Why Your USB-C Cable Isn’t Charging Your Device Fast Enough
When USB-C first came out, it seemed like we’d finally achieved the digital dream of one universal plug that could do everything. But the reality is far more frustrating. While everything from your laptop to your tablet to your phone can connect to the same cable or charger, they can produce vastly different results depending on which charger or cable you use. Worse, it’s not always clear why.
This problem arises from two main issues. The first is cables that conform to different USB specifications, not necessarily labeled as such. The second is charging bricks that provide different power levels, often with at least some labeling, but with less clarity about what those labels mean.
There’s a good chance you’ve encountered this problem without even realizing it. For example, a friend of mine had an external portable monitor that connected to her laptop exclusively via a USB-C cable — a special cable she called the “magic cable.” She called it that because, for some reason she couldn’t figure out, any other cable simply wouldn’t work. Those other cables were useful for charging her phone or connecting peripherals, but not for this portable monitor.
If you find yourself in a similar situation, here’s what makes these cables so magical.
Why Not All USB-C Cables Are Created Equal
To illustrate the basic problem, what do you picture when I say “USB-C”? If you pictured a squat little oval connector, you’re right! However, if you pictured that oval attached to a cable, well, that’s a slightly different story. Technically – and we’re going to have to get pretty technical for this explanation – “USB-C” only refers to the port and connector type.
In addition, USB specifications are used to specify minimum data transfer rates and power delivery. This can be complicated, but the important part for charging purposes is the Power Delivery rating of the cable or charger.
Power Delivery (often referred to as USB-PD) is a subset of the USB specification that allows the cable to provide enough power to charge your devices. However, “enough” is a relative term. Each USB port provides a little bit of power—after all, that’s why your wired mouse or keyboard turns on when you plug it in—but when it comes to charging devices like your smartphone or tablet, the power requirements increase.
Why is it important to use the right charger?
Power Delivery is a feature added to the USB specifications to prevent manufacturers from stating exactly how much power a particular charger can deliver. It’s typically measured in watts (or W). For example, a laptop might come with a 100W power supply, while a smartphone might only need a 20W charger to charge quickly.
This also brings us to another complicating factor: fast charging. Technically, if you plug a lower-wattage charger into a more powerful device, it will still be able to charge from it; it just might take a long time. A 5W charger might charge your phone overnight, while a 20W charger will top up its battery in an hour or two.
For devices like laptops or tablets, the amount of power you use just by using the device can actually exceed how much power a slow charging cable can provide. That’s why my friend’s portable monitor needed a special cable. Turning on a bright screen takes a fair amount of power, and non-magic cables were probably only meant for things like plugging in a mouse or charging headphones. If the device you’re plugging in requires more power than the cable or charging brick can provide, it will either continue to drain the battery (though perhaps a little more slowly) or shut down completely.
If you’re plugging your cable into a standalone charging unit, that’s another important piece of the puzzle. Charging units that plug into a wall outlet don’t always provide the maximum power for the cables plugged into them. Some units that have multiple outlets may even provide different power levels for different plugs.
It’s important to make sure that no matter what you use to charge your devices, you need to make sure that each step in the chain is up to the task. The outlet in your home provides enough power (hopefully), but beyond that, the charging block, cable, and even the device itself need to support the amount of power you need.
So how do you find the right charging cable?
The most annoying thing about all this is that between the standards agency that manages the USB specs and manufacturers trying to differentiate their own products, USB cable labeling has become a nightmare. To put it into perspective, cables capable of transferring data at up to 5 Gbps have been called USB 3.0, USB 3.1 Gen 1 , and USB 3.2 Gen 1 over the past decade or so. All of these labels, more or less , mean basically the same thing.
So forget all that. If you only care about how fast you charge your gadgets, there are two main things you should pay attention to:
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What charger does your device come with? This is the easiest option. If your device comes with a charger or cable, that’s likely what will charge it the fastest. If you use a slower cable, your device will slow down to match it, and if you use a faster one, your device won’t charge any faster than it’s programmed to.
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What is the wattage of the charger? If you’re buying a third-party product, many manufacturers list the maximum wattage of their products. This is usually a little more common for charging bricks than the cables themselves, but in general, the higher the better. Your phone doesn’t need a 100W charger at all, but your laptop might. And as mentioned earlier, your devices will default to the slowest element in the chain.
In some cases, you may find a label on the charger that says how much power it delivers, such as “100W,” although if this isn’t printed directly on the device, you can look up its model online. Another handy trick if your cable doesn’t have a label but you know what device it came with is to look at the product itself. If, say, your smartphone says it requires a 20W charger to fast charge, then it’s safe to assume that any cables that came with it support at least that much power.
What happens if you use the “wrong” charger?
The good news is that in the vast majority of cases, you won’t damage your devices if you use the wrong charger on them. A 100W charger can still charge your phone quickly, even if it’s not using its full capacity. Even a slow charger will still deliver power; it just might take a while. In fact, if you had a smartphone before companies started advertising “fast charging,” that’s exactly what was happening.
The only real way things can go wrong is if you try to use your device for something that requires more power than the charger can provide. Gaming laptops are particularly susceptible to this. Even powerful 100-watt USB-C chargers can’t always provide enough juice to keep up with the demand of AAA games, which heat up your GPU. Incidentally, this is why gaming laptops are one of the few devices that still come with a giant, humming charger.
Even then, you’re unlikely to damage your device, but it will rely on whatever power is left in the battery to keep it running. It will drain more slowly because it’s trying to get power from both the battery and the wall outlet at the same time, but if you do anything too demanding, it will eventually die.
However, when it comes to peripherals, like my friend’s portable monitor, that don’t have their own batteries, they simply won’t turn on. If you plug in a device that requires USB power and it doesn’t turn on, there’s a good chance you’re either using a cable that isn’t rated to carry enough power, or the device you’re plugging it into can’t provide enough.