USB charge time.

I know there is a series of USB types and the charge time is controlled by many things, the USB outlet, the lead, and the item being charged.

I must have at least 20 USB leads which will connect my phone or tablet to a USB outlet, the 13A sockets with USB are clearly marked 2.1 amp for example, but car chargers and plug in chargers often either not marked or so small I can't read it.

So I plug my tablet into my desk top and it says 16.5 hours to fully charge and already 75% charged, move it to 13A socket with USB outlet marked 3.1 A for pair (only one outlet used) and the reported time drops to 14.5 hours within 5 minutes, 1/2 hour latter it's fully charged.

Reasonably sure the lead I was using was genuine Samsung and clearly with that lead and 3.1 Amp per pair it is fast. Even the wall sockets vary from 2.1 A a pair to 3.1 A a pair to 4.2 A for a 4 USB socket outlet, rare that I use a wallwart type, one I have just looked at is 800 mA.

I know the flat red lead which came from Pound World is slow, and the Samsung lead is fast, however most the leads not a clue which are fast and which are slow.

Is there a way to test to find out which are which leads and USB outlets? Clearly the report on the Samsung tablet was wrong, 14.5 hours and then fully charged in 1/2 hour. Is there an app or something which will actually tell you the charge rate?

Is there in real terms any difference between 2.1 A and 3.1 A and 4.2 A marked on a USB outlet with just one lead plugged in? Or does the lead limit the output anyway?

In the main I am not in a hurry, phone and tablet is charged over night, but when I am in a hurry, need to know which are slow and which are fast leads and USB outputs.

Can't help with leads apart from saying branded leads are probably faster than £ shop ones.

However one of these is very useful to find the charging current:

https://www.ebay.co.uk/itm/USB-Char...widiI6Mywic28iOjE1MDAsImMiOjQ2Nzh9&rmvSB=true

Just plug it in line.

That looks the bees knees, it would it seem test both lead and outlet not got paypal so must put it down on want list.

ericmark said:

That looks the bees knees, it would it seem test both lead and outlet not got paypal so must put it down on want list.

Click to expand...

At £2.98, you can hardly go wrong.

You don't appear to need a PayPal account to buy it - you seem to be able to make payment directly with a credit/debit card.

Kind Regards, John

I find genuine chargers are better quality and quicker charging.

Charging from a desktop I do find the slowest. Longer leads can slow down charging.

My lad has a Moto G4 plus with a "turbo" charger that tops up superquick, but I have not measured it.

You can get the charger doctor from Amazon too.

There are several things that impact on charge rate.
First off, in the absence of any signalling to the contrary, connected devices must (in theory) assume that only 0.5A is available as that's all the spec allows for. However there are methods for the supply to signal that more power (or even higher voltage) is available - in the normal fashion, standards are a good thing, each manufacturer has some of it's own
I strongly suspect that some devices try the "lets see what I can pull" method of determining available power - ie ramp up the current and look for the voltage dropping as the supply shuts down on overload.

And then there is the cable. One way of making a cable cheaper is to use less copper - and one can assume that "cheaper" cables are likely to have less copper than a good quality one. Since we're only talking about 5V, it doesn't take much volt drop in the cable to affect the device at the end. This will either directly limit charging current, or cause the device to think there's less current available than the supply can provide.

So "it's complicated" and realistically, once you depart from using the manufacturers supply and cable, then it's "pot luck" what results you'll get

SimonH2 said:

and one can assume that "cheaper" cables are likely to have less copper than a good quality one.

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and in some cases, cables which contain other metals and no copper at all.

As far as I understand the cable has a built in resistor which tells the charger the cable limit, the same with the device, what is unclear is what happens with a USB extension lead. But around the home and in the car there are so many USB outlets and some will charge fast, and others can hardly maintain the battery at current level never mind charge it.

A quick look around this room for USB outlets shows two 13A sockets with built in USB outlets but hard to access, also a sewing machine, TV, hard drive, and desktop. As you move around one sees all sorts of items with USB, my car radio, the sky box, printer most clearly not designed for pure charging but for hard drives or USB sticks. I know some have a very low power output as the hard drives will not work, only the self powered ones and sticks will work.

I think the caravan is the place where we have the biggest problems, the radio has USB, the cigarette lighter converter/extension has 2 USB this plugs into caravan 12 volt system, and two outlets in a double 13A socket. As to wallwarts every socket has more than one item we want to plug in so really don't want to use them. Two phones and two tablets means every USB is used. What I want is USB from 12 volt, does not matter then if hook up or not, however all night on charge and still not full with some outlets.

So that meter should cure the problem, at least we will know which is which.

I've bought 20 AWG cables from https://www.juicebitz.co.uk as I was fed up of connections cutting out when transferring files. Got 0.5m ones which could be a useful benchmarking tool for you as well as being pretty fast.

Fat cables for current and fat cables for data? Nah! It won't help data transfer one jot - UNLESS you're powering an OTG hub from a crappy cable, and the hub keeps dying.

Nozzle

I've invariably found that whatever the charger, it outputs at or close to it stated current, and the cause of slow charging is always the usb lead - typically 400-700 mA. Having tried countless ones, I only use Anker or RAVpower leads now (normally from amazon) as they always work at top speed.

Gentlemen (and any Ladies reading this) I find it difficult to believe that in such an erudite community such a discussion is taking place.

The only way in which one can "charge" a battery (of cells) is to provide a voltage higher than the output of the cells and a relatively low resistance charging path to the cells concerned, which will then force current to produce a chemical change within the cells concerned.
Considering the very small current involved in this process when charging any "5 volt" Smart Phone battery of cells, the prime consideration must be the voltage of the charging supply.
(The resistance of any conceivable "Wire" concerned must be negligible.)

I have noted that the charging of any such device from a computer USB port takes a very long time, if indeed any significant charge does take place.
My conclusion is that the Computer power supply is so well regulated (at 5 V) as to really not be suitable for "charging" purposes.

I also note that a "Brand Name" charger appropriate to the Smart Phone concerned and a "Reputable Brand" of Socket Outlet USB charger both provide charging of the same Smart Phone from almost "flat" to 100% within 2 hours.
From that I conclude that the Voltage supplied by the "Charger" is the most significant factor.

As an aside, I do have a device similar to the "Charger Doctor" illustrated previously.
I obtained this device and I continue to use it because I had the unfortunate experience of using a 12 V to 5 V power supply which was defective in that it "oscillated" in providing 5 V then 12 V in a cycle, which damaged/destroyed the equipment for which it was supposedly providing the requisite (5 V) voltage.

Once bitten, twice shy.

Ah, but you miss a very important detail - the battery is NOT connected directly to the USB port. Aside from "dumb" devices that just use USB as a convenient 5V supply, all the devices have a power management system in place that controls power flow to/from various devices.
Depending on the battery voltage, there will be a buck or boost converter between the power in on the USB socket and the battery - that will break the linkage between supply voltage and battery requirements.

FrodoOne said:

Gentlemen (and any Ladies reading this) I find it difficult to believe that in such an erudite community such a discussion is taking place.

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No-one is forcing you to read it

FrodoOne said:

.... the prime consideration must be the voltage of the charging supply. ... (The resistance of any conceivable "Wire" concerned must be negligible.)

Click to expand...

It sounds as if you've never dissected the leads of some of the 'less reputable' chargers. One can find 0.1mm² or less, and, as has been said, not necessarily even copper. Even if it's a dumb charging system (which most aren't), say, 1 metre of that can amount to 0.5Ω or more, hence a voltage drop of about 1V at 2A current - a pretty significant drop in relation to the relatively small marginal difference between charger voltage and battery voltage.

Kind Regards, John

Nozzle said:

Fat cables for current and fat cables for data? Nah! It won't help data transfer one jot - UNLESS you're powering an OTG hub from a crappy cable, and the hub keeps dying.

Click to expand...

Well it still works. I usually need to transfer 20+ files at a time and the heavier cable or the stubby one my old BlackBerry came with are the only two which perform adequately. I hate having to rebuild a camera full of file thumbnails every time it reconnects.