November 21, 2017, 04:55:38 PM

collapse

Author Topic: USB cable & charging question.  (Read 3847 times)

Offline raisantos

  • Newbie
  • *
  • Posts: 6
  • Popularity: 0
    • View Profile
USB cable & charging question.
« on: August 14, 2012, 09:49:47 PM »
I will try and make this as clear as possible because it is hard even for me to see the pattern of how charging works for this device. So far, these are what i have:

cables:
OEM cable,
6-ft cable,
1-ft cable,

chargers:
OEM wall charger,
iPad wall charger,
portable battery charger(with both .5Ah and 1Ah sockets),
USB car charger.

so far these are the combination that works:

OEM wall charger + any of the cables I have available
any charger + 1ft cable.
Macbook air + any of the cables I have available

This means that my portable battery charger and car charger only works if I use the 1 ft cable.

I understand that chargers have diff amperage and that might be the reason why some works and some doesn't. I'm wondering what the diff in the cables that I have though. How come some of them work and some don't? And why is my 1ft cable even better than the OEM that my N7 came with? I've had Apple devices for the longest time and they are all interchangeable. I thought micro USB would be the same. I was mistaken. Can someone here shed some light on this matter?



Offline tsruggles

  • Newbie
  • *
  • Posts: 49
  • Popularity: 3
    • View Profile
Re: USB cable & charging question.
« Reply #1 on: August 14, 2012, 10:09:39 PM »
There are a lot of variables here. First of all, the OEM charger will provide enough amperage to the device, which is two amps.

Some USB cables are either "energy saving" or, just plain crap. Thin internal wires can't deliver the amperage in doses that are conducive to charging. You may noice that the oem cabe is thicker than the others. Also, length plays a part in charging. The shorter cords have less resistance.

I'm guessing that the macbook has a fairly substantial output as far as the amperage. I'm not up to snuff on my apple device knowledge. It is a fairly logical guess though.

There are a lot of tablets that won't charge via micro USB cords. If they do it can take them days to absorb a charge.

Its all about amperage with the chargers and resistance with the cords. Playing around with the combos can yield some good knowledge as far as effective charging configurations, which you seem to have discovered already.

Offline raisantos

  • Newbie
  • *
  • Posts: 6
  • Popularity: 0
    • View Profile
Re: USB cable & charging question.
« Reply #2 on: August 14, 2012, 10:16:11 PM »
the weirdest part of all the trials and errors that I've had is that the OEM cable only works with my laptop and OEM wall charger. I would assume it would be the best of all the cables but it doesn't work with the iPad charger (10W but I'm not sure how much Amps), car charger, or the portable battery. Only the 1 ft cable works on all chargers, problem is, it's short, meaning I can't charge and use my device at the same time.

Oh well.


Thanks for a quick response btw.  :)

Offline tsruggles

  • Newbie
  • *
  • Posts: 49
  • Popularity: 3
    • View Profile
Re: USB cable & charging question.
« Reply #3 on: August 14, 2012, 10:27:58 PM »
My reply was only based on electrical knowledge. Electronics are in a league all of their own. The "ten watt" charger may consume ten watts in total but it's the amperage output that you should look at to be certain. Two amps is necessary. Typically the wattage spec is only indicative of the power consumption, not the output. Amps x volts = watts. Chances are the wattage is determined by the input current, or in other words, the outlet it is plugged into. The chargers are basically transformers. They change your house voltage into a lower voltage. Otherwise you would have yourself a very expensive and short lived toaster. Always read the output specs on a charger to be sure of the amperage rating.

Hope this helps !

Offline raisantos

  • Newbie
  • *
  • Posts: 6
  • Popularity: 0
    • View Profile
Re: USB cable & charging question.
« Reply #4 on: August 15, 2012, 01:14:59 PM »
that makes sense. I'm glad I get to know more of these stuff. I have a follow up questions and I hope this is the appropriate place to ask it. I guess I was paying attention to the wrong spec on the charger. Here are the spec sheet.

Asus wall charger(Nexus 7):   input 100-240~50/60Hz 0.3 A    output 5.0V 2.0A
Apple wall charger(iPad 3):     input 100-240~50/60Hz 0.45 A  output 5.1V 2.1A

now this is what I noticed. Of course the devices(iPad and N7) charged with no problem using their own chargers. Additionally, the iPad charges using the Asus charger but the N7 wont charge using the Apple charger. I can see that the output of the Apple is a little more (voltage and amperage) than the Asus. Can you explain this if you can? I hope I'm not asking for too much. Thank you in advance.  :D


Offline tsruggles

  • Newbie
  • *
  • Posts: 49
  • Popularity: 3
    • View Profile
Re: USB cable & charging question.
« Reply #5 on: August 15, 2012, 09:25:02 PM »
Unfortunately this escapes my realm of electrical knowledge and delves into the mystical land of electronics. On paper those slight differences shouldn't matter at all. Wish I could help. I'll look into it for curiosities sake.

Offline birdastrompgman

  • Hero Member
  • *****
  • Posts: 840
  • Popularity: 28
    • View Profile
Re: USB cable & charging question.
« Reply #6 on: August 29, 2012, 11:35:44 AM »
I found an interesting claim (I don't know how accurate it is) that most 2 amp chargers only supply 2A to iPhones/iPads.  Other devices are pinned or cabled differently, and the chargers only supply .5A to non-Apple devices. 

Here's the link.

Here's the review with the charger claim:
-------------------------------------------------------------
This product has two major issues:

1. While it's description claims it has a 2 Amp port and a 1 Amp port, the reality is that it has bridged the two ports and it can only source 2 Amps total. It is not capable of delivering 3 Amps combined like the description implicitly claims and could never simultaneously charge an iPad and a smart phone. (UPDATE: The technical details section now indicates more clearly the 2A total, which is appreciated.)

2. The 2 Amp port appears to be using the Apple protocol for USB power, so that port will only provide 0.5 Amps to most other devices.

The upside of this is the 1 Amp port somewhat over delivers, and can source 2 Amps if nothing else is connected and 1.5 Amps if the 2 Amp port is sourcing 0.5 Amps for a non-Apple device. Thus this product can support one-high power non-Apple device (in the 1 Amp port) and one lower power device (in the 2 Amp port).

Now some more background/details...

First, a little background on USB charging for those who don't know:

The USB power spec is for 0.5 Amps at 5 Volts... or 2.5 Watts. This was great up until the last couple years when devices have gotten really power hungry, particularly smartphones and tablets and to a lesser extent dedicated GPS's. Some of these devices use over 2 Amps, particularly the tablets like the iPad (or in my case the HP Touchpad).

Manufacturers of these devices therefore had a dilemma. If they had their devices pull more than 0.5 Amps, they risked damaging the power source, which could be a computer, that was only prepared to source 0.5 Amps. Thus the manufacturers have used tricks to determine whether their device is connected to an unknown source, at which point they purposely only draw 0.5 Amps, or to the dedicated charger that was provided with the device, where they can draw all the power they need.

There seem to be two common tricks used. The first is to short the two data-wires together in the charger. This is what most non-Apple devices do. Since a computer or older device wouldn't have done this, the device can assume it is safe to draw all the power it needs.

Apple seems to have taken a different approach, one that I don't fully understand but know can be seen by the fact that the data lines are neither open nor shorted when the charger is plugged in, and is more sophisticated and probably superior, because I suspect it allows the device to know exactly how much power it can use.

While Apple taking a better approach might be nice in concept, it's created chaos in the USB charger product category. What is the non-specific charger to do? They can't support both.

This device chose to go the Apple route for the 2 Amp port. I don't own any high-power Apple devices, so I can't say for sure, but I suspect this unit performs well with Apple devices. Using electronic equipment I was able to draw 2 Amps when putting a fixed load on this USB charging port. However, when I connect any of the 3 high-power devices I have (HP Touchpad (2 Amps), Motorola Triumph Android phone (0.85 Amps) and the LG Optimus Slider (0.7 Amps)), none of them drew all the current they could have, because they were expecting a shorted set of data-lines.

Luckily for my purposes, the 1 Amp port on this device uses the data-line shorting method. As such, it was able to deliver all the power my Triumph and Optimus wanted. However, for some reason, even when it was the only device connected, it would not fully charge the HP Touchpad at the 2 Amps it could have, because for one reason or another, the HP Touchpad rejected it as a high power charger.

To be honest, this surprised me because it was able to source the 2 Amps the Touchpad claims it needs and the HP Touchpad charger has the data-lines shorted. So I'm not sure why this didn't work.

Thus this device gets 3 stars (UDPATE: 4 stars) because it can source the current it claims (minus the somewhat deceptive 2A + 1A notation (UPDATE: Which is now more clear in the technical details)), would likely support an iPad like it claims, but falls short in other regards noted elsewhere.

For non-Apple users, or even more so mixed users (say an iPad and an Android phone?) this device is superior to the other device I purchased, the "Kensington K33497US PowerBolt Duo Car Charger" (http://www.amazon.com/gp/product/B003PU01M4/ref=oh_o02_s00_i00_details) because on that device, NEITHER port works with non-Apple devices (although it performed better power-wise, see my review over there for details).

I've ordered two additional devices:
- "Ultra Compact High Output Dual USB Car Charger - 2.1A Output" (http://www.amazon.com/gp/product/B00470C35E/ref=oh_o01_s00_i00_details)
- "Bracketron Universal Dual USB Car Adapter (UGC-298-BL)" (http://www.amazon.com/gp/product/B0056VNVV8/ref=oh_o00_s00_i00_details)

Hopefully one of the two of them will be able to deliver to their specs for my devices.

UPDATE: I've increased my review to 4 stars for two reasons:

1. The changed technical details text makes it more clear its total power capacity.
2. Of the 4 models I purchased, it's one of the two I kept and it's the only one I kept in unmodified form. That's got to count for something. :)
Bird has seen >650 North American bird species
Rooted Nexus 7
49.5 mpg avg for 53k miles in non-hybrid Scion xB
Retired 9 yrs, and loving it

Offline radiocycle

  • Hero Member
  • *****
  • Posts: 653
  • Popularity: 9
    • View Profile
Re: USB cable & charging question.
« Reply #7 on: August 29, 2012, 11:41:31 AM »
Just like a**le; to make up their own standards...

r
Time flies like arrows... Fruit flies like bananas!

Offline birdastrompgman

  • Hero Member
  • *****
  • Posts: 840
  • Popularity: 28
    • View Profile
Re: USB cable & charging question.
« Reply #8 on: August 29, 2012, 01:04:06 PM »
Here's the workaround.  Buy a $2.88 USB extension cable from eBay, and short the green and white data wires from the supply (male) end.  Then you can use any iPhone-compatible 2.1A USB car charger.
Bird has seen >650 North American bird species
Rooted Nexus 7
49.5 mpg avg for 53k miles in non-hybrid Scion xB
Retired 9 yrs, and loving it

 


* Top Boards

* 'Like' And 'Follow' Us!

* Top Posters

bjs229 bjs229
2682 Posts
JayJ JayJ
2100 Posts
S.Prime S.Prime
2017 Posts
Babyfacemagee Babyfacemagee
1261 Posts
matt matt
936 Posts
birdastrompgman birdastrompgman
840 Posts
loociddreemr loociddreemr
708 Posts