What You Don’t Know About USB Charging

Stay Informed

In the relationship between a smartphone and a USB charging port, it’s the phone that has the power.

That’s because mobile devices such as phones and tablets largely determine how much power they draw when charging. Yet many people believe it’s the USB port that’s in control. That’s just one of the common misconceptions surrounding USB charging. Another is the amount of power a device needs to charge.

Debunking USB Charging Myths

Dispelling these myths is important because USB chargers, like those integral to a receptacle, are becoming more common in commercial, public and residential settings as the number of mobile devices people own continues to grow. Users prefer USB charging because of the convenience. They don’t have to carry around a charging brick or AC adapter. And they provide an added benefit – having constant access to power reduces low-battery anxiety.

60 percent of people in all major cities reported anxiety from a low or dead cell phone battery. (Source)

However, many end users, specifiers, and professional installers do not fully understand the USB charging needs for their space. Often, they’re operating under the assumption that more power advertised at the USB charging receptacle equals faster charging — for example, that a USB receptacle with 5-amps of charging capacity will always charge devices faster than a 2-amp product.

There are three significant problems with that thinking.

  1. The mobile device determines how much current to draw from a port. Current draw is largely based on the device’s internal electrical schematic and also how much charge it needs. A phone with 5 percent battery life will usually demand more current than it will at 90 percent.
  2. Most devices need far less power than people realize.
  3. The total amperage advertised at the receptacle is typically shared across ports. A phone plugged into a 5-amp receptacle with four ports is not getting all 5 amps.

What decision-makers should be asking themselves when spec’ing a project is, “What devices will be charged and how much power will those need?” A restaurant will likely focus on patrons charging smartphones, which need less power than larger devices. An office, on the other hand, will have a mixture of smartphones, tablets and wearables.

What mobile devices actually need to charge?

Legrand has researched how various devices charge, and the results may surprise you. This information could help you decide what USB products are the right fit for your facility. It shows the ranges in current draw of smartphones and tablets tested by Legrand at various stages of battery life.


Understanding USB Charging Needs

With the average American consumer owning 3.64 connected devices, specifiers and installers need to understand the USB charging needs for their space. Remember, when it comes to who holds the power, mobile phones and tablets own the space.  

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The opinions expressed in this piece are solely Legrand's. They do not necessarily represent WESCO’s views.