In the lithium battery pack, multiple lithium batteries are connected in series to obtain the required operating voltage. If you need higher capacity and higher current, you should connect power lithium batteries in parallel. The aging cabinet of the lithium battery assembly equipment can know the high voltage and high capacity standards by combining the two methods of series and parallel.
1. Lithium battery series and parallel method
Lithium batteries in parallel: the voltage remains the same, the battery capacity is added, the internal resistance is reduced, and the power supply time is prolonged
Lithium batteries in series: the voltage is added, the capacity remains unchanged
Parallel connection In order to obtain more power, multiple batteries can be connected in parallel. In addition to connecting batteries in parallel, another option is to use larger batteries, because the available batteries are limited and this method is not suitable for all applications. In addition, large-size batteries are not suitable for the form factor required for dedicated batteries. Most chemical batteries can be used in parallel, and lithium batteries are most suitable for parallel use.
For example, the battery voltage of the parallel connection of five batteries is maintained at 3.6V, and the current and running time are increased by five times. High-impedance or "open" batteries have less impact on the battery parallel circuit than with batteries in series, but parallel battery packs can reduce load capacity and shorten running time.
When using the series-parallel connection, the design is flexible and can reach the rated voltage and current required by the standard battery size. It should be noted that the total power will not change due to the different connection methods used by the lithium battery spot welder to produce lithium batteries. Power is equal to the voltage multiplied by current. For lithium batteries, series and parallel connections are common. The most commonly used battery pack is the 18650 lithium battery, which has a protection circuit and a lithium battery protection board. The lithium battery protection board can monitor each battery connected in series, so its maximum actual voltage is 42V. The lithium battery protection circuit (ie, lithium battery protection board) can also be used to monitor the status of each battery connected in series.
When using 18650 lithium batteries in series, the following basic requirements must be followed: the voltage should be consistent, the internal resistance should not exceed 5 milliohms, and the capacity difference should not exceed 10 milliamps. The other is to keep the connection points of the battery clean, each connection point has a certain resistance. If the connection point is not clean or the connection point is increased, the internal resistance may be high, which may affect the performance of the entire lithium battery pack.
2. Precautions for serial and parallel lithium batteries
Generally, lithium battery cell pairing is required for the serial and parallel use of lithium batteries. The pairing standard: lithium battery cell voltage difference ≤10mV, lithium battery core internal resistance difference ≤5mΩ, lithium battery cell capacity difference ≤20mA.
When connecting batteries in parallel, the same type of batteries must be used. Different batteries have different voltages. After parallel connection, the high-voltage battery charges the low-voltage battery and consumes electrical energy.
The same battery should also be used when connecting batteries in series. Otherwise, after batteries with different capacities are connected in series (for example, batteries of the same type are of different old and new levels), batteries with small capacities will discharge light first, and the internal resistance will increase. At this time, batteries with large capacities will be discharged through the internal resistance of batteries with small capacities, consuming electric energy, and It will be reverse charged. In this way, the voltage on the load will be greatly reduced and cannot work. A battery with a large capacity is only equivalent to a battery with a small capacity.
