Just how safe is your smartphone battery?

Editorial / Tech
smartphone battery

Even with the advanced technologies in place to contain the volatile power, sometimes it isn’t enough to hold back natures forces.

Samsung’s Galaxy Note7 problems seem to be compounding on a daily basis. Not only has their flagship device been blamed for numerous explosions and fires, but now other Samsung phones have been reported to be exploding or catching fire as well. But the smartphone battery explosions aren’t limited to Samsung. While the current news cycle has been focusing on Samsung due to the company’s unprecedented Note7 recall, Apple isn’t immune to smartphone battery problems either. The FAA is currently investigating a case where an iPhone apparently burst into flames in mid-flight. Here are just a few stories about smartphone explosions or fires.

While the Note7 problem seems to extend far into the supply chain, you have to ask: just how safe is your smartphone battery? Even with the advanced technologies in place to contain the volatile power, sometimes it isn’t enough to hold back natures forces. Should consumers be concerned that their smartphones could explode at any given moment? There are pros and cons to the battery technology most smartphones use today, lithium-ion. Some of the pros include, the ability to recharge multiple times and high capacity cells. Some of the cons include cell degradation and they can become volatile in high temperatures such as direct sunlight. Lion Technology Inc. has the following to say about lithium-ion batteries.

The risk of a lithium-battery-related event is low—occurring only in about two or three battery packs per million. However, when an event does occur, it is likely to involve fire, venting of gases, flying metal shrapnel, harmful smoke, and even an explosion.

A battery can catch fire due to an internal short circuit. When a short circuit occurs, it causes overheating of the cells within a battery, which can ultimately lead to a condition known as “thermal runaway.” Thermal runaway is a cycle of events that begins with an increase in temperature inside a cell. The rise in temperature results in increased current, which in turn accelerates the cell’s chemical reaction rate. As the chemical reaction rate increases, more heat is produced, again causing an increase in temperature. And the cycle continues, typically only ending when the battery explodes or erupts into flames.

What’s particularly dangerous about thermal runaway is that is doesn’t typically confine itself to just one cell. The buildup of pressure and temperature within a cell can become too much for the cell to contain, causing it to explode and vent its contents. This can lead to neighboring cells going into thermal runaway as well.

As Lion Technology says, the risk of an event occurring is low, or at least low enough for it to be acceptable by the government. The industry knows there could be an event that might occur and those events could produce collateral damage. But those are risks both manufactures and consumers are taking when using products with these batteries in them. In the case of a smartphone like the Note7, the waterproofing of the chassis also creates a very nice pressure seal that doesn’t allow the expanding battery to dissipate its energy. Therefore it just pushes and pushes until it finally explodes. If the chassis wasn’t around the battery, you’d get more of an instant flash fire than an explosion.

New lithium-ion technology developed at Stanford University could be the answer to making these batteries safer. The new materials created at Stanford could shut down lithium-ion batteries before they get to a no return overheating stage and then restart the battery once its at acceptable cool levels.

“People have tried different strategies to solve the problem of accidental fires in lithium-ion batteries,” Zhenan Bao, a professor of chemical engineering at Stanford, said in a pres release. “We’ve designed the first battery that can be shut down and revived over repeated heating and cooling cycles without compromising performance.”

“Compared with previous approaches, our design provides a reliable, fast, reversible strategy that can achieve both high battery performance and improved safety,” Cui added. “This strategy holds great promise for practical battery applications.”

It’s unclear if the new method Stanford has been working on would have been successful in the Samsung cases, as most speculate the batteries were just defective. But it will be interesting to see if this new method can be brought to the consumer level giving lithium-ion batteries more fail safes. For now, you’re probably OK not to worry too much about your smartphone battery exploding. First off, if you still haven’t returned your Note7 then we suggest you do that immediately. When a manufacturer is voluntarily recalling a product worldwide, that is indeed a serious matter.

Second, for other smartphone owners, using common sense is key. When using your smartphone for prolonged periods understand that your battery is working hard and it will get hot. Give your phone and its battery some time to cool down and take a break. When you’re traveling in your car be sure to try and place your phone in a shaded area out of the sun, exposing it to the sun can heat it up further and the battery inside. Finally, don’t be a wallhugger, you know you people who have to plug your phone in anytime an outlet is around. Lithium-ion batteries should be cared for gently and charging methods paid attention to. Overcharging your phone can happen, even with failsafes built into modern smartphones.

Lithium-ion operates safely within the designated operating voltages; however, the battery becomes unstable if inadvertently charged to a higher than specified voltage. Prolonged charging above 4.30V on a Li-ion designed for 4.20V/cell will plate metallic lithium on the anode. The cathode material becomes an oxidizing agent, loses stability and produces carbon dioxide (CO2). The cell pressure rises and if the charge is allowed to continue, the current interrupt device (CID) responsible for cell safety disconnects at 1,000–1,380kPa (145–200psi). Should the pressure rise further, the safety membrane on some Li-ion bursts open at about 3,450kPa (500psi) and the cell might eventually vent with flame.

If you’re really concerned about charging your battery and want to follow some guidelines, Battery University gives these guidelines.

  • Turn off the device or disconnect the load on charge to allow the current to drop unhindered during saturation. A parasitic load confuses the charger.
  • Charge at a moderate temperature. Do not charge at freezing temperature. (See BU-410: Charging at High and Low Temperatures)
  • Lithium-ion does not need to be fully charged; a partial charge is better.
  • Not all chargers apply a full topping charge and the battery may not be fully charged when the “ready” signal appears; a 100 percent charge on a fuel gauge may be a lie.
  • Discontinue using charger and/or battery if the battery gets excessively warm.
  • Apply some charge to an empty battery before storing (40–50 percent SoC is ideal). (See BU-702: How to Store Batteries.)

For the most part the smartphone batteries of today are perfectly safe. There are those rare occasions when one might go rogue like in some of the cases above, then there the case like the Note7 where the manufacturer just knows that there is a large scale problem. I wouldn’t worry too much about your smartphone turning into a bomb.

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