Lithium battery pack equalization charging method, lithium battery pack
charging equalization principle. Balancing is a key technology to solve the
differences of battery cells. For lithium batteries to be used in groups, each
lithium battery requires protection from charging overvoltage, discharge
undervoltage, overcurrent, and short circuit. During the charging process,
balanced charging of the entire group of batteries must be achieved. This
article will introduce the equalizing charging method and charging equalizing
principle of lithium battery pack.
What is charge equalization?
Charge balancing, referred to as equalizing charge, is charging that
balances battery characteristics. It means that during the use of the battery,
the battery terminal voltage is unbalanced due to individual differences,
temperature differences, etc. of the battery. In order to avoid the worsening of
this imbalance trend, It is necessary to increase the charging voltage of the
battery pack and activate the battery to achieve a maintenance method that
balances the characteristics of each battery in the lithium battery pack and
extends the battery life.
Commonly used balancing charging technologies include constant shunt
resistor balancing charging, on-off shunt resistor balancing charging, average
battery voltage balancing charging, switched capacitor balancing charging, buck
converter balancing charging, inductor balancing charging, etc. When charging a
group of lithium batteries in series, each battery should be charged evenly,
otherwise the performance and life of the entire battery group will be affected
during use. However, the existing single-cell lithium battery protection chips
do not include the balanced charge control function. The balanced charge control
function of the multi-cell lithium battery protection chip requires an external
CPU; it is implemented through serial communication with the protection chip,
which increases the complexity of the protection circuit. degree and design
difficulty, reducing system efficiency and reliability, and increasing power
consumption.
Lithium battery pack equalization charging method
When the lithium battery pack is produced and stored for a long time, due
to the different static power consumption of each channel of the protection
board and the different self-discharge rate of each cell, the voltage of each
battery string in the entire battery pack is inconsistent. Balance has the
function of equalizing the voltage of the lithium battery pack, so that the
battery pack capacity can be fully charged and discharged, so that the battery
pack can exert its maximum effect.
Commonly used lithium battery pack balancing charging technologies include
constant shunt resistance balancing charging, on-off shunt resistor balancing
charging, average battery voltage balancing charging, switched capacitor
balancing charging, buck converter balancing charging, inductor balancing
charging, etc. When a set of lithium batteries is charged in series, each
battery should be charged evenly, otherwise the performance and life of the
entire set of batteries will be affected during use.
1. Attach a parallel balancing circuit to each single cell of the lithium
battery pack to achieve a shunt function. In this mode, when a battery reaches
full charge first, the balancing device can prevent it from overcharging and
convert the excess energy into heat energy to continue charging the
under-charged battery. This method is simple, but it will cause energy loss and
is not suitable for fast charging systems.
2. Before charging, discharge each cell one by one through the same load to
the same level, and then perform constant current charging to ensure a more
accurate equilibrium state between each cell. However, for battery packs, due to
physical differences between individuals, it is difficult for each cell to
achieve completely consistent ideal effects after deep discharge. Even if the
same effect is achieved after discharging, new imbalances will appear during the
charging process.
3. Timing, sequencing, and individually detecting and evenly charging the
single cells in the lithium battery pack. When charging the lithium battery
pack, it can be ensured that each lithium battery in the battery pack will not
be overcharged or overdischarged, thus ensuring that each battery in the lithium
battery pack is in normal working condition.
4. Using the time-sharing principle, through the control and switching of
switch components, additional 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.
5. Use 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 can better solve the problem
of battery pack voltage imbalance, but this method is mainly used in situations
where the number of batteries is small.
6. 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
it will greatly increase the cost when the number of single cells is large, and
is not conducive to reducing the system volume.
Lithium battery pack charging equalization principle
The number of single-cell lithium battery protection chips is determined
based on the number of cells in the lithium battery pack, and they are used in
series to protect the corresponding single-cell lithium battery from the charge
and discharge, overcurrent, and short-circuit conditions. While charging
protection, the system uses the protection chip to control the on and off of the
shunt discharge branch switching device to achieve balanced charging. This
solution is different from the traditional approach of achieving balanced
charging at the charger end and reduces the design of lithium battery pack
chargers. Application cost.
A lithium battery pack is composed of multiple single lithium batteries
connected in series. Due to the differences in the cells, inconsistent rise in
terminal voltage during series charging will cause some cells to be overcharged
and some cells to be undercharged. All batteries are connected in parallel
during equalizing charging and in series during normal charging and power use.
During balanced charging, the parallel voltages of all batteries are equal,
achieving forced balancing of each battery.
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