Parameters defining the charging rate

[Electroenthusiast]

I was charging my cellphone from a wall wart, and through the USB cable, and through a low rated wall wart. What i find was that the speed of charging was different with different wall warts, and one charging cable doesn't seem to charge so fast when i connect it to the PC.

On what does the charging time depend on? Does using a cheap cable increase the charging time? If so? How? Since voltmeter always show zero resistance.

 

[rjenkinsgb]

However, as i earlier said how can i make sure that a adapter i use will be good enough for a particular phone, considering that it didn't come with the original make.

The phone information should say what current rating is needed for fast charging. If the power unit meets or exceeds that current rating, and is made to conform to the relevant specifications, the phone should fast charge - otherwise it will charge at a lower rate.

For best overall battery life, it's not so much what charger you use, it's more down to when and how much you charge it!

Lithium cells age fastest when fully charged, and that aging is accelerated by temperature.

Ideally they should be taken off charge as soon as they are full, or better still at eg. 80%
Some phones now only charge to 80% if they are regularly charged on the same schedule, automatically charging the last bit shortly before they are usually taken off charge.

Also, not running them down completely extends the life significantly - eg. keeping the charge "span" from 75% to 25% gives four times the charge cycles, compared to 100% - 0%, for the same level of capacity reduction.

Mobile phones are not the worst thing, as at least the battery is being discharged again as soon as they are taken off charge.

The effects can be far worse with laptops, as they are often either charged and left to stand or run continuously on external power - that's the worst possible state for the battery, as it's held at full charge and with many laptop, they run quite warm.

The life of a new battery used like that can be three months or less, compared to a good few years if the charge range is limited and it's taken off charge once the battery is near full.

They do need an occasion long charge for cell equalisation, that's fine as long as the machine is off, so not heating the battery. Likewise, an occasional run down to turn-off point to keep the capacity reading correct.

 

[Electroenthusiast]

Thanks. But, may I know whether this comes from where. Like is this your personal experience or did you read these collectively anywhere.

I upgraded my OS to the next variant, and I saw that my laptop battery is not getting charged to full as easily. Most of the times it is stuck at 92%, not as it was before while kept on use with external power for hours. So, I believe that the latest software is managing them well.

I did check the current rating of my mobile phone, and the manual doesn't have any information as such. I was using a 1A wall wart, and it was taking some hours to fully charge. I doubt if it is 1A now, since it might have seen a overuse damage (dont know - now possibly like 500mA, how?). I shall use this wallwart for overnight charging usually.

 

[Tony Stewart]

Charging rate is always controlled by the load regulator in mobiles, but may be power limited by the source or the lack of smart negotiated current in USB for non-OEM chargers for some products as Apple did for many.

So how to increase depends on where the problem lies. Common USB phone chargers started at 0.5A, 0.9A to 2.4A (12W) for USB-A and up for USB-C. Fast Chargers that heat-up the phone should not be used unless it is an emergency. Charging the phone while it is powered up or not on standby add even more heat and reduces the charge rate. If this your problem then turn the brightness down to minimal required.

 

[Electroenthusiast]

Yes.It is still over my head that how these self intelligent mobile phones and chargers can control the charging rate spontaneously.

Considering a 1A charger take 1 hour to fully charge, while with these self-controlled systems may control the charging rate of a 3A unit to 3 hours is something that I don't fully grasp on how.

 

[rjenkinsgb]

Thanks. But, may I know whether this comes from where. Like is this your personal experience or did you read these collectively anywhere.

Both. My own experiences with laptops & seeing the effects with others who use them permanently on charge, and making and using lithium packs.

I have two batteries for my main laptop, which I swap around every so often. The older one was bought in 2009 & I've only just scrapped it. That was down to running the machine for around 4-5 hours, while the "new" 2020 one will run if for ~11 hours.
(I ordered a new battery for a different machine a couple of months ago, & was sent one for this in error - the supplier told me to keep it, so free spare & the older one has gone).


It's also well documented:

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

 

[Nigel Goodwin]

Yes.It is still over my head that how these self intelligent mobile phones and chargers can control the charging rate spontaneously.

Considering a 1A charger take 1 hour to fully charge, while with these self-controlled systems may control the charging rate of a 3A unit to 3 hours is something that I don't fully grasp on how.

On older chargers it was quite crude, just using a couple of resistors - have a look here:

Minty Boost

This project details a small & simple, but very powerful USB charger for your mp3 player, camera, cell phone, and just about any other gadget you can plug into a USB port to charge!

learn.adafruit.com

And this is why you might get different charging rates with different leads, some leads are for charging only, and don't have the data wires - so the phone may will only charge at the lowest possible rate.

 

[Electroenthusiast]

Nigel, I mean how can the Minty Boost control the impedance of the charging equipment? That's my question.

Same with regards to the Laptop? The laptop with Windows 8 OS has a capability of slowing down the charging after it reaches 80+%, while the same with Windows 7 always used to charge to 100% while always plugged in.

What i mean is how is that the software is capable of controlling the hardware?

 

[rjenkinsgb]

What i mean is how is that the software is capable of controlling the hardware?

The actual charge control in the equipment is a PWM system that allows the charge current and voltage to be directly controlled by either the system CPU or a dedicated charge controller IC, with a data to & from the main CPU to allow monitoring and control.

Edit - some info on charge system topologies:

Understanding battery charger features and charging topologies

In my previous blog “ Selecting the right battery charger for industrial applications ”, we discussed the standalone vs. host controlled chargers and external...

e2e.ti.com

 

[Nigel Goodwin]

Nigel, I mean how can the Minty Boost control the impedance of the charging equipment? That's my question.

Same with regards to the Laptop? The laptop with Windows 8 OS has a capability of slowing down the charging after it reaches 80+%, while the same with Windows 7 always used to charge to 100% while always plugged in.

What i mean is how is that the software is capable of controlling the hardware?

Read the article I linked to - which explains it all (in that specific case) - simply resistors in the charger connected to the unused data lines. The phone reads what the resistors are, and that tells it the charging capability of the supply, and the phone draws the relevant amount of current.

 

[Electroenthusiast]

Got an AC-DC adaptor which mentions itself to be of the wattage 25 W, which also mentions that it is a Fast Charger. I don't know how it works, but the mobile phone says that i have 1.25 Hours to get it charged full from 40% (How is that fast charging?)

But, what intrugues me is that it mentions that it is self-intelligent, which is the first of a kind which i am seeing on hand. I doubt on the other branded chargers i have till now.

 

[Nigel Goodwin]

Got an AC-DC adaptor which mentions itself to be of the wattage 25 W, which also mentions that it is a Fast Charger. I don't know how it works, but the mobile phone says that i have 1.25 Hours to get it charged full from 40% (How is that fast charging?)

But, what intrugues me is that it mentions that it is self-intelligent, which is the first of a kind which i am seeing on hand. I doubt on the other branded chargers i have till now.

Why?, just because a charger has a stupid label it means nothing - the charging is done in the phone, not in the 'charger' which isn't a charger at all, just a power supply.

 

[Tony Stewart]

My iPhone 13 has an intelligent charge that slows down the rate after 80% and it tells me. Normally you charge it at the rate that is gets consumed or slower if you want to extend the lifetime.

 

[Nigel Goodwin]

My iPhone 13 has an intelligent charge that slows down the rate after 80% and it tells me. Normally you charge it at the rate that is gets consumed or slower if you want to extend the lifetime.

I imagine most phones do similar (but perhaps without telling you?), but it's a function of the phone, not the external power supply

 

[Electroenthusiast]

On the other hand, this charger does is said to support phones from Samsung to iPhone on it's wrapper label. I know that the charging rate would go slow as the phone approaches the full charge due to back-emf/back-voltage from the Li battery. I don't know whether special setup is required to control the charging rate for most of the mobiles. If it does be like that, please do explain.

Nigel, It also mentions output voltage as both 12V, 9V and 5V. So, that completely confuses me on how a battery designed for 5V will work on this AC-DC adapter if this was a normal one, so it has to be intelligent in some way or the other. Sadly, the schools didn't teach us enough to understand this fact well enough later.

 

[Nigel Goodwin]

On the other hand, this charger does is said to support phones from Samsung to iPhone on it's wrapper label. I know that the charging rate would go slow as the phone approaches the full charge due to back-emf/back-voltage from the Li battery. I don't know whether special setup is required to control the charging rate for most of the mobiles. If it does be like that, please do explain.

Nigel, It also mentions output voltage as both 12V, 9V and 5V. So, that completely confuses me on how a battery designed for 5V will work on this AC-DC adapter if this was a normal one, so it has to be intelligent in some way or the other. Sadly, the schools didn't teach us enough to understand this fact well enough later.

Some of the latest power supplies are multi-voltage, and communicate with compatible phones, and (if it wants to can tell the power supply to provide a higher voltage), by default (as far as I'm aware) it will output 5V to remain compatible with older phones and devices.

So it's 'intelligent' in that it can receive instructions from the phone (or other device) to change voltage, not intelligent charging, which is entirely down to the phone.

 

[Electroenthusiast]

Thanks, Nigel. I do think that the consumer electronics industry is developing in a faster pace than before. Lot of developments are happening across, that even an adapter of this kind has evolved to a great extent so that it is compatible to most phone ranging from Samsung to iPhone.

I know that you have posted the url (minty boost) in one of the previous posts, i shall check that to clear doubts in the future.

 

[rjenkinsgb]

A multi-voltage unit will almost certainly conform to the "Power delivery" - PD - standard.

That defaults to 5V normally, but if another device with PD capability is connected it can communicate via the data lines and request a higher voltage, if that would allow it to charge faster or if it is needed to charge at all, such as devices with two or three series cells.

Non-PD devices just see the power unit as a 5V USB source.

USB hardware - Wikipedia

en.wikipedia.org

 

[Electroenthusiast]

I did check the above Wikipedia link. I never knew that a USB Charger like this could deliver up to 240W (as in the link).

I did find something unusual about the pinouts of Type-C USB (from the same link). How is that it is not symmetric on either sides, though we can plug a Type-C pin on either way?

Check out the pin outs here. The pins are not same on both top and bottom.

Type-C Pinouts

 

[Tony Stewart]

I imagine most phones do similar (but perhaps without telling you?), but it's a function of the phone, not the external power supply

Perhaps you knew as I did from Battery University long ago that time spent during CV mode after CC severely reduces life cycles. This remaining capacity is < 20% and if the charger and phone is used simultaneously, this may extend the time during CV mode.

Most phones have not done this and Apple just started reporting this on the latest IOS update on my iPhone 13 Pro. This prompted me to verify what I said and it was iOS13 as the recent version update.

About Optimized Battery Charging on your iPhone - Apple Support (CA)

In iOS 13, your iPhone learns from your daily charging habits to improve the lifespan of your battery.

support.apple.com

I expect Samsung has also cut-in this change for overnight charging to top the battery. sometime in the last year. So going forward with new phones "most" should have this by now on phones that use that OS.

 

[rjenkinsgb]

Check out the pin outs here. The pins are not same on both top and bottom.

That's a plug pinout; look at the socket pinout and compare:

USB-C - Wikipedia

en.wikipedia.org

The plug and socket combination allow them to connect either way around.