Skip to main content

The Proof: Poor USB cables slow phone charging by 77%

Inexpensive cellphone charging cables, commonly sold online, at drug stores, and at discount stores can exhibit poor phone charging speed. Some times the charging performance is so poor that people think their phone has gone bad. Here, I'll show how cheap cable construction can compromise charging performance.

Verifying Cable Quality

The following experiment is designed to show how bad cables ruin charging speeds. I will be measuring various USB extension cables to experimentally show how poor cable construction can have a significant negative impact on smart phone charging rates.

In order to standardize the experiment and eliminate variables, I will be using a genuine Apple "1 Amp" USB charger along with a genuine Apple USB lightning cable. These components were delivered new by Apple with my iPhone 11, so I know they are "legitimate" (not clones or counterfeits). They are name brand components sold by a reliable retailer.

But I'm not here to test these well-known cables. Instead I am testing general purpose USB extension cables in order to show how a  poor cable can negatively impact charging rates.

Two Experiments

  • Experiment 1 will report the power delivered by the standard charging setup, without any USB extension cable in the system.
  • Experiment 2 will report the power delivered by the standard charging setup, but with a USB extension cable in the system.

Will a simple USB extension cord added to the charging setup change the amount of power delivered?  Many people might conclude that there will be negligible difference between the above charging setups.

To figure this out, we will look at a sample of the energy delivered (Watts) through the power meter. Watts is calculated my multiplying amperage times voltage. 

Data Collection

Experiment 1 is simply measuring the power being delivered to my iPhone 11 through the Apple-provided AC adapter and cable. As you can see in Photo 1, this test shows the charging system delivering 0.96 Amps at 4.90 Volts. This seems reasonable given the specifications of the charger (1 Amp at 5 VDC).

Experiment 1 data: 0.96A x 4.90v = 4.704 Watts

Photo 1: The baseline test delivers 4.704 watts

 

Experiment 2 has the exact same setup, except that a USB extension cable has been inserted between the Apple AC power adapter and the power meter. All other aspects of the experiment are identical. As you can see in Photo 2, this test shows the system delivering a mere 0.26 Amps at 4.08 Volts.

Experiment 2 data: 0.26A x 4.08v = 1.061 Watts

Photo 2: with the cheap USB cord in the circuit, 77% less energy is provided

 

Results and Analysis

Experiment 1, without USB Extension..: 4.704 Watts Delivered
Experiment 2, with the USB Extension.: 1.061 Watts Delivered

The results from this simple test show that there is a 77% reduction in energy delivered if the USB extension cable is in the charging path.

One explanation for this is that the USB extension cable is poorly constructed. Thin conductors would make the cable notably less expensive to manufacturer, but would result in higher electrical resistance. 

In particular, the short USB extension cable adds 10.5Ω of resistance to the charging circuit.  A well-constructed short USB cable would have a resistance of less than 1Ω.

Ultimately, this results in very slow charging times.

Other low-end USB cables, including cables with microUSB and lightning connectors, may also be constructed with low-quality conductors, leading to charging times that are much lower than expected.

Conclusion

It is impossible to say how good a cable is without directly measuring its qualities. However, shorter, thicker, stiffer cables are probably better in terms of charging speed. Thinner, longer, or highly flexible cables are far more likely to be lousy cables.

Only buy legitimate brand-name cables from a truly reputable source. Otherwise, you might be buying high-resistance cables that are not able to charge your phone as quickly as it drains. 

Labels:

Popular posts from this blog

Fixing a SodaStream Jet, part 1: Disassembly Guide

I've had my SodaStream Jet for years, and once in a while something has gone wrong. Disassembly is the first step to repair.  Start with this article to see how to disassemble the SodaStream, and then once you have that down, scroll through my other articles to see how I repaired specfic SodaStream problems. SodaStream Jet Disassembly Guide Tools Required Flat head screwdriver Phillips head screwdriver 1. Remove the Carbonator.  Duh. 2. Remove the black panel lever The front big black tilt lever needs to be removed first. Removing this panel is tricky, but it isn't impossible. Looking up at the bottom of the black panel, there are two tabs, one on the left and one on the right. These tabs fully secure the panel in place. The trick is to use a flat-head screwdriver under the plastic to gently lever the tabs out of the way.  Note in the pictures how I approach these tabs with my screwdriver.  I usually release the left side first, and then I release ...
Read more

Fixing a SodaStream Jet, Repair #2 - Broken Fill Button

My Soda Stream Jet's fill button broke, which means I can not longer carbonate water by pressing the pushbutton. This caused all sorts of grief in my household. Here is how I managed to repair my Jet to give it another 10 years of life (hopefully). First, a look at the button The fill button on the top of the SodaStream is actually a simple lever. Pressing down on the button moves a pin that does the actual work of pressing open the Carbonator's valve. Unfortunately, the axis point is fairly thin and can see a lot of stress. That's where my Soda Stream button cracked. [ I think the usage tip here is "don't over-press the button like a gorilla, it doesn't do anything but put high stress on the button."] Cracked levering point of the button The Pesky Lever Retaining Pin The Fix It was pretty easy for me to replace the button: Take off the back of the Soda Stream and remove the carbonator. Push out the the button lever's steel retaining pin. This takes qu...
Read more

Macintosh: Upgrading an eMac

It's been a long time since I wrote this article, but the fact remains: The good old eMac can still be useful if you take the simple steps to keep it as good as it can be.  All can run Tiger, and most can run Leopard - great operating systems for their day with a bit of useful life.  This article describes the procedure I used to upgrade my old eMac, including: Replacing the internal hard disk with a large capacity drive. Increasing the memory for performance Upgrading the operating system Here I'm upgrading a 700 MHz eMac, but the procedure and tasks for upgrading other eMac models should be almost identical. Upgrading versus Replacing My sister's eMac is of the 700 mhz variety, with 256 MB of memory. The machine seemed to be getting "slower", and the original 40 GB disk was becoming jammed packed with photos and iTunes, and within a few months she'd be out of disk space. There were two options to address the problems: upgrade the eMac, or go o...
Read more

Installing a CarPlay radio in a Honda CRV

I ended up buying a 2013 Honda CRV and decided to replace the stock radio/CD player with an upgraded unit.  This was far easier and cheaper than I imagined, but the hardest part was selecting a unit to buy  This article covers how I made my choice.   The basic form factor for my CRV head unit Selecting a Unit The Car I have a 2013 CR/V, which is the same series of all of the CR/Vs from model year 2012 through 2016. Therefore it was important to find a radio unit that fits this model. The CRV has steering wheel radio controls, and I wanted to use them.  This uses a technology called CAN-Bus, which is kind of like USB for cars.  Therefore, a CAN-Bus capability would be able to leverage all these steering wheel features.  In addition, the CRV has a backup camera that would be nice to tie into. And of course I wanted to leverage the existing speakers and USB port. Form Factor I wanted a unit that had a big display, and I wanted a unit that was easy to purchas...
Read more

Using a Garmin eTrex with a Macintosh or Linux

The Garmin eTrex series consists of decent, full featured handheld GPS units. The cheaper monochrome eTrex models have a basic RS-232 serial interface, and the color eTrex models sport USB connectivity. In this article I'll talk about my experience with connecting both USB and serial port versions of the eTrex series to my Mac and to my Linux-based PC. I personally use the Garmin Vista HCx GPS now, but the other Garmins in the eTrex series, including the inexpensive but well specified Garmin eTrex Venture should work the same way. Dealing with the eTrex Series with USB Most of the eTrex units with a color screen have a USB port on the back. Happily, this USB port uses a common USB connector, so it is easy to physically connect a USB eTrex to a Mac or a PC running Linux. The USB Port on an eTrex I have found two pieces of software perfect for use with a USB eTrex, without the need for special drivers: GPSBabel+ and Google Earth . The Mac version of the freeware program ...
Read more

Old Apple gear that keeps on ticking

I've been dealing with Apple computer gear for a long time, as have my friends and family. Here is a list of the old gear that me and/or my friends have in active service.   Note that this gear is in real service, and isn't treated as museum pieces or as part of a retro-computing hobby. 2008: Apple Airport Express, draft-N, first generation 2009: Apple MacBook, late 2009 (utility use only) 2010: Apple iPod nano, 6th generation 2013: Apple Airport Extreme AC 2015: Apple TV HD (4th generation) The big winner here is the Airport Express, which is modern enough to do its job, and it just keeps on going.  The device that my friend runs has been in operation for more than 125000 hours.  It received its most recent firmware update on 28 August 2018, 10+ years after its initial release. In terms of security: it has no open, unpatched CVE vulnerability reports.  Many generations of other routers have come and go while this one keeps going.
Read more

Other Posts

Show more