How fast is fast charging, and is it safe for your battery?

For years, there have been quite a few myths floating around about various settings and actions that can harm a battery's lifespan, or worse, cause dangerous overheating or even explosions. Thankfully - aside from the Galaxy Note 7 fiasco - we've seen next to zero danger of smartphones spontaneously exploding, but there are certain behaviors that can have detrimental effects, although they do take a long time to actually manifest.

First off, here's what's not true. It's not possible to "overcharge" a phone; once it's at 100%, the circuit stops the charging process and won't provide any more power to the device than is necessary for its standard operation. Second, in 2020, there's no pressing need to disable location services such as GPS or local Bluetooth scanning, as those protocols have been optimized to significantly reduce their power drain.

Furthermore, it doesn't really help and can possibly waste electricity to constantly close background apps when you're not using them, especially if you're likely to open those apps again in the near future. The fact is that takes more electricity for your phone to close and then reopen apps than it does for them to remain in the background occupying a minimal amount of RAM. Finally, it's not hugely important - as far as actual battery health is concerned - to use converters and cables made by your phone's manufacturers, although it can affect fast charging speeds in some cases. Some protocols work slightly better with an OEM-branded cable, while some won't fast charge and will revert to traditional wattages, but there's no actual risk when mixing reputable brands of chargers, cables, and phones.

So what difference does it make whether or not you even pay attention to long-term battery health? Most obviously is the fact that battery capacity degrades over time simply due to the nature of the physics involved. You may well remember the relatively massive outcry when iOS was found to slow devices as the battery life decreased. Apple appears to have backed off that stance after offering discounted battery replacements for affected devices. For most, if not all electronics on the market today, though, the biggest drawback of careless battery management is an increasingly lower capacity.

As far as actual risks to battery lifespan go, heat is one of the main agitators. Excess heat is the bane of almost all electronics, and batteries are no exception. Keeping a phone under your pillow at night as it charges, for example, is one behavior that is definitely a terrible idea (yes, people do this). Additionally, lithium ion cells have only a finite number of charging cycles. This number is, admittedly, quite high, and average users shouldn't have to worry a whole lot about using them up in the course of the one to three years they own their smartphone. If, however, you typically use your mobile device for high-drain activities such as a mobile hot spot or video streaming device, it's worth considering plugging it in while you're using it so as to offload the power drain to a wall outlet or more easily replaceable battery pack.

Possibly the most harmful to long-term battery life, though - and totally separate from fast charging rates - is extreme cycling. The chemistry of Li-ion cells means that they're most stable at between 50% and 70% charge, generally speaking, and the farther you get from that range, the more likely you are to be hurting your overall capacity. Of course, we're not saying that dipping below 30% or even running the battery out every now and then will actually cause noticeable damage - these behaviors only cause problems if they become habits. If you do find yourself regularly operating at or below 20% charge, it's entirely possible you will notice a degraded battery after a year of use.

Similarly, if you always keep devices topped off at 100%, you run the risk of that 100% number not meaning quite what it did 18 months ago. If you're the type of electronics junkie who upgrades their phone every year to be in line with the newest releases, then more power to you, because you might just not care. Because not everyone is so inclined, however, it's an important concept to keep in the back of your mind. Naturally, don't hesitate to top it off all the way when necessary, because why would you pay for such a capable phone if you can't use it when you need it? On the other hand, being aware of real-world battery issues is a good way to maximize your investment and keep a phone in peak condition for as long as you want to use it.

Because Qualcomm's responsible for the Snapdragon chipset line, which generates more revenue than any other SoC on the market, Qualcomm QC is one of the most widespread standards. From the original specification through versions 1.0 and 2.0, this common protocol offers 10W, 18W, and 36W maximums, and moves up to a full 100W for Quick Charge 4 and 4+. While an overwhelming majority of Snapdragon smartphones have the hardware capability to utilize at least one form of the standard, it is still up to device manufacturers to enable the feature. As mentioned above, some producers are loathe to include the high-wattage versions, although Samsung has finally caved and included QC 2.0 in their latest flagship phones.

Aside from just a high maximum output, there are several interesting features that manufacturers can implement using QC. One of them is Dual Charge technology, which involves having a second charging circuit alongside the first, which shares the load and significantly reduces heat dissipation, allowing for faster recharging with less long-term damage from increased temperatures. Another is dynamic voltage adjustment, starting with 200mV steps in version 3.0 and moving to 20mV increments in 4 and beyond. This technology is known as INOV, which stands for Intelligent negotiation for Optimum Voltage.

In a rare case of various companies adopting the same or similar high-quality protocol, any of these third-party systems should work quite well with an advanced enough Qualcomm Quick Charge converter. Due to the huge prevalence of Qualcomm QC chargers, many consumers will be more than satisfied if they fall back on its cross-compatibility.

This an interesting one because, like USB Power Delivery and Qualcomm Quick charge, it's designed to work across various manufacturers' hardware, although it's not quite as well known or as widespread as PD and it's a little bit tougher to navigate than QC; it works perfectly with many popular smartphones, decently with others, and very poorly with some. Generally speaking, PowerIQ 2.0 is noticeably slower than Quick Charge 3.0, although it can and does beat standard 500mA charging rates.

PowerIQ 3.0 certainly appears to do a great job of joining all the competing standards, and coupled with the generally agreeable prices and reliability of the brand's products, it's a worthwhile choice for many users. It claims to be as fast as QC 3.0 and to charge high-end Samsung Galaxies and iPhones to 50% in about 30 minutes. Outside of those two families, your mileage may vary (for example, some Motorola owners report that it charges their phones at standard rates only), but it's definitely worth a look if you want a single charger that can accommodate various devices, and if you don't necessarily need the absolute fastest speeds on the planet.

Huawei also has its own proprietary standard called Super Fast Charging, which tops out at 40W. Like Oppo's method, it uses dynamic current adjustment that could theoretically cause long-term heat issues, although the evidence has yet to determine if that's true. Honestly, one of its biggest drawbacks, Huawei's recent forced departure from the Google Play Services ecosystem, also applies to all their handsets. It remains to be seen if the coming months lead to the Chinese smartphone giant's reentry into the US market, but we're not holding breath. Unfortunately, a smartphone without access to the Google Play Store is just not terribly useful outside of China. On the other hand, if you have an older Huawei model that Google still supports, its proprietary charging method performs on a par with the very fastest.