Complete Guide to Using the Correct Charger or Power Adapter (and What Happens If You Don’t)

The other weekend, I sat down and sorted through all my random electronics junk. As part of that process, I took all my power supplies and adapters and threw them into a box. It ended up being a pretty big box. I’m willing to bet that any given household has a dozen or more of different types of cell phone chargers, AC/DC adapters, power bricks, power cables, and charger plugs.

Having so many chargers can be pretty frustrating. It’s easy to get them separated from the phone or laptop or tablet or router. And once that happens, it can be incredibly difficult to figure out which goes with which. The default solution to this is to try random plugs until you find one that fits into your device. However, this is a big gamble. If you grab an incompatible power adapter, your best case scenario is that it works, albeit not the way the manufacturer intended. The second worst case scenario is that you fry the gadget you are trying to power up. The worst case scenario is that you burn down your house.

In this article, I’m going to walk you through the process of digging through your junk drawer and finding the right power adapter for your device. Then, I’ll tell you why it’s so important to do so.

Fudging It: What Happens if You Use the Wrong Adapter?

Ideally, you’ll have the same voltage, current, and polarity on your adapter and device.

But what if you accidentally (or purposefully) use the wrong adapter? In some cases, the plug won’t fit. But there are many instances where an incompatible power adapter will plug into your device. Here’s what you can expect in each scenario:

Wrong polarity – If you reverse the polarity, a few things can happen. If you’re lucky, nothing will happen, and no damage will occur. If you are unlucky, your device will be damaged. There’s a middle ground, too. Some laptops and other devices include polarity protection, which is essentially a fuse that burns out if you use the wrong polarity. If this happens, you might hear a pop and see smoke. But the device may still work on battery power. However, your DC input will be toast. To fix this, either replace the polarity protection fuse or get it serviced. The good news is that the main circuitry wasn’t fried.Voltage too low – If the voltage on an adapter is lower than the device, but the current is the same, then the device may work, albeit erratically. If we think back to our analogy of voltage being water pressure, then it would mean that the  device has “low blood pressure.”  The effect of low voltage depends on the complexity of the device. A speaker, for example, may be okay, but it just won’t get as loud. More sophisticated devices will falter, and may even shut themselves off when they detect an under-voltage condition. Usually, an under-voltage condition won’t cause damage or shorten the life of your device.Voltage too high – If the adapter has a higher voltage, but the current is the same, then the device will likely shut itself off when it detects an over voltage. If it doesn’t, then it may run hotter than normal, which can shorten the life of the device or cause immediate damage.Current too high – If the adapter has the correct voltage, but the current is greater than what the device input requires, then you shouldn’t see any problems. For example, if you have a laptop that calls for a 19V / 5A DC input, but you use a 19V / 8A DC adapter, your laptop will still get the 19V voltage it requires, but it will only draw 5A of current. As far as current goes, the device calls the shots, and the adapter will have to do less work.Current too Low – If the adapter has the correct voltage, but the adapter’s rated current is lower than what the device input, then a few things might happen. The device could power on, and just draw more current from the adapter than it’s designed for. This could cause the adapter to overheat or fail. Or, the device may power on, but the adapter may not be able to keep up, causing the voltage to drop (see voltage too low above). For laptops running on undercurrent adapters, you might see the battery charge, but the laptop is not powering on, or it may run on power, but the battery won’t charge. Bottom-line: it’s a bad idea to use a lower current rating adapter since it could cause excess heat.