Everyone knows the phenomenon that even unused mobile devices discharge themselves in no time. Scientists from Canada now want to have found the reason for this. And all by accident.

Why is the cell phone empty again? If there is simply too much day left at the end of the battery, the desperate search for an outlet quickly begins. According to a group of scientists from the University of Halifax, this happens more often than necessary. They discovered a bug that is said to be responsible for the faster discharge of numerous smartphones and notebooks.

“It was completely unexpected, probably nobody would have thought of it,” assistant professor Michael Metzger told Canadian TV broadcaster CBC. The group was actually researching the question of why batteries self-discharge. The fact that they found an answer was pure coincidence – because part of the battery suddenly and completely unexpectedly turned bright red. Actually, the electrolyte liquid used should simply remain colorless. The fact that this changed indicated a previously unknown chemical reaction.

And suddenly it’s red

Batteries always work in the same way: Inside, electrons move through the liquid electrolyte between two electrodes with different polarities. If you connect the positive and negative electrodes each with a cable, a current flow is created and the electrodes leave the battery. However, the discoloration showed that something else was happening in the experiment.

Researchers set out to find the cause of this surprising reaction. “A battery is a closed system,” explains Metzger. That’s why they originally wanted to find out whether the electrolyte or one of the electrodes could cause a discharge. However, when they analyzed the now discolored substance, they came across a different explanation: they came across the plastic dimethyl terephthalate, or DMT for short. And discovered its effect within the battery. Instead of exiting through the electrodes, the electrons were moved back and forth inside the battery by the DMT – thereby discharging it.

Surprising realization

But where did the unexpected DMT inside the sealed battery come from? With an exact chemical composition, the researchers came across a clue. The plastic is chemically very close to polyethylene terephthalate – the PET known from plastic bottles. And after an intensive search of the components, that was actually found in the battery: in tiny strips of adhesive tape that held parts of the battery together.

“Realizing that these strips are not an inactive part of the battery is a pretty important finding,” explains Metzger. Many manufacturers of notebooks, smartphones and other devices use exactly this type of plastic in their own batteries. And would have shown themselves to be very interested after being contacted by the researchers. “They want to change something to remove these parts from the battery cells to avoid self-discharge.”

Easy to avoid

In practice, it’s not that difficult. As Metzger and his team discovered, the effect can be avoided with a similar but slightly stronger plastic such as polypropylene, while the battery’s other functions remain unaffected. The only disadvantage: the alternative is slightly more expensive.

As a customer, however, you should not expect gigantic leaps in battery life. On the one hand, it is completely unclear how many manufacturers actually use PET in their devices. In addition, only devices with a revised battery should benefit from this. On the other hand, the self-discharge happens very slowly, it is a problem especially with devices that are only used occasionally. If a smartphone or laptop is in use every day, frequently used or resource-hungry apps are likely to remain the main cause of the falling battery level in everyday life.

What: CBC