What are the applications of photovoltaic welding strip rolling mill in the energy storage equipment industry

       The application of photovoltaic welding strip rolling mill in the energy storage equipment industry relies on its "high-precision thin metal strip rolling technology" to produce key conductive connection components in energy storage batteries and energy storage systems. These components require high dimensional accuracy, surface quality, conductivity, and mechanical performance of the metal strip, which is highly compatible with the photovoltaic strip (such as thickness tolerance ± 0.005mm, surface scratch free, low internal resistance, etc.). Its specific application scenarios focus on the three core links of "cell connection", "current collection", and "system conduction" in energy storage devices. The following is a detailed breakdown:

1、 Core application scenario: Conductive connections inside energy storage batteries

       Energy storage batteries (such as lithium iron phosphate batteries, ternary lithium batteries, all vanadium flow batteries, etc.) are the core of energy storage devices, and their internal components require "precision conductive strips" to achieve series/parallel connection of battery cells and current collection, in order to ensure the charging and discharging efficiency, internal resistance stability, and safety performance of the battery pack. The copper strip (or nickel/tin plated copper strip) produced by the photovoltaic strip rolling mill is the core raw material for such conductive connection components, and is specifically applied in the following sub scenarios:

1. "Ear connection strap" for square/cylindrical energy storage cells

       Application requirements: The pole ears (positive and negative terminals) of square (such as lithium iron phosphate large cells) and cylindrical energy storage cells (such as 18650/21700 type) need to be connected through conductive tape to achieve multi cell series parallel connection (such as connecting 10 cells in series to form a 3.2V × 10=32V battery module). This type of connecting strap must meet the following requirements:

       Thickness 0.1-0.3mm (too thick will increase battery volume, too thin is prone to heating and melting);

       No oxidation or scratches on the surface (to avoid increasing contact resistance and causing local overheating);

       Good bending performance (suitable for compact installation space of battery modules).

       Rolling mill function: Through "multi pass progressive rolling" (such as 3-5 passes), the original copper strip (thickness 0.5-1.0mm) is rolled into a thin copper strip that meets the size, while ensuring the flatness of the strip (tolerance ≤± 0.003mm) through "tension control"; If oxidation prevention is required, subsequent nickel/tin plating processes can be used. The surface roughness (Ra ≤ 0.2 μ m) of the copper strip produced by the rolling mill can ensure the adhesion of the coating.

2. "Current collecting conductive strip" of flow battery

       Application requirements: In the stack of all vanadium flow batteries (mainstream long-term energy storage technology), a "current collecting conductive strip" is needed to collect the current of a single battery to the external circuit. Its material is mostly pure copper (high conductivity) or copper alloy (corrosion-resistant). Requirements:

       Width suitable for stack size (usually 50-200mm), thickness 0.2-0.5mm (balanced conductivity and lightweight);

       The edge of the strip should be free of burrs (to avoid puncturing the stack membrane and causing electrolyte leakage);

       Resistance to vanadium ion corrosion (some scenarios require surface passivation treatment after rolling).

       The function of the rolling mill is to produce wide and flat copper strips through customized rolling rolls (designed according to the width of the stack), while eliminating burrs generated during the rolling process through an edge grinding device; The "temperature control" of the rolling mill (copper strip temperature ≤ 60 ℃ during rolling) can prevent the growth of copper strip grains, ensure its mechanical strength (tensile strength ≥ 200MPa), and adapt to the long-term operation of liquid flow battery stacks (design life of more than 20 years).

2、 Extended application scenario: External conductive components of energy storage systems

        In addition to internal connections within the battery, precision copper strips produced by photovoltaic strip mills can also be used for "external conductive connections" in energy storage systems such as energy storage containers and household energy storage cabinets, solving the adaptation problem of traditional conductive components such as cables and copper bars in compact spaces

1. "Flexible conductive strip" for energy storage module and inverter

        Application requirements: In energy storage containers, the connection space between battery modules (mostly vertically stacked) and inverters is narrow, and traditional hard copper bars (strong rigidity, not easy to bend) are difficult to install. A "flexible conductive strip" (foldable, bendable) is required to achieve the connection. Its requirements are:

        Thickness 0.1-0.2mm, width 10-30mm (customized according to current size, such as 200A current compatible with 20mm wide copper strip);

        Can be stacked in multiple layers (such as 3-5 layers of copper strips stacked to enhance current carrying capacity);

        The surface insulation coating has strong adhesion (it needs to be coated with insulation layer after copper strip rolling to avoid short circuit).

        Function of rolling mill: The thin copper strip produced has high flatness (no wave shape), which can ensure tight contact when multiple layers are stacked (no gap, reducing contact resistance); The "continuous rolling process" of the rolling mill can achieve the production of long coils of copper strip (single coil length of 500-1000m), meeting the needs of batch assembly of energy storage systems and replacing the traditional "stamping and cutting" scattered processing mode (increasing efficiency by more than 30%).

2. "Micro conductive connectors" for household energy storage cabinets

       Application requirements: The household energy storage cabinet (capacity 5-20kWh) has a small volume, and the connection between the internal battery cells, BMS (battery management system), and interfaces requires "micro conductive connectors". The size is usually 3-8mm in width and 0.1-0.15mm in thickness. Requirements:

       The dimensional tolerance is extremely small (width ± 0.02mm, thickness ± 0.002mm) to avoid interference with other components;

       Surface tin plating (anti-oxidation, suitable for low-temperature welding process);

       Lightweight (reduces the overall weight of the energy storage cabinet and facilitates installation).

       The function of the rolling mill is to produce narrow precision copper strip through "narrow width rolling mill+high-precision servo control", and then make connecting pieces through subsequent slitting and tin plating processes; The "rolling accuracy" of the rolling mill can ensure the consistency of the connecting plate size (pass rate ≥ 99.5%), avoiding installation failures caused by size deviations (such as poor contact and inability to insert interfaces).

3、 Application advantages: Why does the energy storage industry choose photovoltaic welding and rolling mills?

       Compared to traditional metal strip production equipment such as punching machines and ordinary rolling mills, the application advantages of photovoltaic welding strip rolling mills in the energy storage industry are mainly reflected in three points:

       Accuracy matching: The thickness tolerance (± 0.003-0.005mm) and surface roughness (Ra ≤ 0.2 μ m) of the energy storage conductive strip are required to be consistent with the height of the photovoltaic welding strip, without the need for significant modifications to the rolling mill. Only adjusting the rolling parameters (such as roll gap and speed) is needed to adapt;

       Cost advantage: The "continuous rolling process" of photovoltaic strip rolling mills can achieve large-scale production (with a daily production capacity of 1-2 tons per equipment). Compared with the "intermittent processing" of stamping machines, the unit product cost is reduced by 15% -20%, which meets the core demand of the energy storage industry for "cost reduction and efficiency improvement";

       Material compatibility: It can roll various materials such as pure copper, copper alloy, nickel plated copper, etc., to meet the conductivity needs of different energy storage batteries (such as pure copper for lithium iron phosphate and copper alloy for flow batteries), without the need to replace core equipment.