My Samsung Galaxy S5 smartphone charges too slow, how can I make it faster?

I noticed lately that as a heavy smartphone user, the charging rate of my Galaxy S5 running the Android v6 Marshmallow firmware was barely outpacing drain rate.  Sometimes even an overnight charge would not be enough to bring it back to a full charge.  After installing the free app Ampere, I realized that regardless of what the phone was connected to (wall charger, USB2, USB3 ports), it was charging at only the 500mA rate that is the maximum allowed for computer USB 1.1/2.0 ports.  So I did some investigation and this is how I found that I was able to increase the rate to 2.0A on both my Galaxy S5 and my wife’s Google Nexus 5, dramatically reducing charge time over most of the battery’s capacity range.

There are three main factors that affect micro-USB charge rate on Android and other types of battery-powered devices:

  • The device’s internal hardware and system software
  • The type of charging cable
  • The type of charger equipment

I will explain each one of these concepts as it relates to Android smartphones, then make some recommendations.

How phone internals affect charge rate

Android phones are powered by system-on-chip (SoC) logic which includes not only CPU cores, but memory controller, interrupt controller, SD controller, GPIO, video hardware, generally everything needed to create a generic interactive system.  Additional hardware such as GPS, Bluetooth, Wifi radio, and NAND flash are connected to compose what we are familiar with as a smartphone.  The SoC itself can be manufactured by a variety of parties, and in smartphones it is often manufactured by Qualcomm.  The core logic embedded into such a SoC is a combination of licensed items such as the ARM CPU cores and technology that is developed and integrated by Qualcomm itself.

One such Qualcomm-developed technology is what is known as Quick Charge.  Quick Charge is an evolving proprietary standard that device manufacturers license from Qualcomm, which allows a USB device and charger to agree, under certain conditions, to exceed the limits on power supplied through a USB cable that would otherwise be imposed by the USB 1.1/2.0 standard.

Why do we need to do this?  The USB specification originally evolved in a world where power consumption capacity of USB devices was much lower and could be satisfied by the 2.5W power (5V@500mA) available from a computer’s USB port.  Today’s devices are much more powerful and require ever more powerful batteries to sustain usable runtime.  The old 2.5W port power, having never been designed for charging batteries, is simply not enough to charge today’s larger capacity batteries in a reasonable amount of time, and often cannot even maintain the battery charge against the drain of merely actively using the device.  Additionally, lack of standardization resulted in interoperability issues as detailed in this article in the “Cheating” section.

Here are some excellent articles about the state of USB charging today (2016):

How USB charging works, or how to avoid blowing up your smartphone

The Basics of USB Battery Charging: A Survival Guide

Introduction to USB Power Delivery

With Quick Charge in the picture, a higher voltage and/or more current can be received by the device across the same 4-wire USB1.1/2.0 cables, with the end result of providing more charging power when connected to a Quick Charge capable device.  Quick Charge 1.0 increases the charging current drawn by the device only, while the 2.0 and 3.0 revisions also can increase the voltage supplied to it, allowing the same amount of power to pass over poorer quality USB cables than 1.0.  Also of note is that Quick Charge 2.0 goes by many names and that Qualcomm maintains a device compatibility list for Quick Charge 2.0 and 3.0.

While Quick Charge is a proprietary standard, it is widespread in the Android ecosystem and the existence of it and proprietary protocols like it forced rapid iteration of the official USB standards to keep up with the device marketplace.

Qualcomm Quick Charge vs USB Battery Charging Specification vs USB Power Delivery Specification

While the various standards have similar aims (increase the amount of power delivered to a charging device over that of legacy USB1.1/2.0), the implementations differ.

  • USB3.0 allows the device to draw up to 900mA of charging current from a standard port when using a USB3 cable, for a maximum charging power of 4.5W.
  • USB Battery Charging Specification (now part of USB2.0 and USB3.0) defines special port types and allows a device compliant to the new specification to negotiate to draw up to 1.5A of charging current from a PC or other device through any USB cable via the data lines and to pass data over the same cable if connected to a “charging downstream port (CDP)”; or, to pull up to 1.5A of charging current unconditionally if connected to a “dedicated charging port (DCP)”, for a maximum charging power of 7.5W in either case.  Among benefits of the latter is that a charge-only cable can be used, which is thinner at the same wire gauge (and more secure).  (The CDP and DCP ports are intended to be marked as such, but in practice are not always.)
  • Qualcomm Quick Charge 1.0 allows the device to negotiate to draw up to 2A of charging current from a charging accessory through a normal Micro-USB 2.0 cable, for a maximum charging power of 10W.
  • Qualcomm Quick Charge 2.0 allows the device to negotiate to draw up to 1.5A of charging current from a charging accessory through a normal Micro-USB 2.0 cable, and to vary the voltage in predefined steps between 5V and 12V, subject to a maximum charging power of 18W.
  • Qualcomm Quick Charge 3.0 allows the device to negotiate to draw up to 1.5A of charging current from a charging accessory through a normal Micro-USB 2.0 cable, and to vary the voltage continuously between 3.2V and 20V, subject to a maximum charging power of 18W.
  • USB Power Delivery Specification (released with USB 3.1) allows the device to negotiate one of five ‘profiles’ consisting of voltage/current pairs of between 5V to 20V and 2A to 5A, providing a range from 10W to a maximum 100W of charging power delivered.  It also allows bidirectional power flow so that a device can both charge or be charged via the same port.

The common theme for all of these schemes is that while a USB port can deliver more power than the 2.5W allowed by legacy USB, in order for the port to do so, the connected device’s electronics must be able to negotiate, receive, and convert that power into a battery charge.  However, without a USB3 cable or a laptop or PC that has CDP/DCP charging ports, the various Quick Charge iterations are the only options generally available for charging Android devices at greater than the legacy 2.5W rate.

System Software

In addition to the electronics supporting the higher power modes, the device’s software must also negotiate for it.  There are many reports that despite the highest quality cable and QC-capable charger, the Samsung Galaxy S5 only charges at a maximum 1200mA rate, at least when the screen is on (also my experience). Custom Android kernels have been developed with a feature to allow the user to configure the current drawn by the device, ignoring the standards-based port negotiation or any maximums set by the manufacturer’s firmware.

There are additional steps required when charging the Samsung Galaxy S5 from a USB3 host in order to attain the higher 900mA USB3 charging rate.  When the S5 is plugged into a USB3 port using a USB3 cable, it defaults to USB2 mode, limiting the device to charging at 500mA.  A persistent notification will be present in the notification tray indicating “Connected as a media device – Touch for other USB options”.  Touching this will present several options, one of which is “Media device (USB 3.0) – Allows you to transfer media files in Windows via USB 3.0”.  Selecting this option will do a few things.  First, it will disconnect from the USB port and reconnect in USB3 mode, and immediately begin to charge at the 900mA rate.  It will also force the phone into airplane mode!  Why?  It turns out that USB3 interferes with nearby 2.4GHz wireless signals and as a result, the Samsung Galaxy S5 firmware disables the phone’s radio while in USB3 mode.  It also automatically disconnects and reconnects in USB2 mode if the USB connection is idle for five minutes.

How terrible!  I can’t use the data features of my Samsung Galaxy S5 while charging at the 900mA USB3 rate?  Well actually, the workaround is easy.  Once you’ve selected USB3 mode and airplane mode has been forced on, just turn off airplane mode.  This will force the phone’s data rate back to USB2, but regardless of the data rate, the 900mA USB3 charging rate remains in effect until the USB cable is disconnected!  (This is also the case if the USB3 connection hits the five minute idle threshold and the firmware drops back to USB2 mode.)

One final note on using USB 3.0 mode on the Samsung Galaxy S5: neither USB 3.0 data nor charging will work on the S5 if “USB Debugging” is enabled in the Developer settings, so disable USB debugging when charging the phone, or else you’ll be stuck with the legacy 500mA charging rate.

Recap: The Samsung Galaxy S5 and Google Nexus 5

Sadly, in the case of the Samsung Galaxy S5, only the Japanese model is capable of negotiating Quick Charge 2.0. Other models are limited to Quick Charge 1.0.  The S5 does support USB3, however, unlike its successors.  So there are four options for charging the non-Japanese Samsung Galaxy S5, from the device’s perspective: use a USB2 or USB3 cable with a USB2 port for up to 2.5W; use a USB3 cable with a USB3 port for up to 4.5W; use a USB CDP/DCP charging port with any cable for up to 7.5W; or use a Quick Charge 1.0 charging accessory with any cable for up to 10W.

A kit that provides the S5 with all of the above charging options can be purchased here:

KingAcc(TM) Galaxy S5 / Note 3 Home Wall Charger and Car Charger Kit 4 in 1

If somehow you’ve obtained a Quick Charge 2.0 capable model, here’s a cheap and quality QC2.0 charger:

Quick Charge 2.0 AUKEY Wall Charger with Micro-USB Cable

In the case of the Google Nexus S, USB3 is not available and only Quick Charge 1.0 is implemented.  So the three options for charging the Google Nexus 5, from the device’s perspective, are: use a USB2 cable for up to 2.5W; use a USB CDP/DCP charging port with a USB2 cable for up to 7.5W; or use a Quick Charge 1.0 charging accessory with a USB2 cable for up to 10W.

If you don’t have the USB CDP/DCP charging ports on your PC or laptop, here is a great solution for charging the Google Nexus 5 (and also for the S5 if a Quick Charge capable wall charger is all you need or if you don’t want to buy a USB3 cable):

KingAcc 2-Pack 10W Dual USB Wall Charger With PowerSmart Technology

And just use any old Micro-USB cables I have laying around, right?  Well…

Cable quality

The basic difference between USB2 and USB3 cables is: more pins in the latter to carry more data and power.  USB3.1 cables are additionally orientation agnostic and can carry additional signals in the same harness.

Aside from the new standards and different types of connectors, is there anything else to be concerned about?  Yes.  Charging standards that increase the amperage drawn through the cable increase the quality demands on the cable.  A cable that carries more current requires higher quality and/or thicker gauge wire.  That increases the expense of the cable.  The connectors must also be more robust to make a consistently snug connection over sufficient connector surface area, and the solder joints between the solid connectors and stranded wires must also be of high quality.  Quality is, on the whole, inversely proportional to price, but there are examples of high quality cables at low prices and low quality cables at high prices.

Some ways to test cable quality:

  • Fire up the Ampere app while charging and wiggle the cable ends and roll and unroll the cable itself.  The measured charging current should not fluctuate.
  • Fire up the Ampere app while charging with a configuration that provides 10W or greater charging power.  Check that the cable and connectors are not getting hot.  Check that the measured current matches the intended current drawn in that configuration.
  • Read the 1-star and 2-star reviews on websites like Amazon before you buy the product to determine whether heat or connection quality are issues with that item.  Amazon has banned low-quality cables, so the selection should be somewhat trustworthy.

One good rule of thumb is that for charging at any power level greater than the legacy 2.5W, at a minimum select a 28/24 USB cable (28AWG data, 24AWG power).  For USB3.1 and its up to 100W charging power, yet higher quality cable may be necessary.  The drawback is that a higher quality cable will be thicker, unless it is a charge-only cable.  A very high quality charge-only USB2 cable can be found here, but note the incompatibility with Quick Charge 2.0:

PortaPow Specialised 5ft 20AWG Charge Only Micro USB Cable

A similar cable that is thinner (but still very high quality) that will work with Quick Charge is here:

PortaPow Specialised 3.3ft 20AWG Charge+Sync Micro USB Cable

And for a much thinner cable but still very high quality:

Monoprice 3-Feet USB 2.0 A Male to Micro B 5pin Male 28/24AWG Cable with Ferrite Core

The latter cable, having a ferrite RF choke, can also solve problems with touchscreen misbehavior while charging as observed on earlier revisions of the Google Nexus 5.

Another article with much more on charging and cables can be found here:

Let’s talk about Quick Charge 3.0 and USB Type-C charging

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