I would just like some advice since I melted a USB cable today and I realized I don't have the proper troubleshooting skills.
I bought over a half-dozen "Hype Volt" 6.8Amp USB chargers for stuffing the Christmas stockings:
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I kept one for myself, but, when I used it last night on an iPad and on an Android phone, the iPad lightning cable melted!
When I pulled it off the iPad, it was noticeably extremely hot, but it doesn't seem to have damaged the iPad (AFAIK).
So, I'm just wondering what happened, and, more importantly, when I look at the specs for this device, they don't make sense to me, so, I have difficulty troubleshooting what the problem is/was.
Here are all the specs off the package and off the device: DGL Group Ltd. Hype Volt HV-6PT Model: HC363-5U (also listed as HV-6PT-WHT) Input: AC 110VAC/60Hz - 220VAC/50Hz (800mA max) Output: DC 5V, 6.8A total Maximum Power: 40W Supercharge: 5V@2.4A maximum Universal: 5V@1A maximum
Description:
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My questions are varied, because I don't understand how it works, nor how it could have overheated the cable to the tablet.
Here's what it says on the package: "Smart USB Technology: This adapter automatically adjusts power output to fit your charging device. Tablets and e-readers require 2 Amp charging, and this adapter will reroute power to the appropriate USB port you use." "Charging Combinations: - 2 tablets + 3 mobile devices - 1 tablet + 4 mobile devices - 5 mobile devices - 3 tablets"
I am confused about both the pure math and how this operates.
Q1: Since 6.8A times 5VDC is only 34Watts (not 40 Watts), how can they very clearly label it as a 40Watt device?
Q2: How does the device "know" to give tablets 2.4 Amps (12 Watts) but a "mobile device" only 1Amp (5 Watts).
Q3: What if a mobile device "wants" more than 1 amp? Does the charger give more than 1A to the device?
usb devices initially get 100ma and then request how much power they really want. the charger responds with how much it can supply.
some non-compliant devices ignore the negotiation phase and either output whatever power is needed and/or the device uses whatever is available. that's probably the case here. however, that alone is not a problem.
an easy way to think about this is a lightbulb. if you screw in a 15w bulb, it will use 15w. if you screw in a 60w bulb, it will use 60w. with a 200w bulb, it will use 200w. nothing about the light socket or the house wiring has changed. it uses what it needs. a 15w bulb won't be overloaded because the socket *can* supply more power.
a properly designed charger won't because it can't. it tells the device "all you're getting is 1a" and the device says "ok".
a shitty charger might, which can cause it to overheat.
Scott Lurndal wrote, on Mon, 30 Nov 2015 17:38:04 +0000:
Here is a better (bigger) picture of the unit:
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And a better (bigger) picture of the package:
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I thank you for the reference, but, after reading it, I don't see how that article helps explain the *output* wattage descrepancy between 6.8A x 5VDC and the stated output spec of 40Watts.
That article explains how to convert Volt-Amps to Watts. "How to convert VA to Watts and KVA to Kilowatts"
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The input voltage is AC so roughly the input wattage is: 110VAC RMS times 800mA (max) which is roughly 88VA
But it's the OUTPUT wattage that is stated to be 40Watts. 6.8Amps x 5.0VDC is only 34 Watts
Hence, a rather large 15% descrepancy (6 watts less than
40 watts).
I'm sure my math on the output wattage is wrong because the package can't be wrong (that would be illegal), so, I don't see where my math went wrong yet though.
So, any advice is welcome and I will check it out.
Scott Lurndal wrote, on Mon, 30 Nov 2015 17:38:04 +0000:
Thanks for that article, titled: How USB charging works, or how to avoid blowing up your smartphone
The article explained that USB 3.0 "cables" have 9 wires but when I looked at the 6.8Amp charger, each USB slot seems to have only 4 gold pins on the white protruding tab. I presume the surrounding metal is ground, so, that makes 5 electrical connections that I can see in each USB slot of the 6.8Amp/40Watt "Smart" wall charger.
The article says there are three types of USB 3.0 ports:
Standard downstream port (900mA at 5VDC = 4.5Watts)
Charging downstream port (1.5A at 5VDC = 7.5Watts)
Dedicated charging port (1.5A at 5VDC = 7.5Watts)
The article did say "A regular USB 1.0 or 2.0 socket has four pins", so, I wonder if they counted the ground shield because the sockets on mine only have 4 gold strips on the white protruding tab, so, I'm not sure which USB spec my sockets are.
While this is interesting, after reading that article, I didn't see anything in there that explained the problem nor how to troubleshoot it.
Scott Lurndal wrote, on Mon, 30 Nov 2015 17:38:04 +0000:
Here are some more specs:
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The manufacturer is listed as "DLG Group LTD" on the package:
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And, as "Hype Volt" on the device:
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Looking for a phone number, I find this description which says they're based out of "Edision, New Jersey" (with the USPTO giving the HYPE VOLT trademark serial number of 86138884 which was subsequently "abandoned"):
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The contact was provided as: URI DALLAL PO BOX 340256 BROOKLYN, NY 11234-0256
Googling further, the DGL Group seems to be located here:
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195 Raritan Center Pkwy Edison, New Jersey 08837-3650 (718) 499-1000
That explains why each USB socket only has four gold pins on the white protruding tab.
I did call the company in Edison NJ at 718-499-1000, and, after going through their operator, I spoke with "Bob", a salesman at the office.
I told him, nicely, that it must be true, otherwise it would seem to me to be illegal to over represent the output power by 15%.
He didn't know the answer to why it says it outputs 40Watts but at the same time it says the maximum is 6.8Amps at 5VDC, but Bob said he'd try to find out and for me to call him back tomorrow.
It can't be the input because 100-220VAC times the maximum stated
800mA input current is 80 Watts (give or take) input, which would be about right assuming 50% efficiency.
That is interesting. So, when I plugged in the iPad, it "asked" for
100mA, and then it asked for more, so the charger gave it more?
But, then, why did the cord melt?
I understand that a current "source", which is the charger, is just a source of current (sort of like being a big tank of water); it's not going to "push" that current into the current "sink", which is the iPad at any rate more than what the iPad "asks" for.
So, I'm assuming that the cable is bad (maybe pins are shorted, for example, between power and ground).
But that still doesn't explain why the device says it's both 40Watts output and that its maximum output is 6.8Amps at 5VDC.
The device can be powered by 110V at 60Hz (US market) *or*
220V at 50Hz (european). Internally, the device can be thought of as "autosensing" the input and adjusting, accordingly. (in practice, there's no real "sensing" involved; it will also work at 190V/53Hz as well as a multitude of other combinations! Possibly even DC!)
In those conditions, it will not draw more than 800mA.
The output will be 5V (nominally... it may actually be 5.1V, etc.) The TOTAL current available is 6.8A. Think of current as water flowing through a pipe -- at a particular RATE (amps). This says that the "pipe" can supply water (current) at a rate of 6.8A.
The power supply/charger will consume a maximum of 40W. As it will only DELIVER 34W (6.8A x 5V) to your "loads", this suggests the device is ~75% efficient (34/40). The extra "power" drawn from the AC mains is lost -- as heat.
Each connector in "supercharge mode" can deliver 2.4A at the stated 5V.
This is what a "regular" USB connector delivers
That would depend on what's inside the tablet. The short answer is: there was a potential (voltage) drop across the cable (i.e., from the charger end to the tablet end) *and* current flowing through the cable. The drop at that current rate expresses a power (heat) that is dissipated *in* the cable.
Hook a *stiff* car battery charger to a *good* battery (in techno-speak, both devices want to have low apparent impedances... not easily "pulled" from their desired state). Charger puts out X volts. Battery is *at* Y volts. X > Y causes current to flow TOWARDS the battery; Y > X causes current to flow FROM the battery.
But, neither the battery nor the charger are "moving" -- so, the difference (X-Y) is appearing across the length of the wire connecting them. I.e., the *wire* is handling the mismatch -- by getting hot! :>
See above. You consume foodstuffs every day. If you don't gain weight, AND, don't sh*t, you are 100% efficient in your utilization of those calories (hand-waving as not everything you "take in" CAN be "burned").
The 40W is what you are consuming; what the electric company is billing you for [sic]. The 34W is what you are actually able to *use* (in your tablet, etc.) from that. An "ideal" device would consume exactly as much as your tablet requires -- no "insertion/conversion" losses.
You'll note that the device gets warmer as your load increases -- cuz the losses tend to increase (in absolute terms -- power/heat) as your demand increases.
A USB device can "negotiate" it's power requirements. The socket (charger) can only deliver what it can deliver. A conforming device will not ask for more than can be delivered.
E.g., I can connect an iPod to a low power USB connector on a
*keyboard* (notoriously low power because THEY use some of the LIMITED power available to them on *their* USB connection to the computer!) and access the contents of the iPod as well as transfer files to/from.
But, I can't *charge* the iPod over that connection -- because there isn't enough AVAILABLE power to do so (at least, not quickly)
USB ports (on computers) have sensors in them that will sense if a connected device has drawn more power than it should. In that case, the USB port will shutdown -- like tripping a circuit breaker -- until the device is removed. At that point, the circuit will (should) reset so another PROPERLY BEHAVING device can be connected -- without having to replace any real fuses (which was a problem with old PS/2 and XT keyboards) or having to "reboot".
Not all USB sockets are well behaved -- as loads *or* supplies! Caveat emptor.
if it's a third party cable, it might be compliant. some are and some aren't. generally, cheaper cables are not compliant. really cheap cables are almost certainly not compliant.
the cable itself might not say but the packaging will. companies like to brag that it's compliant.
non-compliant cables don't always melt. it simply means it doesn't meet apple's standards of quality and construction and may not work properly, notably with syncing (charging usually works but not always).
if a device needs more (many do), they need to request more power, and must do so using less than 100ma.
standard usb ports should be able to provide 500ma. a bus-powered hub, such as a keyboard, can't supply 500ma to downstream devices (it could only supply 500-whatever it takes) so it will decline any request, which is what causes the 'this device uses too much power' warnings.
recent usb ports can source more current because of usb hard drives that need >500ma to spin up the drive as well as phones and tablets that want more to charge faster.
it's hard to say without looking at it.
one possibility is a defective cord but there could be other reasons.
if you have a continuity tester, try checking the cable for shorts.
the fact that it says 'full compatibility with ios 7' rather than saying it's 'mfi certified' which would guarantee compatibility no matter what suggests that it's *not* mfi certified.
a cable that's mfi certified would say so, as it's a competitive advantage over generic cables:
apple has this to say about how to check the cables:
Call the CPSC and put them on *RED ALERT* for a recall. The problem is that it is not an Apple product so therefore you are bleeped. Sound the klaxton.
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