USB Ports seem to fade in power output over time

Thread Starter

Lumenosity

Joined Mar 1, 2017
614
It seems that almost all the USB ports that I use for charging devices eventually get very slow to charge.
When I put a device in them to check output voltage it is often around 4.8v - 4.9v instead of 5.1v so devices charge too slowly after a while.
I've tried many different USB cables and none help so it does seem to be the port.

What I'm wondering is what causes this?

Is there a capacitor, resistor or transistor that could be replaced to restore their full charging capability?

This seems to happen regardless of where the port is whether it's in a PC, an inverter, a wall dongle etc.

Thanks
 

Delta Prime

Joined Nov 15, 2019
1,326
Hello there! :)
What I'm wondering is what causes this?
What is the battery chemistry?In other words what type of battery are you charging ,make,model, serial number of charger?
Independent of what type of battery or battery chemistry is used ,energy in the battery diminishes over time.
Rechargeable batteries and the way they are charged can be very confusing if you don't have the information, that's okay. Can you perhaps take a photo of the items in question.We could go from there.
 
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Alec_t

Joined Sep 17, 2013
12,744
When I put a device in them to check output voltage it is often around 4.8v - 4.9v instead of 5.1v
Those voltages are all within the normal range and well above the terminal voltage of any common battery that is charging. The problem therefore is much more likely to be due to the battery rather than the charger. As DP mentioned, batteries lose capacity as they age.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
614
Hello,

I'm not sure what you mean.
The ports in question are inside a PC (personal computer desktop) and in an inverter.
With the inverter it makes no difference what battery it is connected to or it's SOC.
So I have ruled out any battery issue.

Is there nothing in a USB circuit that could cause this?

Thanks
 

Tonyr1084

Joined Sep 24, 2015
6,861
As batteries charge their charge current drops. When the charge voltage equals the battery voltage all current stops flowing. Same as a capacitor when it reaches 5T.

I have two older DeWalt 18 volt battery for my tools. One battery reaches full charge within 30 minutes while the other takes a couple hours to charge - all on the same charger. The faster charging battery also gets hot when charging and when in use, and loses its power quickly. One or more of the 1.2V NiCad batteries have gone bad internally. This battery will just sit and wait until the other battery starts showing signs of trouble. I will then disassemble both batteries and select the strongest cells and combine them into a single unit so that I'll have one 18V battery. Replacements are hugely expensive, mostly because NiCad's are getting to be hard to come by.

I wouldn't be surprised if it turns out that all the batteries you've tested have grown weak. But without actually observing your testing technique none of us can be sure you're doing it right - - - or wrong. All we have is your word you've eliminated certain possibilities. However, it would seem like all the charging sources you're using appear to be working properly. Again, without observing - - - . Logic seems to suggest the issue is with the batteries and not the many chargers you've tried. I would especially trust the PC USB port. Wall warts ? ? ? Now that's a different subject.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
614
Do they get ”slow” during a charging session or do you mean they become slower to charge from the start?
Hello,
You make a good point.
I think some of the previous comments assumed I was using the ports to charge a battery, such as a cell phone
That is not the case here.

I am referring to the raw output voltage and current of the voltage and amps measured with a test device.

It is true that the USB ports in question are slow in charging batteries also.
 

Delta Prime

Joined Nov 15, 2019
1,326
Hello,
You make a good point.
I think some of the previous comments assumed I was using the ports to charge a battery, such as a cell phone
That is not the case here.

I am referring to the raw output voltage and current of the voltage and amps measured with a test device.

It is true that the USB ports in question are slow in charging batteries also.
Hello there again! :)
We try our best with the information provided, we were gently nudging you!
Unfortunately many times we must make assumptions which is counterintuitive to our train of thought!
In no way are we trying to beat you up! I mean that in the best possible way.;)
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
614
Hello there again! :)
We try our best with the information provided, we were gently nudging you!
Unfortunately many times we must make assumptions which is counterintuitive to our train of thought!
In no way are we trying to beat you up! I mean that in the best possible way.;)
Understood.
Sometimes the description posted does not include the complete information.

Thanks for your patience.:)
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
614
As an experiment, I took a particular cell phone and a particular USB cable and plugged them into various USB ports on various devices. All of the ones I have used for a while say either "Your device is SLOW CHARGING" or do not charge at all.

putting that exact same phone and exact same cable into a new device with USB ports and there is no "Slow Charging" warning and the phone begins to charge MUCH faster. The only variable is the device with the USB port and the age of the device and how much the USB port has been used.

It "seems" clear at least to me that something is happening to the USB ports over time and use that is dropping their voltage and or current.

I'm going to tryo to probe the protector IC as suggested and look for 0 ohm resistors
 

Deleted member 115935

Joined Dec 31, 1969
0
EDIT ***
from what I hear you saying, It seems its unlikely to be this
EDIT ***

BUT

Some USB ports use a simple PTC resistor, to limit the current at the 500mA of the original USB1 spec,

If you try to take more current, then the voltage is dropped,
the interesting thing is there "cold" resistance gets higher as they are repeatably over currented.
So if your load is more than 500 mA, and the ports have simple PTC limits, this could be the cause.

To be honest, its amazing how many devices have no current limit,
and can provide amps,,,

Decent laptops and computers have always used good circuits,
and the proper protection circuits are now as cheap as the "cheap" PTC version,
so most computers I would say now use proper protection circuits.

There is also the range of negotiated powers,
that depend upon what version of USB the two ends support.
 
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Thread Starter

Lumenosity

Joined Mar 1, 2017
614
from what I hear you saying, It seems unlikely
BUT

Some USB ports use a simple PTC resistor, to limit the current at the 500mA of the original USB1 spec,

If you try to take more current, then the voltage is dropped,
the interesting thing is there "cold" resistance gets higher as they are repeatably over currented.
So if your load is more than 500 mA, and the ports have simple PTC limits, this could be the cause.

To be honest, its amazing how many devices have no current limit,
and can provide amps,,,

Decent laptops and computers have always used good circuits,
and the proper protection circuits are now as cheap as the "cheap" PTC version,
so most computers I would say now use proper protection circuits.

There is also the range of negotiated powers,
that depend upon what version of USB the two ends support.
Very good information. Thank you.

Whenever I connect a device to USB that draws a current, let's just say a cell phone for example, I have no control over the current draw. it seems that whatever device with a battery that is connected will draw as much current as it can and often that exceeds 500mA.;....or used to.

A resistor that has increased in resistance will limit current but leave voltage alone right?
This sounds precisely like what is happening.
 

Tonyr1084

Joined Sep 24, 2015
6,861
I took a particular cell phone
Don't recall hearing "Cell Phone" before. They have their own internal charge control board inside. Your source voltage may have 20 amps available but the phone will limit the charge current according to the battery chemistry and according to the state of charge. Cell phones don't just supply a certain amperage throughout the recharge cycle; they hold currents at specific levels for specific times or voltages (or both). As the battery nears full charge the current drops. I'm not the expert on cell phone charging systems but I do know that the current into the battery has to change. So charging on one charger for a while then charging on a different charger MIGHT be the reason why you are getting a "Slow Charging" alert. Again, I'm not the expert here.

Another thing that comes to mind is USB ports. I recently bought one of those wall socket outlets that have two USB ports for charging devices. The upper port can deliver 2 amps whereas the bottom port delivers only 1 amp. Now, those numbers are from memory - which ages like cheap wine - but I DO recall information that clearly said one port has a higher charge rate than the other. Combine a lower output with a battery that is already close to full and you could see the slow charge warning. But again, I'm not the expert on this subject.
 

Tonyr1084

Joined Sep 24, 2015
6,861
such as a cell phone ((post 8))
I took a particular cell phone ((Post 13))
These are the only instances where you mentioned a cell phone. In post #8 you said "Such As", which did not make me think you were charging cell phone batteries. I don't always quickly pick up on things, but I thought you were talking about battery chargers that plug into USB ports. I have a few of those. Or other "Devices", which made me think of an iPad. Other devices can also include iPods and Vape devices. So there's a lot of ways one can interpret your words. You know what you're thinking. I don't have that luxury. So I make assumptions and sometimes draw the wrong conclusions. Still, I suspect your "Control" method of charging cell phones may not be as precise, or may be under misunderstood parameters such as starting state of charge of the battery. A near full battery will reach full charge faster than a near dead battery. If you compare two batteries - one will have a higher state of charge than the other. If you use the same charger for each battery you will see an accurate comparison of how fast each battery charges. But using different chargers - even the same exact type and manufacturer, it's possible one charger can put out a little more current than the other.

Not here to beat you up over any of this. Just wanting to point out the possibilities of variances in chargers, phones, batteries and cables.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
614
These are the only instances where you mentioned a cell phone. In post #8 you said "Such As", which did not make me think you were charging cell phone batteries. I don't always quickly pick up on things, but I thought you were talking about battery chargers that plug into USB ports. I have a few of those. Or other "Devices", which made me think of an iPad. Other devices can also include iPods and Vape devices. So there's a lot of ways one can interpret your words. You know what you're thinking. I don't have that luxury. So I make assumptions and sometimes draw the wrong conclusions. Still, I suspect your "Control" method of charging cell phones may not be as precise, or may be under misunderstood parameters such as starting state of charge of the battery. A near full battery will reach full charge faster than a near dead battery. If you compare two batteries - one will have a higher state of charge than the other. If you use the same charger for each battery you will see an accurate comparison of how fast each battery charges. But using different chargers - even the same exact type and manufacturer, it's possible one charger can put out a little more current than the other.

Not here to beat you up over any of this. Just wanting to point out the possibilities of variances in chargers, phones, batteries and cables.
batteries is one thing I'm probably well above average in knowledge.
I've done extensive reading on most types of batteries from 18650's to LA, SLA AGM, LiIo, LiFePO4.
I'm familiar with their chemistries and differences.
I know most of the discharge and charge rates and curves and recommendations for them all.
I know all about float charge, saturation charging, absorption and bulk charging.
I know all about internal resistance, how to test it (the long way) and have equipment for doing so as well.
I build my own battery packs from 18650, LiFePO4 cells and many others. And have a lot of equipment for testing them.
I was into RC models for 40 years so knowledge of batteries runs deep.

I own a number of Riden power supplies among others and have a number of capacity testing devices.
Just to clear up any confusion about my confusion with batteries :)

What I am not keen on is USB ports and why they decline in power output.
However, the suggestion in a previous post about how resistors increase in resistance and IC controller chips can become bad are very useful.

As always, the assistance I get here is always very appreciated and respected.
 
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BobaMosfet

Joined Jul 1, 2009
1,952
Hello,
You make a good point.
I think some of the previous comments assumed I was using the ports to charge a battery, such as a cell phone
That is not the case here.

I am referring to the raw output voltage and current of the voltage and amps measured with a test device.

It is true that the USB ports in question are slow in charging batteries also.
If you put a test device, like a meter on your USB output, you may not accurately get voltage reading. Output devices like USB ports (as well as other such energy output devices) are designed to have a load. If you put a DMM on it, there is effectively no load, and if your voltage is low, it' is because of an impedance reflection caused by lack of load.
 

MisterBill2

Joined Jan 23, 2018
11,623
Using the USB port of a peronal computer for battery charging is at best a very poor choice, unless the PC is otherwise worthless. Buy a $5 charger and use it instead. PC usb ports are intended to power a mouse or a similar load, they were not intended to charge every item around. It may also be that the ports you are using have become worn or dirty. Both will add series resistance.

In addition, the charging current into a battery is forced only by the difference in voltages between the battery and the charging source. so as the battery voltage rises the charging current will drop. And so if the voltage drops just a bit it will just barely charge.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
614
I see that from time to time and it can be traced back to abuse.
What exactly constitutes "abuse" ?
I never thought I was abusing them ...just using them.

I use them (not my PC) to recharge tablets, cellphones, bluetooth headsets or pretty much what I thought was normal stuff.
I cannot set the current that the device draws, it just pulls what it can from the port.
Is that the abuse you speak of?
 
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