USB ???

[AES]

Interesting & useful info here, thanks too all.

BUT (and I may well be quite wrong) didn't I read somewhere (here?) that there are some types of these combined wall sockets on the market which are really dangerous? Obviously not by respected makes such as MK, but some (Chinese??) had badly positioned and poorly selected internal components (transformer??) which have led to the whole socket on the wall catching fire. Or am I thinking of something completely different?

Just interested because they're coming on the market here now (Switzerland) and I'm considering at least 2 (one for the new work shop wiring for the phone; one for the kitchen).

AES

 

[AndyT]

If you want to learn more about low grade, dangerous electronic kit, a good place to go is Big Clive's channel on YouTube. He buys a lot of stuff from eBay or pound shops, takes it apart, and explains what's good or bad about it. He's a professional in theatrical electrics and seems to know what he's talking about.

This one is looking at a usb mains socket:

https://youtu.be/zoZ1_aEDPos

Spoiler alert: he doesn't recommend it!

 

[monkeybiter]

I'm a big Clive subscriber too, dry but interesting, his brother the whisky critic is a Mr.Chicken though. [IMHO]

 

[AES]

Thanks gents, I'll check him out.

AES

 

[John Brown]

The exchange between the device and charger is the monitoring of each individual cell's voltage and state of charge, to the point of discharging a cell that is drawing too much to equalise it with its partners, this is important to prevent one cell from being charged more than its partners to prevent over discharge of adjacent cells during use, once any of these cells are out of balance it is almost impossible to re-balance them without a more sophisticated charger.

Mike

I'm sorry, but that is simply not true of most USB chargers. The cell balancing takes place within multi-cell battery packs, but your average USB charger has no way of monitoring individual cell voltages. As I said earlier, one of the data pins is pulled up to a specific voltage to signal, to the device under charge, how much current is available.
There is, however, a "negotiation", that takes place when a USB device(as opposed to a battery/cell being charged) is connected to a USB host, during which the device can ask for, and possibly be granted, permission to draw more currnt than the baseline USB current, the value of which I can't remember,and can't be bothered to look up right now.

Also, USB being a 5V system, and most device these days using Li cells, which generally require 4.x volts in the later stages of charging, it's my belief that most devices charged via USB are single cell anyway.

 

[John Brown]

Usually the device that's plugged in controls the charging so it doesn't matter how much current the socket can supply.


Pete

I disagree. It does matter if the device attempt to charge its battery(cell) at 2 Amps if the charger is only good for 500mA. That's why the "pull a data pin up to a specified voltage" system was devised.

 

[MikeJhn]

The exchange between the device and charger is the monitoring of each individual cell's voltage and state of charge, to the point of discharging a cell that is drawing too much to equalise it with its partners, this is important to prevent one cell from being charged more than its partners to prevent over discharge of adjacent cells during use, once any of these cells are out of balance it is almost impossible to re-balance them without a more sophisticated charger.

Mike

I'm sorry, but that is simply not true of most USB chargers. The cell balancing takes place within multi-cell battery packs, but your average USB charger has no way of monitoring individual cell voltages. As I said earlier, one of the data pins is pulled up to a specific voltage to signal, to the device under charge, how much current is available.
There is, however, a "negotiation", that takes place when a USB device(as opposed to a battery/cell being charged) is connected to a USB host, during which the device can ask for, and possibly be granted, permission to draw more currnt than the baseline USB current, the value of which I can't remember,and can't be bothered to look up right now.

Also, USB being a 5V system, and most device these days using Li cells, which generally require 4.x volts in the later stages of charging, it's my belief that most devices charged via USB are single cell anyway.

As you say not true of USB chargers, I am afraid I am guilty of thread drift and was not talking about USB charges, but Li, LP, Fe multi cell batteries and the requirements from the charger, some batteries do indeed have the balance circuit built into the batter block, especially true of the ten cell Lithium Nano Phosphate batteries on DeWalt 24volt drills, unfortunately they changed from the A123 chemistry and now use an inferior LiFe source.

Mike

 

[graduate_owner]

I have just browsed a few Clivedotcom videos and I am very surprised at the poor, even dangerous quality of some of the imported electrical goods, imported from China of course. I shall never insert a bulb again without switching off the mcb, especially in a 2 way set up where you don't know if the pendant is live.
He mentions CE as being short for Chinese Export - perhaps it should be Chinese Excrement!!!

K