When trying to charge my android devices (Arc S and Nexus 7 (2013)), I noticed that when using new USB-cables, the charging process is going quite fast, but after some weeks (usually four-five) the charging process rapidly slows down, and some weeks later the devices don't charge anymore, i.e. resulting in the need of new cables. Is that a hardware failure, or why do I have to replace the cables every second to third month?

  • Have you checked the USB contacts for wear and tear? Both in your phone(s) and the cable(s). Jan 22 '16 at 12:50
  • The USB contacts in the phone can definitely be old, due to 5 years extensive usage. But why do the cables work at the beginning, and fail later?
    – arc_lupus
    Jan 22 '16 at 14:04
  • Have you considered changing cables as suggested in my solution?
    – beeshyams
    Jan 22 '16 at 15:00
  • Changing cables works for some months, then I have to change again...
    – arc_lupus
    Jan 22 '16 at 17:10
  • I understand that. Is that the case with thick cables also as mentioned in my answer below, is what needs to be checked
    – beeshyams
    Jan 22 '16 at 17:15

Hardware is not "capable" to decide charging rate based on "newness" or otherwise of cables

In all probability, USB cables you are using are of poor quality, wrong length and thickness

What I would suggest:

  1. Google for "24 awg micro USB cables Less than or equal 2 meter length and purchase from reputed vendor

Why these specs for USB cable? Long explanation but needed to emphasize choosing the right USB cable

  • Current carrying capacity depends on resistance, for the same Voltage.

    Ohm's Law Current = Voltage divided by Resistance

Resistance in turn depends on thickness

Resistance = Length divided by Area (ignoring resistivity)

Resistance is inversely proportional to the area of the wire

Less area = Thinner Wire = More Resistance = Less Current (you cannot make out thickness of the conductor by looking at it- they all seem to be equally thick but internally the conductor thickness varies)

Similarly, reducing length of wire decreases resistance

Arc S has 800 mA and Nexus 7 has 1150 mA Charging current rating and the cable should support that

Cable Length ,thickness, current rating required for device both matter when choosing the right cable. USB Cable Resistance: Why your phone/tablet might be charging slow relevant to your device specs says

For smartphones, with a requirement closer to 1A, 24AWG wires up to 2m could be sufficient, or 1m at 26AWG, and 50cm at 28AWG.

Nexus 7 is more choosy: It will stop charging if voltage levels drop and resistance comes into play again. Google Nexus 7 Charging goes into details and says

Nexus 7 will stop charging if the input voltage is less than the internal battery voltage plus 0.2 volts.

  1. Use an app like Ampere or 3C Toolbox to measure the charging current (somewhere midway of your regular charging time is a good time to measure, as the values may be different just when you plugged in or towards end of charging)
  2. Calculate the charging time required using the Battery Charge Time Calculator ( choose efficiency of charging at 90 %)

Repeating this test say once a month for a few months at least would give an indication if it is a hardware issue (weird as it sounds). If there isn't a significant change, it only confirms that poor USB cables being culprit

For everyone: USB Cable Resistance: Why your phone/tablet might be charging slow is a useful read to understand why it is a good idea to spend more but buy the right USB cable

  • 1
    It's hard to imagine how a mechanical fault in the cable could cause the charging to get gradually slower, but I admit I don't have a better hypothesis.
    – Dan Hulme
    Jan 21 '16 at 13:12
  • @DanHulme : edited the answer with supporting sources. Point is that these cheap USB cables with use and abuse develop more resistance, ascend this goes worse with time. This is the only explanation that I can think of that fits the situation described by OP
    – beeshyams
    Jan 21 '16 at 15:36

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