Need recommendation for USB power analyzer tool.

I have various USB chargers, cords, and portable devices around the house. One of my devices, a Kindle Fire from around 2013, which works fine, seems to have a nonlinear charging rate. Maybe that's OK. I don't know. For example, it seems to take much longer to go from 15% to 16% than from 95%-100%. In any case, I'd be curious to know how much the charging current is fluctuating and if there is any variation in performance between the wall chargers I have in my drawer. There's a very large selection of USB power analyzers available but I mostly want something that will test "C" ports as well as the older ones. Any recommendations? It seems that every review I read contains more than a few complaints about reliability and sturdiness.

Thanks for your reply.

Reply to
David Farber
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More likely to be a non-linearity in the gauge monitoring method. A 15% gauge is a crude guess - a 95% gauge will depend on settings and tolerances. Both reported values will likely shift dramatically when transferring from charge to discharge mode or vice versa.

A linear charger, thermally limited, will be more restricted in delivering power when the battery terminal voltage is lower (bigger drop across the regulator). Linears will only be found in the oldest or cheapest devices, at USB power and voltage levels.

The deviation you've noted is probably not worth the time, trouble or expense to pursue, unless you're in the design/ build/test/repair/volume-trade businesses.

RL

Reply to
legg

Consider a battery very similar to a clock spring. And the charger similar to the key winding that spring. The key turns at a constant rate, so the first 30 (of 100) turns seems to do almost nothing. Whereas the last turn requires the most effort and gives the largest measurable results. The gauge that you are reading measures the tension on the spring, not how fully it is wound, but for practical purposes, the same thing at the end of the process. Charging a battery is by no means similar to filling a gas tank - just keep that in mind.

Peter Wieck Melrose Park, PA

Reply to
Peter W.

Hi RL,

Thanks for all those operational details but these USB power meters are not that expensive:

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Most of them are in the $10-$40 range. My Kindle can take more than 8 hours to charge so I'd like to do some investigating.

Thanks for your reply.

Reply to
David Farber

Hi Peter,

Funny you should mention the clock spring analogy. Last year I completed my first course in clock repair. I was motivated to do so when a 100+ year old mantel clock stopped functioning. It was professionally repaired many years ago and it did very well for 10 years after that. When it stopped working again, I really wanted to learn how to do my own repairs.

Getting back to the USB charging issue, I was hoping someone in this group had a power meter in their toolbox and could recommend one.

Thanks for your reply.

Reply to
David Farber

Thanks for demonstrating to us that you know almost nothing about either clock springs or battery chargers!

Clock springs are usually retained inside a barrel (except in the cheapest clocks), so that each turn of the winding key unfurls another rotation of the spring from being tight against the inside of the rest of the spring. This results in *very little* progression of spring force from run-down to fully wound. This is essential to proper time-keeping, depending on the Q of the escapement mechanism (a Q of say 100 means that the spring force can affect 1% of the clock's rate, clearly unacceptable).

Battery chargers radically lower the charge rate when the battery gets above about 80% full. The key *doesn't* turn at a constant rate.

Reply to
Clifford Heath

On Sat, 5 Feb 2022 10:54:40 -0800, David Farber snipped-for-privacy@aol.com wrote as underneath :

I have about 4 different makes/types over the years all Chinese, all work on the A USB plug/socket Id have to find adaptors for use with USBC. Just get the cheapest from eBay but make sure is counts mAh cumulative with a reset as well as V and A, some dont. Some will read A to .000 most only do 2 places. C+

Reply to
Charlie+

I think this was the one I bought. I am very happy with it but don't have much need for the power sink add-on or the built-in mAh accumulator etc. I think it also monitors the charge control negotiation and displays the result. There's a user-manual PDF link.

Reply to
Mike Coon

Here in the US, spring-driven pendulum clocks did not, and do not, for the most part, use barrels. They did, however, use the deadbeat escapement (Seth Thomas patent in the US) that does tolerate a wide range of spring force. Making accurate clocks much cheaper than before, as to get that level of accuracy, they often required a fusee drive. And for exactly the reason given. Any escapement with backlash as you suggest, allows the drive force (spring) to overcome the pendulum swing, introducing all sorts of inaccuracy.

Peter Wieck Melrose Park, PA

Reply to
Peter W.

Overnight charging time of a Kindle-era device is not unusual. If you are relying on the Kindles gauge for reporting, the most accurate monitor will be your memory/experience in converting those numbers to the practical performance delivered.

As your issue is slow charge time and not reducing run-time, keeping the thing plugged in or replacing the battery probably won't resolve it.

I encounter lousy gauges in expensive equipment all the time, but repairing/improving them usually isn't an option. Once the programmer has ben paid, at time of development, that's what you're going to get.

I don't know that having a second gauge telling you something different is going to help - they can only tell you what current is flowing through USB power lines: not what current is flowing into or out of the internal battery, before or after conversion, dependent on direction of current flow.

RL

Reply to
legg

pendulum swing, introducing all sorts of inaccuracy.

Anyone really interested in clock mechanisms could study "chain fusee"

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Reply to
Mike Coon

Hi Mike,

Did you inadvertently leave out the description of, "... the one I bought"?

Thanks for your reply.

Reply to
David Farber

These will not tell you actual battery status as they have no access to the battery terminals - only converter socket input and output.

Currents will differ on both sides of the converters, in both directions and the external dongle will ignore the influence of both battery charging efficiency and converter losses in the transactions.

. . . but then so do most built-in gauges, even for varying internal consumption. The best you'll ever get is a ball park estimate that your own experience has to qualify.

RL

Reply to
legg

I didn't do it on purpose(!), and browser history has helped me get back to the page:

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Link to manual:

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Reply to
Mike Coon

That's 9 years old. You could be dealing with an almost dead battery.

Complaint: EVERY time you post a question, you either leave out or truncate the details on what you're working with. Some Kindle Fire models have "issues" and it's helpful to look for these "issues" or recalls before assaulting the alleged symptoms. In this case, None/HD/HDX/Kids, screen size, and what year Kindle Fire. Extra credit for some details on the charger.

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Hmmm... That's about what I would guess happens when you plug in an underpowered charger. As I vaguely recall, some of the Kindle tablets required a 5V 1.5A or 2.0A charger. Commodity chargers only deliver

0.5A. If the USB controller chip in the charger is over-heating, I would expect something similar to what you're experiencing.

Perhaps providing how long it takes (in minutes) might also be helpful? How long did it take to charge when it was new?

You won't see much of that with an inline USB power meter unless you want to record voltage and current every few minutes and draw a graph. Something like this: "USB Current Sensor"

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Software:
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Setup your computah as a data logger and measure the voltage output produced by the current sensor (1amp = 1volt). Graph the results and you can see what it's doing. My guess(tm) is that the graph is going to be far more erratic than you've already observed. If you don't want a pretty graph, just use the current senor and put voltmeters across the 5V line for the voltage, and across the output for current.

Also, put an oscilloscope across USB 5V line. You might see oscillation and/or noise spikes.

I only have a pile of USB 2.0 type volt/amp USB meters. For fun, I put them all in series and compared readings. Not too horrible +/-5% on both voltage and current. However, you need something that will do USB 3.0:

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Gone to split some more firewood.

Reply to
Jeff Liebermann

Deadbeat removes one source of inaccuracy, but at the end of the day, the spring has to deliver power to the pendulum to keep it swinging, and that coupling varies with spring force. The bottom line is that it's easier to e.g. use a heavier pendulum than it is to make a spring with a flatter power curve. The Taiwanese 31-day clocks can often tolerate a pendulum 3x heavier, and that dramatically improves their timekeeping.

CH

Reply to
Clifford Heath

Hi Jeff and all the other contributors to this group,

I really do appreciate all the feedback I get from this community. I've been posting messages and getting expert help here for over 20 years.

As to your complaint about me leaving out important details every time, I am not doing that intentionally. I was expecting to purchase a USB tool that would help me figure out if one of my chargers, cords, or USB port on the Kindle were intermittent. I didn't think that it would be a manufacturing glitch or defect specific to this device.

The Kindle model is: P48WVB4 otherwise known as a Fire HD (3rd generation) with a 7" screen. On the back, near the model number it says "Input: 5.0 VDC MAX 1.8A" I received the device 2nd hand when the owner upgraded to a new one. I don't have the original charger. I have three chargers which came from various devices and sources. Two of them are

5.0 VDC 1A and the third one is, 5.0 VDC 0.85A. I have three USB cords. One is quite old and I suspect this is part of the problem.

I viewed the link to the current sensor tool you mentioned

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Though it does not have a display, it does have output terminals which the others do not. Again, I think the problem my Kindle has is a loose connection or a bad wire that can be easily detected by just monitoring the current while tapping on the connectors and flexing the wires. The battery when fully charged, will last around a week before needing to be recharged. I use it from 1-3 hours a day and leave the wireless disabled and brightness set to one step above minimum as I read in the evening with the text set to a white font and the background set to dark.

Thanks for your reply.

Reply to
David Farber

In the Amazonian language, that's a "Kindle Fire HD 7, 2013, 3rd Generation"

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Note that this is the 2nd version of the Kindle Fire HD 7, but since it was released in the 3rd year after the original, Amazon decided to call it the 3rd generation. Bigger numbers are better.

I couldn't find anything that looked like a manufacturer's defect or chronic problem, just the usual bugs and glitches:

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Bingo. That's either a 2Amp or 10 Watt charger. I found a few references that indicate that the Kindle Fire HD 7 3rd generation supports PD (power delivery) for fast charging. You might want to borrow a 10 watt or 15 watt PD charger and see if it magically fixing the charge time problem.

Sigh. He probably kept the PD charger (if that's what the Kindle Fire HD 7 3rd generation uses).

Both of those chargers should default to charging at 5V 0.5A. They'll probably work, but very sloooooooowly.

I'll assume USB-C cables. A large percentage of the USB-C cables seem to use very fine wire and therefore have a substantial voltage drop. Phones, tablets, gizmos, and the guys who wrote the USB specs, will do strange things if the voltage drops below: 5.0V -5% = 4.75V A bad cable might be a problem, but I don't think so. When I see bad cables, it's usually very "digital". It either works, or it doesn't, with nothing in between.

Please re-read what I wrote. You need to supply a voltmeter (DVM) in order to read the current. The device converts USB current into a measurable voltage (1Amp = 1Volt) while introducing only a tiny voltage loss.

OK. I give up. Please purchase a USB 3.0 tester, any tester, and see if it can detect an intermittent cable or connector. When that fails, come back here and I'll try to convince you to try a 10 watt (or 15 watt) charger, or consider a replacement battery. "How to Replace Your Amazon Kindle Fire HD 7 3rd Generation Battery"

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Hmmm... a bit expensive. More batteries:
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I can't tell much from that without knowing how long it would run under similar conditions when it was new. CNet test show 9.3 hrs runtime for their video test.

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Reply to
Jeff Liebermann

That's wrong. I did some more digging and could not find any references to the Kindle Fire HD 7 2013 3rd generation supporting PD (power delivery). The closest approximation to a spec sheet doesn't mention PD (or any other fast charging specs):

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Therefore, any 5V charger that will provide 2amps (10 watts) and a USB

2.0 Micro-B connector, should work.
Reply to
Jeff Liebermann

On Sun, 06 Feb 2022 13:26:32 -0500, legg snipped-for-privacy@nospam.magma.ca> wrote as underneath :

Yep! C+

Reply to
Charlie+

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