I. Introduction to Types
Commonly used batteries on the market include button cells, dry cell batteries, nickel-metal hydride batteries, and lithium batteries. These batteries differ in chemical composition, voltage, and capacity, so some principles need to be observed when using them in parallel.
II. Parallel Principle
1. Same voltage: Different types of batteries do not necessarily have the same voltage. Therefore, when connecting them in parallel, you should choose batteries with the same voltage as much as possible. Otherwise, the high and low voltages may interfere with each other, leading to rapid battery depletion or other dangerous situations.
2. Similar Capacities: When using batteries in parallel, try to choose batteries with similar capacities, because batteries with different capacities will affect each other during charging and discharging, resulting in an imbalance in charging or discharging and affecting battery life.
3. Different types of batteries cannot be directly connected in parallel: Different types of batteries have different chemical compositions and different internal reaction properties. Therefore, different types of batteries cannot be directly connected in parallel, otherwise it will cause problems such as insufficient battery capacity and inconsistent internal resistance.
Different battery models can be used in parallel, but there are certain safety risks involved, and it is necessary to strictly follow the operating specifications and precautions.
I. Feasibility and Risks of Parallel Connection of Different Battery Models
Some people may encounter this situation: they have several batteries of different models, all unused. Is it possible to connect them in parallel to increase their capacity? The answer is yes, connecting batteries in parallel can increase capacity, but there are certain risks. Improper parallel connection of batteries can lead to uneven voltage and current, potentially shortening their lifespan or causing dangers such as overcurrent.
II. Correct Battery Parallel Connection Method
The correct way to connect batteries in parallel is to connect batteries of the same model, capacity, and voltage. This ensures that the batteries discharge consistently, preventing damage caused by inconsistencies in battery polarity. When connecting batteries in parallel, it is crucial that the battery polarity is correct; otherwise, it can lead to overheating, explosion, and other safety issues. The battery terminals should be connected to each other, and the front sides of the batteries should be connected together; otherwise, there may be a risk of overcurrent.
III. Precautions for parallel battery connection
1. The battery model, capacity, and voltage should be the same;
2. The battery polarity must be correct;
3. When connected in parallel, the battery terminals should be connected to each other, and the front sides of the batteries should be connected to each other.
4. Before using the battery, check for any damage or leakage.
5. Avoid using the battery in high temperature, humid, or vibrating environments;
6. Avoid short-circuiting the battery;
7. Avoid overcharging or over-discharging.
Lithium batteries of different capacities can be connected in parallel, but this requires careful operation and certain conditions must be met.
I. Theoretical Feasibility
In principle, it is feasible to connect lithium batteries in parallel. Parallel connection can increase the total capacity while maintaining a constant voltage. When lithium batteries of different capacities are connected in parallel, their terminal voltages should ideally be equal, so that after parallel connection, the voltage output by the entire battery pack is the same as the voltage of a single battery.
II. Potential Risks
Capacity difference problem
Lithium-ion batteries of different capacities may behave differently during charging and discharging. Larger capacity batteries may absorb more electricity during charging and output more electricity during discharging. This can lead to overcharging and over-discharging of smaller capacity batteries, thus affecting their lifespan and performance.
Over time, small-capacity batteries may age faster or even become damaged.
Internal resistance difference problem
Lithium batteries of different capacities typically have different internal resistances. When connected in parallel, the battery with lower internal resistance will carry more current, which may lead to more severe heat generation and even safety issues.
If the internal resistance difference is large, it may also lead to an uneven current distribution inside the battery pack, affecting the performance and lifespan of the entire battery pack.
Consistency problem
Lithium batteries of different capacities may differ during production, such as in electrode materials and manufacturing processes. These differences can lead to inconsistencies in battery performance, such as charge-discharge curves and self-discharge rates. When used in parallel, these inconsistencies may interact, further exacerbating the instability of the battery pack.
Misconceptions about Parallel Use of Lithium Batteries The booming development of new energy vehicles has driven the rapid progress of the lithium battery industry. Today, lithium batteries are widely used not only in passenger electric vehicles but also in electric forklifts, AGVs, and other fields. However, many people have misconceptions about the parallel use of lithium batteries. Today, we will explore this topic in depth.
◉ Parallel principle
When connecting rechargeable batteries in parallel, a crucial principle is that batteries made of different materials must never be mixed. Furthermore, even if the materials are the same, multiple rounds of charge-discharge screening are necessary to ensure that the voltage differences between the selected batteries are controlled within a minimal range before parallel connection. Otherwise, not only will the battery pack's performance be compromised, but its lifespan will also be significantly shortened.
Batteries made of different materials, even if they have identical voltages initially, should never be connected in parallel. This is because during charging and discharging, batteries made of different materials exhibit different energy densities and discharge characteristics, leading to voltage inconsistencies. If connected in parallel, the battery with the higher voltage may reverse-charge the battery with the lower voltage, causing severe overheating. Simultaneously, due to differences in residual charge, the charging speeds of the batteries will also differ, potentially causing some batteries to overcharge, leading to a series of problems, and in severe cases, even fire or explosion. Therefore, from a safety and lifespan perspective, batteries made of different materials should never be connected in parallel.
◉ Risk of inconsistent battery voltages due to the same material
During battery pack production, manufacturers follow a rigorous screening process to ensure battery quality. They conduct multiple rounds of charge-discharge tests on batteries from the same batch to identify those with inconsistent characteristic curves. After this screening, batteries with essentially the same charge-discharge characteristics are grouped together in series and parallel to form a battery pack, which is then delivered to the user. However, if a battery cell in this pack has a voltage inconsistent with the others, the higher-voltage cell may attempt to charge the lower-voltage cell, causing a rapid rise in temperature in that area and posing a risk of overcharging. Over time, this situation may worsen, leading to performance degradation of the entire battery pack and potentially even causing a safety hazard.
