Safety using external battery to charge Macbook Retina VIA adaptor cable

[dsc106]

Shiny new haswell 15" Retina MBP decked out. I do a lot of video editing, international travel. Need longer battery life while taxing the computer for video edit. BUT, there's no official external battery/charger I can find.


There's this for $250 with crappy reviews on build quality, and it goes through a car charger first to connect to Apple's Magsafe:

http://www.amazon.com/HyperJuice-Ext...ternal+battery

More ideally, there's this from Anker for $120. Little less power but better brand, build quality, and price:

http://www.amazon.com/20000mAh-Ultra...ternal+battery

But no direct support via adaptor for Macbook (is this because Apple does not license the Magsafe adaptor?)

I read I could use this DC adaptor to Magsafe2:

http://www.bixnet.com/cabms2.html

Thing is, no reviews on that, and I can't find much information about people doing this. I don't know much about electrical currents, and I do not want to fry my over-priced decked out MBP Retina. But I do want to double my battery life so I can edit for 10-12 hours on an international flight.

So I *think* the Magsafe2 85w for MBP Retina puts out 20v 4.25A ...? But I'm not sure, and I'm not sure how exactly that all relates to the Anker's product which states:

Choose from between DC 12V / 4A, 16V / 3.5A, 19V / 3A and USB 5V / 2.1A outputs for greater accessibility. The three voltage selections enable this external battery to charge laptops (that meet compatibility requirements) - in addition to virtually all USB-charged devices.

The only discussion I could find that seemed relevant was here:
https://discussions.apple.com/thread/4872398

But I didn't really understand the solution here, or what this may mean for me.

Questions:

Safe to use this DC to Magsafe adaptor with one of these settings? If so, which setting and why, and what risks do I run? Can you help me understand how this works?

If not safe to use above, could I get a DC to auto adaptor plug, and then use a car/airline adaptor to magsafe 2 accessory? Would this make sure the power coming through is OK, and would I lose power efficiency along the way? If so, how much?


Bottom line:

Looking for the best and safest solution, but also to understand the concepts and why or why not to do certain things. Want to keep laptop powered, but protect the investment as well!


Thanks for the help!

 

[dsc106]

I know this is sort of long - but anyone here who can help?

 

[podspi]

I don't know for sure, but it sounds to me like it *might* work. At worst, it just wouldn't charge, since 19V < 20V.

You never ever want to put more volts in than you are supposed to. That is how things go poof. Typically as long as you are +/- 5% it will work, and 19V is within 5% of 20V

Also, this would charge slower than a wall wart if it does work, but I suppose that is to be expected anyway?


It sounds like the other thing you could do is jerryrig some type of solution to convert whatever voltage you have to 20V, and then feed it through that cord. It is doable but I wouldn't know how.