Protection Techniques for Small to Medium-Sized Battery Packs

April 6, 2017

Built-in protection devices for Li-ion battery packs help gird against their sensitivity to overvoltage, high temperature, and overcurrent.

Paul Pickering

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Batteries based on lithium ion hold many advantages over other battery chemistries, such as high power density and a flat discharge curve, and are the dominant choice in everything from smartphones to electric vehicles.

Depending on the particular Li-ion chemistry used, the voltage of a single cell is between 3.3 V (LiFePO₄) and 3.7 V (LiCoO₂). A battery pack consists of several cells connected in series—a pack with two cells is a “2S” battery and outputs 7.4 V; a 3S battery outputs 11.1 V; and so on.

In consumer applications, a 1S battery supplies enough power for a personal electronics device such as a fitness band or smartwatch. Industrial and heavier-use consumer applications require larger sizes: 3S or 4S for small power tools or drones; 5S for professional power tools; 7S for vacuums; 10S for garden tools or larger power tools such as saws; and even 20S for heavy-duty applications like forklifts.

About the Author

Paul Pickering

Paul Pickering has over 35 years of engineering and marketing experience, including stints in automotive electronics, precision analog, power semiconductors, flight simulation and robotics. Originally from the North-East of England, he has lived and worked in Europe, the US, and Japan. He has a B.Sc. (Hons) in Physics & Electronics from Royal Holloway College, University of London, and has done graduate work at Tulsa University. In his spare time, he plays and teaches the guitar in the Phoenix, Ariz. area