Smartphones are now so integral to our daily life. So much so that their batteries couldn’t ever keep up with our daytime needs. (Why can’t we get better batteries already!?)
Which leads to charging phone overnight. Because what’s a better time to recharge than when we’re sleeping? But then the paranoia and fear come hailing down on us: overcharging phone and battery explosion. Leaving in us a dilemma we’re all too familiar with …But is it really bad to charge your phone overnight?
So you leave your phone charging overnight … what terrible fate awaits you? The Big Bang? The Reign of Fire? Neither. Your phone gets charged, just that. The myth that this overcharges your phone – oh wait we’ve said it – it’s A MYTH. At least since phones have evolved into smartphones. And as their newly-earned prefix implies, they’re smart, in that they have an inbuilt protection chip that prevents overcharging at full battery.
In place of the now-debunked overcharging threat is trickle charging. It lowers the current matching the discharge rate (or consumption) to maintain 100% charge level.
During overnight charging, your phone constantly uses battery to stay functional, much like all things living; and when consumption happens, recharging happens. And this opens up to a hell of short-lived battery for whoever couldn’t bear to replace their phones every year or two. (If you do, however … Well, you may skip this reading.)The Real Issues With Charging Phone Overnight
Most phones nowadays use Lithium-ion batteries (LiB). They’re rechargeable and do so faster than rechargeable batteries in the past. They race to 80% in a flash, what with all the fast charging technology boasted by many a clashing smartphone titans (e.g., Huawei and Samsung). Owing to that, phones now take 1 to 2 hours top to fully charge. That’s really saying your precious phone spends most time hooked to the charger at 100% battery while you’re fast asleep. But … what’s the deal?
Stress on Lithium-ion battery. There’s no arguing that Li-ion is superior among batteries. But a champion is not without its weakness. In fact, it’s bordering counterintuitive: Li-ion suffers from stress when dwelling at full state-of-charge (100%). And when it does so consistently month after month, its recoverable capacity will drop; though the decline may not amount to much in the short run, it does leave a dent in the battery capacity that will be a long-term thorn in your side.
Adding insult to injury, it’s not even advisable to fully charge a Li-ion battery for the same reason; what’s more, prolonging it overnight? The closer it gets to 100%, the more degradation it stomachs. Generally, battery level outside the 20% – 80% range will degrade the battery more. But what could be behind this counterintuitive existence?
How Prolonged Charging Degrades Battery
Surely, you’ve heard that Li-ion batteries are bound to decay since day one; everything they do – cycling, discharging, and charging – wastes away their lifespan. But that isn’t to say the process couldn’t be hastened or delayed by your actions.
When charging, Lithium ions swim across the cathode (the positive electrode of a battery) to anode (the negative electrode), which is exactly how it should be. But it is during which that an irreversible damage also takes place: electrically-insulating rock-salts form & buildup over the cathode. Overtime, the buildup grows and battery capacity shrinks.
The worst of all, the buildup blooms like wildflowers after rainy days at higher battery levels and temperatures. Certainly, maintaining a high battery level longer will degrade the battery faster. And this is even more harmful than cycling a battery.
Which is why many, including Apple, recommend storing your battery at half charge …
To clarify, the problem isn’t inherent in trickle charging but charging and high state-of-charge themselves. However, trickle charging lends itself to prolonging charging and high state-of-charge more than needed, more pronouncedly, in an overnight charging session.
We may have phased out of the old Nickel-era, which condemned users to charge their devices fully on every session, lest batteries’ cyclic memory forget their maximum capacity; now, Li-ion suffers from full charge instead.What about heat during overnight charging?
It’s widely known that heat damages the battery capacity too. It’s just less an issue concerning overnight charging because, well, it happens whenever you charge anyway. Most heat is stoked up before nearing 100% owing to fast charging; the low voltage of trickle charge means its generated heat is negligible.