Measuring charging amps

[thecaptain42]

I bought a white MediaBridge dual USB car charger with 2 usb ports: 1.0 amp & 2.4 amp. I saw, what seems to be slow charging, so customized a cable to measure the actual amps. I got a 3' microUSB extension cable. Dug the red positive wire out of this cable and cut it. Got a digital dc amp meter and can see the amps going into the tablet.

Connected the white charging cable that came with my SM-P600 16GB wifi Note 2014 to this short extension, going thru the amp meter. While using the Samsung 2.0 amp charger, I see drawing 1.31 amps from the charger. Note 2014 is 25% charged, so I expect should charge at a pretty high rate.

When I use the MediaBridge, plugged into the 2.4 amp port instead of the Samsung charger (all cables and amp meter are the same in both tests), the amp meter shows .44 amps. If I plug into the 1.0 amp port (as a test), I get the same .44 amps. I know about the Android need to short the 2 data wires, and the box actually says "shorted".

For the heck of it, I plugged these same cables into a usb 3.0 port, see .34 amps.

I talked to MediaBridge and they agree I should see over 1 amp of charging with their charger. They actually sent me a new white charger, both of them act the exact same way.

In the very beginning, I bought a black MediaBridge charger (which actually said for iOS devices), as I figured all 2.4 amp USB chargers were the same. That charger charges at the same .44 amps.

I've also been running the Galaxy Charging Current *Lite* app, which doesn't give me any valuable info.

I'm thinking of chopping up a USB cable, to see if the 2 data wires are shorted while it is plugged into the charger (while not plugged into a cig lighter port.

Does anyone know if this is a valid test (measuring the amp draw between a charger and the tablet)?
Does anyone have any other easy tests I can try before giving up on trying to charge at a decent rate?

Thanks.

 

[thecaptain42]

Fascinating! Still charged at 25%, I connected the MediaBridge charger to monitor the charging amps. When the screen blanked (5 minute timeout), charging current went to .05 amps. After about 10 minutes (5 minutes of .44 amp charging and 5 mins of .05 amp charging), got rid of the screen saver, still charged at 25%. That tells me this charger would never charge the Note.

Changed over to the Samsung charger, still charging at 1.31 amps.

 

[Dale_M]

Dont understand how the two data wire can be shorted when cable is universal and can send/receive data to PC with same cord.... The data leads "shorted" statement seems bogus to me....

I always have fallen back on the amperage output of "charge" and voltage .... I have never had a charge problem as long as the charger is stated putting out (capable of) 5.1 volts at 2.1 amps or
more....

Of you are using a USB port on a PC for charging they are limited to about 500ma (.5 amp) and voltage is not always quite up there....

Wish I had a extra cord I could sacrifice...

Dale

 

[thecaptain42]

A pretty good description on shorting the data wires can be found here:
http://forums.androidcentral.com/samsung-galaxy-s4/284055-we-need-special-samsung-usb-cable-charge-2amps.html

Be sure to read garublador's answer. That is why iOS and Android chargers greater than 1 amp are different. Even MediaBridge uses the term shorted.

That's why the "shorting" takes place inside the >1 amp charger, so a standard USB cable could be used.

I just cut up a USB cable. I measure 5.11 volts from the MediaBridge, a bit low. I measure 5.36 volts from the Samsung charger.

One very small issue could be that I'm using a 120 volt AC to 13.5 volt DC adapter rated at 1.0 amps. That should still produce more than .44 amps at 5 volts.

Took my test to the car, with a fully charged battery. MediaBridge shows 5.22 volts. I still charge in the .44 amp range. Started the motor to see if the alternator made any difference, see no difference.

The other factor I recently noticed, the Samsung charger, of course shows the lightning bolt, indicating it is charging. MediaBridge never shows the lightning bolt. That is consistent with the small amp charge I see.

From what I'm seeing, I wonder why they can sell these, as I can't get the lightning bolt to show a charge with the MediaBridge.

 

[Dale_M]

OK.... Just verified the data lines and in 2.1 amp SAMSUNG charger the are shorted in charger not in cable..... Seem sort of problematic (?) to have a cable with shorted data leads and somebody might be unaware what it is ..... Also with data leads shorted in charger, it probably negates the possibility of using a combo OTG/Charge cable with Samsung (high amp) charger... OR one needs to have data lines open towards charger with charge/OTG (or any other adapter (HDMI ?)) cable and be satisfied with lower charge rate....

Power source for "Charger" should not matter whether it be 12VDC (?) mobile charger or 120VAC source, the output should be self regulated at "5 volts" and voltage should not change unless internal regulator is slightly different in each chip. So any variation of output voltage will be a internal charger regulator issue and not dependent on external voltage source.......

Dale

 

[thecaptain42]

Good idea testing Sammy charger pins being shorted--as I expected, they are.

I have seen cables for sale with data wires shorted. I agree, that could be tried as a data cable and would fail.

I think if you're using an OTG usb adapter, you would not be using the charger at the same time, so there would be no issue there.

I just called MediaBridge (maker of charger I have been discussing). They read a list of incompatible devices. A few Sammy tablets were listed as incompatible, but Note 2014 was not on their list. Hopefully, they now realize the 2014 should be in their list. They recommended I return the devices to Amazon. Guess I'll do that, but prefer having a charger that can charge my Note above .5 amps at the same time as my S3 phone, from 1 cigar lighter port.

Does anyone know of a 2-port charger that handles the Note properly?

Just tried another experiment. I have a cheapo coiled cigar lighter charger with micro USB. Put my in-line amp meter, I read .43 amps. The big difference is the charging lightning bolt indicator on the Note lights up. I started my test with the Note at 88% charged, after 12 minutes, went to 89% (screen off, wifi & gps on). That tells me, it is charging, though at a very slow rate.

Technically, I'm still a bit confused why this doesn't work. The data wires have been confirmed to be shorted in the Sammy and MB chargers. The same cable is used for both. The MB voltage is 5.11, Sammy 5.36, I don't think that is a factor. There's got to be something else going on, wish I knew what it was.

 

[Dale_M]

Might try doing a little research over at XDA Developers site.... They are more hardware hackers over there...

http://www.xda-developers.com/

And ther is this....

http://forums.androidcentral.com/sa...87-otg-cable-supports-charging-same-time.html

Dale

 

[John Woo1]

Might try doing a little research over at XDA Developers site.... They are more hardware hackers over there...

http://www.xda-developers.com/

And ther is this....

http://forums.androidcentral.com/sa...87-otg-cable-supports-charging-same-time.html

Dale

That cable doesnt support charging. Read the red note: "Note:The USB power can't charger for your tablet or cellphone,only supply power for OTG ports."

 

[Dale_M]

But it is a plus because if you have large power draw USB item(s) plugged in at least it does not zap tablet battery....

Like the XDA kludge hub anyway....

Dale