Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 21
Like Tree1Likes

Thread: Charging issues, anybody else tried this?

  1. #1
    Soundwave
    Member #
    65231
    Join Date
    Jan 2014
    Tablet
    TF Book T100
    Posts
    12
    Liked
    1 times

    Charging issues, anybody else tried this?

    Hello all.

    I've recently encountered the 'not charging much under use' issue.

    When I first got my T100, it never had an issue. But now, there's something funny going on.

    I have a USB tester, i.e. you plug it into your USB host and your device into the tester. It shows current and voltage from which you can see what voltage the laptop is receiving and how quickly it's charging.

    The strange thing is, the voltage and current is all over the show. For example, a minute ago it was 4.5V and 300mA, but, I unplug the charger from the wall, plug it back in and suddenly it's 4.93V and 1.13A

    Would suggest that the chargers have a mind of their own and decide to charge when they want to rather than when needed.

    USB tester

    USB Power Current and Voltage Tester USB Mobile Power Current Test T5 | eBay

  2. #2
    rscheller
    Guest
    Interesting device... when you're monitoring current/voltage with it on the T100 is the T100 on in use, in sleep or shutdown?

  3. #3
    Soundwave
    Member #
    65231
    Join Date
    Jan 2014
    Tablet
    TF Book T100
    Posts
    12
    Liked
    1 times
    When I took those figures yesterday it was with the device on and about 68% battery. Have a look this morning and it's 96%.

    I'm watching it now and it's at 98% not charging, 0A and 5.2V so the T100 has full control over how and when to charge

    97% and its charging now, 1.09A.

    I believe that the T100 runs primarily as a tablet and charges when it needs too. It's just not that intelligent about how it does it.

  4. #4
    Administrator
    Member #
    2531
    Join Date
    Jun 2011
    Location
    Thailand
    Tablet
    TF101
    Posts
    8,595
    Liked
    976 times
    Thanks for the heads up..

  5. #5
    Ratchet
    Member #
    64311
    Join Date
    Dec 2013
    Tablet
    TF Book T100
    Posts
    215
    Liked
    11 times
    there are plenty of 3rd party usb cables that dont work to charge the T100 because supposedly they "trickle" the charge or something.

    maybe your t100 isn't charging properly because of your measuring device

  6. #6
    rscheller
    Guest
    The T100 is a tablet... and it will function fantastically well without the docking keyboard.
    The docking keyboard (unless you've got the 500GB hard-drive built in to the keyboard or something plugged into the USB connector on the keyboard) is just along for the ride and likely has very minimal power drain. I would guess the battery charging circuit in the T100 is quite intelligent and is quite capable of supplying the proper volt/amps draw from the power brick to charge the internal batteries but sadly not much more. It is well documented here and elsewhere that the standard T100 charger/cable will not necessarily supply enough power to keep up with the T100 when it's in use.

    The wide volts/amps variance in what you saw while the T100 is powered on would likely be any number of foreground and/or background processes, network activity, etc. that would cause variance in hardware power draw.
    A better test would be to disable wifi, bluetooth, etc. and have the T100 powered off and see if the volts/amps are stable but I'm not exactly sure what you're trying to validate.

  7. #7
    Soundwave
    Member #
    65231
    Join Date
    Jan 2014
    Tablet
    TF Book T100
    Posts
    12
    Liked
    1 times
    Quote Originally Posted by rscheller View Post
    The T100 is a tablet... and it will function fantastically well without the docking keyboard.
    Agreed, Does a good job at it.

    Quote Originally Posted by rscheller View Post
    The docking keyboard (unless you've got the 500GB hard-drive built in to the keyboard or something plugged into the USB connector on the keyboard) is just along for the ride and likely has very minimal power drain.
    Also agreed, the keyboard is very minimal unless like you say you have the hard drive or devices plugged into the USB port, were talking milliamps here.

    Quote Originally Posted by rscheller View Post
    I would guess the battery charging circuit in the T100 is quite intelligent and is quite capable of supplying the proper volt/amps draw from the power brick to charge the internal batteries but sadly not much more. It is well documented here and elsewhere that the standard T100 charger/cable will not necessarily supply enough power to keep up with the T100 when it's in use.
    Disagree with you there. The charging circuit is intelligent to a certain extent however. I have seen the charger supply 5V at 1.8+ amps, that is very close to the allotted 10W of the supply so it is possible to get that with the standard hardware.

    The USB micro cable is definitely an issue however as most micro cables are about 28AWG which according to Wire Gauge Guide is about 226mA Maximum.

    So, if the asus cable uses 28 gauge then it's limited from the onset. If it uses 28/24 gauge, 28 for data and 24 for power, it's still only 577mA.

    To make the most of it, 18AWG cable or 0.8mm^2 cable is the way to go to know that the cable isn't a hindrance.


    Quote Originally Posted by rscheller View Post
    The wide volts/amps variance in what you saw while the T100 is powered on would likely be any number of foreground and/or background processes, network activity, etc. that would cause variance in hardware power draw.
    Disagree also. If you read my previous post thoroughly you'll see that I actually measured the power draw, switched off the charger, switched it back on and then see a higher rate of power use. This would suggest that the T100 is physically capable at a hardware level of determining how much power it draws from the charger.

    Quote Originally Posted by rscheller View Post
    A better test would be to disable wifi, bluetooth, etc. and have the T100 powered off and see if the volts/amps are stable but I'm not exactly sure what you're trying to validate
    I'm not necessary attempting to validate anything. It's clear that the T100 is capable at a hardware level of controlling rate of charge.

    I've also seen some erroneous values also, like 4.5V and 0A from the charger. This is strange as I would expect to see a voltage drop as the current draw is increased. Considering the charger is merely a simple switch mode power supply, I would suggest that perhaps the charger itself has a form of intelligence also.

  8. #8
    Supporting Member
    Supporting Member

    Member #
    64427
    Join Date
    Jan 2014
    Tablet
    Too lazy to choose
    Posts
    1,249
    Liked
    291 times
    One thing to remember though is, some depends on the length of the cable. A shorter cable will have less voltage drop.

    A 2ft foot 28GA USB cable, supposing the charger was outputting 5V true, ends up barely a hair under spec at 1 amp, you have 4.74v with the voltage drop, which is just out of the 5v +/-.25v spec of USB2.0. So you could use a 1ft charging cable that used 28 gauge wire for the conductors. For 24 gauge you get a 2ft cable that keeps it within spec for a 2 amp current, as you have a Vdrop of .21, or 4.79V. Again though, that assumes that the charger is outputing 5V. If it is slightly below that, you'll not get enough voltage.

    On the other hand, if it actually outputs more like 5.1-5.2V, still within USB spec, you could easily get away with a 3ft 24 Gauge wire and be within the specs.

    The chart at the link doesn't say what it is using for the amperage rating, but it looks badly inaccurate. Just looking at the 14 Gauge listing, it says 5.9A. In general, for house hold wiring, 120V single phase, 14 Gauge is limited to 15 Amps, not 5.9. Well, unless you were going to have a VERY long wiring run, but then that is more an issue of Vdrop than it is an issue of actual wire thermal capacity. That's for 60C rated house hold wiring.

    I'd bet my sweet left...uh, well, you get the picture, that even low temperature rated wiring (it just mentions plastic insulated, which Romex is BTW), would probably be good at 8-10 Amps, close to double what is listed, for something like 40C rated wiring. So figure you can use double the current at a MINIMUM based on what is listed in the chart.

    21Ga wiring for a 5ft conductor USB cable would get you just a hair outside of spec for 2A charging current if the USB charger was outputing 5V, so 20Ga wire would cover it just fine.

    As a note, the article on Wikipedia specifically mentions for USB3, that there is no maximum cable length specified, but that for it to meet spec, 26Ga wire would mean a maximum cable length of 3m/10ft (that is .9A). USB3 spec allows a bit more varience in voltage, but for 10ft 26Ga, you get a Vdrop of .73V, what SHOULD be out of specification.

    In effect, I think you'll see pretty skinny wires working just fine. Of course you generally want THICKER wires, if you can help it. Especially with a long charging cable.

    That 26Ga wire at 10ft would mean you are losing roughly 15% of the power you are trying to deliver to your device because of lowered voltage. Of course on a 3ft cable, the losses would be substantially less.

    Rule of thumb, the higher the amperage and the longer the cable, the thicker you need/want it to be.

  9. #9
    Soundwave
    Member #
    65231
    Join Date
    Jan 2014
    Tablet
    TF Book T100
    Posts
    12
    Liked
    1 times
    Indeed, I thought those current references for those gauges are a bit inaccurate.

    Apparently the 0.22A is for power transmission and it's 1.4A for 28GA chassis wiring. The explanation being the difference of heat distribution because of the voltage drop over the cable. Power transmission is for cables in a bundle with minimal cooling whilst chassis is for open air with maximum cooling.

    Considering we are talking low voltage and low power rating and short cabling, there is no cooling required for a standard cable so the 28GA rating for USB and 1.4A is fine.

    So, really, this actually puts to bed the difference in USB cabling and charging current and that standard cables should be good for 1.4A easy.
    This is furthermore backed by something I just found out.

    The quality of the USB connection itself.
    I found just now with my current tester plugged into the charger that if I push the tester upwards, the charging current increases DRAMATICALLY, i.e. my tablet is on, being used, 72% and charging at 1.88A, practically flat out.

    So, with the charger on my desk, unplugged of course, I just took a small object and pushed it under the charging pins in the charger (and my USB tester) bending them up slightly thus increasing the mechanical force of the pins against the USB cable plug.

    Plugged my T100 back into the charger and it is now charging at 1.88A and 5.1V or 9.6W, very close to the rated 10W of the charger. Thus considering the battery is 31Wh, with the device off, it should take just over 3 hours to fully charge from flat.

    I'll now attempt to explain why:
    In high power transmission, when connecting 2 devices together you'll use a crimp with suitable surface area held together under mechanical pressure/force. Take for example connectors used in RC, the bullet style. They are HUGE banana connectors with multiple points of contact, gold plated and so on for nominal current carrying seeing as some RC motors handle hundreds of amps, not 1 or 2.

    The actual USB footprint inside the charger is very small and the connection itself is a raised pin with a rounded end to protrude in the charger and a flat pin inside the USB connector itself. Pressure of the connection is very small as there is only 1 point of contact, 1 pin.
    this small footprint creates a bottleneck effect limiting the charging current.

    This would also explain my erroneous values of 4.5V and 0A when plugged in, must of had a terrible connection then.

    REALLY, the BEST style of USB charger for this T100 is a high current (2A or more) charger with a FIXED Micro USB cable and NOT a removable cable.

    Disclaimer: In no way do I recommend inserting objects into electrical items or devices such as those mentioned in this post. I only did it because I know what I'm doing and in doing so knew the risk involved.
    Don't play with electricity!
    Last edited by dazmatic; 01-27-2014 at 10:44 AM.

  10. #10
    rscheller
    Guest
    Super info. Now I get your point...
    REALLY, the BEST style of USB charger for this T100 is a high current (2A or more) charger with a FIXED Micro USB cable and NOT a removable cable.
    With at least 28AWG (better yet 26AWG) wire and no longer than 3 feet.

 

 
Page 1 of 3 1 2 3 LastLast

Remove Ads

Sponsored Links

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Similar Threads

  1. My observations about charging issues
    By guitarpete987 in forum Asus Transformer Book T100 Battery Issues
    Replies: 5
    Last Post: 02-14-2014, 10:01 AM
  2. Charging Issues
    By TearyJewelEyes in forum Transformer Pad 300 Help
    Replies: 1
    Last Post: 06-11-2012, 07:48 AM
  3. Slider charging issues
    By MattW in forum Asus Eee Pad Slider Help
    Replies: 12
    Last Post: 05-18-2012, 10:20 PM
  4. Charging ... Technology Issues
    By fgte in forum Asus Transformer (TF101) General Discussions
    Replies: 1
    Last Post: 03-11-2012, 06:36 PM
Powered by vBulletin® Version 4.2.3
Copyright © 2021 vBulletin Solutions, Inc. All rights reserved.
Search Engine Optimization by vBSEO 3.6.1
All times are GMT -6. The time now is 10:15 AM.