Using self-made Magsafe possible?

fl89

macrumors newbie
Original poster
Jan 24, 2011
19
0
Hello,
afaik, the Magsafe 85W has a voltage of 18,5V.

So if I buy an 18,5v supply and put a magsafe connector on it, there would be no problems right?

I'm asking because the macbook pro changes voltage on demand. When charging, on idle.... is the power adaptor doing that or a converter on the logic board inside the mbp? :confused:
 

fl89

macrumors newbie
Original poster
Jan 24, 2011
19
0
Cause I like doing this stuff...strange for a mac user right? :D (using linux/windows too)

And the magsafe it too pricey and has not enough power...draining battery when converting/processing videos.

So, do I miss something? :confused:
 
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stuaz

macrumors 6502
Jun 16, 2012
446
1
Sounds like something not to fool around with - could be a potential fire risk if you mess with the electricity like that.
 

chibisukee

macrumors newbie
Jun 23, 2012
17
0
Magsafe has a charge control pin (the middle one) that sends information between the charger and the laptop - I don't think that you can just connect the Magsafe connector to any power adapter.

And where would you get a Magsafe connector without the actual power adapter? I thought Apple has issues with people manufacturing their own Magsafe connectors.
 

quasinormal

macrumors 6502a
Oct 26, 2007
736
4
Sydney, Australia.
Magsafe has a charge control pin (the middle one) that sends information between the charger and the laptop - I don't think that you can just connect the Magsafe connector to any power adapter.

And where would you get a Magsafe connector without the actual power adapter? I thought Apple has issues with people manufacturing their own Magsafe connectors.
I'm not entirely sure about that. I've only ever seen two wires on the dc end of MagSafe cable.

I don't think it would be a problem if the power quality from tranformer is adequate. I've used a few 3rd party dc adapters and the Hypermac battery pack without any obvious issues over the last 5 years.
 

fl89

macrumors newbie
Original poster
Jan 24, 2011
19
0
Magsafe has a charge control pin (the middle one) that sends information between the charger and the laptop - I don't think that you can just connect the Magsafe connector to any power adapter.

And where would you get a Magsafe connector without the actual power adapter? I thought Apple has issues with people manufacturing their own Magsafe connectors.
1. Are you sure? So how can these guys do it?

Look here: Magsafe do it yourself

From Wikipedia

The tiny center pin is a charge control pin that assists with changing the LED color, and also assists with switching the adapter off. No power will be output from any of the other pins until contact is made with the center Charge Control pin. This pin is also used to transfer additional information, such as the power type and serial number of the power supply.
2. The magsafe connector is from an old, damaged magsafe.

Not sure that calling the users of this forum stupid is the best way to get help.
Hold on, never said that. It was just a joke, because he asked me what the point of doing this was. ok? ;)

So can someone tell me why this should not work? For example, this one is selling parts for building your own adapter. http://mikegyver.com/Store/

I'm not entirely sure about that. I've only ever seen two wires on the dc end of MagSafe cable.

I don't think it would be a problem if the power quality from tranformer is adequate. I've used a few 3rd party dc adapters and the Hypermac battery pack without any obvious issues over the last 5 years.
Oh wow, thanks buddy. Finally someone having a point and not just tellin me that it could be a problem without a reason :rolleyes:

So the macbook is regulating the voltage on the inside, right? ...maybe i will try to measure the output of the magsafe, its just hard to bridge the dock connector without cutting the wire :(
 
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Dark Void

macrumors 68030
Jun 1, 2011
2,614
465
I would stay away from this whether it's possible or not, does not seem worth it and even more so if something goes wrong you'll end up setting yourself way back in comparison to just purchasing a new magsafe charger.
 

alphaod

macrumors Core
Feb 9, 2008
22,046
1,104
NYC
If you're asking, you're not qualified. I do a lot DIY stuff and I don't go onto some random forum asking people if it's possible; even I'm not very qualified. I've fried a lot of stuff, including myself.

In answering your question, the MagSafe charger is self sensing. Assuming you have the 85W adapter, it can provide 45W, 60W, or 85W based on if you have a MacBook Air, 13" MacBook [Pro], or a 15" and 17" MacBook Pro, respectively.
 

fl89

macrumors newbie
Original poster
Jan 24, 2011
19
0
Thank you. Great links. So there is no extra cable inside. Only +VDC and ground.

Now I just need to find out if the 6,86V with no load are produced inside the magsafe or the magsafe-connector. Will measure that when my multimeter arrives.

If the magsafe-connector does all the work, my problem is solved. :cool:

In the end its so easy. Even for someone who is not an Electrical engineer.
 

avalys

macrumors 6502
Jun 4, 2004
300
23
If you're asking, you're not qualified. I do a lot DIY stuff and I don't go onto some random forum asking people if it's possible; even I'm not very qualified. I've fried a lot of stuff, including myself.

In answering your question, the MagSafe charger is self sensing. Assuming you have the 85W adapter, it can provide 45W, 60W, or 85W based on if you have a MacBook Air, 13" MacBook [Pro], or a 15" and 17" MacBook Pro, respectively.
Nitpick: this is not some unique or special property of Apple power supplies. All power supplies can be used at or below their maximum rated power (e.g. an 85W power supply can provide any power from 0W-85W), as long as the voltage is correct. The reason Apple's power supplies are interchangeable is that they all provide the same voltage.

Additionally, the numbers you listed (45W, 60W, 85W) are simply the maximum ratings of the power supplies Apple shipped with each computer. That doesn't mean the MBA uses 45W, and the MacBook Pro draws 85W. It all depends on load. You can power a MacBook Pro perfectly adequately on a 45W power supply, as long as the battery is charged and you're not doing anything CPU/GPU-intensitve.
 

fl89

macrumors newbie
Original poster
Jan 24, 2011
19
0
Good luck!
Thank you. I know it's not that easy. But maybe I'm really that lucky and everything works just fine. :D


Nitpick: this is not some unique or special property of Apple power supplies. All power supplies can be used at or below their maximum rated power (e.g. an 85W power supply can provide any power from 0W-85W), as long as the voltage is correct. The reason Apple's power supplies are interchangeable is that they all provide the same voltage.

Additionally, the numbers you listed (45W, 60W, 85W) are simply the maximum ratings of the power supplies Apple shipped with each computer. That doesn't mean the MBA uses 45W, and the MacBook Pro draws 85W. It all depends on load. You can power a MacBook Pro perfectly adequately on a 45W power supply, as long as the battery is charged and you're not doing anything CPU/GPU-intensitve.
Yes, but only the 85w supply can provide a higher voltage 18,5V than the others 16,5.


I found this quite useful information. It's about what output voltage you should use on the universal power adapter they sell.

A: The macbook pro apple adapter (85w) actually put's out 16.5v just like the macbook adapter (60w) for normal usage. But if you are a heavy graphics user, then it'll automatically up the voltage to 18.5 volts(85w). During our tests, we've found that not a whole lot of people tax their macbooks Pro to the max, so the 70w is actually enough for a lot of people. If you are within the 3%, your laptop will simply slow down or stop charging your battery. It will resume charging when you reduce CPU tasks. We also choose this voltage because of Airline wattage limitations.

Q: Your site seems out of date, you say N2(B) tip, but it should be N3(B).
A: Please read above question. N2(B) outputs 16.5v. N3(B) 18.5v. We recommend N2(B) because of above answer to question, and to stay within limits of the power supplied on Airlines. N3(B) is recommended for those who are heavy CPU users, and not on airlines.
mikegyver.com Q&A

In my case I would choose N3(B) tip with 18,5V. :D

Here's some more information on how the magsafe works.

Stanford Magsafe

Hmmm, the voltage switching is kind of weird. But 18,5V should work nonetheless.
I'm trying to contact that mikegyver.com guy, maybe he knows more since he sells adapters like that.
 
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n748

macrumors newbie
Jun 19, 2010
2
0
Hey fl89

Great thread - thank you. I was a bit surprised about the discouraging feedback you received in the beginning.

It has been one year since your last post and I was wondering if you could give a short follow-up. I would like to do something similar: Power my MBP from a 12V solar-charged lead acid battery. The most efficient way is to get good components and start soldering, it seems.

I would be especially curious if 18.5V turned out the right option or is the 16.5V (60W) option more suitable? As far as I understood, the power rating is programmed into the cable (not the power supply - cf. here). So what happens if I only can find a 60W-rated cable and turn the voltage to 18.5V. After reading all of your links and some more, it seems to be more reasonable to go 16.5V and accept a battery drain when playing the latest shooter games ;)
 

Swampus

macrumors 6502
Jun 20, 2013
396
1
Winterfell
...I would like to do something similar: Power my MBP from a 12V solar-charged lead acid battery. The most efficient way is to get good components and start soldering, it seems.
Before you build something to step the voltage up and provide some in-line protection, the most "efficient" way might be to simply spend $30 on a car adapter? Something like this?

Solar panel --> charge controller --> battery --> car adapter --> MBP.
 

magbarn

macrumors 68000
Oct 25, 2008
1,916
1,084
Before you build something to step the voltage up and provide some in-line protection, the most "efficient" way might be to simply spend $30 on a car adapter? Something like this?

Solar panel --> charge controller --> battery --> car adapter --> MBP.
Yup, this is what I'm doing. I have the solar panel charging via a charge controller a 12v deep cycle which is then wired to a 150 watt 120V AC inverter which then my regular magsafe power adapter is plugged into.

I also fly RC helis and I've converted a few of my lipo battery packs to 4S which gives around 16 volts which is perfect for a magsafe connector like the ones from macgyver.
 

g4cube

macrumors 6502a
Apr 22, 2003
760
13
Great thread and links.

I too was planning to tinker to build a mobile setup powered by the more common +12v from vehicles and standby battery packs used to start cars when their battery is dead.

  1. refurb working Apple official adapters are available at OWC for $45-55 according to an email I got today
  2. I had planned to use a DC-to-DC converter to step up the nominal +12v to nominal +18v (for example, the airline adapter Apple sells will power but not charge a laptop due to voltage being only +15v - EmPower)
  3. lots of "broken" adapters on ebay to scavenge for official MagSafe connectors

Why? More efficient and less bulky than using +12vdc to 120vac converters and then using the Apple laptop chargers. Also, many hard drives use simple +12vdc power, so was planning to generate regulated +12vdc from the battery source.

Finally, investigated some lithium power packs if car battery power not available. Then would have to also worry about charging circuitry.

Overall, an interesting project.
 

Freddruppel

macrumors newbie
Jul 17, 2016
1
0
Belgium
Just reviving the thread here ^^ (it might be useful for someone !)

Hello,
afaik, the Magsafe 85W has a voltage of 18,5V.

So if I buy an 18,5v supply and put a magsafe connector on it, there would be no problems right?

I'm asking because the macbook pro changes voltage on demand. When charging, on idle.... is the power adaptor doing that or a converter on the logic board inside the mbp? :confused:
My MagSafe transformer died after 4 weeks of use (it was a chinese knockoff I found on eBay for ~20)
As I didn't want to borrow my mom's charger for too long, I decided to try and make a new charger. So I salvaged the MagSafe cable (and other components for other projects ^^) from my charger, and hooked it up to a DC-DC boost converter (you can find those on eBay relatively cheaply). I used a basic 12V transformer as power source, and after many verifications of the output voltage (18V instead of 18.5V, just to be sure), I took a deep breath and plugged the cable into my MacBook, and it worked just fine !!

Although it's not really recommended, it works as a "short-time" solution, as I don't have the time and money now to buy a genuine one..

Hope this helps !!
 

jerryk

macrumors 601
Nov 3, 2011
4,840
2,397
SF Bay Area
Just reviving the thread here ^^ (it might be useful for someone !)



My MagSafe transformer died after 4 weeks of use (it was a chinese knockoff I found on eBay for ~20)
As I didn't want to borrow my mom's charger for too long, I decided to try and make a new charger. So I salvaged the MagSafe cable (and other components for other projects ^^) from my charger, and hooked it up to a DC-DC boost converter (you can find those on eBay relatively cheaply). I used a basic 12V transformer as power source, and after many verifications of the output voltage (18V instead of 18.5V, just to be sure), I took a deep breath and plugged the cable into my MacBook, and it worked just fine !!

Although it's not really recommended, it works as a "short-time" solution, as I don't have the time and money now to buy a genuine one..

Hope this helps !!
I use this one for my MacBook Pro. Works well and is cheap.

https://www.amazon.com/Morange-Magsafe-adapter-charger-Replacement/dp/B00W3BY0JG/ref=sr_1_13?ie=UTF8&qid=1468775756&sr=8-13&keywords=macbook+charger+85w