1r1vlt1 11 dl11'1ottrl1tlc ot 11 cbarpd cell adequate CIJladt)'f If the &"'IP 1pecSftc 1t1vltf of Ill C01Ut .. tcJ CCIII la found 10 be 20 pofntl bDIOW **l11ll valut and *artier readfap bave bttn at tlle acmlnal 'Yllult wit.-amo111t* of

• c1pacff1Ctecllntcau1 ltltMf-cbarp)

IW bee1 IOlt' How 1* Chu detennlaedf C11t lt lfatad that tbt b1het)' hM 111lftclt10 capadt1 to ptrfllrm "" laatendtd function ud maintain 1 **rsla dlltetft 3. II blftley ftoat charsln1 cur111u 1 .method or deaerm1nrn1 Che 1e1te of c:harp GI a lead-add Jtauteyt t111 It bt 11ed In lleu cl 1ptelt1e trntt1 rw1dlnp1 WhJ It a Uade&doa taarowtna

• rwllarp afvtra tor lu HI tn *1&* ITSf Notti The attached 1C1chnJ1al piptr dfRllUll thlt ..a.tllln'*'L

4. WblC '&Jpn of Umlt1 lrt nqulrtl oa tncenell conntctlotl t11fltaneo1 tor maJnteuuc:1?

ro .. perftrmlna llM lnttncled functlon(operabllltf)?

Rr&w lhould cable ...,t11usc11 la datlawplnck

""'*'ltu la .11aa111tttd tort 'Wauld the PM or a Umh fDr tMb 1¥p11 ut CGllMC'liml

... p MrllJ tohl Umle IN 1ccepllbleP Al *oted 1 Ctr:Ulul paper en U01111ta1 tile 1t1tc er cba.._ at 1 le1d*1cf d b1i111"1 hllaS float cb1rsta1 cu..,. ta utache* for mttw and comm11U. Thia paper wfll b1 pn*ttd at INTILlt' N ID Novemller.

I ua ukt111for1111 cram1111nt1 trttn the IWO m1111bl1a.

In i:cmJunctlon wleb J, 1bcM, 1 like the IWG io ntmrm th Dll ao 1t1ttmfnU Jn aocdo* 4,1 amd Appendt1 .I coaomdn1 tM uN ol cbaralna cu mat. Wt ara 11tJ1orf111 aam* additional daf

• on dal1 meibocl dla I hpe to bl¥t lt'IUQle at die metdq. (I 1111 Mndlq tltll 10 Ill tbt .IWG mtmben &Ince )'DU ha\'C Alrerld1 ma!ltd th1 111oeel111 aotlce.l l f:;LJG 17 '94 18:07 CfxD PU MTG P.6 e ASSESSMENT OF LEAD-ACID BATTERY STATE OF CHARGE BY MONITORING FLOAT CHARGING CURRENT Kyle D. f1oyd .. Souihem Company Semccs Inc., P.O. Box 2625, Birmingham, AL 3$202 USA Z. Noworollki

• Pol)'uonics Engineorin1 Ltd. * .5200 Dixie Road Unit J 8 Miaissagga, Onwio L4W 1E4 CANADA 1.M. Noworollld

• Univmity of'Betkeley, Berkeley.

Califomia USA w. Sokolski

• Ontario Hydro, Toronto, CANADA INTRQDUCTJO:i There are two methodl for 8llCliina the sune of charge of a Jead-acld battery discuaed in the latest IEEE std. 4.SO(J]. The most common method used in the past baa been eloetrolyte spec!Ac (S.O.) measurement readiup taken with a hydrometer ftom ont: or more ceJls ot the 1-ttel')'.

The other method 10 determine the battery lta&c oI charp is the use of 1 ltabilized charging (ftoal) current maaurcd with a &aWtiw: elamp-on ammem or a Nit.able shunt and voltmeter.

Seven.I cbangee within Ille ba1U:ly user community have n°* made the me of specific Jri\lil)'

readfnp vory COltly hi aoam: cues and impasaible in othc:n. For example, some users have Nmed to automatic monitoring systems with remote capabilities to zouanoly collccc battery data. Then iJ only one known monitorin1 syltcm that bu provisicns to meuwe specil\c pavity. rt i1 still being tested and may not be cost effCetive for many small battel)' iDlta.llations.

In addition., some of thae lnsttllatiom have valve. regula1cd lud"ICid (VRLA) batteries which have no provil.ion tor measuring lf2Mty. In fKt. the electrolyte iA itttmabillz.ed.

making the 111cuurement of IPCCific:

gravity With the lar1e nvmben ofVRLA blttcriel now in service and being sold t.oclty, the 1111 or I.he flCll& ,,;umnt method of asacain1 11111 ot charge i1 oxpected to h1crease.

In 1918 ane user of flooded lead acid batteriea in a plant began to measure bt current in addition to S.O. readings.

A COtaJ of 780 cells were monitmcct.

The reaultr of this experience are summarized In lhia paper. A review of some of the elcc:uochemisay involved it also J)l"aeDted.

The analysis of lhe collecuxi data has led to the eondwsion I.hat floa& cumnt monitoring is preferred 1 O'ICr &peeiflc gravity readings for usastns 1be swe ot cbarge oC a lead-acid battmy, Now the problem tw2ll the availability of COlt-etreetiw, acca1lte proviDOJll for mouuring tloat ewrenL The last pan of thls paper presenu a test imuument dalsn for taking .float c:urrent .readings.

F!liLp DAIMVIRllNCJ SUMMAB}'.'.

In 1988, one nue.lear pneratiq station blpn raJdns battery float cumm rcadinp &Ions with the roudae specific gravity mdh1p. Shunts wore alnldy imtalled in the circuits that tho currem iDto or out of the banay r:ould be mciuwed. A porllbll mi;rovoltmeter WU ullCl to take the readiftp.

A&r c:ol\!Ulting the batwy manufa'7Nnrs in 1988, inlda1 ceil1ng values of 1 ampere and o.s ampere \tCl'C establishod for the lcpr IWicn baaeric1 am the *mailer dJesel battariea, rnpcc:Uvely.

Tbae current values were believed to live rmanable aauranee chat tho battlriea wore fully charged. Float wrnnt readmp were added to the weekly IUrwLllallee pl'CICOdura for 9 batteries coDlisUJ11 of I total of 780 oelll. The overall wminai voltqe, :ftolt c:urrent, and oomctcd IJ*iJIC gravity an summarized in the tibia below for batteries S lB, SlA. and D02A. Thil data is typical far the ot.bu lderia. The nominal l*hour ampere.hour ntinp of the batteries were 2400, 1650, and 340 (410) for batteries SIB, S2A. and DG2A respcctMly.

S1tteriea SlB and S2A each have 120 '-kalciwn cells with 1.21! nominal specific pvity electrolyte.

Batteiy D02A had 60 lcad-antimotty cdll, with 1.2U nominal sped.fie ll'lvity Wltil nlPlaced' with 410 ampere*bauf tead-calcium celli in April 1992.

AUG 17 '94 18:08 C&D PLY MIG e (. u.n1ax 1;.1 DJ.Tl BATr'UY FLOAT cou. VOLTAOB CURUN'I' IPEC. (Volll) (Anl;ll) ORAY. MIN'OO,JM 132.l 0.12 J.20! AVEll.AOE IJ4.7 o.o 1..211 MAXJMUM 13$..C O.M l.2:17 STD.DEV. 0.61 0.14 0.00, pmax 121 DA'l'A BA'mRY 1LOAT CORK. VOLTA.OE CURRENT SPEC. (Volll) c.-.> ORAV. MINIM\n.f IJ:Z.4 0.06 J.198* AV!.RACIE 134.-' 0.50 1.211 MAX1M'UM 140.0 2.:P *. 1.231 m::>.I>!V.

Ulll 0.22 0.004 IUQBX PQ2A QAD BATTERY FLOAT CORR. VOLT AO! ctJllENT SPEC. (Volll) (Ampl) OJtAV, MINIMUM 130.0 0.01 l.20d AVERAGE m.o us l.219 MAXEMUM t3U 1 0.41 l.234 STD.DEV. l.29 O.OI 0.006 Ndt: n. nlu. muU4 wilh UI Ul.i.k (') Ui .. to IN ...... a.& ¥0ha91,...

wMi CIJlll WIN npllcil4 .ttJa i..n.-Jcilllll C.111 1n April 1992. uo1Cm1uans may oe maa.e 1r0m an analysis of the detailed data 81 well .. th* statistical data tabulated above. The detail data shows 'very liltle correlation betweea the spec:ifig gravity llllclinga and tbc llClUal state at Cbarte at a given point in time. JJ 2 P.7 deftned in IEEE Std the battay is O"'"ridercd cbarpd wmn the float cwrent baa llabllWx:l

(:DO lipli11c:an1 cbuap for J hours) at the f1olt valtaae. Thll WU roulinely

• contitmed during each recbl1p after lold diacharp cm may bstteria.

M a wr/ at illusuatin1 the chaqing cycle, let'1 look at a typical example. Typical data for the ncharp tallawin1 a pedDrmaia tat for a llad-Qld11m blUCfy i1 shown in Fipre l. I: 120 1.21 100 1.2 .. eo 1.1* I I ea c 40 1.11 i 20 -0 1.1?' D 5 10 15 20 2S 'TMNHJ\.N fl(BA.T.Ahf!G

+SPEC. GRAV-AMP-lo-AN tOClii. BAT, AMflll * 'C!Oi 1oo.i AMfloH" IN* 1323 The hi1h initial limited oaly by the cumm Umit letting oithe eharger, flows for about 3 haun. There l1 then a rapid drop in current fbllowocl by a transition into a slowly decaying current. Over 100% of the di&ebarge ampen-houn wen rcmmod within J houri. but it wu not until after 17 hcun that tho charging Cmre11l ltabilized.

Notice that the apecifig sravUy rtldiDg ii only u 1.205 at 24 haun. 7 houn after the chargin1 current hu ltabllbled.

nm i* still 10 point1 below the narma1, fllll-charp lpleiftc gravity ot 1.215. From tho example lboYe, ii should be clear that charlins cummt rapondl more quickly than iplCi& pity readinp io changes in the S111e-of<hlrae and provides 1 better illdicatioa ol a tOturn to full cbar1e. V1vm1 1.1ruy me ***nap1nar

\1VOISCI)'

pilot-cell readinp. a muoh better lllCllmCDt of mu: oC charp c:an be made with tloat current than with specific jp'l'Vhy.

These ob.orvationa are also supported by the blttely syllem opaaticin m"iew given below. '

• I 1. I . I AUG 17 '94 18=09 C&D PLY MTG e A tew by paint.a ooiaming battery l)'ltem operation are here. Ill tlolt open.lion, tbe hlttmy, charpr, and IOlds ue collMCted in paralld. The cbarpr normally nppliu the loads and the float cwnnt iDtO Ulo battery. lf dle cblrpr output ii lolt '1t madequate to IUPPlY die lOlds, the batael)' immediacely mppliu the requinld eurrena. Nonual hcl1le IO&dl OD the di-1 gcam1U)r and lllltion bltterim are ilL Iha rap ot 10 to 100 amperes. :rapectiwly.

Tbacfore, on a kla of charger Olltpu&. the bluery Q1ITCm immediately changes di1'Wcm Ind inmeuet dJ'amldcally, al lcut by I lac:tor ot 1 o. 'Ibil &harp current wowd continue until the chlrpr omput ii l"ClltOred or tbe batteries are ftalJy dllicJwaed.

If the battery bas beef! dilCharaed and then placc:d on chlqc, the battay currem will inidally ilaeuc in the charging difectioa and remain 1tp.iftcantly hiper(ampa VI milliamp) tJwl normal until the chirp* hu been returmld.

The rwlative mapitudo and dlrection of the battcry(f1oat) current itt conjundicm with the battery mminal voltage pmvidel a timely, accurate il2dtcadon of swe-af-charp.

Ono 1111 obieMtion concemina the n0&1 i:umnt data should be made. The ceillilg value far float current muse be selected.

to allow ror \he variadon1 oxpected during Mtmal opention.

Since lhe float currem readin1 will lncreue dram*dwly for a partiall)t dilcharpd battery, some MhiOll aboYe the nonna1 "raled 11 float CWTC'N ii polliblo ud even desirable.

11te statlltical dita *howl that the avenge flOll current plus 2.5 lltandard deviations was under the ceilina value on all the bacteria.

The detailed data trom battay S2A tam dmins the panial uhlrp also ahowa that cvcn f'or putial dilldw9e1, Ule float cwmrt hlcrMlies dramaUc:ally to correctJy alert the um ta pcllliblc probleml.

ILECTBOCQMJCM BIACJ'IONSJll\'llW

[2,3,4) A review of some of tbe charge and ditcbal'ge nac:tiom of a lead.acid battery may prove helpful hctc. The daublHUJAtc rheory ii now commonly aCCCl*d 10 delc:ribe the buic chenW;aI 1*tiona oc:c:umn1 witbln. a lead-acid cell during cbmge and discharge.

The chlmK:IJ equation below mmrflllM the overall suctions ot this theory. Pb0 2 +Pb+H 2 So 4 =2PbS0 4 +2H 2 0 (1) J P.8 e Lead and sponge lead (Pb) an &be ac:tiw matmala isl positive and neptiVl!I Thi acid CH2804) ii die elCU'0!)1cs and the llld sa1fltt and W8sar UV prodw:ls of tho dilcbarp The cUcblrp rwtioa. gae1 ftom left t.o riaht and the chl'l'p mcdoD from risbt to Id. Both the platel amt the elecUalyta ue inwlvm ill iu rmaion. Leid IUl&te ii fonned Ii botb tbe petid.je and ne,.UV. plMel during cUICblrp and thl nli\iric add ii cxmvertld in theprocm.

M noted above. durinl a d!lcbarp, the SUlturic ICld ii belq oonverted to lea4 sulfate ad MW It tbl plates. Thi weaker acid ft'om the pl1111 dJmJlll imo the bulk electrotyte, decreuin1 the spocifk; gravity. While cbarpng, the lead IUllate ii canvertecl blCk to plate 8'.1h'I materilll and sullWic acid. It is important to keep in mind that thl1 reaction is o=urrlng in the active nweriab of the plates, not in the blllk electrolyte.

AJ the add within the plala bec:Ome11 more demc. it leaves the plates and diffucs VflfY slowly through the ileetrolyte nilln1 tho specitie grayity ot the bulk elocuol)'te to the tull* c:barp level. Alf'/ currenl hi ex=-al that requited to convert tb1 .vailable lead IUlf'aUI pa lam tbl electrol)'si11 of water ill the elo:troJ)'te, t!ml reta*n1 hydroaen at the nepavc plates and DXYJell ai tbe positive plates. It 11 thil paiq ICtlon that helpl to mix the elecirolyte.

Since both discblrp and cbarle reactiom involve cUmWon ot the electrolyte, the Rate of cbarp indicated b)' apeciftc pavity readlnp inberattly Lap the actual state of charge of tho cell. especially durins charge. In a lead-calcium cell. -which pua much 1eN than a lcad"8l\lirnoDy cell, tho mi"'1\g ot the electn:ilyte ii much mare dependent on cUtl\Won.

and tho lag in lpll:iftc:

gtl\'ity readinp i1 inore .,ronounced.

Thi open circuit voltage of a cell is d.lrectly nlat&ld ta the specific ,mity of the eleeuolyte and maN specifically to lhe acid in the .nwcrial*

or the plate&. In a abilizod cell, where che electrolyte ls homcpncioua, the &pec:l& pavitJ ot the bulk elc:ctrolyte la the 1&n10 u that near tho pla1n. The open circuit volrap of a fully dmpd cell with a nominal 5J*iftc gmity of l.21S ii approximately 2.06 volts. Tho voltage of a discharged cell will ba lower. Al soon u charging starts. tu1lUric acid ls formed in the plates and the cell rises, opposing 1he applied cbarpq voltage. ConceptUall)'.

this pJOQC:Sa can be explaintld by eqwalion (2) below. II AUG 17 '94 rn: 10 C&D PL'r MTG e E-Eb l=--(2) R The applied wltap *!II fl held CDDAUl by the chargor. The cell w.ltage i1 dependent on the concentration of lead ioal. dMJent ud tetmalent, awillble tor reac:daa.

Thill nladmlihip is exprmed in tbl followinJ equadon. whic.b hU been derived hm the Nemst' equatiott.

See reference

[$] or anocher elecuochemistry text fbr the derivation.

• (Pb++++) p; 111 1.87 + 0.0291og 2 (3) (Pb++) The quantities enclosed in parentheles are the number of lead ions available for BKtlon and are small !n number. The 80Urc:e ot the ions I I I ) ,, the small amount ot tho lwl dioxide that i1 lcaized. The only source of divalent Jons i1 lead auJAte which ii produced duriq diacharp u above. Tbe uncunt ol llld IUlfatc within the cell will be at 1 nwdmwn when the cell i1 fuily clischatsed and at a minimum whea 1\J.Uy charged. Therc:rore.

tar a Allly d!lcharpcl cell the c:oll vcltaSC will be It I minimum Whan ftn& COnmctod to the cbarar. The int=nal czll l'Mimtn'!

1 wry low value md doesn't cbanp putly whether the c*l is ftllly charpd or di.tcharpd, but it wm be bipr in a fully dilclwgod cell. llcferriq

&o equation (2) abow. Jt can bl teen that the current will be 11 a awdmum 'llDdel' theae conditiona tor a given dulflin1 volt.Ip The dhc:barpd coll continue.

to cbarse at or near the maximum c:urrent available flOm the charger until the awilahle lead mllatc is almost cxhauted.

At this paint. &he reduction in the supply at divalent*

iom causes the cell voJtase to incfoue to I value appioaching that of the charger. When au tho nailable lead sulfate bu been converted.

the cell i1 ftlUy dwpd and the only etimnt ftowin1 i1 that required to overcome the self-dilcharp l'CICdOlll at U. plates and any electroJysj1 of Wltn caUICd by lhc applied vo1ta11e.

The cbargi.fti emrcnt can be made up of thn:c componenu uai in (l)rccharpng the Cf.11 by convertin9 lcad sulf&te, solt-di1ehar1e by .main1a.lntng proper plate potentials, and (3) 4 P.9 rcleubt1 sues through electrolysis Of water. rAMOUlly, the ftnt c:ompcmmr.

is the rwt impol\llll

and, It ii the prot'enntial chemical rm.ctkln u MD. Tiie leCODd eompcment only limU after the cell voltap bu rillD *"" the open cUcuit \11.luc. Tho tu& component 11 not desirlble.

but DY cmrent in excm cf U1at needed for t.be Int two ClOlllponcn&I ii WIOcl Jn thil way. While equatiOn (2) smn ii holpftll to viM11ze what ii blppeniq m the cell. it does little to quamlf1 tbe rmaJca 1e111 ill the voltqe and curiat durin1 cl'llqiq.

apeeJ&Uy during float opntioa. Flcat operadoD is more cloar:IY delCribod uiq Tafel Una u dllcribtd On .floet cbarp. the wrreni ftawin1 thtculh a lear.l* add cell and the applied voJtqe arc rcJatcd by iu Tafel charlcteristics.

A typical Tafel Iii. graph is &l\own in Fipro 2. Each cell type will gcnetally have its own spocit1c paph. These snpbi have several line* 1howins tbe relationship of the (;Cil voltqe to the :float cwmat, lllUally givm in mJcroampaes per a .. hour ?ldng, The poaiti'.\19 and nepdve plate polarization voltap1 1te a110 lhown. but miy be ipored tor our p.uposes.

Knowing the applied cbarsin1 voltage and the cell nominal l'llinl in &mpere*houn, one call determine the expecled flalt current for a liven cell type. The actual tmralled value of flaa1 cutrent varies with temperature and ap. AJIO some allowance must be made f'or manut'ac.turing tolerances between cells. A portion -:Jf . ' i I

. . RUG 17 '94 18:11 C&D PLY MTG e this data ii confitmod routinely aAer the batte.des an wembled into .vibp prior to the uory c:apagity ta Only the .float current aad cell voltqea are

• IYlillble, but UU. ia all thaC is needed for our puipo5e1.

tJlin1 data obtained ftom the ppha and/or ftctoiy teCCl'dl, c:eili.ng vaJua of floac(ehaqinl) cumm can be developed for mrvoill&nce purpcllei.

The battery wndor can help in IO!ectiq these values. Blled on the expericitce with the W10 of both methCJdl of dewminiq the ltat9 of cb.rge of I battery, we have dltennimd that the cbargi111 current method oft'en 1m1ral ldvanlapl over the apecific gravity method. Socne ot the advantaaa are lilltd below.

• l. Cbaraina is a more meaninlfui lndic:ator than speciAc gn.vity since wmnt is the primary means ol delivering power into and out of the bitter)'.

2. Chargin1 eutreft1 responda more quickly to eha.nps In state-of-<:harge, In fact, lhc carefuJ aclection of a ceilin1 current value Is very important to allow for normal variations.

3. CharsiJlg cummt mote cloMly the condition ot the whole battery than the specitic gravjly ot a pilot cell. In conciumon, m of determining the state of chars-cf a lcad<<id battery have been in llOme detail. One method ot readinc charging curnnt bu been explained.

while me rcmJts of aevcra1 )'W'S of uing both methods has been presented.

Bued oa tho experie.acc piaed with the clwJins c:uncnt m=dlod, the secluW:al background and the general trend 'Within the bauery indusiry, we r.comtncnd the use of dw'sins cumm to determine the .i.ate of charge of 1 llld<<id battery. While It i! true tl1at not iaany baUcry l)'lteml were initially dllipcl with provi1ions for n:adinl charging current. there are othor meuurement teehniqua that W0\1Jd allow t.ho retro.fit of those systems. The operatioo of one such technique t1 dOllCribed below. JNSTBYMENT OPIMTJON The float cumnt in a fully cbarpd battery ia in the milliamperes ran1e tor the more common sizes used in stadonary applicatiom.

Insttuments used to monitor this curtent ml.lit be capable of accurately meuming thit small cummt and also be able to . s ,, P.10 withlWld the maximum battery c:um:nt wi1baul damlp. The ib.unt and portable \>Oltmeter melhod may not be prac:lical or CY'lll P*fulc far many applicatiom.

Allboulh Hall Eff'ect meterl will witbitaDd biP eurrents, a=urtte SMllW'ellkats below a few unpora are dil!ku.11 to obtain. In addition ro Hall E&ct amsora, therCI me meUIOdll of nMUing tho core of a current traufonner ml meuuring the llCODdary current immediately after a rnei pulM [6,8). Si=e, illitially WI core will bo

• fully rc:sec. die woNtary current 111 dirsrly ptOpOr* tional to the primary current Md <:111 be mil)' muswed. With the pwap of time the =e wW be driven into saturation and wUl lose its tiaa.stbnNsr MuactoMict.

1be l1IRI pu1ac ii applied apin Ind the procc11 ii repeeitecl.

By utag thil md.bod measurement ol OC current can be easily obtained.

Howcm, the misc oC IUCh a "DC cunent transformer" is limited by the reset current puJtc amplitude and 10ilQ in the COf1, The appllcatioll of large cumnts lO the primary of such a uanaformer will not destroy IOmicanduaor dMcu on lbe MC:Ondary.

The physical OOle 11izc to be llsed for float current measurements ruun be abJe to accept laqe conduc:t0n Cllt)'ing full dilcharge cmrent. Hence the core will be of !dgniftwit dimensions.

Since core loua dc&ennine the lower end al current Rftlin11 drcuiuy, It is dimcult to obtain reliable raultl Uling a *oc* current trudo.rmer when the primuy current Is lower than a few tena of millla.mpma.

measured current Conlrol FipreJ Figu.re 3 shows the device, on the prindplc of a 18.lurable reac:ror <lteillator, which addreuu some of these limitations.

The measured current puses through the cenler of the ferrite com. The winding of the ferrite itself is cannocted to &be QDJ'e SET circuitry.

0

• AUG 17 '94 18= 1i C&D PLY MTG e The magnetization flux magnitude in the ferrite core ii the sum of flux pncatecl by die meuund current aa.d the nux of the SET windiDS on the ferrite. Conaider a cue where the meuwed current is equal to zero. A voltap VL* is applied acroaa the SET windin1 ot tho con. The cunent will atart to rise with tile speed given by the followmg equation.

f!_Kt_ di L ...... ; VL

• Volrap ...._I<< wW!1ne (4) The masnr:tie flux in the core will start to 'rise and after a cenain amount of time, ti, will reach the satumion point. -B 1)xl0 8 18 ..

v wt.I; ti* tllllll required 1o A* C.. ....-Gl'U. oan( amA) N .. lllllllM o£1111m V* lpplled valiaet Bo, Bl* IDi&W-' ..wr.umaavx dmlity (O.J (-') At this point. uic c:umnt will im:rme rapidly, an tNe1U which can be e.ullv detected bv the loa:ic's circuitry.

Note that lhl time to rr.ach sanuation (ts) is a function of lhe initial fillX density. Natura.II)', thi1 implies a IWnple depondeme on semed CC current. With a comtant voltap applied to the set winding, lhc time required to reach 1 llturation point will depend OD. ma&Ntude and direction ot the sensed DC cum:nL For example, it the flux produced by the sensed current bas the same di!Wdion as the flll'I: ptOducecl by the SET winding, ts will be shortened.

ot all anaJos vllvee; time i1 the one which oan be meuured the molt accurately.

With proper sizing af a sensins transformer we CUI obtain quamizod ts values for 1 rango. A particular problem of this delign is the influence ot GUier paramoten on ts, In when attemptJng to mwuR small currents, extcmal influences ean have a c:omparativc:ly lar1e influence 6 P.11 e oa ts. Some of the paruitic contributm which we haw identi11ed are.:

• resistance of the winding and the cumnt loop ued to SET the cote

• raidua1 mpaic :Seid ln the con

• external mlpWC field

• ncill ia the meuared conductor

• tmllpenlUn Topther. these pm.sidcl sipUlcantly deteriorate our &tsnal-to-JIOilo rado (SNR). P:igun 4 preeenll 1 technique to roducD the intluenee of many of tbe above P1P115itie1.

I I 81:1' Figun 4 A known DC vclcage ii applied to the SET windhlp by a MOSFET switch. with an Internal resilllnCC whieh is very low compared to Ulc total rnillance of the SET wimli111.

OllQO tho fCIU.ltin1 wrrw rca;bcs a referc:ncc value, the MOSPET is named ojf. allowing the ferrite core lO raet. NtltJr a predetermined Ume (which is not critic:al far m*m1P1P.mfl!ltt*)i.

i* tn....M -. 1110-:.., and the process ia RIU&ed. A mlcrcproc:essor mwuR1 the ON time of thl MOSFET and calwlates an avenge of many meuW11ments.

An average ON time is ltmd by a rnieroproc:eAOr.

Nm, the curnm direcdon Jn the SET core i1 revened and the pro=u la repeated.

lbe meuunns. averasin1 and storing procm is repcatod apln. Finally, the diffC11nce between the two l\'CJlied reac!inp 11 c:alcwattd.

This "differential" result ii proportional to the current nowm, throu1h the 1CNO wire. Nate t.tw chis di11'erentiaJ techniquo areatly reduces the dfeeU of changes in temperature.

voltage and The only unbalanced influence is the extcma1 mqnetic quasi-suuioiwy field (e9. earth'* maptic field), Tht tldudion of thia error soun:e j1 poAlible by placing additional ferrite cores on each side of the JDQsuring COl'C! and COl'lductinJ oft'set meuurmnents during initial installation.

Of course. in most

.. " . -AUG 17 '94 1s:12 C&D PLY MTG e iu**tn*iom Chcl error c:oatribudon from magnaic 8elcb ii ne&lisihle.

Fillllly, high frequency WI low frequency noise. comribu&iou are paily dec'eued by use or multiple avenpd umple1. It i1 iateltltiq ta noie that when the meuurement cmreut is iDCl'lllMd owr cerilin whidi gm be ciemcted by tJw: mechDd delcribed, WI)' tmail modilc:ation will permit dcllaioa of a large currcnt f2owiq through the lallll eote. (Pig. !) Now the circuit will work on 1 cWfemu principle:.

The coro will be reset only in the dJrection oppo1ite to tM mwured ;urmi&. and immediately after resetting, the voltage acrou the burden raisior will be meuured. The limple 11111ple and hold amplifier will measure tho cmrcnt during the time immediately precediJ1I tho reset pulse, Iii dacribed 1.n111. Furthermore it ii a11a worth cbicrvins th.al the SET pulle praent on the soxmd*ry at the mcuuring care will, ia fact, bVoct a much Jarpr cumnt into the battecy DC clrcuit It the froquttU:y and current of tbJ1 SET pullC: ii ommollcd ud volta10 meuu.rement1 acnm indMdual c:ell1 or the battery are sampled with synchronous frequency, it is poaible tc use suc:h c:ircu.Ury not only to measure float and charge cumnt 1Nt also intemal impedance ot individual celll when thl battary is on float The PCJlyU'Onics Eqineerina.

BTMJOOOP battery momtoring illltnll'llCnt baaed OD the abcM prillQple is being used u 11 permanently hutalled.

monitorin1 1)'111111 on stationary and UPS blttcric..

Thi.a l)'ttem perm.ha the oblervati.on 1 lmA float c:umnt change on the 500 MCM condUCIOI' cable in the presence of the hip ripple AC c:utftftt normally present on UPS battery inmllatiom.

BERUNC'E§:

(1) !EBB R.ccommended PractiOD for Maimenance.

Testing, and Replacement of 7 P.12 Large 1-d Storage b&Ucries for Generatins Stadom and Subltatlou.

IEEE Std. 4$0. 1987 {l) CJ. W. Vinal, Storap Fourth Edition. New York. John Wiley A Som. 19.SS. (3] !. A. Hoxie. .. Some Cbargiq Cbanaeristic:I of Leid-Add Batteries", A.I.!.!. Conference Paper #'6*1036. H. B. Haring and U. B. 'l'bamU. Electrocbemicll Behavior or Lmtd. Leid* Alldmaayt lad Lcld-Ca1dum Cella", Tramacdol1I ot the Electmchemical Soeiety, Vol. 61, l 935. [$1 H. I. Crei&htoa.

Prlncipl11 and App/lcotlon1 of Vol I. Founh Edition, New York. John Wiley, &:. Sons. 19S l [6] ll Severns, w1mprovin1 and Simplifying HF DC Currmit Semcml". Confem.co Pro=iedinp of the 1986 IEEE Applied Power Blectronic:I Confereaco (APSC '16), pp. 180*183, Now OrlCllDI, Lcuisisn1 1 April/May l 986 (71 c. Swlondcr, *Mapctic Current Sensors for Spam S&alion Pnicdom*, Confema Proceedfnp of the 1991 IEEB Applied Power BlcQtronica Confennt:e (APEC '91), pp. 635-. 641, Dalla, Texas. [8] A. Radum and J, Rulison. 11 An Alternative low-cou c:umnt*RDlinl

&eheme for current power dcctronics circuiu*, Conferm Proceedinp of the 1990 IEEE lrulmtry Appllcadorui Society Annual Meetins, pp. 619-625, Seattle, Wu!Unston.

October 1990 {9) T. Sonoda and R. Ueda, "A Current Snor or High l.ftd Hish Seuitivtty't, Conference Proceedinp ot the 1990 IEEE Industry Applicttiom Society ADpnal Mcctini. pp. 626-631, Seattle, Wuhingten, October l !190 (101 w. A. Geyser, 11 Dl11pOZidve Mqnetice Neliniue".

Editura tehnic:a.

BbCUl'elli, 1968 ,\