Mobile Phone Batteries Are Becoming Less Durable: Is "Planned Obsolescence" at Play?

Similar urban legends are usually just a source of amusement for me, but I didn't expect my elders to pass them down and treat them as "user scripture."

In fact, these usage techniques leftover from the nickel-cadmium battery era not only fail to protect current batteries but also reduce battery capacity and even increase safety hazards…

To understand why good habits from a decade or two ago are now detrimental to batteries, let's talk about what mobile phone batteries have gone through over the years and what truly benefits them. To discuss battery usage habits, we can't avoid the "root of all evil" – the nickel-cadmium battery.

When nickel-cadmium (Ni-Cd) batteries first appeared, they received a lot of positive feedback. Firstly, compared to disposable batteries, they could be repeatedly charged and reused, saving money. Secondly, they promoted the development of portable electronic products.

However, the origin of these strange usage techniques lies in the drawbacks of nickel-cadmium batteries.

The most annoying issue was the "memory effect." If repeatedly charged without being fully discharged, the battery would "remember" that usage range.

For example, if you charge it whenever the battery reaches 20%, tiny crystals will accumulate inside the battery. Over time, the battery will think it's empty at 20%, and it will automatically shut down whenever the charge drops to that level.

The best way to alleviate the memory effect was to fully charge and discharge it, letting the battery remember the feeling of being completely drained. Gradually, people developed the habit of charging only when the phone automatically shut down, and the idea that fully charging and discharging was good for the battery became a consensus of that era.

Besides fully charging and discharging, nickel-cadmium batteries also left behind a lasting belief: batteries are polluting.

This is because cadmium, a heavy metal pollutant in nickel-cadmium batteries, can cause irreversible damage to the human body through diet, breathing, and skin contact. When discarding batteries, they needed extra harmless treatment, which is why environmental education always emphasized the separate recycling of batteries.

Precisely because of these drawbacks, nickel-cadmium batteries were banned for sale in many countries. However, to meet market demand, a similar battery, the nickel-metal hydride (Ni-MH) battery, appeared in 1989. It replaced the polluting cadmium with metal hydride and largely ignored the memory effect.

It sounds a bit unfamiliar, but our 90s friends should have come into contact with it. Toys, cameras, and flashlights used this type of battery when we were kids. Why haven't we seen them in recent years?

That's because nickel-based batteries have another drawback – low voltage. The standard voltage of a nickel-metal hydride battery is usually only 1.2V. Most electronic devices require a supply voltage higher than 3V, so multiple batteries had to be connected in series, increasing the volume and weight.

We can now use batteries that are both "thin and light" and powerful thanks to a company – Sony.

In 1991, Sony partnered with Asahi Kasei to commercialize lithium-ion batteries for the first time. This type of battery is not only small in size and has high energy density and a high nominal voltage (3.7V), but also has no memory effect. Compared to nickel-based batteries, it's more than three times better.

With thinner batteries, products on the market became lighter and more compact. In the early 2000s, classic products like Apple's iPod and BlackBerry's 7100 were born, all thanks to high-density lithium-ion batteries.

Many people are probably confused to see this – bulky feature phones from the past were actually from the same era as the iPod.

Indeed, during the period from 1991 to the early 2000s, although lithium batteries began to be commercialized, they were only available in some high-end products. Most still used nickel-based batteries, resulting in a "new and old coexistence" state in the entire battery market.

But consumers at the time couldn't tell the difference. Even if they bought a phone with a lithium battery, they would still use the habits they had developed before when charging – not charging until the phone shut down, and plugging in the charger overnight. Even if the battery bulged, they would only think the battery was of "poor quality"...

But this isn't really the battery manufacturers' fault. On the one hand, lithium-ion batteries are chemically active. Once the battery is depleted and the voltage is too low, irreversible damage will occur inside the battery, leading to reduced capacity and shorter cycle life.

On the other hand, the technology wasn't mature at the time, and many lithium-ion batteries lacked complete protection circuits. Coupled with the popularity of "universal chargers" that mostly lacked overcharge protection, this combination of "bad habits + crude equipment" kept battery safety on the verge of danger.

Even mature international manufacturers have stumbled on lithium-ion batteries. These experiences and safety issues have driven the gradual transition of batteries in electronic devices to the integrated designs we see today.

However, no one likes integrated batteries, right? The only benefits of integrated design that I can think of are large capacity and fast charging.

Although the capacity is larger, it's still essentially a lithium battery, with the difference being the addition of silicon to the negative electrode material, trading "partial cycle life" and "expansion coefficient" for larger capacity and faster charging speeds.

I wonder if anyone has noticed that battery capacity has increased, but it doesn't seem to last as long.

You may need to charge it two or three times a day after a couple of years, and your phone may become sluggish. This isn't your illusion. This is because most silicon-carbon negative electrode batteries have a cycle life of 500-800 times. When the number of complete charge and discharge cycles approaches this value, the battery capacity will drop below 80%.

To reduce the perceived drop in battery performance, some manufacturers adopt a "frequency reduction" strategy, reducing processor power consumption to avoid rapid battery discharge at low voltage. The Apple battery gate incident was about this.

In addition to capacity decline, battery safety also decreases with usage time. Simply put, the longer you use a lithium-ion battery, the greater the safety hazard.

To prevent accidents, manufacturers will proactively reduce the battery's working voltage range as its health declines, reducing capacity – the so-called "capacity locking."

Is it really for "planned obsolescence"?

We consulted experts in the battery field and learned that, based on current industry technology, battery health is something that cannot be accurately measured. No manufacturer can know the true health of a battery without damaging it.

The health status we see on our phones is actually based on models created by phone and battery manufacturers, combined with usage habits, and is just an estimated value. In simple terms, the algorithm is guessing how healthy your phone battery is and how much capacity it has left.

For manufacturers, since all data is estimated, they plan ahead to ensure battery safety: when the health drops to a certain level, they reduce the voltage to prevent the battery from working at high load.

Because explaining the cost is too high and no one will come forward, capacity locking has become an "under-the-table" OTA update across the industry…

Are manufacturers doing this because battery safety is still as uncontrollable as it was a decade or two ago? We asked the experts again.

Currently, the number of battery safety incidents that can be statistically tracked domestically has been controlled to "one in a million," meaning only 1 thermal runaway case occurs for every million phones. But even at such a low frequency, no manufacturer dares to gamble with safety, so they have to let old batteries do less work.

For us consumers, the safest way to use a phone now is to keep the battery within a comfortable working range and stop the "full charge and discharge" ritual.

Looking back at the decades of battery development, from charging rituals to today's power anxiety. Perhaps when new battery technology arrives, those numbers in the upper right corner of the screen will no longer be a burden on the experience.