An evaluation of formation charge power conversion technologies and their effect on battery quality and performance

Transcription

1 An evaluation of formation charge power conversion technologies and their effect on battery quality and performance Slide 1

2 Overview General Introduction Introduction to charge power conversion technologies Experiments Results Conclusion Slide 2

3 Overview General Introduction Introduction to charge power conversion technologies Experiments Results Conclusion Slide 3

4 Introduction General The formation process is still the most time and energy consuming process when manufacturing batteries. The requirement to increase capacity while reducing operating expenses is a common request. Formation times have been significantly reduced by battery design, the use of addititives and process changes. Slide 4 A goal of any progressive battery manufacturer is to shorten formation time while reducing energy consumed during the process. The requirement to increase capacity while reducing operating expense is a common request. Battery manufactures are looking for innovative solutions from formation system suppliers that provide a competitive edge. That edge may be lower cost to manufacture, improved product quality or some combination of both.

5 Introduction General Digatron/Firing Circuits formation charging rectifiers provide high current output and allow PC controlled formation processes to take advantage of the efficient cooling methods optimizing the formation processes.? There are two leading power conversion technologies used in formation charging rectifiers. Slide 5 Digatron/Firing Circuits formation charging rectifiers provide high current output and allow PC controlled formation processes to take advantage of the efficient cooling methods optimizing the formation processes. There are two leading power conversion technologies used in formation charging rectifiers

6 Introduction General The objective is to evaluate the two power conversion technologies in terms of the following characteristics: Process efficiency Battery quality and performance Crystalline structure of active material Slide 6 The objective of this paper is to evaluate the two power conversion technologies in terms of the following characteristics: - Process efficiency - Battery quality and performance - Crystalline structure of active material

7 Overview General Introduction Introduction to charge power conversion technologies Experiments Results Conclusion Slide 7

8 Introduction SCR Technology The traditional SCR technology uses phase angle control to regulate DC output. 60A 6A Slide 8 The traditional SCR technology uses phase angle control to regulate DC output. The DC output signal contains a characteristic 300 Hz current ripple component with an almost constant RMS value within the output range of 10 to 100%.

9 Introduction SCR Current Ripple AC current ripple (i rms ) to DC output current (Id ) 70% 60% 50% 40% 30% 20% 10% 65% 33% 22% 16% 13% SCR 0% 0,0 0,2 0,4 0,6 0,8 1,0 DC output current (I d ) to Full scale DC output current (I dnom ) Slide 9 For this reason ripple as a percentage of total DC output is greatest at low current levels.

10 Introduction SCR Power Factor cosφ 1,0 0,87 Power Factor cosphi 0,8 0,6 0,4 0,35 0,53 0,70 0,2 0,18 0,0 0,0 0,2 0,4 0,6 0,8 1,0 Output Voltage as a Percentage of Full Scale Slide 10 There is a direct correlation between power factor and output voltage. When battery string voltage is low with respect to full scale output the power factor will also be low. As battery string voltage increases the power factor improves in an almost linear relationship. Phase angle control technology requires reactive power which must be compensated for, with Power Factor Correction (PFC) equipment. SCR based rectifiers introduce undesirable harmonics to the AC power line which must be considered when specifing PFC equipment.

11 Introduction IGBT Technology The IGBT based switch mode technology uses pulse width modulation to regulate DC output. 60A 6A Slide 11 The IGBT based switch mode technology uses pulse width modulation to regulate DC output. Filter components such as chokes and capacitors of a given package size are significantly more effective when used at 20 khz than when used in SCR circuits at 300 Hz.

12 Introduction Current Ripple 70% 65% AC current ripple (i rms ) to DC output current (Id ) 60% 50% 40% 30% 20% 10% 33% 22% 16% 13% SCR IGBT 0% 0,0 0,2 0,4 0,6 0,8 1,0 DC output current (I d ) to Full scale DC output current (I dnom ) Slide 12 A characteristic of IGBT circuits is that current ripple is very low, typically less than 1% throughout the output range with worst case ripple at 50% of full scale output and best case at the output extremes.

13 Introduction Power Factor cosφ 1,0 0,98 0,87 Power Factor cosphi 0,8 0,6 0,4 0,35 0,53 0,70 SCR IGBT 0,2 0,18 0,0 0,0 0,2 0,4 0,6 0,8 1,0 Output Voltage to Full Scale Output Voltage Slide 13 The power factor of IGBT circuits is constant at 0.98 throughout the output range.

14 Introduction Individual Harmonic Distortion ,0 Amplitude [%] ,0 7,5 7,3 SCR IGBT 5 0 4,0 4,0 4,0 3,8 2,7 2,8 0,5 1,0 0,8 1, Harmonics Slide 14 This slide displays the individual harmonics at full output for SCR and IGBT circuits. It is obvious that the 5th, 7th and 11th harmonics are the most significant. Harmonics must be considered when specifing Power Factor Correction equipment.

15 Introduction This presentation attempts to answering the following common questions: Is one power conversion technology inherently better suited to shorten formation time? more efficient than the other? Does power conversion technology influence battery performance? influence heat generation in batteries during formation process? influence the crystalline structure of active material? Slide 15 This presentations attempts to answering the following common questions: Is one power conversion technology inherently better suited to shorten formation time? more efficient than the other? Does power conversion technology influence battery performance? influence heat generation in batteries during formation process? influence the crystalline structure of active material?

16 Overview General Introduction Introduction of charge power conversion technologies Experiments Results Conclusion Slide 16

17 Experiments Description One formation process was started with DIN EN 630xx truck batteries (130Ah) optimized for cold cranking applications using 6x 60A/360V SCR charge circuits, each circuit 18 batteries and 6x 60A/360V IGBT charge circuits, each circuit 18 batteries One formation process was started with DIN EN 640xx truck batteries (140Ah) optimized for cycle life using 6x 60A/360V SCR charge circuits, each circuit 18 batteries and 6x 60A/360V IGBT charge circuits, each circuit 18 batteries For each battery type processes were started at the same time with identical programs Slide 17 One formation process was started with DIN EN 630xx truck batteries (130Ah) optimized for cold cranking applications using 6x 60A/360V SCR charge circuits, each circuit 18 batteries and 6x 60A/360V IGBT charge circuits, each circuit 18 batteries. One formation process was started with DIN EN 640xx truck batteries (140Ah) optimized for cycle life using 6x 60A/360V SCR charge circuits, each circuit 18 batteries and 6x 60A/360V IGBT charge circuits, each circuit 18 batteries For each battery type processes were started at the same time with identical programs

18 Experiments Test to evaluate AC data Battery Manager Formation PC to evaluate DC data 12x 60A/360V SCR IGBT 12x 60A/360V Water bath 12 strings each of 18 batteries AC power net analyzer to evaluate AC data Water bath 12 strings each of 18 batteries Slide 18 One 3-phase power net analyzer was connected to the AC input of the SCR rectifier and another was connected to the AC input of the IGBT rectifier. The analyzer was used to evaluate AC data for real power, reactive power, cosphi and total harmonics distortion (THD). Battery Manager PC software was used to control the formation process and to evaluate all DC data and electrolyte temperatures

19 Experiments Test to evaluate battery performance Evaluation in compliance with DIN EN Data Battery 1 Battery 2 Battery 3 Battery 4 Battery 5 t 10.5V Capacity C20 Capacity C20 Capacity C20 Capacity C20 Capacity C20 V 10s, t 6V Cold cranking Cold cranking Cold cranking Cold cranking Cold cranking t 10.5V Capacity C20 Capacity C20 Capacity C20 Capacity C20 Capacity C20 V 10s, t 6V Cold cranking Cold cranking Cold cranking Cold cranking Cold cranking t 10.5V Capacity C20 Capacity C20 Capacity C20 Capacity C20 Capacity C20 V 10s, t 6V Cold cranking Cold cranking Cold cranking Cold cranking Cold cranking C, I 10min Charge acceptance Charge acceptance Charge acceptance Charge acceptance Charge acceptance Slide 19 5 sample batteries per formation batch were selected for test and shipped to an independant battery laboratory. One additional sample was selected for scanning electronic microscope (SEM) analysis. The tests were conducted in compliance with DIN EN Three cycles were completed consisting of capacity C20 test and a cold cranking test followed by a single charge acceptance test. Data from each 5 sample batch was averaged. Testing generated 7 data files per battery times 5 batteries per test batch times 4 formation batches consisting of the following: - DIN EN 630xx battery formation using SCR rectifier - DIN EN 630xx battery formation using IGBT rectifier - DIN EN 640xx battery formation using SCR rectifier - DIN EN 640xx battery formation using IGBT rectifier which resulted in 140 datafiles to be evaluated.

20 Experiments Test to evaluate heat generated during formation Temperature datalogger SCR formation circuit IGBT formation circuit Water baths with 20 C initial temperature Slide 20 Water baths were filled with 20 C water to establish a common temperature at the start of test. Separate water baths were used to isolate the test samples from the formation system water bath. Battery in bath 1 was connected to the formation string of the SCR rectifier. Battery in bath 2 was connected to the formation string of the IGBT rectifier. Battery Manager PC software was used to control the formation processes and to monitor electrolyte temperature data.

21 Overview General Introduction Introduction of charge power conversion technologies Experiments Results Conclusion Slide 21

22 Results DC Output Power 12h Formation Profile DC Output Power [kw] :00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 Formation Process Time Slide 22 This graph represents the DC output power profile generated by the charge regime defined in the Battery Manager program editor. This profile is identical for both SCR and IGBT circuits.

23 Results DC Output Power compared to IGBT AC Input Power Power [kw] :00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 AC input Formation Process Time DC output Slide 23 When we compare the DC output power profile to the AC input power profile we see how insignificant the losses are with IGBT technology.

24 Results IGBT AC Input Power compared to SCR AC Input Power Power [kw] Daten pflegen :00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 Formation Process Time IGBT AC input SCR AC input Slide 24 When we compare the IGBT AC input power profile to the SCR AC input power profile we can see the efficiency advantage gained with IGBT technology.

25 Results SCR Real AC Input Power compared to Reactive Input Power AC Input Power [kw] :00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 Formation Process Time Real AC input Reactive AC input Slide 25 In addition to real power the SCR circuits consume a significant amount of reactive power which will require special power factor correction (PFC).

26 Results IGBT Energy Counter and Efficiency Input AC Energy Counter Output DC Energy Counter Real kwh kwh Reactive kvarh 94,2% IGBT efficiency [%] Minimum 85,5 Average 94,2 Maximum 97,6 Slide 26 During the 12h formation period the charged energy was 1170 kwh and the real energy consumed was 1242 kwh yielding an average efficiency of 94,2%. The minimum efficiency of 85,5% occures only during the inital phase of formation when battery string voltage and charge currents are low. High efficiency is achieved if battery string voltage is above 50% and current is around 75% of full scale output. Maximum efficiency of 97.6% was recorded at 262V and 44.75A. Because the reactive power is so low it is not compensated for or considered in this calculation.

27 Results SCR Energy Counter and Efficiency Real Input AC Energy Counter kwh Output DC Energy Counter kwh SCR efficiency [%] kvarh Reactive 91,2% Minimum 89,9 Average 91,2 Maximum 94,6 Slide 27 During the 12h formation period the charged energy was 1170 kwh and the real energy consumed was 1283 kwh yielding an average efficiency of 91,2%. The minimum efficiency of 89,9% occures only during the inital phase of formation when battery string voltage and charge currents are low. High efficiency is achieved at maximum DC power output. Unlike the IGBT circuits the reactive power is so high and must be compensated for. The inefficiencies associated with PFC compensation are not considered here.

28 Results Efficiency 1,00 Output Power to Input Power 0,98 0,96 0,94 0,92 0,90 0,88 0,86 0,84 0,00 0,20 0,40 0,60 0,80 1,00 Output Power to Nominal Power SCR IGBT Slide 28 The graph compares the measured efficiency of SCR and IGBT power conversion technologies throughout the DC output power range. IGBT circuits are up to 5% more efficient than SCR circuits within the output range from 30 to 80%.

29 Results Power Factor cosφ versus output power range 1,1 1,0 Power Factor cosphi 0,9 0,8 0,7 0,6 SCR IGBT 0,5 0,4 0,0 0,2 0,4 0,6 0,8 1,0 Output Power to Nominal Power Slide 29 The graph compares the measured cosphi of SCR and IGBT power conversion technologies throughout the DC output power range. The power factor for the IGBT circuit is significantly greater than the SCR circuits throughout the output range and approaches a factor of 1.0 from 40% to 100% of full scale power.

30 Results Power Factor cosφ versus formation process time 1,1 1,0 Power Factor cosphi 0,9 0,8 0,7 0,6 SCR IGBT 0,5 0,4 18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 Formation Process Time Slide 30 This graph shows the measured power factor for each technology throughout the 12h formation profile. The average power factor for the SCR was 0,66 and for the IGBT 0,98.

31 Results Total Harmonic Distortion versus formation process time 50 Total Harmonics Distortion (THD) [%] :00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 Formation Process Time SCR IGBT Slide 31 This graph shows the measured total harmonic distortion (THD) for each technology throughout the 12h formation profile. The average THD for the SCR was 32% and for the IGBT 13%. With Digatron / Firing Circuits transformer techniques the harmonic characteristic of an SCR rectifier can be reduced down to 20% THD.

32 Results Temperature Formation Profile Electrolyte temperature [ C] SCR IGBT 0 0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 24:00 0:00 Formation process time [h] Slide 32 The data collected here goes against the widely held asumption that there is a strong correlation between the output ripple typical of SCR circuits and heat generated during the formation process. One must conclude that there is no significant difference between SCR and IGBT circuits relating to heat generation during formation for the battery types tested.

33 Results C20 capacity test, discharged and recharged capacity SCR DCH SCR CHA IGBT DCH IGBT CHA SCR DCH SCR CHA IGBT DCH IGBT CHA Capacity (charge/recharge) [Ah] 225,00 200,00 175,00 150,00 125,00 100,00 1,00 2,00 3,00 Testcycle DIN EN 630xx Capacity (charge/recharge) [Ah] 225,00 200,00 175,00 150,00 125,00 100,00 1,00 2,00 3,00 Testcycle DIN EN 640xx Slide 33 The data here indicates there is no siginificant difference after the third cycle in discharge and recharge capacity for both battery types.

34 Results C20 discharge time down to 10.5V 1 1 Testcy cle Time [h] IGBT SCR Time [h] DIN EN 630xx DIN EN 640xx Slide 34 Again the data indicates there is no significant difference between the two technologies in the C20 discharge test.

35 Results Cold cranking test, voltage after 10s discharge 8,50 8,50 Voltage after 10s discharge [V] 8,00 7,50 7,00 6,50 8,00 7,50 7,00 6,50 6, Testcycle SCR 6,00 IGBT Testcycle DIN EN 630xx DIN EN 640xx Slide 35 The 10s voltage data during cold cranking provides similar results.

36 Results Cold cranking discharge time down to 6V 1 Testcy cle Time [ min] IGBT SCR Time [ min] DIN EN 630xx DIN EN 640xx Slide 36 And also cold cranking discharge time to 6V.

37 Results Charge acceptance current after 10 min at 14.4V ,0 Ah 8,8 Ah Charge current [A] ,9 Ah 5,1 Ah SCR IGBT 10 0 DIN EN DIN EN Battery group Slide 37 Unlike the previous tests we do find a significant difference in charge acceptance performance of batteries formed with IGBT circuits. This data is especially significant due to the small standard deviation in the data collected.

38 Results Crystalline structure SCR DIN EN130xx IGBT Slide 38 SEM analyzis of the crystalline structure of active material revieled no significant difference in crystal size, quantity and surface area.

39 Results Crystalline Structure SCR DIN EN140xx IGBT Slide 39

40 Overview General Introduction Introduction of charge power conversion technologies Experiments Results Conclusion Slide 40

41 Conclusion Answers to the following common questions: Is one power conversion technology inherently better suited to shorten formation time? more efficient than the other? Does power conversion technology inherently influence heat generation in batteries during formation process? influence battery performance? influence the crystalline structure of active mass? Slide 41 Based on the test results we can conclude the power conversion technology does not influence formation time.

42 Conclusion Formation Process Time depends on: Formation process and battery chemistry (Electrolyte circulating, new additives to active material) Formation process (Cooling method, varying acid density, increase of charging current) Final capacity at the end of formation Charging factor Formation Process 6h 12h Formation Process Time 48h Slide 42 Formation process time is determined by: - charging factor - final capacity to be achieved during the process as set by the manufacturer - formation process methods such as cooling, varying acid density, increasing charging currents - battery chemistry and use of additives - the reliability of the process control equipment

43 Conclusion This presentation attempts to answering the following common questions: Is one power conversion technology inherently better suited to shorten formation time? more efficient than the other? Does power conversion technology inherently influence heat generation in batteries during formation process? influence battery performance? influence the crystalline structure of active mass? Slide 43

44 Conclusion Energy cost calculation based on the experiment Nominal DC power DC energy Real AC energy Rectifier efficiency Efficiency losses due to PFC 10W/kvar * 130 kvar Total efficiency Total AC energy Energy cost difference SCR: 259,2 kw kwh kwh 91,2 % -0.5 % 90,7 % kwh +3,8 % IGBT: 259,2 kw kwh kwh 94,2 % not required 94,2 % kwh Slide 44 The table shows that the SCR circuits will consume 3.8% more energy than an IGBT circuit during the formation process.

45 Conclusion This presentation attempts to answering the following common questions: Is one power conversion technology inherently better suited to shorten formation time? more efficient than the other? Does power conversion technology inherently influence heat generation in batteries during formation process? influence battery performance? influence the crystalline structure of active mass? Slide 45 There is no significant difference between SCR and IGBT circuits relating to heat generation during formation for the battery types tested.

46 Conclusion This presentation attempts to answering the following common questions: Is one power conversion technology inherently better suited to shorten formation time? more efficient than the other? Does power conversion technology inherently influence heat generation in batteries during formation process? influence battery performance? influence the crystalline structure of active mass? Slide 46 There is no significant difference between SCR and IGBT circuits relating to battery performance except charge acceptance for the battery types tested.

47 Conclusion This presentation attempts to answering the following common questions: Is one power conversion technology inherently better suited to shorten formation time? more efficient than the other? Does power conversion technology inherently influence heat generation in batteries during formation process? influence battery performance? influence the crystalline structure of active material? Slide 47 SEM analyzis of the crystalline structure of active material revieled no significant difference in crystal size, quantity and surface area.

48 Conclusion Ultimately it is the goal of this presentation to reduce the test results and conclusions to a set of practical guidelines that can be applied by battery manufacturers when making decisions regarding the selection and purchase formation rectifier equipment. The test results indicate there is no significant advantage to either SCR or IGBT technology when considering key factors including process control, battery quality or battery life. That given one must consider the financial aspects when making a purchase decision. If your formation line includes SCR rectifiers with significant service life remaining there is no financial justification for replacement with IGBT. The 3-5% energy savings with IGBT will not result in positive return on investment in the near term. If your local utility has required PFC that investment has already been made and cannot be recouped. Maintenance personnel are already quite familiar with SCR technology, PM procedures, repair processes and typically there has been a significant investment in spare parts inventory that would not be compatible with IGBT rectifiers. If your formation line includes IGBT rectifiers we recommend continuing with this technology. There is the benefit of energy savings and you will avoid the need for additional PFC equipment when increasing capacity. If your objective is to outfit a new facility we recommend you consider IGBT technology for the same reasons. Slide 48 Ultimately it is the goal of this presentation to reduce the test results and conclusions to a set of practical guidelines that can be applied by battery manufacturers when making decisions regarding the selection and purchase formation rectifier equipment. The test results indicate there is no significant advantage to either SCR or IGBT technology when considering key factors including process control, battery quality or battery life. That given one must consider the financial aspects when making a purchase decision. If your production line includes SCR rectifiers with significant service life remaining there is no financial justification for replacement with IGBT. The 3-5% energy savings with IGBT will not result in positive return on investment in the near term. If you local utility has required PFC that investment has already been made and cannot be recouped. Maintenance personnel are already quite familiar with SCR technology, PM procedures, repair processes and typically there has been a significant investment in spare parts inventory that would not be compatible with IGBT rectifiers. If your formation line includes IGBT rectifiers we recommend continuing with this technology. There is the benefit of energy savings and you will avoid the need for additional PFC equipment when increasing capacity. If your objective is to outfit a new facility we recommend you consider IGBT technology for the same reasons.

49 Conclusion Digatron/Firing Circuits is a leading supplier of both SCR and IGBT formation rectifiers. SCR rectifiers have been furnished to hundreds of battery manufacturers worldwide over more than three decades. Our first installation of IGBT rectifiers was commissioned some 8 years ago and has proven extremely reliable. Technical data for IGBT rectifiers is as follows: Standard current ranges from 30A to 60A Voltage ranges up to 440VDC Up to 16 circuits in one cabinet Efficiency up to 98% Power factor up to 0,98 Isolated secondary for each circuit to eliminate circuit interaction and for safety Paralleling of circuits for higher current output Constant current pulse discharge and depolarization discharge Slide 49 Digatron/Firing Circuits is a leading supplier of both SCR and IGBT formation rectifiers. SCR rectifiers have been furnished to hundreds of battery manufacturers worldwide over more than three decades. Our first installation of IGBT rectifiers was commissioned some 8 years ago and has proven extremely reliable. Technical data for IGBT rectifiers is as follows: Standard current ranges from 30-60A, other ranges available Voltage output to 440VDC Up to 16 circuits in a cabinet Efficiency up to 98% Power factor up to 0.98 Isolated secondary for each circuit to eliminate circuit interaction and enhance safety Paralleling of circuits for higher current output

50 Contact us today and get the new formation brochure Slide 50