Battery Pack Design MVKF25-vt17

Transcription

1 Battery Pack Design MVKF25-vt17 Mechanical and electrical layout, Thermal modeling, Battery management 25-27/4 Avo Reinap, IEA/LU

2 Goals Design and dimensioning of battery pack based on suitable models evaluate suitable battery technologies, specify cell and packing, electric and thermal termination battery development and energy management systems, predict state of charge, health, function,.. testbattery compatibility to operating conditions, current waveforms Ageing model Thermal model Electrical model Avo R MVKF25-vt17 Battery Pack Design 2

3 Background A Battery and Propulsion Vehicular application Electrification improves energy usage hybrids use ICE at 35% instead of 10-20% efficiency Reuse deceleration energy for acceleration Pure renewable fuel/energy System view Charging, static vs dynamic Compatability, AC current loading Avo R MVKF25-vt17 Battery Pack Design 3

4 Background B Part-III Battery usage Pack design (Ch5) Management (Ch6) State and degradation (Ch7) Part-I & II Li-ion battery technology Cell components (Ch1) Cell materials (Ch3) Cell design (Ch4) Avo R MVKF25-vt17 Battery Pack Design 4

5 Fig.Ref.: EDPC 14, EDPC 15 Background C Electrical machine design Directly air-cooled cooled laminated machine windings Indirect oil-cooled stator-core and end-turns Enhanced winding thermal conductivity Avo R MVKF25-vt17 Battery Pack Design 5

6 Content Design path from topology sketching to practical realization Cell, Module, Pack/Bank Battery = Energy storage [Wh] & Power supply [W] Applications: Vehicle/Grid Technologies: Li-ion Battery cell Geometries and dimensions Characteristics and properties Cell virtual packing Electro-Thermal models Packing examples Thermal design Cells, modules, backs Battery Management System Avo R MVKF25-vt17 Battery Pack Design 6

7 Design Energy Conversion kg Construction Production kw, kwh A cross-road of different disciplines Multi-dimensional (analysis) & multi-objective (synthesis).. Avo R MVKF25-vt17 Battery Pack Design 7

8 Specific energy and power Specific energy originates from material chemistry Capacity capability Specific power is related to material physics and production Internal power losses and thermal constrains durability and safety Avo R MVKF25-vt17 Battery Pack Design 8

9 Fig.Ref.: B. Averill, P. Eldredge, General Chemistry: Principles, Patterns and Applications Value chain for EV batteries From cell realization to recycling (excluding raw materials) Vehicle power (performance), energy (range) and integration (BMS) Avo R MVKF25-vt17 Battery Pack Design 9

10 Lithium-ion batteries: How do they work? Avo R MVKF25-vt17 Battery Pack Design 10

11 B. Averill, P. Eldredge, General Chemistry: Principles, Patterns and Applications Electrochemical cell Chemical reaction = two half-reactions: oxidation+reduction=redox Side reactions due to thermal loads, pressure? Active, electrodes, non-active, the rest including electrolyte, components Avo R MVKF25-vt17 Battery Pack Design 11

12 R. Purkayastha, R.M. McMeeking, "A Linearized Model for Lithium Ion Batteries and Maps for their Performance and Failure" ASME Lithium Battery Technologies Optimal performance and lifetime capacity Case sensitive: application vs cell configuration Abbr Wh/kg Lithium cobalt oxide LiCoO 2 LCO Lithium manganese oxide LiMn LMO 4.0V Lithium iron phosphate LiFePO 4 LFP 3.2V Lithium nickel manganese cobalt oxide LiNiMnCo0 2 NMC 3.7V Lithium nickel manganese aluminum oxide LiNiCoAlO 2 NCA Lithium titanate Li 4 Ti 5 O 12 LTO Avo R MVKF25-vt17 Battery Pack Design 12

13 M. Yazdanpour, A circuit-based approach for electro-thermal modeling of Lithium-Ion batteries Cell material properties example material Thickness [μm] Thermal conductivity [W/mK] Electrical conductivity [S/m] + I collector aluminum e6 + Electrode (wet) 13.9 (wet) Electrolyte wet Separator (wet) - Electrode (wet) 100 (wet) - I collector copper e6 case Avo R MVKF25-vt17 Battery Pack Design 13

14 Thermal management system Historic usage affects availability of energy and power in future BMS = preferred and optimized usage BTMS includes temperature control Purpose of BTMS Maintain operational temperature Assure temperature uniformity Challenges Temperature increase at high power load Heat-up time in prior to start-up Avo R MVKF25-vt17 Battery Pack Design 14

15 Battery performance degradation Degradation deterioration of useful capacity and power capabilities Identification of physical and chemical processes behind degradation mechanisms. Origins related to technology and usage. SoH state of health remaining capacity due to ageing Avo R MVKF25-vt17 Battery Pack Design 15

16 Battery failure Safety=thermal stability BTMS is very important for performance and safety Failure mechanisms External/internal internal short circuits Mechanical, electrical, thermal abusive conditions Failure propagation from cell to module and pack Avo R MVKF25-vt17 Battery Pack Design 16

17 Thermal runaway Rapid temperature increase Most likely due to internal spontaneous short circuits due to impurities (that can grow during time as side effect of chemical reactions) Avoid thermal runaway Overcharge/discharge protection activated by over pressure Current interrupt device (CID) Positive temperature coefficient (PTC) Separator specified for PTC & CID, layered separators for reducing internal short circuits Avo R MVKF25-vt17 Battery Pack Design 17

18 Question 1.1 What are the criteria for the design of suitable thermal management system for a battery back? Battery (cell) design? Parameters related to heating? Factors influencing the heat transport and dissipation? Avo R MVKF25-vt17 Battery Pack Design 18

19 Battery modelling A Simple limited data Cell voltage U=E o -R o I where R o is internal resistance and E o is open circuit voltage (OCV) Ignoring that E o and R o depends on SoC and temperature Heating power Q=(R o I) 2 only Ohmic losses Ignoring reversible heat loss, R o depends on SoC and temperature Transient temperature rise T=QRh(1-e -t/rhch ) Thermal properties are not an easy target! Avo R MVKF25-vt17 Battery Pack Design 19

20 Equivalent circuit relations Relation Electrical circuit Magnetic circuit Thermal circuit Cooling circuit Potential U=E l N I=H l =G l P= l Flow I=J A Φ=B A Q=q A Q=v A Conductive element G=γ A/ l G=μ A/l G=λ A/l G= A/l Ohm s Law U=I R N I=Φ R =Q R P=Q R Avo R MVKF25-vt17 Battery Pack Design 20

21 Battery modelling B current voltage DoD Electrical model SoH Ageing model power temperature Thermal model Depth of discharge DoD {0 1} {max(u cell ) min(u cell )} Inner voltage source (OCV) E(DoD)=U cell (I,DoD)R dch (DoD)*I Charge R ch and discharge R dch resistors depends only on DoD Usually Eo and Ro available Also U and T Avo R MVKF25-vt17 Battery Pack Design 21

22 Cell construction Electrode arrangement: spiral wound jelly roll, stacked electrodes, bobbin type Geometry: Cylindrical, Prismatic, Pouch, Button Components Case: plastic (PET) or metallic (steel, Al) Core=active components +collectors, separator Terminals Avo R MVKF25-vt17 Battery Pack Design 22

23 18650 Li-ion Standard (size) cylindrical Li-ion cells ø18h65mm Avo R MVKF25-vt17 Battery Pack Design 23

24 Prismatic Cells Some cell producers Hitachi, Samsung-SDI, Panasonic (Sanyo) Prismatic cell L, [mm] W, [mm] T, [mm] M, [kg] U, [V] C,[Ah] p, [W/kg] c, [Wh/kg] Hitatchi SDI-1 37 SDI-2 60 SDI-3 94 Avo R MVKF25-vt17 Battery Pack Design 24

25 Kokam.com Kokam s SLPB cell SLPB Superior Lithium Polymer Battery Pouch type improved heat dissipation due to larger surfaces Example 240Ah 4.8kg cell 480A Acool=2x0.15 m 2 V=46.2x32.7x1.58 cm specific energy, w cell [Wh/kg] Kokam large cells SLPB specific power, p cell [W/kg] Avo R MVKF25-vt17 Battery Pack Design 25

26 Overview of cell producers for xevs It is easier to find producer than product ;) Avo R MVKF25-vt17 Battery Pack Design 26

27 Battery back sizing Number of series connected cells in strings Ns=Udc/Ucell Number of parallel connected strings Np=Energy/(Ns*[Wh/kg]*[kg]) Np=Energy/(Ucell* cell capacity ) Avo R MVKF25-vt17 Battery Pack Design 27

28 Calculation example Ch4 Cell data Ch5 EV and HEV spec 300 V * 100 A Pmax = 2*30kW P/E ratio 2 and 20 Avo R MVKF25-vt17 Battery Pack Design 28

29 Specification list Forced heating/cooling for battery back Concepts, topologies, realization ideas, Battery cell Construction, properties, heat sources, thermal loads, Heat conductor Thermal accessibility, thermal contacts, Cooling plate Realisation, performance, Source Link Sink Avo R MVKF25-vt17 Battery Pack Design 29

30 Question 1.2 Battery pack specification Power demand? Capacity? Weight or size? Avo R MVKF25-vt17 BTMS Battery Pack Design 30

31 Thermal design Heat Electricity Methods, models, calculation examples for thermal design Practical realisation examples from some car manufacturers Avo R MVKF25-vt17 Battery Pack Design 31

32 Thermal modelling Models 1D, 2D, 3D analytic or numeric Computation time vs accuracy, Single cell, a module of cells, battery back Specification of equivalent cell volume with specific losses, Assembling, heat transport and temperature distribution Mechanical assembly and thermal accessibility, thermal contacts Integration of active cooling circuits Realisation, estimation of coolant flow and performance, Source Link Sink Avo R MVKF25-vt17 Battery Pack Design 32

33 Thermal integration Direct cooling where it is most needed in order to minimize heat transport through the solids that causes interior temperature rise and uneven temperature distribution Consider the effects of thermal cycling and expansion Experiences from other electric drive components Avo R MVKF25-vt17 Battery Pack Design 33

34 Thermal design simplifies control and BMS Cells (EL+Chemi) modules (Heat) battery pack (Duty) Battery thermal management Keep temperature & use little energy for operation Keep it Simple is the rule of the day Prototype development and prototyping supported buy models CAD (SW) components and parts (Ansys or Comsol fluids and solids) system (Simulink/Matlab) Avo R MVKF25-vt17 Battery Pack Design 34

35 Thermal model Ccell d dt Q cell C P cell c P fluid, out cell h surf R cell Rcell P cell fluid, in 1 C cell surf Rlink fluid representing physical reality (?) Main focus on only on reasonable cell surface temperature surf as cell is remains unknown (?) surf = fluid + R*P Thermal resistances: simplifications vs idealisation Practical realization for fluid dynamics Thermography for rapid thermal assessment Avo R MVKF25-vt17 Battery Pack Design 35

36 Model library Impedance based equivalent circuit models, dynamic experiment based Physics and chemistry-based models relay on model parameterisation and properties Energy or power-flow models are typically used on a system level Empirical models black box models suitable for control not design Avo R MVKF25-vt17 Battery Pack Design 36

37 Avo R MVKF25-vt17 Battery Pack Design 37

38 Cell library Selected cell examples: cylindrical, prismatic, pouch This information is used for virtual packing and rough estimation on temperature rise and distribution Manufacturer configuration Geometry Voltage Capacity Specific power Weight [mm] [V] [Ah] [W/kg] [g] Panasonic Cylindrical Ø18.5x Hitatchi Prismatic 148x91x Kokam Pouch 462x327x Avo R MVKF25-vt17 Battery Pack Design 38

39 Cell virtual packing For 300V there is need of 84 series connected 3.6V cells First draft of 148x26.5 mm prismatic cell arrangement where 5 mm distance is left between the rows and groups of 7 cells First draft of ø18 mm 4 parallel cylindrical cell arrangement with cooling channel in between the cells Not only visualization but a parameterized model with coupling to finite element analysis (FEA) Avo R MVKF25-vt17 Battery Pack Design 39

40 Electric connection of cells Series-parallel connections Connection-bars and cables are part of heat generation but also distribution Nickel plate + spot welding = healthy low resistance connections Avo R MVKF25-vt17 Battery Pack Design 40

41 Estimation of thermal conductivity L eff eff ins L k f cond cond ins k 1 k f L cond 1 k L k 1 k ins f f ins f cond cond ins f Equivalent thermal conductivity of a coil is given by the filling factor of the conductor foil (copper in this example) and the thermal conductivity of the medium between the conductor foils jelly-roll:12% Al+Cu λ>200w/mk, 6% eparator λ<0.35w/mk, rest λ~1w/mk Across coil or roll λ~1w/mk, along λ>>1w/mk Avo R MVKF25-vt17 Battery Pack Design 41

42 Using 2D FE for sketching FEMM electromagnetism, heat transfer, electric currents Easy to use, library of Matlab functions Drawing the endpoints of the lines and arc segments for a region, Connecting the endpoints with either line segments or arc segments to complete the region, Defining material properties and mesh sizing for each region, Specifying boundary conditions on the outer edges of the geometry. Avo R MVKF25-vt17 Battery Pack Design 42

43 Battery pack with cylindrical cells Empty space between cells Cross-flow through battery module Narrow spacing expectedly no cooling Large spacing for sake of better cooling is often considered impractical CFD vs fast design approaches Avo R MVKF25-vt17 Battery Pack Design 43

44 Battery back with prismatic cells Temperature homogenization analysis Analysis of thermal runaway Avo R MVKF25-vt17 Battery Pack Design 44

45 Battery pack with pouch cells Coupled electro-thermal FE+model order reduction (MOR) simulation compared to thermographic images A reduced order model (ROM) based on singular value decomposition (SVD) Direct air-cooled Li-ion pouch battery cell in order to improve the understanding (modelling) and practical realization of battery module Avo R MVKF25-vt17 Battery Pack Design 45

46 Vehicular application Avo R MVKF25-vt17 Battery Pack Design 46

47 Avo R MVKF25-vt17 Battery Pack Design 47

48 Chevy 104kW 20kWh GM Volt and Spark EV use thin prismatic shaped cooling plates in between the cells with the liquid coolant circulating thru the plate. The Volt cooling scheme is very effective from a cooling point of view but it is complicated. The cells are encased in multiple plastic frames Avo R MVKF25-vt17 Battery Pack Design 48

49 Tesla S 285kW 70kWh Tesla snakes a flattened cooling tube thru their cylindrical cells resulting in a very simple cooling scheme with very few points for leakage. Avo R MVKF25-vt17 Battery Pack Design 49

50 BWM i3 125kW 21-33kWh The BMW i3 cools the bottom of the battery case with refrigerant eliminating the liquid coolant entirely. New energy dense lithium ion cells (50% more) Avo R MVKF25-vt17 Battery Pack Design 50

51 Integration example by BMW Avo R MVKF25-vt17 Battery Pack Design 51

52 Integration example by Tesla 60kWh, 352V, 14 modules, 6216 cells in groups of 74=6x14 85kWh, 402V, 16 modules, 7104 cells Avo R MVKF25-vt17 Battery Pack Design 52

53 Integration example by Tesla Avo R MVKF25-vt17 Battery Pack Design 53

54 Accommodation of cylindrical cells Avo R MVKF25-vt17 Battery Pack Design 54

55 Cool-plate and coolant Single stage heat transfer insufficient ha vs UA Avo R MVKF25-vt17 Battery Pack Design 55

56 Coolant Air H 2 C0 2 H 2 0 Tr Oil, degc c, kj/kgk , kg/m λ,mw/mk , upas Avo R MVKF25-vt17 BTMS Battery Pack Design 56

57 Conjugate heat transfer The character of flow is described by Reinolds number, Re 1 vdh Q A the heat transfer is expressed by Nusselt number Nu h k D h k in wall D h qdh bulk in and the coolant is described by Prandtl number c p Pr k The hydraulic diameter is related to the geometric layout of the cooling channel area D h 4 perimeter P cool cq P ha out heat cool win d cool d cond Avo R MVKF25-vt17 Battery Pack Design 57 L h L

58 B. Sundén, Introduction to Heat transfer Heat transfer mapping Cooling power, p= c p Q( out - in ) [W] Heat transfer coefficient, h=nu k/d 30 [W/(m 2 K)] h Temperature across boundary, P cool /(ha cool ) [ C] Pressure drop, dp 28 [Pa] Ideal cooling supply power, 27 dpq [-] Cooling power, p= c flow rate, Q [L/min] p Q( out - in ) [W] flow rate, Q [L/min] flow rate, Q [L/min] flow rate, Q [L/min] flow rate, Q [L/min] flow rate, Q [L/min] flow rate, Q [L/min] Driving parameters for cooling P=f( out,q) at in Flow (Re) and coolant (Pr) characterization Reynolds number, Re=2d h Q/(A ) [-] Nusselts number, Nu=f(Re,Pr) [-] Heat transfer correlations (Nu) and coefficient h Wall and winding temperature Pressure across cooling channel Power for supply Expected cooling power P=f( w,q) at in Avo R MVKF25-vt17 Battery Pack Design 58 outlet temperature, out [ C] outlet temperature, out [ C] outlet temperature, out [ C] outlet temperature, out [ C] outlet temperature, out [ C] outlet temperature, out [ C] outlet temperature, out [ C] wall temperature, out [ C] outlet temperature, out [ C] flow rate, Q [L/min] c=3500j/kgk, =900kg/m 3 cooling power, p= c p Q( out - in ) [W] flow rate, Q [L/min]

59 Thermal analysis of cell assembly Hitachi 3.6v 35Ah 155x27x118 incl terminals 810g Geometric data Defined by German standard DIN Heat transfer inside the cell From cell to module and pack Cell = Jelly-roll (heater) + carrier (assembly) Heating power Worst case P=I 2 R o =50W Avo R MVKF25-vt17 Battery Pack Design 59

60 Thermal accessibility of a cell Available thermal connection areas Large long sides 2x134cm 2 but low thermal conductivity Sides, lateral sides 2x24cm 2 and Bottom side 39cm 2 Bottom and short sides have expectedly better inherit thermal contact Avo R MVKF25-vt17 Battery Pack Design 60

61 H. Lundgren et al, Thermal Management of Large-Format Prismatic Lithium-Ion Battery in PHEV Application Inside a battery cell Cell dimensions are known, jelly-roll geometry only guessed DIN SPEC 91252:2011 Lundgren et al 2016 Heat conductivity defined in-plane and cross-plane for whole cell unit and jelly roll (including heat capacity) Important part for thermal models are termination and equivalent jelly-roll Avo R MVKF25-vt17 Battery Pack Design 61

62 H. Lundgren et al, Thermal Management of Large-Format Prismatic Lithium-Ion Battery in PHEV Application Surface temperature response Thermal vs electric power extraction and comparison Thermal conductivity Through-foil 0.95W/mK Along foil 30.8 W/mK Avo R MVKF25-vt17 Battery Pack Design 62

63 1 2D FE over cross-sections Q v =140W/dm 3, surf =30 o C 30 Temperature, [ C] λ cell =20 W/mK 60 Case 2 Q base [W] Q lateral [W] max [ o C] λ cell =1 W/mK Avo R MVKF25-vt17 Battery Pack Design 63

64 Observations A Battery cell P=50 W heating, 1/R={ } K/W, ={ } K Heat conductor Ideal 1/R=0 K/W, =0 K Cooling plate Ideal fluid = wall = surf =30 o C surf =30 o C wall =30 o C fluid =30 o cell = surf +Δ C Source Link Sink 50 W per cell Avo R MVKF25-vt17 Battery Pack Design 64

65 Realization A Mechanical assembly in cross plane direction Thermal enhancement both in plane directions.. Lateral clamp or forcing plate Battery to base contact Avo R MVKF25-vt17 Battery Pack Design 65

66 1 Cell clamped into heat conductor Q v =140W/dm 3, surf =30 o C Temperature, [ C] height, [m] length, [m] Case 2 Q base [W] Q lateral [W] max [ o C] μm gap gap =3 o C 100μm gap gap =21 o C Avo R MVKF25-vt17 Battery Pack Design 66

67 1 30 Temperature, [ C] height, [m] Cell linked to cool-plate length, [m] h 1 =1000W/Km 2 wall wall =15 o C h 2 =200W/Km 2 wall wall =95 o C Q v =140W/dm 3, fluid =25 o C Case Q base [W] Q lateral [W] max [ o C] h h Avo R MVKF25-vt17 Battery Pack Design

68 Transient heating 5 minutes between the frames (FEMM transient HT) Hot side of the scale (usually presented in between o C) One dominating heat capacitance only Avo R MVKF25-vt17 Battery Pack Design 68

69 Summary Battery cell b={ } 50W actual load is lower Heat conductor Insufficient thermal contact 0.1 mm air 50W Cooling plate Insufficient heat transfer h 2 =200W/Km 2 wall w l =95 o C cell = surf +Δ b surf = wall +Δ c wall = fluid +Δ w fluid =30 o C Source Link Sink 50 W per cell Avo R MVKF25-vt17 Battery Pack Design 69

70 Evaluation of direct forced cooling Cooling channel arrangements Thermography of heat transients 300 A DC L/min Location of hot-spots turns of the layer edges where the cross section is less than 10 mm 2 Edge layer 1 is closest to air-gap Avo R MVKF25-vt17 Battery Pack Design 70

71 Thermal control and management..by thermal design and active cooling J. Li, Z. Zhu, Battery Thermal Management Systems of Electric Vehicles, MSc Chalmers /17.7 kwh 1700/270 kg Avo R MVKF25-vt17 Battery Pack Design 71

72 Energy Management Battery management system Information Energy Monitoring measure what is important Control keep it optimal and constrained Diagnosis keep battery cells healthy Avo R MVKF25-vt17 Battery Pack Design 72

73 Battery Management System - BMS Best and safe use of energy Voltage U+ U and temperature + management: cell balancing or equalizer, check margins Charge/discharge Integration of current SoC Power and capacity fade SoH Avo R MVKF25-vt17 Battery Pack Design 73

74 Charge and discharge control maintain the voltage limits while respecting the current and temperature limits LOW Constant current charging followed by voltage and temperature control HIGH current for constant voltage charging Combined CV+CC Avo R MVKF25-vt17 Battery Pack Design 74

75 Cell balancing Voltage equalization, which is to fill up energy and maximize capacity and life by removing unbalanced weak links Active/passive taking/wasting energy Avo R MVKF25-vt17 Battery Pack Design 75

76 BMS development Overall functional safety is better match to global FPGA than to local micro processor units parallelism for performance with fail-safe logic Avo R MVKF25-vt17 Battery Pack Design 76

77 Ageing model Thermal model Electrical model BMS function structure I/O, monitoring, decisions and safety relevant funtions Avo R MVKF25-vt17 Battery Pack Design 77

78 BMS control sequence Intelligent batteries due to base functions of a battery management system Avo R MVKF25-vt17 Battery Pack Design 78

79 BMS basic functions Cell protection, charge control, demand management, SoC and SoH determination, cell balancing, authentication and identification, communication are some objectives for BMS Avo R MVKF25-vt17 Battery Pack Design 79

80 BMS Scope and Failure Consequences Avo R MVKF25-vt17 BTMS Battery Pack Design 80

81 BMS architectures for xevs Communication, reliability and accuracy Practical attachment, number of components and connections Few architectures with different features in connections and communication Avo R MVKF25-vt17 Battery Pack Design 81

82 Practical implementation Added intelligence, where and how? Sharing information, history and communication Avo R MVKF25-vt17 Battery Pack Design 82

83 Multicell Battery Stack Monitor Component name LTC6802-1, Up to 12 cells, 13 ms measurement interval, up to 1000V, passive cell balancing Avo R MVKF25-vt17 Battery Pack Design 83

84 BMS sensor module MM9Z Cell Lithium Battery BMS unit battery stack monitor IC can measure a number of cell voltages and provide for the discharge of individual cells to bring them into balance with the rest of the stack Avo R MVKF25-vt17 Battery Pack Design 84

85 Some future trends by Bosch Avo R MVKF25-vt17 Battery Pack Design 85

86 Back to Battery modelling power_battery, power_pattery_temperature State of the art model for concept development and evaluation Avo R MVKF25-vt17 Battery Pack Design 86

87 Physics coupled equivalent circuits Battery equivalent circuit models Rint model Eo, Ro First order (adds) R1, C1 Second order (adds) R2, C2 Impedance model Electrochemical impedance spectroscopy (EIS) Coupled to pfysics (?) Avo R MVKF25-vt17 Battery Pack Design 87

88 Testing batteries Electrochemical dynamic response Respons is related to ioncurrent/diffusion rate in the cell Slower response for weaker batteries Characterization LF dubbed diffusion MF charge transfer HF migration Batteries with faded capacity suffer from low charge transfer and slow active Liion diffusion. Avo R MVKF25-vt17 Battery Pack Design 88

89 Useful links and Aknowledgement mpoweruk.com Batteryuniversity.com liionbms.com/php/cells.php Aknowledged authors and their results shown on the previous pages (with some links and references) Avo R MVKF25-vt17 Battery Pack Design 89