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The over-discharge is potentially dangerous whereas the transom voltage drops are not. It's important to differentiate between transient voltage drops caused by current spikes and continuous low-voltage conditions caused by over-discharge. Over-discharge- also sometimes called "under-voltage"- is a condition where a cell voltage drops below the manufacturer's specified minimal value. Now, let's switch gears and talk about over-discharge. One, it can issue a warning to the host controller through the SMBus or I2C communication lines two, it can open the charge FET or three, ignite the chemical fuse. Depending on severity, the firmware has three possible levels of output control. Also, through the mux of the analog front end and the voltage ADC in the fuel gauge where the firmware compares the measured cell impact voltages to various programmed threshold levels. First, we go directly to the second over-voltage protector whose output ignites a chemical fuse for severe over-voltage. The signal path for over-voltage protection is two-fold. Over-voltage causes thermal runaway and possible fire and/or explosion. Over-voltage, whether applied to the pack from a defective charger or applied to a single cell due to an imbalance condition, is the most dangerous situation. And in accordance with the IEEE 1625 standard, there was a second completely independent over-voltage protector IC. It's companion analog front end circuit, which is often a separate dye within the same IC package, provides a multiplexing of voltage measurement from each cell block, LDL, high-speed, current-monitoring comparators, protection FET drivers, and internal cell-balancing FETs. The gas gauge or fuel gauge IC is an ultra low power microcontroller with high resolution ADCs for measuring voltage, current, and temperature. Now, while there are other typologies in use, this one is most common.
#LETHAL VST OR IGNITE HEAT UP SERIES#
We see here the block diagram for a typical three series cell battery pack. They can come to our rescue in the event of over-voltage, over-discharge, over-current, and over-temperature. While modern lithium-ion cells contain their own mechanical protection devices, we are focused here on the additional electronic protection.
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So lithium-ion protection deserves very serious consideration with best in-class handling, protection circuits, and industry standards. Fortunately, it releases that energy quite a bit slower or else the flaming notebook videos we've all seen would have had a much more lethal outcome. Barsukov and Qian provided a fascinating analysis showing that the typical notebook battery pack contains more combustion energy than a hand grenade.
#LETHAL VST OR IGNITE HEAT UP PORTABLE#
In their book, Battery Power Management for Portable Devices, Drs. This is because of their use of an organic electrolyte that can react with the active materials under high temperature conditions releasing even more heat and spiraling into thermal runaway- which can cause fire, explosion, and venting. Lithium-ion cells are far more dangerous than other types of batteries. We'll cover why needed, over-voltage, over-discharge, over-current, over-temperature, and some solutions. In this video, we'll cover the basics of lithium-ion safety with an emphasis on the circuits and firmware techniques used to implement protection.