So why do some micro-usb plugs

[#1]

work and others don't?

I have several usb leads with micro-usb connectors on them. A few will NOT charge my Kindle but everything else is OK, one will not charge my phone but will charge the Kindle.

Nowt to do with charge/amperage as it is same psu (I have a female usb on the end of a cable).

[#2]

I generally find micro usb a LOT MORE reliable than Apple 'Lightning' (TM) leads that, unfortunately, some members of my family use.  I do know (from cutting one open) that the Apple leads have tiny microchips in the small connector end, I don't know if this is the case for micro usb but it's possible that there's something there to identify current (or other) capabilities of the leads to prevent (for example) a cheap lead being used with a high powered charger on a 'fast-charge' device where the current would melt/fry/burn the lead.

[#3]

Measure the length of the metallic part of the plug.

A few years ago I got an add on disk caddy with a micro connector. It wouldn't work with some of my cables, but would with others. I eventually noticed that the cables it failed with had slightly (2-3mm) shorter plugs than the ones if did work with.

Judicious trimming of the moulded plastic on a failing plug confirmed the issue - the failing plugs didn't go in far enough to make a good connection.

[#4]

Nope usb only have the option of OTG with the 5th wire, no chips. But the phone is 1A anyway so not high power.
I changed to a new one and both are happy again, but it is silly that some work and others don't, and this is only for charging and slow charging at that.

[#5]

It's because micro plugs are too small.

They should have standardised on mini plugs (or full size plugs).

Amazing that I spotted this thread amongst all the dross.

[#6]

A little while back I tested 6 USB leads on my phone.

A had an app running which told me the charging current.

I was a little surprised to find charging rates varying from 1000ma down to 200ma depending on which lead I was using.

I marked the best performing ones.

[#7]

Similar to strat... I have several leads... One (I thought) that came with the Garmin Satnav, would not be recognised by windows on plugging into the USB slot on laptop... a second one, that I had mated to a HDD Caddy, DID get recognised.

Both showed that the Sat Nav was charging !.. i.e. when I removed the lead from the satnav, it dimmed and reported that power had been lost...!..

Trying to "update" the software I logged into Garmin site.. and the first lead was not recognised.. as soon as I put in the second lead, it found the device, and the laptop actually installed the driver for the satnav.. !.

A note shown after the first lead scenario, suggested reasons why Garmin could not find the satnav on the laptop.. it said to change the lead, as some were "power only" and others were made for file transfer and power.

[#8]

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@HairyMcbiker wrote:

work and others don't?

I have several usb leads with micro-usb connectors on them. A few will NOT charge my Kindle but everything else is OK, one will not charge my phone but will charge the Kindle.

Nowt to do with charge/amperage as it is same psu (I have a female usb on the end of a cable).

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because some are made with lower grade wire(s) and skip pins in the connectors so that certain features are locked out.

also some cables have micro circuits in the plugs to limit functionality or do other less savoury things or regulate the power supply side of things often making them slightly lower performers than others, price of cable is no indication in performance of it either as some of the 5 for £2 items work better than some of the £20 ones, although it can be a bit hit and miss

[#9]

That doesn't explain non charging, I would explain why high charge rates are not available on some cables, but not why a cable that will charge one thing will not charge an other (with the same requirements). Both my phone & Kindle take a slow charge. It only needs the 2 power wires connected. I can wire a bare plug and it works but a pre-made cable doesn't.

The requirements for normal current drain are only the 2 wires +/-.

[#10]

sure it does they skip the charge pins and the cable will still work for data transfer, indeed transfer leads are required for pc to pc connections (back in the 98>xp upgrade days) so you could port your data from one machine to another when replacing it without causing a problem due to the power output on the usb plugs ....

some newer cables employ micro circuits to do leak checks and some have micro fuses in them to prevent damage to the charging equipment in the event of a higher power supply than should be produced (so your phone doesn't explode when your 99p wall charger fails) yet they will still work for data transfer/

[#11]

Yes BUT I am only talking about CHARGE not data transfer.
Given 2 cables with ONLY 2 wires each, why does cable 1 work on device a but not device b, but cable 2 works on both. Given that they are from the same supplier at the same time !

[#12]

are the two devices identical or different ?

if the former then its possibly a damaged connector in one of the plugs or devices

if its the latter then possibly one of the devices has a leak return pin that's missing from one of the cables

the next question would be are the two cables of the same age  and batch ?

if yes to both its possible one has been used more than the other and thus become defective in some way

in reality the only way to know why a particular cable doesn't work is to dissect it, but I rather suspect the problem your alluding to will be one of pin missing or link wire missing on pin(s) newer hardware has greater safety built into it older hardware not so much /

[#13]

It might also be related to the distance and size of the connectors on the devices -v- those on the wire, an nth out and it's a no show.

[#14]

As I said in the FIRST post it is my phone and my Kindle, both slow chargers and both running from same psu via a usb female connector.
The cables are the same length, and one will charge both and one will only charge the phone.

[#15]

@HairyMcbiker - If you are referring to my post I don't see it. I am referring to the distance between each of the individual connectors (contacts) on both the leads and the connectors on the devices. So what I am really saying is that the physical ends of the wires may not be identical. If you have a vernier to had you could always check.