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Have you ever encountered such a problem? The newly purchased battery pack "falls off the chain" not long after use, and there are always a few battery cells that get hot during charging, and even the new and old batteries strike directly after being mixed... This is likely caused by the inconsistent voltage of the series circuit battery!
In this article series circuit battery will be introduced in order to help you know more about it from the definition to information about its circuit.
What is the series battery
Due to the limited voltage and capacity of individual batteries, series parallel combination is required in practical use to obtain higher voltage and capacity, in order to meet the actual power supply needs of the equipment. Taking lithium batteries as an example, when connected in series circuit battery configuration, the voltage is added up, the capacity remains unchanged, and the battery internal resistance increases.
What is a series battery circuit
The method of connecting electrical appliances one by one in sequence (end-to-end connection) is called series connection. A circuit composed of electrical appliances connected in series is called a series circuit. The two small light bulbs in the picture are connected in series, so they are a series circuit.
Batteries in series and parallel
In batteries, not only are they connected in series, but they are also connected in parallel. To further understand series circuit battery knowledge, the following is a brief introduction to batteries in parallel vs. series.
Series connection refers to connecting the positive pole of a dry battery to the negative pole of the next battery, and then connecting them in sequence. This is called series connection. The advantage of series circuit battery connection is that it exponentially increases the voltage (V) of the power supply, which is generally used to drive appliances with higher rated voltage.
To obtain more power, two or more batteries can be connected in parallel. The voltage of a typical battery is the rated voltage of the relevant electrical appliance, which is powered by parallel connection of batteries. While ensuring a constant voltage, it can increase the current at the rated voltage and better drive the appliance.
What is the difference between parallel and series batteries
The main difference between parallel and series batteries is in voltage and battery capacity.
For a series circuit battery pack, the voltage increases. Take a lithium battery with a voltage of 3.7V and a capacity of 3000mAh. If two batteries are connected in series, the model of the battery pack is 7.4V/3000mAh. If two batteries are connected in parallel, the model of the battery pack becomes 3.7V/6000mAh. When connected in series, the voltage increases while the capacity remains unchanged, while when connected in parallel, the capacity increases while the voltage remains unchanged. But the batteries we often use are all connected in series and parallel, such as three series and four parallel, etc.
How to make a series circuit with batteries
Due to safety reasons, when building a series circuit battery system with lithium batteries, it must be equipped with an external protection board for monitoring each battery cell. It is generally not recommended to use batteries in parallel. If they are used in parallel, strict pairing is required to ensure the consistency of battery parameters such as battery capacity and internal resistance. Otherwise, the performance of the battery pack will be much worse than that of individual cells.
The purpose of pairing lithium batteries is to ensure that the capacity, voltage, internal resistance, and each battery performance in the battery pack are consistent. Inconsistencies in a series circuit battery pack can cause various parameters of the lithium battery pack to become farther apart during use, resulting in voltage imbalance. Over time, it can lead to overcharging, overdischarging, and inability to fully utilize its capacity, posing a risk of explosion and fire.
What happens when a battery is connected in series
The following is the changes of battery connected in series.
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Voltage increase
In a series circuit battery setup, the total voltage of the battery pack connected in series is equal to the sum of the voltages of each battery. For example, after two 3.7V lithium batteries are connected in series, the total voltage is 7.4V.
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Capacity remains unchanged
The total capacity (mAh) of the battery pack connected in series is the same as the capacity of a single battery.
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The current remains unchanged
The maximum output current of the battery pack connected in series is the same as the maximum output current of a single battery.
Based on these changes, there are pros and cons of series circuit battery for your reference.
The advantages of series circuit battery are that it can increase voltage, suitable for devices that require higher voltage, such as certain electric tools and electric vehicles. The series circuit battery connection method is simple and easy to implement.
But the disadvantages are that the internal resistance of the battery increases, which may affect the output power and current. The discharge time is limited by the battery with the smallest capacity, which can easily result in some batteries not being fully discharged. If one of the batteries is damaged, the entire battery pack may not function properly. Applied to electric tools, electric vehicles, high-voltage electronic devices, etc.
Tips for using series batteries
When batteries are connected in series, the total output voltage is the sum of the voltages of each battery, while the total capacity is limited by the battery with the smallest capacity. This is because when the small capacity battery is discharged first, the performance of the entire battery pack will be limited, which may lead to premature failure of the entire system.
Therefore, in order to ensure optimal performance and safety of the device, it is recommended to always use batteries of the same type and in good condition. If battery replacement is required, it is best to replace them in groups to ensure that all batteries are new and from the same manufacturer and model. Choose batteries with consistent performance. Pairing criteria: voltage difference ≤ 10mV, internal resistance difference ≤ 5m Ω, capacity difference ≤ 20mA.
- Avoid high/low temperature environments
High temperature (>50 ℃) can accelerate self discharge, while low temperature (<0 ℃) can cause voltage drops, both of which may lead to series circuit battery imbalance and destabilize batteries performance. Suggested working temperature: 10-30 ℃.
- Connect in series in the manufacturer's recommended quantity
- Replace all batteries
Rechargeable batteries require a dedicated balanced charger Ordinary chargers cannot balance the voltage of series connected batteries, which can easily lead to overcharging. Recommend using a charger with "balanced charging" function.
- Regularly check the battery
If there is swelling or leakage during continuous consumption, it should be replaced immediately. Batteries of different voltages cannot be used together as a series circuit battery pack. When the voltage difference between a single section is greater than 0.1V, it should be stopped from use.
Conclusion
The series and parallel connections of batteries have their own advantages and disadvantages, and the choice of appropriate connection method depends on specific application requirements. For series connection, it is suitable for scenarios that require high voltage.
Regardless of the connection method chosen for the battery, safe use is key. During daily use, proper use of series circuit battery systems ensures safety. Replacing batteries in groups and controlling the number of series connections (not exceeding the manufacturer's recommended value) can easily extend battery life and avoid equipment damage or safety hazards. Take care of these small details to ensure your electronic devices are fully powered, reliable, and durable!
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