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[FAQ][10/11/10] Samsung Epic USB/Wall/Charger FAQ

This message is a summary of my previous messages. I hope that it will be useful. I wrote this to document what I found out about the Epic. I'm cheap, and I didn't want to buy ANOTHER charger for my car. I had a 3A, 2-port USB charger, and I was mad that my Epic was charging slowly. I managed to modify my charger to get it to perform just like the wall charger that came with my phone.
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Q: How much current does the Epic draw from a normal (bus-powered) USB port when charging?
A: 380mA.
Q: How much current does the Epic draw from the OEM 700mA wall charger when charging?
A: 600mA
Q: How much current does the Epic draw from a car charger or an aftermarket wall charger?
A: It depends...
If the charger has the two data pins (D+ and D-) shorted, the Epic will attempt to draw 600mA. Otherwise, it will draw 380mA.
Q: How can I tell if my phone is charging at 380mA or 600mA?
A: Turn off USB debugging (Home Screen\Settings\Applications\Development\USB debugging).
If you plug into a 380mA source (D+ and D- not shorted), you get a "Charging/Mass Storage/Tethered Mode" popup when you unlock your phone.
If you plug into a 600mA source (D+ and D- shorted), you do not get a popup.
Q: I have a 1A micro USB charger from another phone. Can I use it to charge the Epic?
A: Yes, but you won't get it to charge any faster than the 700mA OEM wall charger. The phone will only draw 600mA at most, regardless of how many amps the charger can supply. (And that assumes that D+ and D- are shorted.)
Q: I have a Palm Pre wall charger. I've heard that it charges the phone faster than the Epic wall charger. Is this true?
A: No. The Palm Pre wall charger does not charge the phone any faster than normal. With my phone hooked up, I measured 590mA (600mA with cable loss). I also saw that the charger had D+ and D- shorted. It behaves exactly like the Epic's charger.
Q: Will these 1A chargers damage my phone?
A: As long as the charger is able to supply the necessary current without overheating, chargers from other phones will not damage the Epic. A charger may be rated for 3A, but the Epic controls how much current it draws.
If you buy a cheap charger, you run the risk of having the charger's chip burn up. Among other things, this could short the charger's input voltage (12V from a car) to the USB V+ line and fry your phone.
Q: I have a USB charger that seems to charge my phone slooooowly. What can I do?
A: Your charger is probably supplying 380mA (or worse). You have a few options:
NOTE: Before doing any of this, make sure that your charger is rated at 700mA or greater. If you have an unmarked charger, chances are that it will not be able to supply 700mA out of the box. Many car charger (such as those for the Nintendo DS) have built-in current limiters that prevent the device from drawing too much current.
1. Modify Your Charger: Open up the charger and look to see if D+ and D- are shorted. (They are the two middle pins on the standard size USB plug.) Modify your charger so that it shorts D+ and D-, and remove any pull-up or pull-down resistors that connect D+ and/or D- to power or ground.
2. Modify A Cable: Slice open a spare micro USB cable (or the cable from your charger), being careful not to damage the red or black wires. Cut the green and white wires (D+ and D-). Strip off a little bit of the insulation from the green and white wires that lead to the micro USB connector. Twist these wires together and wrap in electrical tape.
NOTE: This will prevent the cable from being used as a USB data transfer cable.
3. Buy a USB Charging Cable: Look for a special USB charging cable that already has D+ and D- shorted.
Q: If I buy or make a charging cable, can I get 600mA from a normal (bus-powered) USB port?
A: It depends. The USB spec says that a port can only supply 500mA max. There is usually an overcurrent monitor built into the port that will prevent an overcurrent condition. The OS will pop up a message telling you that you've exceeded the current sourcing capacity of the port.
There are some laptops, however that have ports that allow you to violate the USB spec and draw up to 1A from a port.
Use caution when experimenting.
Q: Can you tell how much current the device draws from the device?
A: No. You CAN, however, get a battery graphing app like Battery Graph.
http://www.appbrain.com/app/battery-...odroid.battery
If you set the monitoring interval to 1 minute and start charging your phone (which should be low on charge) with the wall charger, you'll see a battery curve. You can then repeat this process with your alternate charging method. If you compare the slopes of the charging curves, you'll be able to tell if your alternate charging method is performing the same as your wall charger.
It's not as quick as using a DMM, but it works. It's how I initially saw I was having a problem.
Q: How can you tell if your USB cable has D+/D- shorted?
A: 99% of all cables will not have the lines shorted. You have to buy a "charging cable". But if you are in doubt as to what cable is what, plug it into a PC's USB port. Either the PC will detect the device (not shorted), or you'll trip the USB port's overcurrent mode (shorted).
Or... You can buy a DMM and check the resistance between D+ and D-.
- N

Is there a way to display on the Epic how much current it is drawing? Or some other way to tell if the cable being used is D+/D- shorted?

Thank you. Very helpful.

jasonsf said:
Is there a way to display on the Epic how much current it is drawing? Or some other way to tell if the cable being used is D+/D- shorted?
Click to expand...
Click to collapse
Good questions!
Q: Can you tell how much current the device draws from the device?
A: No. You CAN, however, get a battery graphing app like Battery Graph.
http://www.appbrain.com/app/battery-graph/com.modroid.battery
If you set the monitoring interval to 1 minute and start charging your phone (which should be low on charge) with the wall charger, you'll see a battery curve. You can then repeat this process with your alternate charging method. If you compare the slopes of the charging curves, you'll be able to tell if your alternate charging method is performing the same as your wall charger.
It's not as quick as using a DMM, but it works. It's how I initially saw I was having a problem.
Q: How can you tell if your USB cable has D+/D- shorted?
A: 99% of all cables will not have the lines shorted. You have to buy a "charging cable". But if you are in doubt as to what cable is what, plug it into a PC's USB port. Either the PC will detect the device (not shorted), or you'll trip the USB port's overcurrent mode (shorted).
Or... You can buy a DMM and check the resistance between D+ and D-.

Awesome! Thanks for the info!
Oh, one more thing. Are you saying that the wall charger shorts D+ and D- at the plug? So any cable is essentially shorted when using the wall charger?
Sent from my SPH-D700 using XDA App

jasonsf said:
Awesome! Thanks for the info!
Oh, one more thing. Are you saying that the wall charger shorts D+ and D- at the plug? So any cable is essentially shorted when using the wall charger?
Sent from my SPH-D700 using XDA App
Click to expand...
Click to collapse
You are correct.
For the Epic, the wall charger shorts D+ and D- together.
For wall or car chargers that have a non-removable cable, 99% of the time the short will be inside the charger and NOT in the cable.

Every computer I've used gladly lets me draw 1A without complaints. My old TP was hacked to draw 1A and nothing complained. Didn't even damage the cheapest of the cheap ebay chargers.

Firon said:
Every computer I've used gladly lets me draw 1A without complaints. My old TP was hacked to draw 1A and nothing complained. Didn't even damage the cheapest of the cheap ebay chargers.
Click to expand...
Click to collapse
YMMV. My netbook prevents me from drawing more than 500mA per port.
It all depends on how the USB port circuit is laid out. In the designs I've seen, there's usually a power distribution switch (PDS) in-line with the port that provides overcurrent protection. When that switch trips, it sends a bit to the hub chip that tells the hub that the port is in overcurrent state. (The PDS's secondary function is short-circuit protection. If you stick a car key in your USB port, your computer won't blow up.)
PDS's come in different current cutoff steps, so it is up to the PC manufacturer to choose the right one.
If your PC can't supply the 600mA on a single port to charge the phone, buy one of those USB power splitter cables that lets you draw from 2 ports at once.

I have found that if you plug in the phone and the options for charging, mass storage and tethering pop up, then you are only charging at 380mA. If nothing pops up then you are most likely charging at 600mA.

muyoso said:
I have found that if you plug in the phone and the options for charging, mass storage and tethering pop up, then you are only charging at 380mA. If nothing pops up then you are most likely charging at 600mA.
Click to expand...
Click to collapse
Ding! You are correct. I never noticed because you don't get prompted AT ALL if you have USB debugging turned on.

This is a little off topic. Does the usb cable initiate Dock Mode? I know some other phones use magnets in the dock, but I think I read that the Galaxy S phones detect the car or home dock via the USB cable. Did you discover a mechanism for this in your usb research?

jasonsf said:
This is a little off topic. Does the usb cable initiate Dock Mode? I know some other phones use magnets in the dock, but I think I read that the Galaxy S phones detect the car or home dock via the USB cable. Did you discover a mechanism for this in your usb research?
Click to expand...
Click to collapse
No... I didn't find anything. Maybe I'll "rent" a dock from the Sprint store and find out.

Very nice write up. Answered all the questions I had about the slow charging of this phone. Thanks again.
Sent from my SPH-D700 using XDA App

I am getting substantially faster charges with a 1amp charger than the oem 700, it looks like it is using close to the 1000 ma on some chargers.

aero1 said:
I am getting substantially faster charges with a 1amp charger than the oem 700, it looks like it is using close to the 1000 ma on some chargers.
Click to expand...
Click to collapse
I'll have to pay attention to mine. I started using the 1 amp charger that came with my Touch Pro. I charge it overnight so I don't pay attention to how fast it is charging, but I'll see if I can notice tonight.

aero1 said:
I am getting substantially faster charges with a 1amp charger than the oem 700, it looks like it is using close to the 1000 ma on some chargers.
Click to expand...
Click to collapse
Which chargers? I'll be happy to try any charger that you recommend.

I haven't tested charging by timing the charges, but I have installed a widget that tells me an approximate charge rate called currentwidget, and it gives me the EXACT same values for a 700 ma charger or a 1000 ma charger. Unless this widget is just straight up lying, the phone won't charge any faster than a 700 ma charger no matter how large of a charger you throw at it.

IBNobody said:
2. Modify A Cable: Slice open a spare micro USB cable (or the cable from your charger), being careful not to damage the red or black wires. Cut the green and white wires (D+ and D-). Strip off a little bit of the insulation from the green and white wires that lead to the micro USB connector. Twist these wires together and wrap in electrical tape.
Click to expand...
Click to collapse
I was going to suggest just taping over the data pins in the USB connector (obviously, the regular, non-micro end), but I just tried it and it still popped up the Charging/Mass Storage/Tether, though selecting Mass Storage doesn't work -- the device is not detected by the computer for obvious reasons. I've been using this trick for a while for my mp3 player and my Hero at work and was surprised that it didn't work.

reauxgg said:
I was going to suggest just taping over the data pins in the USB connector (obviously, the regular, non-micro end), but I just tried it and it still popped up the Charging/Mass Storage/Tether, though selecting Mass Storage doesn't work -- the device is not detected by the computer for obvious reasons. I've been using this trick for a while for my mp3 player and my Hero at work and was surprised that it didn't work.
Click to expand...
Click to collapse
No, you need to short those pins together. If you leave them open, it won't go into high-current charge mode.
Those other devices may have had D+ and D- connected across a termination resistor. Putting tape on the pins would have worked then.

IBNobody- I was wondering if you could explain this one- when I plug my epic into the usb port of the cheap charger that came with 2 batteries off of ebay (see here) my epic seems to freeze and the touch screen becomes unresponsive- the charger states it puts out 5.2V 800ma
Could it be that the phone is trying to figure out if its being plugged into a computer vs a simple charger?

USB Charging versus Wall Charger

So I have noticed that charging via the USB cable to my computer takes much longer than charging via the USB cable to the wall-wart (not so much of a wart on this device ).
I understand the differences between trickle-charge and regular-charge (I think), but how does the phone know which source is charging it? When it's plugged into a laptop/desktop, I know it would communicate differently than just recieving a voltage. If it's in charge-only mode, then it shouldn't matter, right?

wall charger puts out more amps
google says usb port puts out 200-500 ma. the factory htc wall charger says 1.0 a or 1000 ma

headcheese said:
wall charger puts out more amps
google says usb port puts out 200-500 ma. the factory htc wall charger says 1.0 a or 1000 ma
Click to expand...
Click to collapse
Hmm. I find that very interesting. I have seen some older external HDs that had two USB connectors on the same line (one labeled Power, the other labeled Data). I wonder if there would be a way to up the power output of my Notebook/Desktop USB.
When I'm at work I don't have access to a power outlet at my terminal, but I can plug my phone into the front USB port of the desktop here (as long as I don't get caught plugging in external peripherals ).

nerozehl said:
Hmm. I find that very interesting. I have seen some older external HDs that had two USB connectors on the same line (one labeled Power, the other labeled Data). I wonder if there would be a way to up the power output of my Notebook/Desktop USB.
When I'm at work I don't have access to a power outlet at my terminal, but I can plug my phone into the front USB port of the desktop here (as long as I don't get caught plugging in external peripherals ).
Click to expand...
Click to collapse
some hdd will consume more power than just the single usb port and requires two... as for upping the mA raiting, it wont happen because usb is limited to 500 mA like previously mention, unless you have a external usb hub spitting out power

I'm sorry I misunderstood you before: I didn't interpret that as having meant that 500mA was the upper limit. Maybe a cable could be rigged to double that by using two connectors?

nerozehl said:
I'm sorry I misunderstood you before: I didn't interpret that as having meant that 500mA was the upper limit. Maybe a cable could be rigged to double that by using two connectors?
Click to expand...
Click to collapse
think of it like a backup and lighten the load your device takes, in this case a external hdd. Idle is uses less power, but when it spins up and starts reading it might need that burst and constant voltage errm i shouldnt say voltage..i meant amps(milliamps in this case)

Perhaps I should have done some more Googling before I started this thread, but to anyone who is curious, I found some cool information here: http://www.girr.org/mac_stuff/usb_stuff.html

[HOW TO] - Charge your phone faster

Hello all. I found some information that some of you may find useful, so I wanted to share.
If you are running a custom kernel, go download Current Widget from the market
https://market.android.com/details?id=com.manor.currentwidget&hl=en
Install it, add the widget to your screen, and plug in your phone. You should be getting 350-380mA, this is AC charging mode. If you are getting in the low 200's you have a charger or cable that is not bypassing the data+ and data- wires in your phone, this is called USB charging.
If it is showing 0mA, then your kernal is not supported and it will not work. You can still do the steps below and get the same results, you will just not be able to see the data visually. I am running Gummy2.0 and the widget works great.
Some chargers are built .. badly.. and rely on a specific cable that will bypass the D+ and D-. the problem is, that cable will not work for anything USB related, such as flashing roms.
If you are anything like me, you have a dozen USB cables laying around and just use the closet one you can find when you need to charge up. However, if you use a data cable with a wall charger that does not disable D+ and D- you will charge at the USB charging rate, which is much slower than when AC charging is enabled, and can be irritating when your phone drains more power than its getting from the charger, resulting in power loss. This happens often while using your phone as a wifi hotspot. In USB charging mode, you can potentially drain the battery faster than the charger can charge. This can be prevented by being in AC charging mode.
You can either dig around for cables and test them out with your charger to see if you can get up to the 380mA range, or you can solder the D+ and D- points together in your charger. I do not recommend the 2nd option unless you are failure with soldering on small IC circuit boards.
But if you are adventurous, the 2 center pins on the USB cable are D+ and D-. If you open up your charger you will see the backside of the USB port and notice the 4 solder points that connect to the USB plug side. Place a bead of solder between this 2 to short them together. This will allow the charger to be in "AC" mode and charge at the higher rate.
This will also work for USB plug car chargers and will allow your phone to continue to have a positive charge even while navigating (which as most people know, Navigating can still drain your battery even when its plugged in).
Hope this helps! Feel free to ask any questions, I will do my best to answer them.
-EDIT-
Make sure to set the update interval in Current Widget to 1, for 1 second updates, this will help when monitoring the charge current.

Let me test this out... I'll report back in a lil bit. Calibrating battery, can't charge. Later...

I'm using a 10' cable from Monoprice. I'm getting 373mA. I'll post on what I get using my car charger... but I'm getting pretty good battery life that I rarely have to charge it in the ride

[Q] Power Usage While Plugged In

Currently using BuoyAOSPsy v131 ROM
I have noticed that my battery still drains while I am plugged in and the phone indicates it is plugged in. Have not tested this while plugged into a wall jack, only in my car or via USB to computer.
When this occurs I am using GPS/Navigation software, active data connection (ofc), and playing music.
Does USB or car adapter not supply enough "juice" for this phone to run multiple applications/features? Is there anything I can do to remedy this, such as try a different car adapter? What specs do I need to look for to ensure appropriate power transfer?
Thanks!
**@ Moderators: Hopefully I placed this in the correct forum. Since it is not necessarily directly related to the ROM I thought it should be kept out of the ROM's thread.

Yes you can easily draw more power then its supplying when using computer or car charger. Most of the time its only charging 500 ma when charging that method. Wall charger's I believe are 1000 ma. Navagation is a HUGE draw on battery.

u921333 said:
Yes you can easily draw more power then its supplying when using computer or car charger. Most of the time its only charging 500 ma when charging that method. Wall charger's I believe are 1000 ma. Navagation is a HUGE draw on battery.
Click to expand...
Click to collapse
Thank you for the info. Guess I'll just have to find a higher quality car adapter.

Actually ive read when using a data cable ie stock or regular micro usb cable on a usb port on your pc or a regular charger the max it will get is 500ma. one of the oem wall chargers (block with usb port) is able to supply 1000ma and the phone is only able to sense this the data pin + and - are shorted together. this tells the phone its charging ac plugged vs usb. now check the output of your car charger and if its able to supply more than 500ma then you can either short pins 2-3 on your cable or on your charger and you will get maximum current draw. Research it you ill there was an article posted on xda somwhere.

I'm getting 1000ma from both my ccar charger and AC adapter. u don't want to pin short a cable and charge from usb. drawing that much power will damage the port, it wasn't designed for that (1.0,2.0). USB 3.0, on the other hand :-D

Charger HTC Question

Hi all.
Could the charger of desire work normally(when check in about phone it must be show AC not USB) for the HTC desire HD and Inspire 4g.
Thanks

If it shows AC that means you are charging through a power outlet and when it's charging by USB you are charging it through a USB cable connected to a computer
Charging through AC is faster then USB
Sent from my Desire HD using xda app-developers app

Why does USB from PC charges slower than the one from the socket?

emptyto said:
Why does USB from PC charges slower than the one from the socket?
Click to expand...
Click to collapse
PC has only 500mA current output, your wall charger has 1A output
greater current faster charging-but this does not mean that battery has not its max. charging current!
higher charging current can easily damage your battery and cell phone.

I charge my phone with Xperia charger, with Kindle charger, with Nokia charger and many more. So far I have no problem with my battery. As long as on the end of the cable you have “micro-b usb” and stable (troublefree) electric transformator to supply that cable you can charge your battery. The time to charge may be different but the result is the same.

bravebg said:
I charge my phone with Xperia charger, with Kindle charger, with Nokia charger and many more. So far I have no problem with my battery. As long as on the end of the cable you have “micro-b usb” and stable (troublefree) electric transformator to supply that cable you can charge your battery. The time to charge may be different but the result is the same.
Click to expand...
Click to collapse
+1 you only have to use a micro usb!

The charger should work with any phone other than iPhones

Quiglesigles said:
The charger should work with any phone other than iPhones
Click to expand...
Click to collapse
Correct!
As long as it is a usb micro charger, it all works....
only the time required to fully charged varies...

I am using a Nokia USB cable as a Charge. Works fine too.
Sent from my Desire HD using xda app-developers app

I'm using Nokia cable, Sony cable ... All work fine !

As long as the two data cables are connected to eachother, the DHD will recognise it as a wall charger, and it will use 1 ampère. Instead of the 0.5 amps when connected to a PC (when the data cables aren't connected to eachother).

You can buy "charging only" cables. They always charge at maximum rate and do not transmit any data. Usually come with external battery packs etc.

Just to clarify some. (Talking about USB2.0 as 3.0 has a little higher power)
The USB on computers are powered by the motherboard (if not using extra PCI USB card).
Usually the motherboard gives about 500mAh to each USB host. If that host has 4 USB connectors all those connectors share the 500mAh.
And just be careful to not go above 500mAh as some (older) motherboards or even add in card's cannot handle the extra power and will fail to work(permanently).
So a charge-only cable will not make a difference in this situation, same goes for using multiple USB ports as that also brings extra problems with it, as power/voltage doesn't flow in just 1 direction (when using 2 poles). You could blow out USB voltage regulators when connecting different USB power leads together.
As for the phone side you can also use a 5000mAh power source, as the phone will 'take' what it needs. For DHD the max charging power is about 800mAh~900mAh if I'm not mistaken.
As long as its 5V and somewhat stable.
So if you want to charge the DHD (or any other USB chargeable phone, mostly all of them) as fast as possible use the original wall charger.
If you have to do it on the PC/Notebook unplug as much USB devices as possible, so most of the power can go to the phone.
Also make sure the screen of the phone is turned off as that's the biggest battery drain of the DHD. Thus also making charging slower (when on).

I'm using htc charger to charge my e-cigarette . It's works good.

If you plug it into USB socket, and enable "Fast charge" option, does it do anything? Does it block the data transfer and acts like a wall socket (1A) ?