18650 lithium 3.7 battery.Balancing principle of battery pack in series UPS power supply

1. The series-connected UPS power battery pack is a high-power battery pack that supplies power to the car in electric vehicles. In order to ensure the capacity of the entire battery pack, balanced management of the battery is necessary.

2. Various battery management ICs on the series UPS power battery pack market provide voltage equalization management functions. Users only need to connect some external components to achieve this. Unfortunately, most battery management ICs use Use resistance shunting/power consumption to achieve balance between cells.

3. Series UPS power battery pack In the lead-acid battery era, various methods have emerged for the balancing of battery packs.

4. The resistance of series connected lithium-ion batteries shunts current and consumes energy. This method is the most common and simplest method on the market. The protective plates for battery packs exhibited at the 2009 Electric Bicycle Exhibition, including those for electric vehicles, are balanced by resistors. The reason is also very simple: it is easy to implement, and there is no better way. In fact, it is also the cheapest way.

Method for balanced charging of series connected UPS power battery packs

●Attach a parallel balancing circuit to each single cell of the battery pack to achieve the purpose of shunting. In this mode, when a certain battery is fully charged first, the balancing device can prevent it from overcharging, and at the same time, the excess energy is converted into heat energy to continue charging the battery that is not fully charged.

●Pass each cell one by one before charging, discharge the same load to the same level, and then perform constant current charging to ensure a more accurate balanced state between each cell. However, due to the physical differences between individual UPS power battery packs, it is difficult for each cell to achieve a consistent effect after deep discharge. Even if the same effect is achieved after discharge, new imbalances will appear during the charging process.

●Test and evenly charge the individual batteries in the battery pack on time, in sequence, and individually. When charging the battery pack, it can be ensured that each battery in the battery pack will not be overcharged or overdischarged, thus ensuring that each battery in the battery pack is in normal working condition.

●Using the time-sharing principle, through the control and switching of switch components, extra current flows into the battery with a relatively low voltage to achieve the purpose of balanced charging. This method is more efficient, but the control is more complicated.

●Take the voltage parameters of each battery as the balancing object to restore the voltage of each battery to be consistent. During equalization charging, the capacitor is alternately connected to two adjacent batteries through a control switch, receives charge from the high-voltage battery, and then discharges to the low-voltage battery until the voltages of the two batteries become consistent. This balancing method better solves the problem of battery pack voltage imbalance, but this method is mainly used in situations where the number of batteries is small.

●The entire system is controlled by a single-chip microcomputer, and each battery has an independent set of modules. The module performs charge management on each single battery according to the set program, and automatically disconnects after charging is completed. This method is relatively simple, but when the number of single cells is large, it will greatly increase the cost and is not conducive to reducing the system volume.