App to see how much current (amps) my device is charging with?

[r314bd]

I bought a new power adapter and want to make sure it's charging at the current it advertises. Any apps that will let me see this?

 

[JohnnytheK]

Turn the adapter over and read the output printed on it.

 

[r314bd]

Turn the adapter over and read the output printed on it.

That's not always accurate. This adapter for example says it outputs 2.1 amps when in fact it only outputs 500-700mA.

 

[JohnnytheK]

Hadn't thought of that, I've measured a few and they either don't work at all or are within 10% of the rated capacity.

At any rate I did a search and can't any app that does what you want. On one Web site a guy insisted it wasn't possible.
/me shrugging

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[Natey2]

Android does output the charging current in the logs. See http://www.droidforums.net/forum/showthread.php?p=1312534

e.g. (values are probably in mA)

02-26 06:45:43.430 I/BATTD ( 1217): set_charge_current=700
02-26 06:45:45.383 I/BATTD ( 1217): set_charge_current=800
02-26 06:45:47.336 I/BATTD ( 1217): set_charge_current=700
02-26 06:45:49.290 I/BATTD ( 1217): set_charge_current=1800
02-26 06:45:57.110 I/BATTD ( 1217): set_charge_current=800
02-26 06:45:59.055 I/BATTD ( 1217): set_charge_current=1800
02-26 06:46:08.829 I/BATTD ( 1217): set_charge_current=700

Anyone here believes this value is not accurate?

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[wcjeep]

Could use a Kill-a-Watt. My battey charges faster in the phone vs the stand alone charger bought from Verizon.

 

[Natey2]

Could use a Kill-a-Watt.

I just did
Kill-a-watt (model P4460) reported 0.08A and 6Watts.
Strange, because that would be 80mA, not 800mA as reported by Android in the logs...

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[wcjeep]

The kill o watt is reporting ac amperage. That would need to converted to amperage.

 

[Natey2]

The kill o watt is reporting ac amperage. That would need to converted to amperage.

Thanks, wcjeep!

"In order to convert AC Amps to DC Amps, all you need to do is multiply the amperage by 10."
- http://www.solarrvpanels.com/index.php/converting-dc-ac-appliance-usage-into-amp-hours/

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[a_lazy_dude]

Thanks, wcjeep!

"In order to convert AC Amps to DC Amps, all you need to do is multiply the amperage by 10."
- Converting DC & AC Appliance Usage Into Amp Hours - Solar RV Panels

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I don't know how to say this without sounding crass, but that is only (kinda) correct for 120 V (AC) converters that output 12 V (DC), and vice versa, which is the example described in the link. Our smartphones take 5 Volts of Direct Current (DC), so this is not a valid way to convert. What you need to do is look at the power that is being transferred, and use some simple algebra. Power (P) = Current (I) x Voltage (V). In short, P=IV. The kill-a-watt mentioned above is reporting that 6 watts of power are being consumed. No voltage converter is perfectly efficient, so let's assume that 1 watt of that is being lost to heat in the converter. That leaves 5 watts of power transferring over to the phone (DC). We know that the voltage on the phone side is 5 V. So we have P (5 Watts), and we have V (5 Volts). Since P=IV, it is calculated that I (current) equals 1. This is in amps, and there are 1000 miliamps in an amp. Thus, it is a reasonably safe assumption that approximately 1 A (1000 mA) of current is charging the phone.

Getting back to the OP. Does anyone know of any apps that report actual current consumption by the phone? The log file is a nice find, but it looks to me that this is only reporting the requested current from the phone to the charger... depending on the charger, I'd imagine that the actual current supplied could be very different... could be wrong though.

 

[LoudRam]

Have you tried "Battery Monitor Widget".

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[a_lazy_dude]

Thanks! This app looks like it would be perfect, but so far it's only telling my that my drain is 2 mA. I could be missing something, but I fear that my Droid 4 may be unsupported at the moment.

 

[JohnnytheK]

That's not always accurate. This adapter for example says it outputs 2.1 amps when in fact it only outputs 500-700mA.

Just curious, how do you know it's only putting out 500-700mA? The only way I know to measure DC amperage is to open the circuit and to mount the amp meter in series with the load. This means cutting one of the wires.

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[a_lazy_dude]

Good question, and for that particular charger, I don't know how that reviewer arrived at their conclusions. However, for this charger, the data seems to jive with what SGDM1 was saying. Charging over USB is apparently not as straight forward as one might think, since the base spec is only 500 mA and various handshakes need to take place in order for a device to determine that the particular charger it's hooked to will be able to supply more current without damaging it.

To answer your question about measuring current, yeah, that's pretty much the only way. You can also play some tricks by splicing in a small value resistor in series with the load and using a voltmeter to measure the voltage drop across it. Since V=IR, you can determine the current by dividing the measured voltage by the resistance.

 

[JohnnytheK]

Good question, and for that particular charger, I don't know how that reviewer arrived at their conclusions. However, for this charger, the data seems to jive with what SGDM1 was saying. Charging over USB is apparently not as straight forward as one might think, since the base spec is only 500 mA and various handshakes need to take place in order for a device to determine that the particular charger it's hooked to will be able to supply more current without damaging it.

To answer your question about measuring current, yeah, that's pretty much the only way. You can also play some tricks by splicing in a small value resistor in series with the load and using a voltmeter to measure the voltage drop across it. Since V=IR, you can determine the current by dividing the measured voltage by the resistance.

Yeah that would work but you're still splitting one of the wires, and yeah the repair would be a piece of cake, but,,,


PS I was checking out the charger and Scosche has an app that is supposed to show the battery drain and it estimates the time left. Not sure how accurate it is but I'll play with it and see. It is in the play store under Scosche reVive free and paid version.

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