Are we suffering under a wrong notion here? Are you going to supply power to a device by means of a USB cable? In this case, the USB cable will simply be used as a power cable into the device, and have no connection to a computer?

Ya. This is my purpose, by supply power to a device with USB adapter. No computer involve in this case.
I just simply to supply some electrical current to USB, in-turn USB maybe connect to a handphone for charging.

 

In that case you can buy a switching charger for very little. I suppose it depends on your location but I buy them retail in China for under $1. I suppose in western countries they might be found for under $5.

 

In that case you can buy a switching charger for very little. I suppose it depends on your location but I buy them retail in China for under $1. I suppose in western countries they might be found for under $5.

Switching charger?
Use for wat?

 

Switching charger?
Use for wat?

An "adapter". You plug it into the wall and it gives you 5 V.

 

In that case you can buy a switching charger for very little. I suppose it depends on your location but I buy them retail in China for under $1. I suppose in western countries they might be found for under $5.

I wouldn't buy those from China, as you don't know what you might get. There are cases or chargers bought to a particular cellphone that blew up the battery. Try to buy them from Europe (UK, Germany, Italy, Spain).

 

No matter where you buy it, it was made in China. I have bought plenty of crap in western countries and I have bought plenty of good stuff in China. You just need to look a bit more carefully in China... and the price difference is well worth it.

 

If you use a charger for a device that is supplied by other than the original equipment manufacturer, you are on your own - and you may very well have something go kaboom.

There are tradeoffs in every design; some good, some not so good.

You can charge a battery quickly, but at best, it won't be fully charged, at worst it will explode.
You can charge a battery slowly, but it takes quite a while, and people are not very patient.

And myriad variatons in between.

The engineers who designed the charger for your particular device did the best they could with what parameters they were given; safety, time; life expectancy, cost, manufacturability among others - and not necessarily in that order.

Get outside of those parameters, and you may find yourself in muddy waters.

Let's try to avoid bashing by country - it's in poor taste, and will just lead to bad feelings.

 

If you use a charger for a device that is supplied by other than the original equipment manufacturer, you are on your own - and you may very well have something go kaboom.

Not really. All mobile phones sold in China and many in other countries as well as many other devices are designed to be charged from any 5V source, including a USB port. Any 5V charger is fine. It is the device, not the charger, which controls the charging. In fact, many times it is the battery itself which has electronics to control the charge.

 

Let's try to avoid bashing by country - it's in poor taste, and will just lead to bad feelings.

Indeed. Of course in China the products are not all bad. It depends mainly on the manufacturer. But it seems there is no quality certification (unless we are talking about products made in China by reputed companies that employ ISO 9001).

I'm aware that most products are made in China, but that is because some wordwide companies prefer having their factories there, therefore practicing work exploitation.

Nevertheless DIY before buying. Nothing beats the quality of a home made product, especially if you are a good fabricator.