Welcome to the MacNN Forums.

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Notebooks > Charging Mac with the Car

Charging Mac with the Car
Thread Tools
kevs
Mac Elite
Join Date: Aug 2003
Status: Offline
Reply With Quote
Jun 2, 2018, 10:51 PM
 
I have a great car charger for iphone, can it work with Macbook? I'm stumped because the charger cord for macbook does not have a usb plug on the end only a US socket to macbook
     
ghporter
Administrator
Join Date: Apr 2001
Location: San Antonio TX USA
Status: Offline
Reply With Quote
Jun 3, 2018, 02:07 PM
 
Assuming you have one of the newer, USB-C MacBooks, AND assuming you have a powerful enough car charger, it’s doable.

Which model of MacBook do you have?

Glenn -----OTR/L, MOT, Tx
     
Spheric Harlot
Clinically Insane
Join Date: Nov 1999
Location: 888500128, C3, 2nd soft.
Status: Offline
Reply With Quote
Jun 4, 2018, 05:35 AM
 
I bought a USB-A to USB-C cable to be able to do just this in an emergency (i. e. I forget my power supply), but I have so far not been able to get my 15” MacBook Pro sufficiently charged to wake from sleep even after a full workday on iPhone power supplies and car chargers.
     
subego
Clinically Insane
Join Date: Jun 2001
Location: Chicago, Bang! Bang!
Status: Offline
Reply With Quote
Jun 4, 2018, 07:51 AM
 
My guess is the USB knocking it down to 5v is the bottleneck.

They make higher voltage laptop car chargers, but getting the right tip may be a problem.
     
P
Moderator
Join Date: Apr 2000
Location: Gothenburg, Sweden
Status: Offline
Reply With Quote
Jun 4, 2018, 09:54 AM
 
USB charging is an absolutely insane hodgepodge of standards right now.

USB 2.0, what we all used to have, had a low-power mode of 0.1A and a high-power mode of 0.5A, both at 5V. Because that is a pretty low power, USB-IF added a supplementary standard called "USB 2.0 Battery Charging" (USB-BC), which in version 1.0 allowed up to 1.5A at 5V, in return for dropping the data transfer speed. There is also a later version of the standard, 1.2, that allows up to 5A@5V, but I have never seen anything that implements it.

USB 3.0 replaced this with "USB Power Delivery" (USB-PD), which starts off at 5V, increases power up to 3A, and then proceeds to increase the voltage to as much as both source and drain can support. Finally, USB-C raised the floor of what devices must support to 3A@5V. This means that a devices that charges over USB-C can fail to charge if it gets less than that without violating the standard.

In the specific case of the 2016 and later Macbook Pro, it appears to work like this:

* It will charge from any device that supports USB-PD over USB-C, which means that it has to supply at least 3A@5V. It will then negotiate itself up to the higher power that both charger and MBP can support.
* It will charge from any charger that supports up to USB-BC 1.0, which is 1.5A@5V.
* It will additionally charge at 2.4A@5V, if using an Apple iPad charger. This is a nonstandard variant (that is detected by setting a certain resistances over the data pins) that appears to work with the MBP as well.

What it will not work with is the base USB 2.0 0.5A@5V. That appears to be too little power to work with.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
subego
Clinically Insane
Join Date: Jun 2001
Location: Chicago, Bang! Bang!
Status: Offline
Reply With Quote
Jun 4, 2018, 02:37 PM
 
I guess I meant amps.
     
turtle777
Clinically Insane
Join Date: Jun 2001
Location: planning a comeback !
Status: Offline
Reply With Quote
Jun 4, 2018, 06:52 PM
 
There are some 2.1A USB car chargers.

Those might work, but it’s not guaranteed.

-t
     
mindwaves
Professional Poster
Join Date: Sep 2000
Location: Irvine, CA
Status: Offline
Reply With Quote
Jun 7, 2018, 04:34 AM
 
Not sure why cars still have a cigarette lighter as opposed to a real three prong plug.
{{{ mindwaves }}}
     
P
Moderator
Join Date: Apr 2000
Location: Gothenburg, Sweden
Status: Offline
Reply With Quote
Jun 7, 2018, 06:48 AM
 
Originally Posted by mindwaves View Post
Not sure why cars still have a cigarette lighter as opposed to a real three prong plug.
Because that three-prong plug would be AC, and the car doesn't produce AC from the alternator. Much easier going forward to put a higher-power USB port or three in stead of the cigarette lighter.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
Oussie
Fresh-Faced Recruit
Join Date: Jun 2018
Status: Offline
Reply With Quote
Jun 8, 2018, 03:53 AM
 
kevs its best not to risk your device for experimental charging
     
ghporter
Administrator
Join Date: Apr 2001
Location: San Antonio TX USA
Status: Offline
Reply With Quote
Jun 9, 2018, 04:37 PM
 
Originally Posted by mindwaves View Post
Not sure why cars still have a cigarette lighter as opposed to a real three prong plug.
Automotobile power systems run on a "nominal" 12VDC, which is typically between 13.5 and 13.9VDC in actuality. It's easy to run a 5v regulator off 14v, so USB chargers do fine with that.

I'm not well versed on the newer Macs that use USB-C charging, but I've done some investigating about USB-C itself, and the charging aspect seems to have to do with the specification's ability to provide either 5v, 12v, or 20v. What I don't know is what voltage the new USB-C Macs need to charge. If they will charge from 12v, that should mean that a car power source would work. If, on the other hand, they need 20v, then without some sort of intermediate power supply that produces 20v from a 12v input, I can't see it working.

Glenn -----OTR/L, MOT, Tx
     
P
Moderator
Join Date: Apr 2000
Location: Gothenburg, Sweden
Status: Offline
Reply With Quote
Jun 9, 2018, 05:15 PM
 
Simply put, the USB-C Macs will haggle until they get as much power as they can get. At least the 13" charger will start at 5V, haggle its way up to 3A, then start haggling the voltage up by steps until they get to 20V. If it gets a no anywhere, it will stop there and use what it can get. The 15" can use 87W, which is 4.4A at 20V. Not sure how it will work, if it will start by haggling up the power to 4.4A and then the voltage, or if it will start like the 13" and just add an extra haggling step by the end.

A quick googling shows that the "12V" that the lighter plug is supposed to provide is a guaranteed minimum, and the 14V that you can usually get is not to be relied on. A USB-C charger connected to automotive power would then provide 36W to a charging MBP, which is pretty decent.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
   
Thread Tools
 
Forum Links
Forum Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Top
Privacy Policy
All times are GMT -4. The time now is 06:20 AM.
All contents of these forums © 1995-2017 MacNN. All rights reserved.
Branding + Design: www.gesamtbild.com
vBulletin v.3.8.8 © 2000-2017, Jelsoft Enterprises Ltd.,