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Can 18650 batteries with different capacities be connected in series or in parallel?
2024-07-20
18650 batteries with different capacities can be connected in series or in parallel, but there are some key points to note:
Series Connection
1. Voltage increase: The total voltage of 18650 batteries in series is the sum of all battery voltages.
2. Capacity is determined by the smallest battery: When connected in series, the total capacity is determined by the smallest battery. If there is a battery with a smaller capacity in a group of batteries, it will be depleted faster than the other batteries, causing the performance of the entire battery pack to deteriorate.
3. Balance problem: 18650 batteries with different capacities will be unbalanced during charging and discharging, which may cause the smaller capacity battery to be overcharged or over-discharged, thus affecting battery life and safety.
Parallel Connection
1. Same voltage: The total voltage of 18650 batteries in parallel is the same as the voltage of a single battery.
2. Increased capacity: The total capacity of 18650 batteries in parallel is the sum of all battery capacities.
3. Current distribution: Batteries of different capacities will distribute different currents. Batteries with large capacities will bear larger currents, while batteries with small capacities will bear smaller currents. If the battery capacities differ greatly, it may cause uneven current distribution, thus affecting the battery life.
Notes
1. Consistency: Try to use 18650 batteries with the same capacity and specifications in series or parallel to ensure the safety and performance of the battery pack.
2. Battery Management System (BMS): If batteries of different capacities must be used, it is recommended to use a battery management system (BMS) to monitor and balance the battery pack to prevent overcharging, over-discharging and other problems.
3. Safety: Batteries of different capacities connected in series or parallel may increase the risk of thermal runaway, so special attention should be paid to the heat dissipation and protection measures of the battery.
In short, in order to ensure safety and extend battery life, it is best to choose 18650 batteries of the same specifications for series or parallel connection.
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