FYI, here is an article on how to best charge your smartphone and prolong the battery life -- basically, not past 80%. Also the following statement is included in the article: "If you own an iPhone, simply turn off Optimized Battery Charging, and your battery capacity will last longer." I checked my iPhone and this function was turned on. The article recommends that I turn it off. Also, I am guilty of always charging my iPhone or iPad to 100%. I might have to rethink that approach, and turn off that 'optimize' function also.
New smartphone? Great! Now don’t charge it past 80%
Jim Hamm
By Brian Livingston
Sales of new smartphones are skyrocketing — Samsung's new S21 line sold three times as many units in the US in March 2021 as last year's S20 series did in the same period, according to SamMobile — but few people are learning from the manufacturers about these phones' dirty little secret.
That's the fact that charging these devices' lithium-ion (Li-ion) batteries to a full 100% wears out a great deal of your battery's capacity within a year or two. This has been written about before. But in this story, I'll show you how to triple the usable life of your gadgets' batteries — either on your own or using a simple app.
You have a life cycle — and your batteries do, too
Many people don't realize the awful truth (though it's usually explained in the fine print). The Li-ion batteries in smartphones, tablets, laptops, and even electric vehicles lose a significant amount of capacity after a certain number of charge cycles.
Definitions vary, but as a rule of thumb, one round trip — a single charge cycle — is consumed when you boost a battery from 0% to 100% and then run it down to 0% again. Fractions of cycles add up. Let's say you charge a battery from 30% to 80% (an increase of 50 percentage points). You run the battery down and then charge it from 30% to 80% again (another 50 points). The sum is 100 points: another way to consume one cycle.
What people need to know is that all charging is not the same. According to smartphone app maker Digibites, "Charging to 81% causes 0.22 cycles of wear." Charging your device the rest of the way, from 80% to 100%, causes much more wear and permanently damages your battery capacity.
You can expect to get the following number of charge cycles from a smartphone's battery before your battery becomes irksome, having permanently lost 30% of its capacity, according to Battery University:
300 to 500 cycles if you charge your battery to 100% (approximately 4.2 volts per cell)
850 to 1,500 cycles if you charge your battery only to 80% to 85%
If you've been blasting your battery to 100% every night, after a year or so your device lasts far fewer hours on a charge. You're not imagining things! You just wonder why you need to buy a new phone every year or two.
Electric vehicles and laptops provide ways to save battery life
Electric vehicles and laptops are much more expensive than smartphones. Savvy car buyers and corporate tech managers wouldn't tolerate replacing these major investments every one or two years. So, many EVs and laptops have built-in solutions to prevent charging to 100%.
Figure 1. Electric vehicles — such as Teslas, Chevy Volts, and others — use Li-ion batteries similar to the ones in laptops and smartphones, which permanently lose capacity when the batteries are frequently charged past 80%. Photo copyright by Paul Gipe/Wind-Works.org
For example, the 2017 Chevy Volt has a feature that limits most charging to 89%. Newer Volts allow you to set the limit to whatever number you like.
Makers of some laptops — Lenovo, Sony, and others — provide software that can prevent the devices from charging past 80% or some other level you prefer.
Figure 2 shows the options available with Lenovo Vantage, a proprietary configuration app. Setting the maximum threshold at 80% makes Lenovo-, Think-, and Idea-brand computers automatically stop charging when the battery reaches that level. You can configure charging to restart at 70%, or at 5% below the maximum threshold (in this case, 75%), or at any other two numbers you wish. Don't let your battery run down to 0%.
If Vantage is not already installed on a Lenovo laptop, you can obtain it free from a Microsoft Store download page. The app requires Windows 10 Build 17134 and higher (March 2018), although later builds are recommended. Vantage replaces earlier configuration tools, including Lenovo Companion and Lenovo Settings, which didn't have battery protection. (To avoid conflicts, you may need to uninstall the Companion and/or Settings app before installing Vantage, according to a Lenovo forum post.)
Figure 2. The Lenovo Vantage app — for laptops running Windows 10 Build 17134 and higher — allows you to keep a machine 70% to 80% charged, or within 5 percentage points of 80%, or any settings you prefer. Source: Lenovo
Personally, I've cajoled an old Sony Vaio laptop to run various tasks for me for more than 10 years. During that entire time, I configured the thing's built-in Battery Care function to stay below 80% charged. After surviving world travels, rain, sleet, and dark of night, the battery capacity of the old hunk of metal still rates as "good," just one step below "excellent." Its battery capacity is more than three-quarters of what it originally was. That's admirable for a spare machine.
You’re intended to repeatedly buy new phones, not make them last
Smartphones' battery-survival situation is more problematic than that of laptops. Phone makers supersize their revenue by selling new models to you every year or two. The name of the game isn't making a phone that will serve you well for a decade (as you might expect of, say, an electric car).
Since Apple introduced iOS 13 in 2019, iPhones have included a feature called Optimized Battery Charging. This app is intended to charge an iPhone up to 80% at night, while the user keeps the device plugged into a charger. Theoretically, the feature "learns" when the user gets up each morning and starts poking at the phone. Long before the user is predicted to wake up, the app automatically charges the battery to 100%.
Figure 3 shows an iPhone's battery level across a typical 24-hour day. The user charges the phone for an hour in the middle of the day (indicated by a lightning bolt in the left half of the graph). That evening, when the phone has worn itself down to around 20%, the user plugs it into a charger and goes to sleep. The dark blue horizontal bar shows when the device is maintained at 80% by the software, in theory. In the wee hours, the light blue bar shows the battery being charged all the way full.
Figure 3. Beginning with iOS 13, iPhones include a feature that pushes the battery capacity to 100% while you sleep. Source: Apple Computer
I don't wish to offend the Apple gods — who will surely smite me — but this "feature" is ludicrous. We want our devices to stop charging at 80% and never get pushed to 100%. What we don't want is our phones to get charged to 100%, especially not every night.
What works in theory doesn't always work in practice. How "battery optimizing" runs and doesn't run has generated numerous complaints on official Apple forums. Perhaps this is why Apple's official webpage titled "Maximizing Battery Life and Lifespan" doesn't even mention Optimized Battery Charging.
Isidor Buchmann, CEO of the battery-analyzer company Cadex Electronics, studied various charging methods. Citing IEEE technical papers, he reports that repeatedly charging a Li-ion battery from 65% to 75% was the best strategy to avoid permanent capacity reduction. (This is similar to Lenovo's 70% to 80% setting.) The worst strategy was repeatedly charging from 25% to 100% (like the iPhone feature). See Figure 6 of Buchmann's article.
Lithium-ion myths come from confusion with older batteries
There are many misconceptions about lithium-ion batteries. A lot of this comes from adages that were drummed into people's heads years ago. Back then, nickel-cadmium (Ni-Cd) and nickle-metal hydride (NiMH) batteries ruled the roost before Li-ion became dominant.
FACT: Li-ion batteries don't suffer from a "memory effect." Ni-Cd and NiMH batteries were sometimes unable to boost themselves past the level of a previous charge. Li-ion batteries largely don't have this problem. See Wikipedia's memory-effect article.
FACT: Li-ion batteries shouldn't be drained to 0%. To cure the so-called memory effect, people were often told to completely discharge Ni-Cd and NiMH batteries and then charge them all the way up. But total drainage can damage a Li-ion battery. (Most smartphones, fortunately, contain circuitry that stops Li-ion batteries from being discharged past a safe point.)
FACT: Li-ion batteries shouldn't be charged past 80%. If you have a choice, it's much better to charge your phone twice a day from 30% to 80% than to charge it once a night from 0% to 100%. The increase in percentage points is the same, but the wear-and-tear of the 80%-to-100% gauntlet adds up. (You won't really damage a Li-ion battery, though, by occasionally charging a phone to 100% for, say, a long flight when there will be no outlets at your seat. Don't obsess over exact percentages.) With the improved battery management in today's devices, you may get by without charging twice a day — but, in any case, don't leave a phone on a charger overnight.
FACT: Don't refrigerate a Li-ion battery or leave it in a hot car. Rechargeable NiCd and NiMH batteries self-discharge by a few percentage points every day at room temperature. In addition, alkaline batteries, such as the common AA and AAA types, self-discharge about 25% per year at 100F (38C). Refrigeration might help in those cases, according to a Green Batteries article. But cold isn't good for Li-ion batteries, and heat definitely makes them wilt. Storing a Li-ion battery for a year at 104F (40C) — a car sitting in the sun easily exceeds that — can permanently eliminate 35% of its capacity, according to Table 3 of a Battery University article.
The answer is an app that alerts you to unplug your phone
The remainder of this story will focus on fixes for Androids, since they comprise 72% of smartphones worldwide as of January 2021, according to Statista. If you own an iPhone, simply turn off Optimized Battery Charging, and your battery capacity will last longer.
On an Android phone, I suppose you could just watch your screen and unplug the thing when it hits 80%. But a much easier solution is to install a free app called AccuBattery, a product of Digibites. I use it myself. There may be a better program out there, but AccuBattery has achieved a rating of 4.6 out of 5 in the Google Play Store, which is one of the highest app scores I've seen.
An install wizard walks you through several configuration steps. By default, the app alerts you with a ringtone when your battery hits 80% charge. But you can change this to any level you prefer. A few one-star reviews complain that this alert isn't audible, the power readings seem off, etc. This is probably because you must configure the phone to protect the app from "task killers" that suspend watchful apps. You must also grant AccuBattery permission to read other apps' power usage, exempt it from "do not disturb" states, and flip other Android switches you may never have tweaked before.
Unlike laptop and EV operating systems, smartphone environments don't allow a mere app to stop charging the battery at a given level. "We cannot stop the phone from charging, as Android devices don't let us control the charging behavior," explains an AccuBattery spokesman who asked to be identified as Chad.
There are zillions of apps that claim to supercharge your battery life. Most of them don't, and a lot of them make the situation worse, as described by the Android Police.
Forget about the wild promises, and just make sure you aren't permanently wrecking your battery capacity.
Figure 4. AccuBattery plays a ringtone when your phone has reached an 80% charge — or any other level you specify. Source: Accubattery guide
Get AccuBattery from the Google Play Store download page. The app learns your phone's battery usage over a seven-day period, which you must wait out to get good results.
After the first few days, the free app includes ads, which are not obtrusive. There's a Pro version based on donations of $3.99 and up, which adds a few types of notifications and eliminates the ads.
I'm happy to have donated a few bucks for the peace of mind of knowing any new phone I buy may actually last a while. Good luck with yours!