I made an external battery for my Air

Discussion in 'MacBook Air' started by Chipg, Jun 12, 2012.

  1. macrumors regular

    Aug 17, 2010
    I needed more portable battery power and did not want to spend $200+ for a hyperjuce so I made my own external battery pack for my Macbook Air. It’s 65w LifePO4 battery, 4400mAh @ 14.8 volts, I do not know the total time it will last for but I used it for 6+ hours and it was still going strong, my Air is a i7 with the bigger processor, the battery is small and light making it convenient and easy to carry in your laptop bag or backpack.

    My total cost including the charger is less than $80, the battery was $28 so after the cost of the mag safe connector and charger I can add more battery packs for $28 each or spend more on a larger capacity one.

    Battery = $27.99 I chose this battery because it fits in a small side pocket in my laptop bag and is not big and heavy. It is 4400 mAh at 14.8 volts or about 65 watts, I think the standard 2011 Macbook airs battery is around 50 watts???? After 6 hours my air was still going off this battery with the screen brightness high and I ripped several dvd’s with handbrake, there was no ‘light’ use during this time.

    Hobby King has a tool for selecting batteries, you choose your type, LifePO4 is what I ordered and select your voltage (14.8 volts) and they list batteries by mAh...

    Charger = $24.95 - smart charger for 1-4 cell, if you buy a battery with more than 4 cells make sure you buy compatible charger for more cells.

    I bought a used apple power adapter for $20 to remove the wire with the mag safe connector, I soldered 4mm radio shack quick connect bullet connectors on the end of the mag safe wire after I unsoldered it from the apple power adapter, the white wire is the positive wire.

    This setup has been REALLY GOOD to me, for another $5 you can buy a car USB cigarette lighter 10w power adapter and connect it to this battery for an iPad or iPhone. I leave the battery in my laptop bag so all that comes out is the wire to plug into, it's a pretty slick setup that you can add more power anytime for not a lot of $.


  2. macrumors 6502a


    Dec 9, 2010
    51 degrees North
    sounds pretty interesting this, got any pictures of the finished product?
  3. TSE
    macrumors 68030


    Jun 25, 2007
    St. Paul, Minnesota
    That's awesome. Mind posting step by step directions and photos?
  4. thread starter macrumors regular

    Aug 17, 2010
    Please give me a day or two and I'll take some pics for you and make the instructions more clear. It was REALLY simple to do, it took me 5 minutes.

    The cool thing about it is if I want more power I can just buy 1 more battery for $28.
  5. macrumors 65816

    Jul 6, 2007
    I was thinking about using some of my heli lipos to do something similar. Good to see you doing this. :)
  6. macrumors 65816

    May 14, 2010
    South FL
    That's freaking awesome. One thing I didn't like about my previous Air was battery life, my 13" Pro lasted longer (i.e. I could watch 2-3 movies on it on a plane). But I'm thinking of picking up a new Air since the 13" Pro was pimp slapped by Apple.

    Does the pack get warm or hot? Wondering if something like this would work if I left it in the briefcase and ran the cord to the computer while on a flight or if it would get to hot and need some breathing room?
  7. thread starter macrumors regular

    Aug 17, 2010
    The pac stays really cool, it is a 15c pack which means it is made to put out voltage over a long time vs a battery like for a r/c helicopter that is made to disperse it's voltage fast. You will have ZERO probs with this battery and heat, it felt room temerature the whole time, perfect to leave in your brief case or backpack.

    I'll get you guys some more details and info soon.
  8. macrumors 65816

    May 14, 2010
    South FL
    Pretty damn sweet since it would work for the Pro's too... nice job man!!
  9. thread starter macrumors regular

    Aug 17, 2010
    Thanks PIMP!

    The reason why I like it better than the hyper juice is because it's really simple, after you soilder the 4mm bullet connectors on the magsafe wire (white wire positive, black wire negative) you can just unplug and plug in another battery for $28.

    You have the ability to mix and match all kinds of battery options, hobby king has a 9800mAh battery for around $85 that should last a Air user days.

    Since you have a pro you'll want to get a little bigger battery or it won't last as long, I do know the pro's use more mAh per hour, exactly how much you'll have to look it up and match the size for the amount of time you want.

    Glad to see others have interest in this, I thought I was the only one :) :D
  10. macrumors 65816

    Dec 2, 2010
    Cant wait for the pics of it. Ill make one aswell :)
    I've been wanting to create some sort of external battery for ages. Never got round to it. This is great though.
  11. macrumors newbie

    Jun 12, 2012
    Pure win. I can't wait for the write-up.

    Would this be allowed in a checked bag on an airplane? Last I heard, battery packs like this are not acceptable. Plus a battery pack and soldered wires looks pretty suspicious lol.
  12. thread starter macrumors regular

    Aug 17, 2010
    I do not know and I agree with you, I'll go through with a write up because there is interest but I'd like to see other people write back with their experiences / time per charge / bat size / airport experiences and on and on...

    Today, I think, and I say I think they can run them through the x-ray and determine it is a battery or not.

    The last thing I want is a person to have to dump it at the airport...

    Is it illegal to fly with a hobby battery? I do not know


    here is a thread, it says the FAA only allows lead acid batteries...


    This is really good stuff btw, it's what we need to know, you can buy a lead acid battery btw and still use it, it does not last as long but the FAA will allow it...

    These rules are from 2010, I will look into the new F.A.R.'s tomorrow
  13. macrumors newbie

    Jun 12, 2012
    I meant to say carry on, not checked. However, it looks like battery packs are allowed only on CARRY ON, not for checked baggage. It looks like it may be okay. But because it is up to the TSA's discretion when you arrive, it may be wise to call ahead to double check.
  14. macrumors regular

    Feb 2, 2012
    Leuven, Belgium
    This is one of the coolest hacks for an MBA that I've seen so far. It should give you more battery time than the internal battery and that at only about 0,5kg. Looking forward to your write-up !

  15. Chipg, Jun 13, 2012
    Last edited: Jun 13, 2012

    thread starter macrumors regular

    Aug 17, 2010
    Hope this helps some more:

    This is the battery I chose for size and weight, it weighs 419 grams so that’s less than half a kilo, it’s a 4400 mAh 14.8 volt 15C (discharge rate) Li-Po type = same type as Apple uses for the Macbooks: http://en.wikipedia.org/wiki/Lithium-ion_polymer_battery

    Hobby King sells larger and smaller batteries, pick one that’s best for your time requirements, the 4400 mAh 14.8 volt one I use (in the above link) provided me with 6+ hours and was still going strong, it’s 65 watts, the Macbook Airs factory battery is around 50 watts. Here is a link to a larger 8000 mAh 14.8 volt battery: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=20823 and here is a link to a smaller 3000 mAh one for $20: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=15010 this little light battery should be about 44 watts.

    The cool thing here is that you can size your batteries however you want, some people might want one big daddy and others 2 or 3 small ones...

    Order these 4mm bullet connectors, pack of 10 = $3.64
    http://www.hobbyking.com/hobbyking/store/__9283__HXT_4mm_Gold_Connector_w_Protector_10pcs_set_.html if you decide to order different batteries some might have a different connector than the 4mm bullet plugs on them so remember to check and order the correct connectors if necessary.

    This is the charger I bought, it is a smart charger that works with any Li-Ion/LiPO battery pack with capacity > 1000mAh that has 1-4 cells, it auto shuts off so you cannot overcharge the battery: http://www.all-battery.com/UniversalSmartChargerfor3.7-14.8VBatteryPack-01281.aspx

    Buy a new or used Apple power supply that has the mag safe plug, I bought one used for $20, I had to crack mine open with a bench vise to remove the plastic casing, then unsolder the two wires from the mag safe wire, one is white, the other black then solder on the 4mm bullet connectors that will plug into the battery, the white wire is positive and goes on the side of the 4mm bullet plug connector that has the red wire for the battery and the black wire is negative and goes on the 4mm bullet plug connector that goes to the batteries black ground wire. It’s really simple to do, I did not take pictures during that process, I didn’t think there would be this much interest. the only 2 wires used coming out of the battery pack are the red and black ones.

    Plug it into your Mac and you now have portable power that will last for hours!

    I wrapped mine in black tape so you couldn’t see the Zippy brand and writing but here is a pic so you can see the size, my Air is the 13” one.

    And here you can see how it perfectly fits in the little side pocket in my laptop bag.


    Attached Files:

  16. macrumors regular

    Feb 14, 2009
    Very nice !

    I can't find a 14.8V battery here in France. Do you think a 12V can do the job ?
  17. macrumors 6502

    Dec 23, 2010
    London, UK
    Looks pretty cool
  18. thread starter macrumors regular

    Aug 17, 2010
    I'd go on Hobby Kings website and order a 14.8volt one from China, mine only took 10 days to get here and shipping was cheap.

    The Apple power adapter puts out 14.5 volts and is the reason I went with the 14.8volt one. I would just order the one with the voltage that we know works with no problems.

    Let me know how it turns out :)
  19. macrumors 65816

    Dec 2, 2010
    Thank you so much. Im in the process of ordering at the moment.
    Couple questions, if you would be so kind to help me :)
    First off, do you know if I will have any problems ordering to germany? like customs and stuff.

    I noticed that the battery you have has a 15C discharge rate. The 8000mAh one you posted the link to is 30C. Whats the difference and will it affect anything?

    Can I use the exact same battery that you have for my 15" MBP? Or are there voltage and Wattage problems?

    Cheers mate
  20. Chipg, Jun 13, 2012
    Last edited: Jun 13, 2012

    thread starter macrumors regular

    Aug 17, 2010
    I have no clue about Germany, I'm in the USA, I'm sure they will ship anywhere and long as you pay for the shipping.

    The 8000mAh is a 30C, that means it can discharge at a faster pace than the smaller 4400 mAh 25C, it's no big deal and will be fine, it'll actually be a little better if you also use it on a Macbook Pro because they require more amps.

    I'm not sure about the Pro's voltage, just find out and order a battery closest to it. Let me know how it turns out!

    EDIT: I just read the Pro's voltage is a little higher, it's 18.5 volts so order a 18ish volt battery and you should be fine.
  21. thread starter macrumors regular

    Aug 17, 2010
    Hey man, if you wanted a 8000 mAh battery this one is 18.5 volts and should be ok with your Pro. http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16227


  22. macrumors newbie

    Jan 25, 2011
    That's awesome! I'm surprised Apple hasn't released something similar yet.
  23. Brandon0448, Jun 13, 2012
    Last edited: Jun 13, 2012

    macrumors regular


    Aug 2, 2011
    Wasilla, Alaska
    So I'm pretty sure I'm gonna be making one of these in the next few weeks. It is such a great idea and so cheap! I'm probably gonna use the same set up except with the 8000mAh battery and an addition of a voltage monitor on the pack. That way you will get a warning when the voltage in one of the cells drops too low, this will greatly improve the life of the battery if you keep all the cells balanced. There are cheaper monitors but this one has a power-saving mode that will only turn the display on once a cell drops below a certain voltage, that way I can leave the monitor on the pack without drawing too much power.

    EDIT: Also for charging did you just leave a bit of the bullet connectors exposed so you could hook the alligator clips from the charger to it? I can't really tell from the pictures you posted. Thanks!
  24. Chipg, Jun 13, 2012
    Last edited: Jun 13, 2012

    thread starter macrumors regular

    Aug 17, 2010
    Sweet 6 pound 8 ounce baby Jesus! That voltage monitor is an awesome idea!!!

    EDIT: ok, I just noticed that they come in different voltages, make sure you buy a compatible one for the battery you get.

    It plugs into the other wires that are already on the battery...

    I'm going to give this one a try for $4, it can tell me the voltage for each cell (to balance them) and the overall total voltage.

  25. thread starter macrumors regular

    Aug 17, 2010
    Yes, that is exactly what I did but I ordered the 4mm bullet connectors from hobby king (I put a link in my write up) that I'm going to put on the end of the charger so I can just plug the charger in.

    I'm also making a cigarette lighter USB power adapter for my iPad, what I think I'm going to do is make a wire that goes from one connector to two so I can plug my AIR into one connection and iPad into the other one. The 4mm bullet connectors come in a 10 pack for under $4. Right now I used temporary radio shack bullet connectors and clip the charger alligator clips to them.

    Let me know how yours turns out!

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