Lithium Ion Cell Balancing

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.

Lithium ion cell balancing.

Active cell balancing it uses capacitive or inductive charge carrying to move charge between battery cells. The means used to perform cell balancing typically include by. Lithium ion batteries will never be out of balance again true balancing is a completely new approach to cell balancing. Only cells from better manufacturers are closely matched and batteries that use them require very little balancing.

Equalizing the socs of the various cells in a battery. Safety hazards from overcharged cells li ion batteries have very high electric energy concentrated in small volume. A problem arises when a cell in a string loses capacity or develops elevated self discharge. The worst thing that can happen is thermal runaway.

Since it is bidirectional charge from any selected cell can be transferred at high efficiency to or from 12 or more adjacent cells. Balancing takes care only of the 1st one. 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. In this arena lithium ion battery technology is fast becoming the standard.

The ltc3300 is a standalone bidirectional flyback controller for lithium and lifepo4 batteries that provides up to 10a of balancing current. As we know lithium cells are very sensitive to overcharging and over discharging. The improved effectiveness is the requirement for extra parts at a greater expense. In a pack of four cells if one cell is 3 5v while the other are 3 2v the charge will charging all the cells together since they are in series and it will charge the 3 5v cell to more than recommended voltage since the other batteries are still require charging.

How do you balance a lithium ion battery. The lithium ion battery balancing act more and more the world is running on lithium ion batteries. Quality li ion cells have uniform capacity and low self discharge when new. Unfortunately cells from many manufacturers have significant cell to cell variations.

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. Adding cell balancing is beneficial especially as the pack ages and the performance of each cell decreases at its own pace. True balancing brings the battery into perfect balance on every charge cycle. 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.