Hello

 

If I leave the USB cable for my phone plugged in for Carplay will it still be using power with no phone plugged in it? Its a bit of a pain keep plugging it out every day. Thanks

No, if there is no phone connected it will not use any power

 

John

Thanks

20 minutes ago, jjc said:

No, if there is no phone connected it will not use any power

 

John

Thanks, I have wifi in my car, pity you cant connect to carplay over wifi. Some cars can.

6 hours ago, jjc said:

No, if there is no phone connected it will not use any power

 

John

That is not strictly true. A charger will always draw a small current, even with nothing connected. Funnily it's called vampire power.

Having said that it is a really small amount of current that it's taking.

1 minute ago, facet edge said:

That is not strictly true. A charger will always draw a small current, even with nothing connected. Funnily it's called vampire power.

Having said that it is a really small amount of current that it's taking.

Thanks. Not sure I will keep it connected anyway. When haven't got the phone plugged in it grid to search for it when I turn the engine on. Will just plug it in when needed I guess. 

51 minutes ago, facet edge said:

That is not strictly true. A charger will always draw a small current, even with nothing connected. Funnily it's called vampire power.

Having said that it is a really small amount of current that it's taking.

But I assumed he meant just a USB cable plugged into the USB plug used for Carplay/Mirrorlink/Android Auto. A cable itself is just wires, I can't see how it would draw any current in itself...

 

A charger plugged in the (always on) cigarette plug, on the other hand, would draw a small amount of current as you say.

Edited 6 April, 20179 yr by grenness
Typo

1 minute ago, grenness said:

But I assumed he meant just a USB cable plugged into the USB plug used for Carplay/Mirrorlink/Android Auto. A cable itself is just wires, I can't see how it would draw any current in itself...

 

A charger plugged in the (always on) cigarette plug, on the other hand, would draw a small amount of current as you say.

Is the USB port always on? 

TBH I don't know! ;-)

 

Just now, grenness said:

TBH I don't know! ;-)

 

Guess there's only one way for me to find out. Plug the phone in and see if it charges. 

It's a USB socket with a standard 5 volt power supply, not a 'charger'. The USB turns off shortly after locking the car (not simply just turning the ignition off).

 

 

As I hark back to the days of my first ever job as an electronics engineer...

 

Current is the flow of electrons from a positive to a negative or ground. If those electrons can't reach negative/ground then they won't flow, so no current.

If there's nothing connected to the end of the USB, with or without a cable, there's no completion of the circuit so no current is being drawn.

 

The battery "charger" element is actually in the device, your phone, which uses 5v DC. What people call a "phone charger" should really be called a transformer. For a plug-in car phone charger it transforms 12v DC to 5v DC, for your home phone charger it's 240v AC to 5v DC.

These "chargers" draw power when plugged in even when not in use because, amongst other things, it uses coils. Current passes through a coil with x number of windings located directly beside a coil with y number of windings. The electromagnetic effect of voltage flowing through coil x causes a proportional voltage to flow in coil y. If x has four times the number of windings as y then the voltage generated in y is 25% of that in x. Because x is a complete and separate circuit from y, it's always allowing a tiny current to flow.

 

At the end of the day it's a convoluted explanation as to why you can safely leave a USB extension lead plugged into the car's USB socket forever and a day, which is exactly what I do in my car.

 

As an aside, if you have a petrol engine you have spark plugs. These need anything from 12,000 to 45,000 volts to spark. And what do we call the device that changes 12 volts to tens of thousand? A "coil".

2 hours ago, BillyJim said:

 

 

The battery "charger" element is actually in the device, your phone, which uses 5v DC. What people call a "phone charger" should really be called a transformer. For a plug-in car phone charger it transforms 12v DC to 5v DC, for your home phone charger it's 240v AC to 5v DC.

 

 

 

Is is the plug-in car phone charger actually a transformer with coils?  I would have thought it just used a +5v voltage regulator. 

 

I use use a multi-way adaptor for powering various items - satnav, dashcam, etc. It has 3x 12v sockets plus a 5v USB socket. The 5v output stopped working, so I dismantled it to find the problem was only a dry joint, but it just uses a 7805 voltage regulator to provide the 5v supply. 

I didn't want to get into semiconductors, I thought I'd blabbed enough to answer the OP's question. Because with 12v/5v we're talking very low voltage change it's easily done with semiconductors like the 78xx series of voltage regulators. Their restriction lies in the amount of current they can carry before they overheat - though many have overload protection to switch off before that happens - and is why some can charge a phone but not a tablet. The more current you want to draw, the bigger the heatsink. Similarly with the coil, the more current you need to draw the larger the coil needs to be. Even the solid state regulators have a constant quiescent current draw, typically of about 6mA, so you wouldn't want to leave it plugged in your permanent-feed 12v socket for any long unattended periods.

On 06/04/2017 at 13:04, tigermad said:

Thanks

Thanks, I have wifi in my car, pity you cant connect to carplay over wifi. Some cars can.

 

I was under the impression the only car that had wireless CarPlay was the new BMW 5 series.

Hi I have my dash cam plugged into the USB port. 
I presume their is no power going to it when the car turns off.

the camera does stay on however for about 30 seconds and then it go’s off. 
 

like wise when I unlock the car the camera comes on. 
So I would presume it is not drawing any power when the ignition is off. 

What’s yur thoughts on this ?

thanks.  

I'm pretty sure the USB ports turn off (unlike the 12v sockets)  - probably worth testing with a cable connected to a phone that will show when it is charging.

 

With MY 2020 cars  now in the options list of the brochure - "1x USB-C port in the rear-view mirror panel."

 

 

 

 

 

Just now, bigjohn said:

I'm pretty sure the USB ports turn off (unlike the 12v sockets)  - probably worth testing with a cable connected to a phone that will show when it is charging.

 

With MY 2020 cars  now in the options list of the brochure - "1x USB-C port in the rear-view mirror panel."

 

Thanks for the reply. 
yes I plugged in my phone to the usb charger and locked the car up and after about 30 seconds the charge stoped. 
 

so I’d say it’s safe to say the power to it go’s off. 
 

that’s great that your 2020 model has the option off a USB-C port in the rear view mirror. 
  

 

 

 

 

31 minutes ago, Notabean said:

that’s great that your 2020 model has the option off a USB-C port in the rear view mirror. 

 

Not mine yet - just considering at the moment but found that option in quite a few Skoda models - will make dashcam installation much easier in the future if specified!

 

I was waiting for the new Octavia to see what that was like but I'm not keen on no buttons to control the climate control and the much smaller small 45l fuel tank. The Superb is back on my radar but I originally wanted to down size!

 

 

Edited 8 August, 20205 yr by bigjohn

The USB socket in front of the gear lever on my 2019 SE-L definitely turns off after a while when the car is locked.

 

If I leave my iPod connected then it gradually discharges over the course of a few days so the USB socket cannot be charging it up.

Left an I-pod connected for three years with no battery issues and, apart from lockdown when the car only moved once a week, the Ipod always started up with the car (it is an old one).