Power Battery and Its Battery Pack
1. Basic Knowledge of Power Batteries
1.1 Individual Power Battery
The smallest unit constituting a power battery module. Generally composed of a positive electrode, negative electrode, electrolyte, separator, casing, terminals (poles), etc., it enables the direct conversion between electrical energy and chemical energy.
1.2 Power Battery Module
Individual power batteries connected in physical structure and circuitry, forming the smallest grouping of a power battery pack or system, replaceable as a single unit.
1.3 Power Battery Pack
An energy storage device comprising individual cells or modules. It typically includes battery electronic components, high-voltage circuits, over-current protection devices, battery cases, and interfaces with other external systems (such as cooling, high-voltage, auxiliary low-voltage, and communication, etc.).
1.4 Battery Series and Parallel Connection
A battery pack is composed of battery cells and modules connected in series and parallel.
Battery:
- Series Connection: Increases voltage, with constant capacity (Vn = nXVi, Cn = Ci).
- Parallel Connection: Increases capacity, with constant voltage (Cn = nXCi, Vn = Vi).
Capacitor:
- Series Connection: Increases voltage, reduces capacity (Vn = nXVi, 1/C = 1/C1 + 1/C2).
- Parallel Connection: Increases capacity, with constant voltage (CF = nXCi, Vn = Vi).
- Combination: Can simultaneously increase both battery voltage and capacity.
Note: The more batteries combined, the lower the reliability of the battery pack.
When combining batteries, it is advisable to use batteries of the same series, size, and identical performance.
This addresses what we commonly refer to as the uniformity issue of batteries.
Parameters typically observed include voltage, capacity, and internal resistance.
1.5 Battery Naming Conventions
Different manufacturers have different naming conventions, but there is a common standard followed by the general battery industry.
The battery name provides information about the battery’s size, among other details.
According to IEC 61960, the rules for cylindrical and prismatic batteries are as follows:
(1) Cylindrical Batteries: Three letters followed by five numbers.
- In the three letters, the first letter indicates the negative electrode material: “I” for lithium-ion, “L” for lithium metal or alloy electrode.
The second letter indicates the positive electrode material: “C” for cobalt, “N” for nickel, “M” for manganese, “V” for vanadium.
The third letter is “R” for cylindrical.
- The five numbers: The first two digits represent the diameter, and the last three digits represent the height, both in millimeters.
(2) Prismatic Batteries: Three letters followed by six numbers.
- The first two letters have the same significance as cylindrical batteries. Whilethe third letter is “P,” indicating a prismatic shape.
- The six numbers: The first two digits represent the thickness. The next two represent the width. And the last two represent the height (length), all in millimeters.
Example:
ICR 18650 represents a common 18650 cylindrical battery with a diameter of 18mm and a height of 65mm.
ICP 053353 represents a prismatic battery with a thickness of 5mm, width of 33mm, and height (length) of 53mm.
2. Power Battery Assembly
2.1 Basic Components of Battery Pack Assembly
NO. | Components | Component Composition | Subcomponent | Single Unit |
1 | Power Battery Assembly | Battery Box |
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Module | Module | Module | ||
Module Fixing and Mounting System | Module | Module | ||
Power Copper Busbar | Module | 2.4Ah Battery Cell | ||
Connector |
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2 | Battery Management System Assembly | Battery Management System (BMS) |
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Main Circuit Fuse | Power supply positive connector |
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Main Relay | Negative power connector |
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3 | Fast Charging (Optional) | Fast Charging Relay | Communication aeronautical insertion |
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Fast Charging Fuse | Management system control module |
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Connector | Hall Current Sensor/Shunt |
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4 | Heating System (Optional) | Heating Module | Low voltage wiring harness |
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Heating Relay | 600V315A |
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Heating Fuse | (250A) |
2.2 Battery Pack Production Process
1 Battery Assembly | 2 Bracket Assembly | 3 Laser Welding | 4 Spot Welding | 5 Pry Welding Points, Apply Epoxy Board |
6 Module Testing | 7 Module Sealing | 8 Power Line Crimping Terminals | 9 Power Line Locking Copper Bars | 10 Pre-installation of High-Low Voltage Box |
11 Module Assembly | 12 Housing Assembly | 13 Hoisting into the Housing | 14 Fixing Copper Busbar Harness | 15 Entering Battery Pack Information |
16 Install Insulation Cover | 17 Injection of Glue | 18 Aging Process | 19 Cover the Box Lid | 20 Packaging and Warehousing |
21 Packaging and Shipment |
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2.3 Cell Matching (2 units)
A. Production:
1) Capacity grading (25+2℃, 0.5C charge and discharge capacity)
2) Internal resistance grading (1KHZ AC internal resistance)
20mΩ≤IR (insulation resistance) <26mΩ
3) Voltage grading: 3mV per level
4) Prohibit mixing cells of different grades
5) The stacking of cells should not exceed 7 boxes
B. Quality:
1) Voltage: Open circuit voltage
- Measure open circuit voltage using a multimeter in DC voltage range
2) Internal resistance: AC internal resistance
- Measure the internal resistance of the cell using an internal resistance tester.
3) Capacity: Cell capacity (nominal capacity)
Others: 1- Shrinkage appearance is good 2- No leakage 3- No scratches
4- No rust 5- No deformation 6- Check for oxidation on the output terminals
2.4 Bracket Assembly
A. Production:
1) Commonly used cells: 20EB and 24EB
2) Number of cells: According to design and customer requirements
Example: The calculation formula for 136P30S is 136 X 30 = 4080 cells
3) Cell distribution refers to cell distribution diagram
4) Assembly precautions:
- Different cells from different battery packs cannot be mixed
- Modules from different battery packs cannot be mixed
- Cells and modules must be placed with the positive pole facing up
B. Quality:
1) Appearance requirements:
- No deformation, damage, burrs, foreign objects, dirt; Bracket is flat, no misalignment.
2) Assembly requirements:
- Assembly matches, no gaps, no reverse assembly, correct cell positioning.
3) QR code:
- Clear numbering, consistent with module numbering, correct position, no missing or duplicated labels.
2.5 Laser Welding
A. Production:
1) Copper busbars and nickel sheets: According to design and customer requirements
Example: For Jiangling E100:
- Large copper busbar and nickel sheet each 1PC, dimensions:
- Small copper busbar and nickel sheet each 2PCS, dimensions:
2) 7 machines; before starting each shift and if a machine has been stopped for over 1 hour, a tension test with N=1 is required. Tension requirements are within the range of 40~120N·m.
B. Quality:
1) Appearance of copper busbars and nickel sheets: Must not be dirty, deformed, cracked, rusted, or have poor ear-to-ear connections.
2) Assembly of nickel sheets and copper busbars: Nickel sheets must be installed flat, and misalignment, looseness, and overlap are not allowed.
3) Welding appearance: No incomplete welding, scorching, penetration, or welding slag. Ear folding or breakage is not allowed.
4) Welding strength: Different models of battery PACKs have different requirements, as specified in the design requirements.
Example: E100 Nickel sheets:
- Separated side: 45-120N
- Integral side: 50-150N
2.6 Spot Welding
A. Production:
1) Modules, composite copper busbars: According to the design and actual model requirements of the customer.
- Place the module in the fixture (negative first, then positive) → Put it into the machine → Start → Observe the spot welding situation → Take it out → Self-check the quality of the weld points → Put it on the trolley.
- Place the module in the fixture:
During operation, pay attention to observe for sparks, welding deviations, and missed welds. If any of the above defects are found, promptly notify on-site adjustment personnel.
2) 20 LOROY spot welding machines.
B. Quality:
1) Modules must not be assembled upside down, missed, or misaligned.
2) Confirm welding fixture cleanliness and flatness; no burrs, wear, or looseness are allowed.
3) Spot welding strength specifications: 45-120N.
4) Welding appearance: No incomplete welding, scorching, penetration, or welding slag is allowed.
2.7 Pry Weld Points, Apply Epoxy Board
A. Production:
1) Pry Weld Points:
The main purpose is to check whether there is incomplete welding, excessive welding, welding deviation, etc., at the module weld points.
2) Apply Epoxy Board:
- Insert the six holes of the epoxy board onto the six cylinders on the module.
- The two buckles at the top of the module must be pressed into place by the epoxy board.
B. Quality:
1)Weld Point Appearance Requirements:
No cracks, penetration, incomplete welding, missed welding, welding deviation, scorching, welding slag, or overlap of pole ears are allowed.
2)Epoxy Board Assembly Requirements:
Proper assembly, intact buckles, and no looseness or damage.
2.8 Module Testing
A. Production:
1) According to the series-parallel number of the battery cells, find the corresponding parameter table on the computer terminal.
- The red pen is perpendicular to the positive pole (blue bracket), and the black pen is perpendicular to the negative pole (white bracket).
2) Equipment: Voltage and Internal Resistance Tester
B. Quality:
1) Voltage and internal resistance within the specified range.
2) Complete and accurate data recording.
3) Correct sequence of QR codes.
4) No mixing of modules between different battery packs.
2.9 Module Sealing
A. Production:
1) Main Purpose: Apply adhesive to the connection points between the upper and lower covers of the module to ensure the proper protection of the battery cells.
2) Tools and Materials: Silicone adhesive, adhesive gun, and scraper.
3) Considerations:
- Ensure full adhesive coverage at the clasps and connection points.
- Do not mix modules from different battery packs.
B. Quality:
1) Sealing is intact at the bracket joints.
2) No missed or excessive adhesive, and uniform adhesive application.
2.10 Power Line Crimping Terminal
A. Production:
1) The power line typically has a standard specification of 35mm2. Cut the power line to the required length based on the specific PACK model (refer to the power line length drawing).
2) Production Tools: Crimping pliers, blades, copper wire pliers, and a heat gun.
3) Materials: Power line, terminals, heat shrink tubing ∮18.
B. Quality:
1) The power line length meets the drawing requirements.
2) Crimping strength ≥185KG, with no exposed wire core.
3) The length of the heat-shrink tubing meets the requirements.
4) The tubing is heat-shrunk well, covering the contact surface of the terminal.
2.11 Power Line Locking Copper Busbar
A. Production:
1) Assemble the power line with crimped terminals, copper busbars, main positive and negative power lines, and series-connected power lines.
2) Tighten the bolts with a torque of 24N.m.
3) Tools: Torque wrench and fixtures.
B. Quality:
1) Bolts are securely tightened with a torque of 24N.m.
2) The terminal outlet faces upward.
3) The length of the heat shrink tubing meets the process requirements.
2.12 Pre-assembly of High-Low Voltage Box
A. Production:
1) Low-voltage box pre-assembly: The screws on the fixing plate must be coated with Dow Corning glue.
2) High-voltage box pre-assembly:
- Insert the insulating column into the corresponding position, ensuring correct orientation.
- Tools: Torque wrench, Phillips screwdriver, 13MM socket, and 8MM socket.
B. Quality:
1) No errors or missing parts in the pre-assembly of high and low-voltage boxes.
2) The torque for tightening bolts on the insulating column is 24N.m.
3) The torque for tightening bolts on the back of the bracket is 6.8Nm.
4) The torque for tightening combination bolts is 10Nm.
2.13 Module Assembly
A. Production:
1) Assemble the modules according to the design requirements, currently with the negative terminal facing outward and the positive terminal inward.
2) Each module has 6 screws; the nuts must be pre-tightened before final fastening, with a tightening torque of 13N.m.
B. Quality:
1) Modules are arranged in sequence, with the outermost modules having the negative terminal (white bracket) facing outward and the positive terminal (blue bracket) facing inward.
2) The screw fastening torque is 13N.M.
2.14 Assembly of the Enclosure
A. Production:
1) Install pre-assembled high and low-voltage components, main positive power line, BMS, communication lines, etc., into the enclosure.
2) Secure the main positive and main negative terminals on the enclosure.
B. Quality:
1) No misplacement or missing parts for each component.
2) No missing or cross-threaded screws.
3) Screws should not be marked with a pen.
2.15 Hanging the Enclosure
A. Production:
1) Hang the assembled modules into the assembled enclosure, first on the BMS side, then on the other side.
2) After module installation, ensure that the module holes align with the enclosure holes, and screw holes align with the enclosure screw holes.
3) Use a torque wrench to tighten the bolts, then affix the enclosure QR code.
B. Quality:
1) Modules in the correct position, QR code facing outward, and the QR code is upright and smooth.
2) Loose or missing bolts are not allowed.
2.16 Fixing the Copper Bar Wiring Harness
A. Production:
Install the cable tray → Place the 2# copper bar → Connect the positive voltage sampling and temperature lines → Connect the negative voltage sampling and temperature lines → Attach the #4 and #3 copper bars.
1) Wear mesh gloves on both hands to prevent injuries.
2) Assemble the components strictly according to the WI in terms of sequence and steps.
3) No foreign objects should be left inside the enclosure.
4) Follow the low-voltage wire installation sequence according to the distribution diagram.
B. Quality:
1) Assemble the components according to the design and drawing requirements.
2) Incorrect or missed assembly of components is not allowed.
3) Loose screws or those without markings are not allowed.
4) Improper installation or omission of voltage lines, temperature lines, and series connection lines is not allowed, and misplacement of positions is not allowed.
5) Voltage, internal resistance, pressure difference, and insulation resistance must be within the specified range.
6) Exposed ports of high and low-voltage lines are not allowed.
2.17 Battery Pack Information Entry
A. Production:
1) Information entry: BMS mainboard → BMS sub-board → Module → Module.
2) Testing: Insulation resistance → Module voltage resistance → Module voltage resistance.
- The positive and negative poles of the test probe must both make contact with the measured part.
- When testing insulation resistance, do not touch the battery pack.
B. Quality:
1) Voltage, internal resistance, pressure difference, and insulation resistance must be within the specified range.
2) QR code detachment, missing parts, and errors are not allowed.
2.18 Cover Insulation Cap
A. Production:
1) The buckle of the insulation cover must be fully inserted into the small holes of the insulation board and securely locked.
2) The insulation cover must be matched with the corresponding copper bars.
B. Quality:
1) The insulation cover must not be loose, misaligned, or missing.
2) Deformation, damage, and dirt on the insulation cover lock are not allowed.
2.19 Potting
A. Production:
1) The black and white adhesive must be thoroughly stirred before dispensing (at least 1 minute).
2) After pouring the adhesive into the glue pot, it must be thoroughly stirred (20-30 minutes).
3) Once the adhesive is properly mixed, set the dispensing speed and dispensing time.
4) The potting technique must follow the WI requirements.
B. Quality:
1) The coverage of potting meets the standard requirements.
2) Silicone adhesive should only be used within the module range.
2.20 Aging
A. Production:
1) Comprehensive testing of the performance of the battery pack‘s modules, modules, and individual battery cells.
- Battery pack performance: cycle life, capacity, voltage difference, etc.
2) The aging charge and discharge conditions for each battery pack are implemented according to the aging process guidelines.
3) Environmental requirements: Temperature at 25±5°C, humidity at 15%~90%.
B. Quality:
1) The battery pack’s performance meets the standard requirements.
2) The testing environment meets the requirements.
2.21 Covering the Box Lid
A. Production:
1) Box lid preparation: Apply a drop of Loctite in the screw holes and coat the surrounding area with adhesive.
2) Cover the box lid: Align the box lid with the box holes, and use a torque wrench to tighten the screws.
B. Quality:
1) No adhesive overflow.
2) Screws must not be loose, missing, or misaligned.
2.22 Packaging and Shipping
A. Production:
Apply high-voltage danger label → Attach lithium battery system nameplate → Certificate of conformity → Suspend the battery PACK in a wooden box → Remove the work order → Insert the inspection report → Seal the wooden box lid.
B. Quality:
1) The battery pack code on the box nameplate corresponds to the battery pack QR code.
2) The QR code on the test report corresponds to the battery pack QR code.
3) Proper and smooth placement of the danger label, nameplate, and certificate.