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Author Topic: Mobile Power for Tablet  (Read 6423 times)
N4SRN
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Posts: 371




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« on: March 13, 2017, 02:39:35 PM »

I have my mobile rig wired to my battery (actually, to my fuse box for positive and chassis ground for negative) with a RIGRunner 4004USB in the passenger front side supplying power to my Yaesu FTM-400XDR. I also have a Dell Venue 11 Pro tablet set up with an external GPS receiver to run APRSIS32 for APRS use. Unfortunately, the tablet discharges and shuts down after a few hours even though connected to the RIGRunner 4004USB, which can supposedly supply up to 4A via the dual USB ports.

The OEM Dell Power Supply is listed as 24W 5.0V/2A. I'm using the OEM USB/miniUSB cable that comes with the Power supply to connect the tablet to the RIGRunner 4004USB USB port. It's charging, but discharging faster than charging it seems.

Any thoughts on how to remedy this problem?

Bret/N4SRN
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Bret/N4SRN
Bedford, NH  USA
W8JX
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Posts: 13268




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« Reply #1 on: March 13, 2017, 03:20:06 PM »

First, does it actually show it is charging? Next if it is charging try going into power profile and limit CPU speed and graphic performance. Typically they default to max CPU and GPU speed. Reducing max CPU speed and graphic performance can extend battery life and reduce drain. They operate on "Speed Step" technology and as speed is reduced so is CPU/GPU voltage which reduced power drain a good bit.  Also on rig runner supplying USB power. USB1 & 2  limits power to about 500 ma (which I have no doubt Rig Runner is) and not 2 amps. You need a USB 3 device supplying power to a USB 3 port to get 2 amps. While USB 3 can talk to USB 1 & 2 it is limited to the limitations of those standards when connected to them.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
N4SRN
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Posts: 371




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« Reply #2 on: March 13, 2017, 04:19:37 PM »

It does say charging when I click the battery icon in the task bar.

I have been disconnecting the tablet from the USB port on the RIGRunner when I leave my car, but perhaps I should leave it plugged in if not away for an extended time? With the tablet shut down, I can't imagine it would drain my car battery over 24-48hr, eh?
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Bret/N4SRN
Bedford, NH  USA
W8JX
Member

Posts: 13268




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« Reply #3 on: March 13, 2017, 04:33:09 PM »

It does say charging when I click the battery icon in the task bar.

I have been disconnecting the tablet from the USB port on the RIGRunner when I leave my car, but perhaps I should leave it plugged in if not away for an extended time? With the tablet shut down, I can't imagine it would drain my car battery over 24-48hr, eh?

It will not run it down and it will stop charging when full too. The power needed to charge tablet is but a very small fraction of power in a car battery.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
N4SRN
Member

Posts: 371




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« Reply #4 on: March 13, 2017, 04:39:04 PM »

I'll give it a go then. I wonder if my USB GPS Receiver was still drawing current after the tablet was shut down and draining its battery? I'll have to check if it's an always-on USB Port. Likely not, on a tablet...
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Bret/N4SRN
Bedford, NH  USA
W9IQ
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Posts: 3244




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« Reply #5 on: March 13, 2017, 05:25:26 PM »

I would be more concerned about the quiescent current of the 4004 USB strip. To supply power to a USB port, it needs to convert the 12 volt source to a 5 volt supply. The efficiency of this conversion under no or low load on the USB port should be investigated. It is likely a switching supply given its 4 amp USB rating. The manual is silent on the topic of quiescent current and conversion efficiency. Some bench measurements would net the missing specifications.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
W8JX
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Posts: 13268




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« Reply #6 on: March 13, 2017, 06:27:34 PM »

I would be more concerned about the quiescent current of the 4004 USB strip. To supply power to a USB port, it needs to convert the 12 volt source to a 5 volt supply. The efficiency of this conversion under no or low load on the USB port should be investigated. It is likely a switching supply given its 4 amp USB rating. The manual is silent on the topic of quiescent current and conversion efficiency. Some bench measurements would net the missing specifications.

- Glenn W9IQ

If its efficiency was that low it would be warm as efficiency loss does not dissipate into thin air. It leaves a trail. 
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KK4YDR
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Posts: 673




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« Reply #7 on: March 13, 2017, 07:56:36 PM »

Just buy an aftermarket charger that has a higher output. I do it with my cell phones. Cheap'o junk chargers actually dissipate heat rather that put energy into the battery. A good 30 dollar charger and my cell phone charges fast as heck.

I have a cheap modified sine wave inverter that I can plug into my 12v socket and I can charge a wide variety of stuff using it. That way you can use the factory charger that plugs into the wall. Problem solved potentially.
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W8JX
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Posts: 13268




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« Reply #8 on: March 14, 2017, 03:25:47 AM »

Just buy an aftermarket charger that has a higher output. I do it with my cell phones. Cheap'o junk chargers actually dissipate heat rather that put energy into the battery. A good 30 dollar charger and my cell phone charges fast as heck.

Never bought or needed a 30 dollar charger. Never had any problem with "cheap" chargers. I have a lot of them scattered around house and in cars so I can always find one.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
K5LXP
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Posts: 6101


WWW

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« Reply #9 on: March 14, 2017, 08:06:10 PM »


If it's anything like my XYL's Samsung tablet, the only time you get the elevated charge current rates is with their proprietary charger.  So it's not just a matter of providing a "2A" charger, the tablet won't accept it.  It will only ramp up to the higher rate when it communicates with the charger.  I even went so far as to disable the data lines and sure enough, the current would only go up to 400 milliamps and change.  Restore the communication and the current would ramp up over an amp.  Makes a big difference when you're trying to charge a 4Ah tablet battery, especially if it's powered up at the same time.

Mark K5LXP
Albuquerque, NM
 
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W8JX
Member

Posts: 13268




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« Reply #10 on: March 15, 2017, 02:00:27 PM »


If it's anything like my XYL's Samsung tablet, the only time you get the elevated charge current rates is with their proprietary charger.  So it's not just a matter of providing a "2A" charger, the tablet won't accept it.  It will only ramp up to the higher rate when it communicates with the charger.  I even went so far as to disable the data lines and sure enough, the current would only go up to 400 milliamps and change.  Restore the communication and the current would ramp up over an amp.  Makes a big difference when you're trying to charge a 4Ah tablet battery, especially if it's powered up at the same time.

Mark K5LXP
Albuquerque, NM
 

I have not seen this. I have not needed a name brand charge for faster charge. Hia bottle neck is USB 2 port on rigblaster which will only do about 500 mah.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
N4SRN
Member

Posts: 371




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« Reply #11 on: April 10, 2017, 05:21:16 PM »

Only problem these days is when temperatures are around freezing and I leave the car outside. The tablet just doesn't like to boot until the heater vent blows on it to warm it up!

Bret/N4SRN
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Bret/N4SRN
Bedford, NH  USA
W8JX
Member

Posts: 13268




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« Reply #12 on: April 11, 2017, 05:50:18 AM »

Only problem these days is when temperatures are around freezing and I leave the car outside. The tablet just doesn't like to boot until the heater vent blows on it to warm it up!

Bret/N4SRN

That's interesting because those temps should not effect it. It should take much colder below zero temps to do that. The touch screen control in our car work fine at zero and it boots same in any temp. I suspect the problem is the tablet being used, not that it is a tablet.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W9IQ
Member

Posts: 3244




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« Reply #13 on: April 11, 2017, 06:15:15 AM »

That could simply be the difference between consumer and automotive grade components and engineering playing out in real life.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
W8JX
Member

Posts: 13268




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« Reply #14 on: April 11, 2017, 06:37:17 AM »

That could simply be the difference between consumer and automotive grade components and engineering playing out in real life.

- Glenn W9IQ

Or the difference between a cheap tablet and a good one.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
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