Week 8 Multi cell Battery Pack
Battery is set of any number of identical batteries or cells. They may be arranged in series, parallel or mixture of both to deliver the required voltage, capacity or power density.
The battery configuration in series or parellel connections have different voltage in each cell. the weaest cell in battery have more stress than the other cells so that it will be the fastest damage. the identifcation of the weakest cell is identified in charging and discharging process. the weakes cell affect the battery pack by the following conditions.
1. It will carry out a limit on complete operation of the battery pack.
2. The weakest cell reaching the limit earlier than other. so battery pack may be under utilised.
3. the cell under voltage and over voltage is required.
4. It imposes limit to overall performance of battery pack.
Mainly there are two mismatches which affects the overall output of the battery.
1. state of charge
2, Capacity or energy mismatch
Solution to solve the problems
Why do we need the cell balancing
cell balancing is a technique in which voltage levels of every individual cell connected in series to form battery pack is maintained to be equal to achive maximum efficiency. When different cells are cooneced to form the battery pack it is always made sure that they are of same chemistry and voltage. but when pack is installed subjected to charging and discharging the voltage value of indidual cell tends to vary. this variation in voltage level causes the cell balancingwhich will lead to following problems
1. Thermal run way
The worst thing that can be happen is thermal runway. As cells are very sensitive to overcharging.
2. Cell degradation
When cell is overcharged even slightly above the recomonded value the efficiency and life will be reduced.
3.In complete charging of pack.
4.Incomplete use of pack energy
Types of cell balancing
Passive cell balancing
Active cell balancing
