T100 slow charging issues, solved.

My 1-month old tablet, the Asus Transformer T100 tablet started draining slowly while it was plugged in.

Today I drained the battery down to around 30%, plugged it in, and continued with web-browsing and streaming music.  An hour later I noticed that the battery percentage wasn’t climbing, and it had actually discharged another 5%.  Windows claimed it was “plugged in, charging” and the LED on the power button was lit up like normal, but the battery percentage was still slowing going down.  Once the battery was below 20% I decided to shut it down and let it charge with the system off.

I waited about an hour to power it back up, when I found it only charged 2%.  I also felt the AC adapter, and it didn’t feel warm at all.  I tried another cable, using a different 5V 2A charger that I knew to be good, but nothing changed.  I wiggled both cables around to see if there were any bad connections, but the light never turned off, so I assumed both were fine.

I searched Google a bit and found a few forum posts where people reported similar issues.  A few said that this was fixed in firmware version 220, but I was already running 220.  223 is available on their site, so I flashed it, but it didn’t fix my charging issue.

I was thinking about cutting up a USB cable so I could meter the power used while charging, but I found some software that promised to tell me the battery’s charge rate, BatteryBar.  Lifehacker checked it out in 2009, along with a few other reputable sites, so It’s nothing new.  It looks just like the battery meter that comes on some on Lenovo laptops.

I decided to give it a try.  The software runs perfectly on Windows 8.1.  I found that both cables I tried earlier were only charging at ~2500mW, which was right around or below the discharge rate.  I then tried a new 5′ long cable that I picked up from Monoprice.  With this cable BatteryBar claims the charge rate is 4500-5000mW on both of the AC adapters I tried, and now it’s actually charging!

5000mW at 5v is only 1A, but I don’t know how the accurate the charge rate is.  Also the PC might be drawing more power since it’s on AC, thus possibly using the full 2 Amps available.  I’ll check the total current draw through a meter another day.

Before I throw away the two ‘bad’ cables, I want to find out what is wrong with them.  When I plug the stock Asus cable in to my phone and to my PC, the device is recognized by Windows, I’m able to copy files over, but it doesn’t even try to charge.  The second cable I tried is apparently a charge-only cable.  It will charge my phone, but my PC doesn’t recognize a device has been plugged in.

TL;DR: T100 charged slow because of bad USB cables.

20 thoughts on “T100 slow charging issues, solved.”

  1. Hey, this is really helpful. Thanks for posting this. I have the same exact problem.

    So it sounds like I should get charge-only cables, then? Which one would you recommend?

    1. One of the two that did not work for me was a charge only cable. I’m confident that any quality sync cable will charge it fine.
      This cheap cable charges mine fine and is about a cheap as they come. The cable seems high quality, but the MicroUSB connectors break a bit easier than others.

    2. You saved me! I had changed the cable more so I bought the notebook and never imagined that the quality of it could prevent the unit noraal carregameto . thank you

    1. It did indeed charge the system while on and being used. I say did because I dropped the computer which broke the digitizer, so I no longer use it.

  2. Oh, one other thing I did to help extend battery life, once charged, was to set the power options to shut off the unit when the screen is closed… otherwise it will go into sleep mode and use more energy.

  3. Hi guys.
    I have two (well I sold one) of these and I joined this forum just to tell everyone that the ORIGINAL USB cable does NOT charge the device properly.
    As soon as I connected another USB charge cable (an old Nokia cable), with ORIGINAL adapter, it charged properly!
    The orange light comes on with the ORIGINAL cable, but it doesn’t really charge: When turned on, the charge light comes on, but Windows doesn’t recognise it as charging for long. With a “better” cable (and ORIGINAL adapter) Windows shows it charging until charged.
    I hope this helps.

  4. The thickness of the wire along with the length of the cable make a big difference. Most cheap cables have a 28 gauge wire for charging which is not enough. You need at least 24 gauge or more (lower gauge = thicker wire = faster charging). I use a 6ft 22AWG (awg = gauge) wire on my T100TA and it chargers at around 2.1 Amps which is the max the AC adapter is rated for. My other cheap ebay cable is only 3 ft but only charges at around 700mA.

  5. This is my second ASUS AT100T Transformer laptop.

    Problem of slow charging with standard replacement
    USB to micro USB cable.

    I use my laptop *every* day and I found the ASUS supplied
    OEM 1′ Micro USB power cable connecter started going out
    rapidly after six month of careful useage. I also noticed
    that the OEM power supply was not always able to charge
    the computer when the laptop was in use. After I put the
    replacement cables on order my OEM power supply died too.

    I now have found the following works really well with my AT1000T;

    (1) Mail ordered from Amazon;
    Easy Access Micro USB 2.0 Cable 5 Pack Charging Cables
    Shorted Data Pins – has no data transfer capabilities.

    (2) Purchased at CVS Pharmacy Store;
    Power XCEL Dual USB 2.1Amp Rapid Charger with dual
    outputs and blue indicator led. Use with a standard
    lamp type extension cord set.

    Now my computer stays at 99% charge when the charger
    is plugged in and the laptop is in use. It also charges
    surprizingly rapidly when the laptop is not in use.

    Also a standard Samsung cell phone .7A charger that has
    a hard wired micro usb connector will work much like the
    original ASUS OEM charger, which could be used in a pinch.

  6. Indeed the Nokia 5800 short cable charges the device without any problems.
    Long and thin cables are the problem, even the original one.

  7. I have two excellent cables, both from Anker. One charges at 2000 mW, the other at 4500 mW. The micro-USB plug is the problem. Google “How to fix a loose micro USB cable.”

  8. I’m having the same problem right now but I’m using the charger that came with it and it charges it just fine until today, it stayed at 2% and shows signs of charging then it turns off. Pls what can I do cos I can’t even find the battery.

  9. I just recovered a deep discharged T100TA which had about 2.9V on the battery pins by plugging in. The only signs of “life” were the few orange blinkenlights in the hole near the powerbutton and then the screen showing red level battery. thanks for this page, as I might have the same problem with my cellphone chargers and several cables. I am in Energysave Win8 and get about 8 % an hour.

  10. Hi,
    Thanks for the valuable information. your blog is very interesting. this app Battery Bar worked great, helped me to see that several of my cables were certainly the jam in the charging process!

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