What happens when a lithium battery is overcharged?

What happens when a lithium battery is overcharged?

What are the Effects of Battery Overcharging? In a lithium-ion battery, overcharging can create unstable conditions inside the battery, increase pressure, and cause thermal runaway. At best, this will lead to reduced capacity and shortened life cycle, and at worst this could cause thermal runaway.

What is charge balancing?

An active charge balancing scheme involves an external power source of some sort (either a voltage source or a current source) to charge batteries in the pack to the voltage level of the battery with the maximum voltage.

How do you balance lithium battery cells?

The means used to perform cell balancing typically include by- passing some of the cells during charge (and sometimes during discharge) by connecting external loads parallel to the cells through controlling corresponding FETs. The typical by-pass current ranges from a few milliamps to amperes.

Which type of battery connection must be balanced charged?

Balancing is only necessary for packs that contain more than one cell in series. Parallel cells will naturally balance since they are directly connected to each other, but groups of parallel wired cells, wired in series (parallel-series wiring) must be balanced between cell groups.

How are cell balancing methods for Li ion battery technology?

Li‐ion batteries are influenced by numerous features such as over‐voltage, undervoltage, overcharge and discharge current, thermal runaway, and cell voltage imbalance. One of the most significant factors is cell imbalance which varies each cell voltage in the battery pack overtime and hence decreases battery capacity rapidly.

What is the point of balancing a battery?

The point of balancing is to maximize the charge that the battery can deliver, limited only by the cell with the lowest capacity. A balanced battery is one in which, at some State Of Charge, all the cells are exactly at the same SOC. This can be done at any SOC level.

What is the self discharge current of a Li ion battery?

Typically, the self-discharge (leakage) current of Li-Ion cells is specified in terms of allowed months in storage at room temperature. (Actually, very few manufacturers specify it.)

What happens when a battery pack is not balanced?

During the charging or discharging process, one or more of the cells in the battery back do not have matched voltage per cell. Therefore, the battery pack is not balanced. The imbalanced charge between cells causes the following: Reduces overall battery pack capacity to the value of the cell with the least capacity.