Portable Charger for Microsoft SurfaceBy Jeff Crystal
First it was Apple with their MagSafe, 30-Pin, and Lightning adapters. Now Microsoft (Surface) and Lenovo (X1 Carbon) are making their own proprietary charging connectors. This is great if you are sitting next to an AC outlet, but not so great if you are trying to charge your new Surface on the road from a car, portable battery or solar charger.
With the help of a couple of kind customers, we have now built a few custom Microsoft Surface charging cables. Here’s what we did.
Please proceed, only if you are comfortable with hacking electronics. Voltaic takes no responsibility for any charging cables created by our customers.
Buy a spare Surface charger. You can pick up the 24-Watt charger from Microsoft. The 48-W version isn’t necessary even if you have the Pro since we’re cutting off the transformer anyway. We’ve also seen some (untested) replicas on eBay.
Cut open the charger to reveal the four wires. Testing with a multimeter indicates the red carries positive 12V, whereas black, yellow, and blue were 0V. Based on standards, we assumed black to be the negative.
We’re not sure what purpose the other two wires serve, but they appear to be unnecessary for charging – if anyone knows, let us know. A few readers have chimed in on the purpose of the yellow and blue wires: the blue wire appears to be for charger detection (so that the Surface does not try to draw more than the charger can supply). It’s not necessary for our V60 battery, which supplies 4A, more than the Surface draws. The yellow wire is for illuminating the plug’s charge LED (and can be connected to red through a resistor – 6K Ohm works well according to this thread). We’ll hopefully be able to check this out soon. Thanks for your input, guys!
Solder the positive and negative on the Surface charger to the positive and negative on a Voltaic cable (if you’re doing this at home, use our 5525 Wire). We trimmed back the white and blue wires so as to insulate them and did not use them. Cover with heat shrink tubing.
Now, connect to the Voltaic V60 Laptop Battery at 12V and charge away. The Microsoft Surface battery size varies from 31.5 (RT) to 42 Watt hours (Pro), so you’ll get more than a full charge on the RT and a full charge on the Pro.
More details on charge times can be found on our Solar Charger for Tablets Guide.