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. Fortunately our V72 laptop battery can supply the 12 Volts required to charge the Surface 2 and Pro 3, so you can enjoy your tablet for weeks or months while off-grid.

You can see all of our solar chargers that work with the Microsoft Surface 2 and Surface Pro 3 here.

Surface 2

To charge the Surface 2, there are official Microsoft car chargers that will work just fine with the car socket of our V72, as well as our Surface 2 Cable which is admittedly a bit lower build quality. You can also hack your own cable (see below)

Surface Pro 3

Microsoft does not yet make a car charger for the Surface Pro 3, so pretty much your only option is something like our Surface Pro 3 cable, a hacked cable like below or another 3rd party cable with a car charger connection on the end.

surface pro 3 solar charger battery for surface pro

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.

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 V72 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 72 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.

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37 Responses

  1. BB

    About the other wires:
    The white (/yellow) wire is for the white charge LED on the plug. The blue wire is used for charger detection. If you use the RT charger on the Surface Pro the Pro will detect the smaller RT charger and limit the current to 2A. If your external battery is able to provide the same current as the Pro charger (3.6A) the blue line seems to be unnecessary.

    Reply
  2. Henrik Johansson

    Hey you guys and Girls!
    Thanks a million for this post! I’ve sent you an RT-charger and will get help with this, I can’t tell you how greatful I am for this!
    I’ll send you some pics once I receive it back, I just got my V60-battery today, so I can’t wait to try this out on my Surface Pro! Thanks again and greets from Sweden! :-D

    Reply
  3. Ryu Ran

    Cool! I bought Surface Pro Charger from HK for 30$, and I wonder if this method works for mine.
    It has no LED and is slightly different from the official one.

    Reply
    • admin

      Hi Ryu,

      We’ve done tests with the knock-off ones and they did work fine (though no LED as you say). The quality of workmanship on them weren’t very good so we aren’t going to strongly recommend them, but we think you can probably go ahead and make the adapter. /jeff

      Reply
  4. rankit

    hi,

    Is there anyways I can buy it from you. appreciate as I am having issues with my surface pro charging I am out. Thanks

    Regds,
    Rankit

    Reply
    • admin

      Hi Rankit,

      We don’t have a supply of Surface cables. If you send us a Surface Pro cable, we can hack it for you and send it back to you. Send an email to support@voltaicsystems.com and we can let you know the delivery address. Thanks, Jeff

      Reply
  5. Aaron

    I cut up an extra Surface Pro Charger cord and found the Red Wire, Blue and white and there were two grounds neither of which were in a black shielding? One ground was small and located in the center of all the wires and the other was wrapped around all the wires. I connected all the grounds (small and large) to the black on the Voltaic wire and the red to the red on the voltaic wire (left the blue and white loose) when plugged in got the charging symbol on my Surface Pro. I think the Surface Pro cable is different from the RT. I hope combining the two grounds does not mess anything up?

    Reply
    • tommy

      That is interesting – we’ve only seen the RT chargers so far, so we can’t say we’ve seen what you’re describing. If it works, that’s certainly a good sign, but we’re not sure what each of those two conductors may be.

      Reply
  6. Esteriel

    This may be a bit off topic, but you seem to know your way around the Surface Pro battery charging components, so I hope you can help. I charged the Pro with no problems when I bought it a week ago, but now the battery needs recharging and I can’t make it work. There is power getting to the transformer and 12V power getting from there to the magnetic connector, but that seems to be where it stops. I have no LED lighting up, and the battery has now run out completely and the Pro is dead. The contacts don’t seem damaged, loose or dirty and I don’t know what else to try. Can you suggest anything else, or will I have to try to get support from Microsoft? I don’t mind buying another charger, but I’m not sure that is where the problem is.

    Reply
    • admin

      I would go to Microsoft. Based on what you’re saying it is either an issue with the connection inside the Surface itself or potentially there is something off in the Voltage of the pin configuration. We can look at this tomorrow as we don’t have one on hand right now, but are getting one shortly.

      Reply
  7. Joseph

    Jeff,

    Do you charge for the modification?
    Also, what batteries would be safe to use with this modification? Will any external battery work, or do I need specific ratings?

    Thanks

    Reply
  8. TGMcCallie@epbfi.com

    Here is charging attachment for Surface which is already constructed properly to work from
    dc outlet in power bank.
    Go to EBay and search for charger cable for
    Surface and you will find it. I have one ordered from Honk Kong. It will plug into your
    surface and the other end will plug into any DC outlet from Power Supply.

    Reply
  9. Justin

    I assume you could use a standard 12V lead-acid car battery, unregulated? But if the battery is charging (so the voltage across the terminals is more like 13V) then it would be best to have a regulator?

    Reply
  10. Ray

    Any chance to hack this with a USB cable so you can charge via USB? Or does the difference in voltage prevent it from working?

    The scenario I have in mind is then being able to charge the Surface with one of those portable external batteries (often have two USB outputs: 5V/1A and 5V/2A)

    Reply
    • admin

      You need a boost circuit to take the 5V up to 12V. The output of the 5V/2A port is 10 Watts. If you boost that up to 12V, there is some loss, lets say 15% so you end up with maybe 12V and 8.5 Watts. The question is whether the Surface will charge off this 700mA current. You could try it with this – http://www.ebay.com/itm/5W-USB-DC-5V-to-12V-Step-Up-Boost-Module-Moter-Wireless-controller-Solar-Charger-/271176652645?pt=LH_DefaultDomain_0&hash=item3f23635765 and let us know how it works.

      Reply
      • Ray

        Assuming everything is put together properly, is there any chance of damaging the Surface with the different voltage/current? Or will it just not charge?

      • admin

        If its put together properly and you connect to a 12V source in the 2-4A range, you aren’t going to damage the Surface. Note that there are a lot of car chargers for the Surface available on eBay these days that will connect into our Car Charger Socket / CLA. Just search “Microsoft Surface Car Charger” on eBay.

      • admin

        You can combine the outputs of two battery packs in parallel pretty easily (double the amperage), but if you put them in series it typically doesn’t work. You can certainly build a cable to test it, but it would probably be easier and more consistent performance to get a battery that outputs 12V.

  11. Adam Hiner

    I am trying to do this with the Turcom M9000. The rated outputs are DC 15V-4A/16V-4A/18V&18.5V-3.3A/19V&19.5V-3.16A/20V-3A/USB 5V-1A.

    Will this work with the microsoft pro? There is no 12V listed. Will this still work? Will it damage the Surface Pro because of the extra voltage?

    Reply
    • admin

      My guess would be that it probably wouldn’t damage the Microsoft Pro when you use the 15V setting, although it simply may not work. We haven’t tested it though and it would certainly be safer to use a battery with a 12V output.

      Reply
  12. Martin Foss

    G’day, THANK-YOU SO MUCH I threw a coat on the charger. It overheated and died. I rumbled through my ‘stuff’ and found a 12v power supply. I used the RED wire as “+” and I used, what looked like a shield, for “-”. I was stuffed w/o a charger and now it I got a back-up until I get a new one.

    Thanks Heaps,
    Omerde

    Reply
  14. Shane

    Can’t I just use the voltaic female car charger adapter with the male car charger adapter that microsoft makes. It’s might be a little more expensive but it won’t require hacking.

    Reply
  15. Chris

    Thanks for this very helpful post.
    What, if I want to charge my Surface Pro on a battery with 2A max? How to connect the blue cable? Any idea?

    Reply
  16. SK

    Can I just connect the red and black wire directly to a car battery? It is 12V and has enough amps to charge the Pro…Do I need a resistor in between?

    Reply
  17. Paul Dean

    Hi,
    I’m interested in buying one of your battery packs to recharge my surface pro. I’ve read all the stuff about hacking cables on your site!! However, I did find a power adapter cable for the surface pro on ebay @
    http://www.ebay.com/itm/New-Power-Charger-Charging-Adapter-Cable-Cord-for-Microsoft-Surface-RT-Pro-1-2-/271644025978?pt=US_Tablet_eReader_Chargers_Sync_Cables&hash=item3f3f3ee47a
    If I get this cable do you think it will work with your battery pack?

    Reply
    • volta

      It has a 5.5×2.5mm plug on the other end so it would connect to the output on our battery pack. I haven’t tested it, so no guarantees, but it would likely work on a Surface 2 (Surface 3 has a different cable).

      Reply

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