Trying to understand the current draw of a Samsung Galaxy S3

[Danny D.]

Today I hurled enough invectives at my Samsung Galaxy S3
to make a whore blush, simply because the GPS wouldn't
work under power.

More specifically, the cigarette lighter car charger is
reputed to be 2.1 Amps, while the standard wall charger
is only 850 mA, so, the 2.1 Amps should have been plenty
to both charge and run the Samsung Galaxy S3.

The battery was down to 17% when all the mischief started
occurring. The GPS kept saying over the bluetooth "GPS
signal lost", "GPS signal re-acquired", over and over
and over and over again, within ten seconds of each other,
such that the GPS was useless - and - worse yet - the
battery went lower and lower until the phone finally
shut off.

Yet, after charging it for an hour on the car, with
the phone off, it got up to about 65%, and then I used
the GPS on the road for another hour, and it STAYED at
65% battery.

What on earth is going on?

Why would a 2.1 Amp charger not be enough to both charge
and run the phone, and why would it lose charge when the
battery is at 17% yet it maintains charge when the battery
is at 65%?

Does any of this make sense to you?

 

[Andy Burns]

Danny D. wrote:

Why would a 2.1 Amp charger not be enough to both charge
and run the phone

Does the phone detect the charger as capable of delivering high current?
If so, it should display "Charging A/C" instead of "Charging USB"
unless Samsung have hobbled that part of Android.

 

[Danny D'Amico]

On Fri, 31 Jan 2014 06:59:53 +0000, Andy Burns wrote:

Does the phone detect the charger as capable of delivering high current?
If so, it should display "Charging A/C" instead of "Charging USB"
unless Samsung have hobbled that part of Android.

Hmmmmmmmm...... I never saw either "charging A/C" or "charging USB".

All I see is a lightning bolt and a percentage in the icon bar.
http://farm4.staticflickr.com/3755/12232054495_b0d9fb71fe_o.gif

However, I just downloaded a bunch of battery-monitor apps to see if
they can help me identify the S3 battery drain problem.

In addition, googling, I found this disturbing reference:
http://forums.androidcentral.com/t-mobile-galaxy-s-iii-accessories/185776-2-amp-charger.html
Which says:
"a lot of 2A chargers are designed for iDevices and their weird way of the
charger signaling to the device that it is ok to draw max power. Absent
fairly specific voltages on the data lines iDevices will either assume they
are connected to a computer and only draw 500mA, or they won't charge at all.
However, most non-iDevices simply look for the two data lines to be shorted
together to let them know they are connected to a dedicated high power charger
and not a computer. That means that most non-iDevices will not recognize 2A
chargers that are designed for Apple products as being high-power and so the
phone will only draw 500mA even hooked up to a 2A charger."

If that statement above is true, then my reputed 2.1 Amp car USB charger
could only be sourcing 500 mA to the Galaxy S3.

 

[Danny D'Amico]

On Fri, 31 Jan 2014 07:31:47 +0000, Danny D'Amico wrote:

If that statement above is true, then my reputed 2.1 Amp car USB charger
could only be sourcing 500 mA to the Galaxy S3.

Here is another reference that intimates that a standard USB cable
under all conditions only allows 500mA to go into the Samsung Galaxy S3:
http://forums.androidcentral.com/samsung-galaxy-s3/195415-max-safe-amps-car-charger-us.html

"With a standard USB data cable the phone recognizes it as a USB charging
source and only pulls 500 mA. You can get "charging only" cables allowing
higher (still safe) amperage"

 

[Danny D'Amico]

On Fri, 31 Jan 2014 06:59:53 +0000, Andy Burns wrote:

it should display "Charging A/C" instead of "Charging USB"
unless Samsung have hobbled that part of Android.

I appreciate that wonderful advice!

It took me a while to FIND what you were talking about on my
T-Mobile Samsung Galaxy S3 with Android 4.3 installed.
http://farm8.staticflickr.com/7366/12232358615_bb6f4d8d5a_o.jpg

I found the "type" of charging when I went to Android 4.3:
Settings->More->About Device->Status

A. When hooked to a PC USB port, it said "Charging (USB)".
B. When hooked to a wall USB port, it said "Charging (AC)".
C. Tomorrow I will test what it says in the car & report back!

 

[Danny D'Amico]

On Fri, 31 Jan 2014 06:53:54 +0000, Danny D. wrote:

2.1 Amps should have been plenty to both charge and run the
Samsung Galaxy S3.

Googling some more, it seems the most the Samsung Galaxy S3
will every draw is 900 mA, at least according to this:
http://forums.androidcentral.com/samsung-galaxy-s3/306607-2-amp-charger-s3.html

"Tests done by users over in xda-developers show [the Samsung Galaxy S3]
limits the amount of current the battery can draw to about 0.9 amps
regardless of the current available ... Also when the battery is fully
charged it shuts down totally -- it doesn't continue trickle charging like
simpler chargers."

 

[Danny D'Amico]

On Fri, 31 Jan 2014 07:35:57 +0000, Danny D'Amico wrote:

"With a standard USB data cable the phone recognizes it as a USB charging
source and only pulls 500 mA. You can get "charging only" cables
allowing higher (still safe) amperage"

Googling for what the difference is between a data & charging cable,
I find this reference:

http://forums.androidcentral.com/samsung-galaxy-s3/306607-2-amp-charger-s3.html
Which says:
The two types of cable are a "charge only" cable and a full data cable.
In order to distinguish which type of port they're connected to and therefore
know how much power can be drawn phones examine the two inside "data" wires
on the USB connection. If they are shorted together the phone says hey I'm
plugged into a charging port and can draw max amps and it reports it as "AC"
--if they are not shorted then it limits amp draw to 0.5amps and reports it
as " USB". Note that some wall wart modules short the data pins internally
--with those you can use any cable and pull max. Others don't so in order
to pull over 0.5amps you must use a special "charging only" USB cable that
does the shorting in the cable--these will NOT work for data usage.

Apple phones do something similar but instead of shorting the data pair
they change the voltage on one data wire.

 

[Danny D'Amico]

On Fri, 31 Jan 2014 08:13:23 +0000, Danny D'Amico wrote:

Googling some more, it seems the most the Samsung Galaxy S3 will every
draw is 900 mA

It seems, that in the car, the problem is that we probably shouldn't
use Apple USB chargers, unless we use special cables:

At least that is what is implied here:
http://forums.androidcentral.com/samsung-galaxy-s3/195415-max-safe-amps-car-charger-us.html
Apples 10W/2A charger puts 2.8v on one of the data lines and 2v on the other
(I forget which is which) to tell an iPad that it can pull up to 2A.
Earlier iphone/ipod wall chargers put 2v on each data line which will
limit the device draw to 500mA. This is why you need to use a "charging cable" with
wall/car chargers made for apple products. The Apple oriented chargers do not
internally short the data lines so most android phones will treat it like a 500mA
source. The charger that ships with your android phone has the data lines shorted
internally so it doesn't matter what cable you use.

 

[Danny D'Amico]

On Fri, 31 Jan 2014 06:53:54 +0000, Danny D. wrote:

> Does any of this make sense to you?

What's going on when GPS is enabled while the S3 is on the car charger is
just starting to make sense now, with respect to the current draw:
http://forums.androidcentral.com/samsung-galaxy-s3/195415-max-safe-amps-car-charger-us-2.html

The S3 uses the defined Micro USB charging standard.
If the charger or cable has the data lines shorted, the S3 thinks it is on an AC charger.
If the data lines are not shorted, the S3 thinks it is plugged into a USB port on a PC.
When the S3 thinks it is plugged into an AC charger, the S3 pulls a maximum current of about 800ma.
If the charger is LESS then 800ma. the phone may fall back to the lower current of a USB port.
When the S3 is plugged into a USB port (where the data lines are not shorted),
then the S3 pulls a miximum current of between 300ma and 400ma.
If the charger DOES have shorted data lines, but it can't handle the 800ma
AC charger setting, the phone falls back to the lower USB port rate of about 300ma.

 

[Danny D'Amico]

On Fri, 31 Jan 2014 09:01:09 +0000, Danny D'Amico wrote:

> Does any of this make sense to you?

Another quote from the same thread, which is instructive:
http://forums.androidcentral.com/samsung-galaxy-s3/195415-max-safe-amps-car-charger-us-2.html#post2997829

Most batteries can handle a charge rate of 1xcapacity.
In the case of the Samsung S3 the battery is 2100mA capacity.
Therefore, the S3 can be safely charged at 2.1A.

The battery has no regulator in it and it not smart in any way.
The S3 has a circuit built in to properly charge a lithium ion
battery and can regulate the source current as needed.

 

[Danny D'Amico]

On Fri, 31 Jan 2014 06:53:54 +0000, Danny D. wrote:

Today I hurled enough invectives at my Samsung Galaxy S3 to make a whore
blush, simply because the GPS wouldn't work under power.

Here's a summary of what I've found out, in bits and pieces:

STUFF I KNEW FROM PRINTING ON THE PHONE & BATTERY:
- The Samsung Galaxy S3 itself, is rated at 3.8V, 1025mA.
- The Samsung Galaxy S3 battery is 3.8V, 7.98Wh, 2100mAh, Li-ion.

STUFF I LEARNED SO FAR:
Note: *** indicates important but unproven statements found on the web.
- The 2100mAh battery can be charged at up to 2.1 Amps (1x Capacity).
- We're told the S3 never allows more than 800 to 900mA of charge current.***
- We're told the S3 does not trickle charge after 100% capacity.***
- Settings->More->About Device->Status->reveals the charge assumption.
- If the S3 sees 2 data pins shorted, it assumes "Charging (AC)".
- If the S3 does not see shorted data pins, it assumes "Charging (USB)".
- Cables can be either "data" or "charging" (with shorted data pins).
- Charging (USB) will be limited to 500mA current draw.
- Charging (AC) is not known to be limited in current draw.
- The stock S3 AC charger is 1A.
- We're told Apple-spec USB chargers put voltage on the data lines.
- So, the S3 will assume "Charging (USB)" with a normal "data cable".
- A "charging cable" switches the S3 to "Charging (AC)" on Apple USB.

CRITICAL FACTORS (the Samsung Galaxy S3 "charge assumption"):
- An S3 assumes "Charging (USB)" with PC USB & a "data cable".
- An S3 assumes "Charging (USB)" with Apple USB & a "data cable".
- An S3 assumes "Charging (AC)" with wall chargers & a "data cable".
- An S3 assumes "Charging (AC)" whenever a "charging cable" is used.

OPEN QUESTIONS:
- I still don't know how to tell how much current is actually drawn.
- None of the Android battery apps I tried gave current draw in amps.
- Instead, they listed charge in cryptic terms such as "12%/h".

 

[Danny D.]

On Fri, 31 Jan 2014 06:59:53 +0000, Andy Burns wrote:

Does the phone detect the charger as capable of delivering high current?
If so, it should display "Charging A/C" instead of "Charging USB"

I checked what the phone says when it's on the 2.1 Amp
cigarette lighter charger, and, interestingly, it does
say "Charging (AC)" (even though that 2.1 Amp figure
has the word "iPad" next to it on the adapter).

So, had it said "Charging (USB)", that would have been
my problem - since it actually says "Charging (AC)", we
know that's not the problem.

I'm think I will need to sacrifice a USB cable, by cutting
it in half, and then checking the wires (or buying a test
fixture that allows me to hook an ammeter in series).

 

[Danny D.]

On Fri, 31 Jan 2014 07:18:44 -0800, Ike wrote:

> Where can I buy 2-3 charge-only cables?

There is a long thread on where to buy charge-only cables:
http://forums.androidcentral.com/samsung-galaxy-s3/195415-max-safe-amps-car-charger-us-2.html

Make sure you read the reviews though, as some
suppliers seem to "confuse them", at least according
to the rather detailed reviews (for a cable) here ...

Amazon Charging-Only USB cables:
http://www.amazon.com/gp/product/B007F1DV76/ref=oh_details_o01_s00_i00?tag=androidcentral00-20
http://www.amazon.com/gp/product/B003VYBCAY/ref=cm_cd_asin_lnk?tag=androidcentral00-20
etc.

 

[Danny D.]

On Fri, 31 Jan 2014 07:01:29 -0800, dave wrote:

Turn off GPS.
Turn off mobile data
Voice and Text are not on Mobile Data.

Luckily, I don't even have mobile data.
I do use GPS navigation all the time in the car though.
That's the whole point!

If the phone can't keep up with the GPS while
on the car charger, um, what good is GPS?

Note: I have gone on long trips (4 hours), and
if the battery is charged (say, >50%) it stays
at about that level; but if the battery is low
(say <20%), then the battery steadily depletes.

That's the enigma I'm trying to understand.

 

[Danny D.]

On Fri, 31 Jan 2014 10:48:34 -0500, (PeteCresswell) wrote:

First thing that came to my mind was that the GPS satellites were harder
to acquire than usual.

I don't disagree.

The first few times this happened, I thought the
same thing.

It was only yesterday, when I REALLY needed the
GPS navigation to work - that I realized the
constant "GPS signal lost" audible warnings
were actually due to the fact the battery was
at 17%.

Worse yet, apparently 17% is the critical point
in the curve where the phone can't keep up with
the GPS and the GPS keeps shutting off (rendering
it useless).

If only the 2.1 Amp charger would keep the phone
running. That's the enigma!

The enigma is that, if the charger is actually
putting out 2.1 Amps, and, if, (as it appears),
the phone recognizes the charger as an AC charger,
then, why isn't 2.1 Amps enough to run the phone?

Note: Yes, I know they it is said that the phone
never draws more than 900 mA, but, even so, that
should be enough to run the GPS, isn't it?

I guess the question is, literally:
Q: How MUCH additional current does the GPS cost us?

 

[Danny D.]

On Fri, 31 Jan 2014 17:23:56 +0000, Danny D. wrote:

The enigma is that, if the charger is actually putting
out 2.1 Amps, then, why isn't 2.1 Amps enough to run the S3?

I should note that I *do* realize the charger doesn't
"put out" current (as it does voltage); what I meant,
clarified, is:

The enigma is that, if the charger is capable of
sourcing 2.1 Amps, then, why isn't that enough to
run the Samsung Galaxy S3 with operative GPS?

How much current does the GPS sink anyway?

 

[Kerry Liles]

Thanks! for posting this valuable information. I have been mystified by batteries in
general for a long time... the older I get, the more I don't understand. I have
always presumed there is the "Apple way" and perhaps several other models of the
universe, so I am not at all surprised by the fact that devices intended for use with
Apple products are the spawn of the devil and may not work in non-Apple situations. I
look forward to more revelations - especially about battery monitoring apps.



On 1/31/2014 7:37 AM, Danny D'Amico wrote:

On Fri, 31 Jan 2014 06:53:54 +0000, Danny D. wrote:

Today I hurled enough invectives at my Samsung Galaxy S3 to make a whore
blush, simply because the GPS wouldn't work under power.

Here's a summary of what I've found out, in bits and pieces:

STUFF I KNEW FROM PRINTING ON THE PHONE & BATTERY:
- The Samsung Galaxy S3 itself, is rated at 3.8V, 1025mA.
- The Samsung Galaxy S3 battery is 3.8V, 7.98Wh, 2100mAh, Li-ion.

STUFF I LEARNED SO FAR:
Note: *** indicates important but unproven statements found on the web.
- The 2100mAh battery can be charged at up to 2.1 Amps (1x Capacity).
- We're told the S3 never allows more than 800 to 900mA of charge current.***
- We're told the S3 does not trickle charge after 100% capacity.***
- Settings->More->About Device->Status->reveals the charge assumption.
- If the S3 sees 2 data pins shorted, it assumes "Charging (AC)".
- If the S3 does not see shorted data pins, it assumes "Charging (USB)".
- Cables can be either "data" or "charging" (with shorted data pins).
- Charging (USB) will be limited to 500mA current draw.
- Charging (AC) is not known to be limited in current draw.
- The stock S3 AC charger is 1A.
- We're told Apple-spec USB chargers put voltage on the data lines.
- So, the S3 will assume "Charging (USB)" with a normal "data cable".
- A "charging cable" switches the S3 to "Charging (AC)" on Apple USB.

CRITICAL FACTORS (the Samsung Galaxy S3 "charge assumption"):
- An S3 assumes "Charging (USB)" with PC USB & a "data cable".
- An S3 assumes "Charging (USB)" with Apple USB & a "data cable".
- An S3 assumes "Charging (AC)" with wall chargers & a "data cable".
- An S3 assumes "Charging (AC)" whenever a "charging cable" is used.

OPEN QUESTIONS:
- I still don't know how to tell how much current is actually drawn.
- None of the Android battery apps I tried gave current draw in amps.
- Instead, they listed charge in cryptic terms such as "12%/h".

 

[dave]

On 01/30/2014 10:53 PM, Danny D. wrote:

Today I hurled enough invectives at my Samsung Galaxy S3
to make a whore blush, simply because the GPS wouldn't
work under power.

More specifically, the cigarette lighter car charger is
reputed to be 2.1 Amps, while the standard wall charger
is only 850 mA, so, the 2.1 Amps should have been plenty
to both charge and run the Samsung Galaxy S3.

The battery was down to 17% when all the mischief started
occurring. The GPS kept saying over the bluetooth "GPS
signal lost", "GPS signal re-acquired", over and over
and over and over again, within ten seconds of each other,
such that the GPS was useless - and - worse yet - the
battery went lower and lower until the phone finally
shut off.

Yet, after charging it for an hour on the car, with
the phone off, it got up to about 65%, and then I used
the GPS on the road for another hour, and it STAYED at
65% battery.

What on earth is going on?

Why would a 2.1 Amp charger not be enough to both charge
and run the phone, and why would it lose charge when the
battery is at 17% yet it maintains charge when the battery
is at 65%?

Does any of this make sense to you?

Turn off GPS. It will drain your battery fast. Turn off mobile data
unless you need it. Voice and Text are not on Mobile Data.

 

[Ike]

WOW! This valuable thread answers some questions, but also raises one.

Where can I buy 2-3 charge-only cables? eBay and Amazon listings don't
seem to indicate whether those pins are shorted or not.

Is there such a thing as a charge-only "adapter" that goes in-line and
shorts the appropriate pins?

THANKS

 

[(PeteCresswell)]

Per Danny D.:

occurring. The GPS kept saying over the bluetooth "GPS
signal lost", "GPS signal re-acquired", over and over
and over and over again, within ten seconds of each other,
such that the GPS was useless - and - worse yet - the
battery went lower and lower until the phone finally
shut off.

Yet, after charging it for an hour on the car, with
the phone off, it got up to about 65%, and then I used
the GPS on the road for another hour, and it STAYED at
65% battery.

What on earth is going on?

First thing that came to my mind was that the GPS satellites were harder
to acquire than usual.

I don't claim to know anything about that stuff, but I do know for sure
that things like tree cover can diminish satellite signals - so I'd have
to wonder if atmospherics could do the same.
--
Pete Cresswell