button cell battery cr2025 process flow and examples

　　Under the background of the current new national standards, the demand for lithium batteries is increasing, and many lead-acid battery companies have also launched lithium battery products. In fact, the lithium battery PACK process is not difficult. If you master this technology, you can assemble the batteries yourself, instead of just acting as a manufacturer. In the role of "battery porter", profits and after-sales service are no longer controlled by others; if you master a technology, you can travel all over the world with "lithium".

　　1

　　PACK composition

　　PACK includes battery pack, bus bar, soft connection, protective board, outer packaging, output (including connector), highland barley paper, plastic bracket and other auxiliary materials to form PACK.

　　2

　　Features of PACK

　　①Battery pack PACK requires batteries to have a high degree of consistency (capacity, internal resistance, voltage, discharge curve, life).

　　②The cycle life of the battery pack PACK is lower than the cycle life of a single battery.

　　③Use under limited conditions (including charging and discharging current, charging method, temperature, etc.)

　　④ After the lithium battery pack PACK is formed, the battery voltage and capacity are greatly improved, and must be protected and monitored for charge equalization, temperature, voltage and overcurrent.

　　⑤The battery pack PACK must meet the voltage and capacity requirements required by the design.

　　3

　　PACK method

　　①Series and parallel composition: The battery is composed of single cells connected in parallel and in series. Parallel connection increases capacity, but the voltage remains unchanged. After series connection, the voltage doubles, but the capacity remains unchanged. For example, a 3.6V/10Ah battery is composed of a single N18650/2Ah through 5 parallels. Parallel first, then series: Parallel connection will affect the battery cycle life after parallel connection due to differences in internal resistance and uneven heat dissipation. However, when a single battery fails, it automatically exits. In addition to the reduction in capacity, it does not affect its use after parallel connection. The parallel connection process is strict. When a unit battery in a parallel connection is short-circuited, the current in the parallel circuit will be very large, which is usually avoided by adding fuse protection technology. Series first, then parallel: Connect in series first according to the capacity of the entire battery pack, for example, 1/3 of the capacity of the entire battery pack, and then connect in parallel, which reduces the probability of failure of large-capacity battery packs.

　　②Battery core requirements: Select the corresponding battery core according to your own design requirements. Batteries connected in parallel and in series must be of the same type and model, and the difference in capacity, internal resistance, and voltage value should not be greater than 2%. Under normal circumstances, after the batteries are combined in parallel and series, the capacity loss is 2%-5%. The more batteries, the greater the capacity loss.

　　Whether it is a soft-packed battery or a cylindrical battery, multiple string combinations are required. If the consistency is poor, the battery capacity will be affected. The battery with the lowest capacity in a group determines the capacity of the entire battery group. High current discharge performance is required.

　　The starting current of the motor is three times the normal operating current. Only high-current discharge can improve the motor's power performance. The battery is required to have good heat dissipation. There are a large number of batteries, and the temperature rise of the batteries inside the battery box is not easy to escape, resulting in uneven temperatures and different discharge characteristics among the batteries, which will lead to long-term degradation of battery performance.

　　The production technology level is high. The battery must be able to withstand the vibration and impact of bumpy roads. The production process, especially the spot welding process, has high requirements. After welding is completed, test it to prevent soldering and desoldering.

　　③PACK process: Battery PACK is realized in two ways. One is through laser welding or ultrasonic welding or pulse welding. This is a commonly used welding method. The advantage is that it has better reliability but is not easy to replace. The second is contact through elastic metal sheets. The advantage is that no welding is required and the battery is easy to replace. The disadvantage is that it may lead to poor contact.

　　pack instance

　　4

　　Charge and discharge time

　　Charging time (hours) = (battery capacity Ahx charging coefficient) / charging current A

　　Discharge rate: The discharge rate of a battery is expressed by the discharge time or the hour factor required to discharge the rated capacity with a certain discharge current. Among them, discharge rate = rated capacity/discharge current

　　5

　　Assembly of busbar soft connections

　　In the PACK process, materials such as nickel sheets, copper-aluminum composite bus bars, copper bus bars, total positive and total negative bus bars, and aluminum bus bars will be used. Copper soft connections, aluminum soft connections, copper foil soft connections, etc. will also be used. The processing quality of busbars and soft connections needs to be evaluated from these aspects.

　　① Whether the material meets the requirements. If the busbar material does not meet the standards, the resistivity will increase. In particular, it is necessary to confirm whether it meets the ROHS related requirements.

　　② Whether the critical dimensions are processed in place. Excessive tolerances in critical dimensions may lead to insufficient safety distances between high-voltage components during the assembly process and cause serious safety hazards.

　　③The bonding force of the hard area of the soft connection and the stress absorption status of the soft area.

　　④ Check whether the overcurrent capacity of the actual processed soft connections and busbars meets the design standards, and whether there is any damage to the insulated thermoplastic sleeve.

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