Lithium Ion Cell Balancing

Different algorithms of cell balancing are often discussed when multiple serial cells are used in a battery pack for particular device.

Lithium ion cell balancing.

The lithium ion battery balancing act more and more the world is running on lithium ion batteries. The worst thing that can happen is thermal runaway. Figure 1 illustrates a five cell balancing circuit with 1 ω resistors setting the transfer ratio which is the ratio of the imbalance voltage v cell v avg to the balancing current i cell. Quality li ion cells have uniform capacity and low self discharge when new.

Since it is bidirectional charge from any selected cell can be transferred at high efficiency to or from 12 or more adjacent cells. Safety hazards from overcharged cells li ion batteries have very high electric energy concentrated in small volume. True balancing brings the battery into perfect balance on every charge cycle. Unfortunately cells from many manufacturers have significant cell to cell variations.

With improved battery cells and new cell chemistry the battery variation is stabilizing. Active cell balancing is an amazing way to handle the cell balancing problem but in terms of system integration and optimization this approach takes a hit on many fronts like cost and complexity. Active cell balancing it uses capacitive or inductive charge carrying to move charge between battery cells. Lithium ion batteries will never be out of balance again true balancing is a completely new approach to cell balancing.

The means used to perform cell balancing typically include by. For batteries of relatively large capacity typically 20 ah or more balancing currents up to 1 a are desirable in order to minimize the time to. As we know lithium cells are very sensitive to overcharging and over discharging. Only cells from better manufacturers are closely matched and batteries that use them require very little balancing.

It is significant progressively productive in light of the fact that energy is moved to the necessary spot. Consumer electronics are basically built for them the combination of low weight to energy and a relatively slow loss of charge making them ideal for portable devices. In this arena lithium ion battery technology is fast becoming the standard. Equalizing the socs of the various cells in a battery.

A problem arises when a cell in a string loses capacity or develops elevated self discharge. The improved effectiveness is the requirement for extra parts at a greater expense. How do you balance a lithium ion battery. Adding cell balancing is beneficial especially as the pack ages and the performance of each cell decreases at its own pace.