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HOW TO: Solar Power a MacBook

by Globetrooper Todd | 45 Responses
Solar Power Macbook

Why on Earth would anyone want a solar-powered MacBook? Well, for most people, they either want to work in remote areas, throw parties ‘off the grid’, or pursue something creative in the wilderness.

For Lauren’s next expedition, the Gobi 2011, she falls into all of these categories. Although she’ll have sporadic access to satellite Internet, she won’t have access to AC power. Since I find solar power pretty fascinating, this makes a great excuse to tinker with a new project: Solar Power for Lauren’s MacBook.

AC vs DC

The Standard AC MacBook Charger

The energy that comes out of a home wall socket is AC, not only because it’s produced by motive power (e.g. a generator at a coal-fired power station), but because AC can be distributed to homes more efficiently. Your MacBook needs DC to charge its battery and run its circuitry. So your standard MacBook charger converts AC from the wall, into DC for the MacBook.

What’s the Difference Between AC and DC?

Alternating Current (AC) is typically produced by motive force, such as that from a generator. As a coil spins between magnets of opposite polarity, electrons are sent in one direction, then the other. The constant reversal of direction, which causes a waveform, is why it’s called ‘alternating’ current.

Direct Current (DC) is typically produced by non-motive force, such as that from batteries or solar panels. The chemicals or light provide a unidirectional, non-alternating, source of energy. Thus, there is no waveform produced and why it’s called ‘direct’ current.

A Question of Efficiency

Have you ever felt your AC wall charger after using your laptop for a while? It’s often warm because the process to convert AC to DC produces heat, which means it isn’t very efficient.

Remember I said solar panels produce DC power? Well, that means, if we want to use our standard AC charger, we’d have to convert the DC from the solar panel to AC for the standard wall charger. That can be achieved with an ‘inverter’, but again, the conversion process is inefficient. And since we want to carry the smallest solar panel possible, inefficiency isn’t our friend.

So we need to ditch all AC components to make our solar-powered rig very efficient.

Voltage, Current and Power

Let’s think of these in terms of water running through a pipe:

  • Voltage (volts) is analogous to the pressure applied to water running through a pipe
  • Current (amps) is analogous to the volume of moving water, restricted by the pipe’s diameter
  • Power (watts) is analogous to the force created by the total volume of moving water; this is a tricky one to visualise, but imagine the water pipe pointed at a spinning waterwheel. Power is analogous to how fast the waterwheel will spin.

The power equation uses these three units:

P = IV (Power = Current x Voltage)

Applying this to the water pipe: the speed of the water wheel equals the water pressure multiplied by the volume of moving water.

A Look at the MacBook AC Wall Charger

This is from my 13 inch MacBook Pro (best laptop ever, by the way).

13 inch MacBook AC Wall Charger

13 inch MacBook AC Wall Charger - 16.5V and 3.65A

We care mostly about the output of our AC charger, because that’s what’s required as the input for our MacBook. As we can see, the output on this 13inch MacBook Pro charger is 16.5 volts and 3.65 amps of current. Using the equation above,

P = IV, and P = 16.5 x 3.65 = 60.225

Guess what’s written on the other side of the charger (see below). Yes, 60W, which is close to our 60.225W from the calculation above.

13 inch MacBook Wall Charger

13 inch MacBook Wall Charger - 60W

Now we know what the MacBook wants, so we can configure a solar power system to suit.

Is There Any Leeway with Volts and Current?

From first-hand experience, the answer is yes. I can plug a 14.5V charger from a 11 inch MacBook Air into my 13 inch MacBook Pro, which has a 16.5V input requirement, and it works just fine. It doesn’t charge as quickly, but it does work. However, in the quest for efficiency (and not ruining my MacBook), we’ll aim for the suggested voltage.

The suggested current of 3.65A will charge the MacBook as fast as the specs suggest. You can certainly supply less current, but it will take longer. But there’s a limit to how low you can go. If you provide too little current, the internal circuitry won’t trigger the charge, and so you’ll get nothing. What’s the minimum current? I have no idea; we’d need a regulated power source to test that. But not to worry as we’ll aim to provide the suggested amount of current anyway.

Where Does this Leave Us?

We need to supply about 16.5V to the MacBook and enough current to keep it charging. In the case of the Gobi 2011 expedition, Lauren will probably use up a fully charged MacBook battery over 3 days (a couple of hours per night). That means we need our solar power rig to provide enough power to charge the MacBook battery every 3 days.

The Solar Power Equipment

At a minimum, we need solar cells to convert the sun’s energy into usable power. We also need the cables and circuitry to connect the solar cells (or solar panel) to our MacBook. Let’s look at all of the required equipment, starting from the MacBook, and working our way back to the solar cells.

UPDATE: See Doug’s comment in the comments section at the bottom. There’s also a way to achieve this without a secondary battery using a capacitor and resistor.

The MacBook Connector

Apple MagSafe Connector MacBook

The proprietary Apple MagSafe Connector

Our standard charger requires AC power. But we want to remove all AC components for greater efficiency. That means we need a DC MacBook charger. This presents a problem due to the proprietary MacBook power connector.

Apple MacBooks use Apple’s own patented MagSafe connector. It’s a magnetic connector designed to easily pull-out in case someone trips over the cord. Being patented, other companies cannot manufacture the MagSafe adapter without permission. And as far as we know, no one has permission.

So we’re left with the following options:

  • Apple’s own DC Airline Adapter (boo!)
  • A ‘breach-of-patent’ adapter from eBay (likely made in China)
  • Cutting our AC charger cable and splicing it to a generic DC charger (hmmm…)
MacBook DC 12 V Car Charger

MacBook DC 12 V Car Charger

Apple’s Airline Adapter is not usable because it contains circuitry to only power the laptop, not charge it. And it doesn’t even work in a car, only on commercial airlines that supply enough voltage to the adapter. Now you see why we have to get tricky.

There are some DC adapters with a replica MagSafe connector for sale on eBay. If you don’t care for the patent protection on this product, then go for it. Otherwise, you need to cut the MagSafe connector off the official charger and splice it with a generic DC charger (there’s a guy on the web, aptly named MikeGyver, who does this for you – more on him later).

Most DC chargers have a cigarette lighter plug on one end, which is pretty universal for the rest of the components we need. The official Apple Airline Adapter requires about 15V, whereas most other DC adapters require 12V to work properly with the average car. This becomes important for the next section: choosing a secondary battery.

The Secondary Battery

This is something I struggled with for a while: why do we need secondary battery if the MacBook already has a battery within it? Well, this is the best I’ve come up with.

A secondary battery…

  • will provide constant and stable power to your MacBook, potentially increasing its life.
  • doesn’t have the same protective circuitry that may disrupt charging as the solar panel moves between sun, clouds and shade; the MacBook circuitry can be quite fickle in this respect.
  • can more easily charge other devices, such as cameras, Kindles, phones, etc.
  • is easy to move around with the solar panel, and less likely to be damaged by movement.

Our DC MacBook charger will connect straight to the secondary battery for power and charge. We can use the solar panel to charge the secondary battery during the day, and use the secondary battery to charge the MacBook at any time.

Power and Time

A battery stores energy. It not only needs to provide the right voltage and current, but it needs to store enough energy to power the MacBook long enough. It’s no good providing 16.5V and 3.65A for only 10 seconds; we need it to last many hours.

We know that our 60W AC adapter charges our MacBook battery in about an hour. That means the battery holds approximately 60 watt-hours of energy. A watt-hour (Wh) is another measurement of energy. Going back to our water analogy, a Wh is analogous to the volume of water passing through the pipe in one hour. A barrel at the end of the pipe may hold 60 litres after one hour of pumping, the same way our MacBook battery holds 60Wh after an hour of charging.

When looking for a secondary battery, we need to keep this 60Wh figure in mind. If we want the battery to hold enough energy to fully charge our MacBook, we need a battery that holds at least 60Wh. Personally, I’d like a battery to hold more because if we get an opportunity with lots of sun, I want to charge up for a few days.

Also, some battery manufacturers don’t use watt-hours, but instead amp-hours, to measure capacity. If you think back to our P = IV equation, you can convert watt-hours to amp-hours as follows:

amp-hours = watt-hours / voltage, or watt-hours = amp-hours x volts

Battery Type

Lead Acid Battery

Lead Acid Battery

We typically have two options:

  • Lead-Acid Battery – bigger and heavier, but cheaper
  • Lithium-Ion Battery – smaller and lighter, but costly

We also need to be aware of the voltage of the battery. The official Apple Airline Adapter requires 15V, so in that case we would need a battery that outputs a similar voltage. Most generic DC chargers require 12V, and 12V batteries are much more common.

Let’s look at a few options from eBay.

Option 1. A 12V 5Ah Lead-Acid Battery

  • Sells for $8.95
  • 5Ah means 5 amp-hours, which is also 5 x 12 = 60Wh
  • Weighs 1.4Kg
  • Dimensions are 9cm x 7cm x 10cm = 630cm3
  • The 60Wh will provide about 1 full charge for our 60Wh MacBook battery

 

Lithium Ion Battery

Lithium Ion Battery

Option 2. A 12V 6.8 Ah Lithium Ion Battery

  • Sells for $31.95
  • 6.8Ah is also 6.8 x 12 = 82Wh
  • Weighs 0.22Kg
  • Dimensions are 11cm x 5cm x 10cm = 550cm3
  • The 82Wh will provide about 1.4 full charges

Imagine hauling around a 1.4Kg lead-acid battery in your backpack. So even though the lithium battery is more than triple the price, I’d pay the $32 to save more than 1Kg of weight. Lead-acid batteries may last longer, but their weight is just too much for this application.

Rather than this bare-bones lithium-ion battery, I can also buy a variable voltage lithium-ion battery from a few specialty companies. That means I can hook it up to any device (iPod, Kindle, camera, etc.), flick a switch, and give it the right voltage. This is a very important consideration, so if you plan to charge more than a MacBook, it’s the best way to go.

The Solar Panel

Powertraveller - Solargorilla

Powertraveller - Solargorilla

We have two primary options with solar panels:

  • Rigid solar panels – much cheaper, more efficient for their size, but typically less portable
  • Flexible solar panels – more expensive, less efficient, but typically more portable

Some flexible solar panels are just a series of smaller rigid panels wired together; they fold up between the edges of the rigid panels. They’re a good compromise between truly rigid and truly flexible solar panels.

The cheapest, lightest and most efficient solar panel option is to buy a series of thin-rigid panels and wire them together. Why? Because rigid panels are more efficient and so your total package could be smaller, lighter and much cheaper. But this requires some serious electronics experience, which I certainly don’t have.

There’s a pre-packaged option though…. woo hoo!!! I’ll talk about it in the next section.

To run our MacBook without any batteries, I suspect we’d need to supply at least 40W to keep the internal circuitry happy. But we need to account for shade and changing sun angles, which means we’d need at least 60W. A flexible solar panel that outputs 60W costs a lot; probably upwards of $1000. And even 60W of rigid panels would be too big.

But luckily, we have our batteries, which can store power throughout the day. And because we don’t need a full day’s worth of energy every day, we can trickle charge the batteries slowly with a smaller solar panel.

Powertraveller - Powergorilla

Powertraveller - Powergorilla

Let’s look at the numbers from our previous assumptions.

  • We’d like more than one full charge as a buffer
  • Our ideal lithium ion battery can hold about 80Wh
  • So we’d like to charge that 80Wh in 3 days
  • Therefore, we need 27Wh per day (80Wh / 3 days)

Since we’re talking about the Gobi Desert, we can assume that we’ll get a good dose of sun each day. On average, you get about 5 peak-sun hours per day in a sunny location. Even though we get many more hours of sunlight per day, that ‘peak’ figure accounts for the start and end of the day, when the sun is less intense.

So if we need 27Wh per day, and we have 5 peak-sun hours, we need about 5.3W per hour (27/5). So with just that data, and on a perfectly sunny day where our panel is perfectly angled to receive full sunlight, we would need a solar panel that supplies 5.3W.

However, in an imperfect world, our solar panel won’t be at the perfect angle for the entire day and the sun will sometimes be blocked by clouds. Just small changes in cloud cover result in large output variations. And although our secondary battery isn’t hindered by tricky protective circuitry (unlike our MacBook battery, which would cut off charging if the voltage or current dropped below a threshold), it will still take longer to charge the battery with less than direct sunlight.

So, at a minimum, we need to double that requirement (at least 10W).

Putting Together a Solar-Powered MacBook Kit

If you’ve made it this far, you’ve done well. And you may even be a little frustrated when I tell you that you can buy all of this stuff without having to worry too much about the science, but it will cost a lot more. There are two manufacturers in particular that I’ll cover, Brunton and Powertraveller.

The Fancy Pre-Packaged Option

Brunton makes most of the components we need, but for a steep price. There’s also another guy on the web who makes a patent-friendly DC charger for MacBooks. He cuts the end off the official AC adapter to adhere to Apple’s patent. But again, the modified DC charger isn’t cheap.

The Cheaper Pre-Packaged Option

Powertraveller makes proprietary solar-power gear for travellers, but they’re more reasonably priced than Brunton. Plus, remember when I said, ‘there’s a pre-packaged [rigid panel] option’, well, this is it.

Also note, this option uses a patent-unfriendly MagSafe DC charger and a few other generic bits and pieces.

Check out that huge battery! It’s not much heavier than the Brunton 6Ah battery, but it supplies a whopping 8.74Ah, which will power a MacBook for almost 2.5 full charges.

The Do-It-Yourself MacBook-Only Option

Generic parts are your friends, that’s if you don’t mind tinkering and searching high and low for suitable adapters. This option is only suited to powering a MacBook because the battery doesn’t have a variable voltage feature.

  • Generic 12V input DC MagSafe charger – $30
  • Generic 12V 6.8Ah lithium ion battery – $32
  • Powertraveller Solargorilla 10W Folding Rigid Solar Panel- $215
  • Various cables and adaptors to fit everything together – $30
  • Total RRP = $307 + shipping

You could shave some more money off this by building your own connected series of rigid panels. But this would take some previous experience. However, if weight is an issue, this could be the lightest option. But your gear wouldn’t be ruggedized like the Powertraveller products.

Final Considerations

What not to do

  • Don’t overestimate the amount of sun you’ll receive; go for a bigger solar panel if possible.
  • Don’t use the official Apple Airline Adapter; it simply doesn’t charge your battery
  • Don’t buy products without checking their weight; pictures can be deceiving

What you should absolutely do

  • Buy items with matching connectors; it can be pain to find adapters afterwards
  • Buy a battery with a higher capacity than you need, but keep an eye on weight
  • Shop around for your solar panel; prices can vary a lot (eBay is good)
  • Test your DC adapter in a car to make sure your MacBook is charging properly

And finally,

If you attempt a similar project, we’d love to hear your results. Similarly, if you have any questions, just shoot. If we don’t know the answer, we’ll defer to an expert. Oh, and lastly, if you are an expert and any of the above is incorrect, please let us know :) Also, many thanks to Stewart from Barefoot Solar who imparted tonnes of solar-power wisdom during his stay with us in India. I’ll talk more about his super-cool company in a subsequent article.

Posted in Featured, Gear & Gadgets, Gobi 2011, How-To Guides | April 20th, 2011

45 Responses to HOW TO: Solar Power a MacBook

  1. I love the idea but the price is well what can you say you get what you pay for. The MacBook is a great piece of equipment I dont think right now though I can really justify spending more money on a solar panel.

    • Hey BK, you’re right, it is expensive, so it’s for people who really need it.I can’t imagine carrying around a solar panel ‘just in case’. But at least for the Gobi 2011 expedition, they know they won’t find an AC power outlet around the next corner. And with bloggers, photographers and filmmakers on the trek, there’s really no other option. When we get a little settled (with travel and working at the same time), I hope to work up to some seriously long expeditions, and this was a better time than any to learn a thing or two about the science. Maybe we can tempt you sometime down the track with a month-long expedition into the wilderness.

  2. This is really helpful, but I think I must be missing something. Does the DC power kit from Mikegyver only come with a car charger style plug? If so, how does it connect to the Brunton Sustain battery? I’ve been looking at getting one, but I don’t know how I’ll connect my macbook to it. Any thoughts? Or does the Mikegyver kit also come with a non-car-charger style dc plug??

    Does that make sense?

    • Hey Scott, I thought the Brunton Sustain had a car-style adapter, but evidently, it doesn’t. So it needs a simple adapter from any electronic shop to change from the car-style to one of the plugs that comes with the Sustain. Unfortunately the Brunton website is light on detail.

      Why not go for the PowerTraveller option? It comes with more adapters than you’d ever need ( including the in-car adapter). Plus it’s cheaper, goes up to 24V, has more DCV selection options, and does some other cool stuff.

      • Thanks for the reply! I think I found a way to use the Sustain. I’m planning on getting both a SollarRoll 14 and Sustain. The solarRoll comes with both a cable to connect it to the sustain and a car charger socket. I’m betting on the car socket cable from the SolarRoll will be able to plug into the DC out outlet on the Sustain since both devices are made by Brunton and designed to go together. I’ll contact Brunton and see if this is indeed the case.

        Thanks again!

    • Sounds good, would love to hear how it all went.

  3. Using a MacBook on solar power? Well, I’m literally speechless! What an awesome idea! And such good presentation too, even beginners like me can understand it very well. Well, I wanted to share with you this amazing book on how to create professional travel blogs and also how to make money from them. I’m sure you’ll like it, and thank you!

  4. Hi there,

    Last year I spent 6 weeks camping/ touring in france, attempting to keep my 13″ black macbook charged with a solargorilla/ powergorilla combo. It didn’t go too well, with approx two days needed to charge the powergorilla, which only gave me one full charge on the macbook!

    I came to the conclusion that to make this sustainable (at least in a european climate), I would need a bigger panel and lead-acid leisure battery – not possible backpacking I know, but fine if you have a vehicle.

    There’s a few blog posts on here that you might find interesting:-

    http://ontheroad.rickhurst.co.uk

    http://ontheroad.rickhurst.co.uk/posts/2010-06-23-power-and-charge-a-macbook-with-a-powergorilla.html

    http://ontheroad.rickhurst.co.uk/posts/2010-07-07-charging-a-powergorilla-from-a-solargorilla-in-the-uk.html

    • Hey Rick,

      That’s interesting about how look it took to charge the battery. Lauren has just left for her desert trek, so we’ll see how the different climate charges the battery. She won’t need a full charge every day, and from all reports,they’ll get a lot of sun, but they’ll also constantly be on the move, not charging in one place.

      That said, I think the solargorilla is only 10W from memory, so it’s pretty small considering a MacBook is 45-85W (depending on model). I used to think the flexible panels would allow you to carry much more potential power around, but they’re also quite heavy when you’re talking 40W or so.

      I read in one of your posts that the battery was only providing 2 hours. That’s not good at all. I wonder what was happening there. My MacBook lasts at least 5-6 hours and the battery has already had 500+ full cycles. I don’t use virtual machines much, but have a full dev environment and photoshop. But if I only got 2 hours out of it, I’d be pretty disappointed.

      As soon as I hear from Lauren, which may be in 2 months depending on the satellite comms, I’l come back to post her experience with the setup. Keep in mind she’s actually using an 11 inch MacBook Air. It’s tiny and quite efficient.

      • Hey Todd,

        my macbook is an older (2008) non-unibody plastic macbook, which I think was advertised originally as having up to 5 hours. I’ve just put a new battery in mine and if I tweak everything – dim the screen (not practical when working outside), turn off wifi, bluetooth and run minimal apps, I might get somewhere near 4 hours. I know the newer ones get better battery life, and the macbook airs. I’m sure the 11 inch MBA will be perfect for trekking.

        As for the solargorilla – i’m sure it would work better in the desert, but I couldn’t get it to directly charge the macbook on a sunny day in the south of france – the only option was to trickle charge the external battery and charge the macbook from that

      • Hey Rick,

        Yeah, from all reports that had a few issues with keeping batteries full. And even though they were in a desert, they had sand storms and cloud cover too. Wasn’t too bad, but still they had days without enough power.

  5. This is a wonderfully written guide, couldn’t be done any better, thank you!

    I’m working on the Cheaper DIY method but am stuck on parts maybe someone can help?

    Found these ebay batteries which have a 2.1mm in/out cable.
    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270748242606&ssPageName=ADME:X:RTQ:US:1123#ht_1286wt_1158

    - Cannot find the cable that turns the 2.1mm male out to a 12V auto female socket.

    - Once converted I hope to also charge my iPhone from the auto socket.

    - I found a lot of solar panels that are 15V such as from powerfilm, will this overcharge the 12V li-ion batteries?

    • Hi Shane,

      Thanks for the kind words; it took me a full day to write that up, so it’s much appreciated.

      Does that battery have both male and female 2.1mm plugs coming out of it? I couldn’t find a 2.1mm direct to female car socket, but what about 2.1mm to male car socket, then a male to female car socket cable?

      I think your best bet might be charging the iPhone from the laptop because the battery doesn’t have variable output. So you’d be giving it 12V when I think it takes 5V (don’t quote me on that).

      From what I know, the solar panel is only 15V with max direct sunlight. Most of the time it will output much less. But assuming it did output a constant 15V, this is actually where my knowledge comes unstuck. I believe lead-acid batteries are much less fickle. But I don’t know exactly what will happen with the Li-ion battery. I think you need to bring in the big guns and consult an electronics forum. I’d love to know the answer too.

      All the best with the project.

      • Hi Todd,

        I contacted powerfilm solar and they confirmed that their 15v solar will often not deliver that voltage and that the ebay li-ion battery seems to have protection so I’m moving forward and will piece this together.

        Thanks!

  6. One other thing I forgot to mention in my last comment – if you have a powergorilla, you don’t need a 12 volt to 16 volt adapter, as the powergorilla can be set to 16 volt output. You will just need some kind of magsafe adapter (home made or aftermarket) to plug into the macbook

  7. Hello, thankyou for the article!

    Do you think that this product:

    http://cgi.ebay.it/20-W-Portable-Solar-Power-Panel-Battery-Charger-Laptop-/250844071765?pt=AU_Solar&hash=item3a6778c755

    can be good with a cigarette adaptator for a macbook AIR 11.6″?

    Thanks a lot

    Marco

    • Hey Marco, looks good in terms of battery storage and solar panel output, but you’ll still need a connector to the MacBook. Try to buy a DC macbook adapter rather than using your normal AC adapter and an inverter (much less efficient). You can get a DC macbook adapter on ebay.

    • I’m quite pleased with the inrfoamtoin in this one. TY!

  8. I’d like to know were you found a – “Generic 12V 6.8Ah lithium ion battery – $32″

  9. Great guide!!!!
    I have found a way to do the above without the battery. Let the solar panel drive a capacitor (I’m using a 33,000ufd 50V, it is 2″ diameter by 2″ long) in place of the battery. Also the solar panel is capible of producing much higher voltage than the Apple wants (16.5V). This can be a problem as the computer battery approaches full charge and the current drawn is low. So I put a 16.5V regulator after the capacitor to limit voltage to 16.5V. The entire piece not counting the computer and solar panel is the about the size of a computer mouse and weighs about the same. To make it will cost under $20 but you need to do a bit of soldering. The other advantage is that you loose considerable energy charging and discharging the battery (conversion efficiency). The energy required to charge a Li Ion battery may be 1.3 times the usable energy available when you discharge it. Also you loose about 10% to 20% of your energy using the car charger. The Capacitor operated this way has very close to 100% conversion efficiency and you are only loosing about 5% to 6% of the solar panels output power in the regulator. There are some even better regulators specifically designed for solar cells (Peak Power Point regulators), but cost and complexity start to go up.

    • Wow, Doug, that’s very helpful. Sounds like a much better solution. I’ll add a reference to your comments in the main article. Many thanks for dropping by and sharing. Much appreciated.

      • Todd,

        Did you manage to find out any more details about this setup?

        Thank you!

    • Doug, would you mind posting where these components can be bought? What housing did you use? Perhaps a link to a schematic? Thanks very much!

    • Doug,

      Any chance of posting the list of components or going a little bit more into detail on the setup?

      Thank you!

  10. Your statement “why do we need secondary battery if the MacBook already has a battery within it?” is very important because certainly Apple is not going to tell us their internal charger has no protection and is volt/amp/watt-specific.

    Hence, I’m taking your advice on the generic Lithium Ion Battery on eBay directly from China. I’ve been looking for battery options such as HyperJuice which are quite expensive. The eBay blurb for the Chinese battery says it has internal protection, so presumably it can handle my PowerFilmSolar 20w/15.4v/1.2a foldable panel, which actually reads 18.68v without a load sans charge controller.

    One possible caveat with the Chinese battery is that it’s 12v, so will need the eBay MacBook charger which I already have. It will also need a custom PowerFilm-to-battery cable, and I don’t know where to get the appropriate connector for the PowerFilm. Any referrals you can offer would be appreciated.

    The nice thing about the expensive selectable-voltage batteries such as HyperJuice is that theoretically it’ll run a MacBook directly by selecting 16v with custom HyperJuice-to-MagSafe cable. For those who want the absolute lightest package, this might be the route to take.

    More about eBay…I was able to find DC chargers for my DSLRs, whereas when I was recently in Yosemite I had to recharge the batteries by using a lead-acid battery connected to an inverter and use the AC charger. Kinda krazy to go dc-ac-dc. eBay has amazing stuff if it all works.

    In essence, the goal for a lot of us intrepid thinkers is DC-power all the way. I have some filmmaking ideas out in the bush, so that’s what I’m gearing up for.

    Your information is vital. I never see anything like it.

    • Hi raqcoon, thanks for the comment. Is there a standard connection to the PowerFilm panel? Maybe take the setup to the nearest electronics shop and they can put something together to connect it to the battery. Did you read the comment above yours? It talks about doing this with just a capacitor and resistor. Glad you liked the post :)

  11. would the Goal Zero Sherpa 50 kit with the 13.5W solar panel also be a good choice with your car charger.

    • Hi Howard,

      Looks like a good kit. Just depends on what you’re charging. The battery seems to only go to 12V. So I’m not sure how it would go with a laptop that may want 14 or 16V.

      Lauren has now been back from Mongolia for a few months and it seemed that had enough power, but they were in the desert, so they received plenty of sun.

      The size of the panel should be fine too.

  12. Thanks for your great guide.
    Considering the size of the battery, what do you think of the smaller battery minigorilla? Can it support macbook well?
    Thanks before

  13. Whoa whoa whoa!! This works with the mid 2010 MBP’s???

  14. Thanks Globetrotter Todd for starting all this – brilliant!

    Fascinated by Doug’s idea as a very basic electronics person myself. A few “simpleton” Q’s. My understanding of a “capacitor” is that it stores a bolt-like charge of energy/electricity so can never replace a battery, and for that reason cannot work like a transportable portable battery..so can only charge the Mac battery when connected to the solar panel. Right? ie you need both “on” for it to work?

    I am “understanding” that you need the voltage regulator as well because the solar panel + capacitor on their own might produce too much juice. If you used solar panel + voltage regulator (without capacitor) same risk/problem. Right?

    Then you need the famous “copy” magsafe plug wired into the voltage regulator?

    ps think the other portable systems are much too expensive, so since the capacitor + voltage regulator are v cheap, it’s just a q of finding/making a small solar panel to go with it?

    So what is smallest size, and what wattage output needed for solar panel with Doug’s solution? Can it be fully small and transportable?

    Any further feedback much appreciated

  15. Thanks for your great guide.

  16. I’m looking to build a system that will give me 12-20hours of laptop power from one battery…that’s built into or simply portable from my truck. Charged both from solar panels and truck’s 12v supply. Thanks for the details – will send pics of my contraption when finished.

    I’m using Goal0 7watt panels as they are light, partially flexible and can be chained. I’m using Lead Acid batteries as weight isn’t a problem and there’s nothing on the market that is both affordable and long lasting for car based activities like this! Cheers from the NZ hills!!!

  17. Thanks for your expertise. I will be for three months on a remote and uninhabited island in the Pacific for archaeological fieldwork. I need a “equipment” to give me the opportunity to recharge (not at the same time!) my MacBookPro, or/and an ASUS EeePC, a CANON 40D camera, some small 1.5v batteries for GPS and others appliances, IRIDIUM telephone,… and to provide each evening light with LED (how) because it’s dark night at 6.30pm. We wille be eight. Could you give some advice on that question. Recommand some equipment. Natirally conditions are scarce and weight (and price) are important. Thanks

  18. Thanks a lot for this great post! I would to use the “Sherpa 50 Kit” (includes solar panel and battery: see http://www.goalzero.com/sherpa50.html) from “Goalzero” to power my Macbook Air 11 (latest version 2012) . Do you think it will work? The sherpa 50 battery provides 19V output and has 50 Wh + (2 x 3 x 3.6V, 2.6Ah cells [???]). Do I need additional adapters?

    Thanks a lot for your help!

  19. Not only are you being able to enjoy your mp3 player in the car, listening to whatever you want to listen to, you are getting full advantage of this product by also charging your mp3 player. So, now when you leave your car and you want to take your mp3 player with you, you no longer have to worry about your mp3 player being uncharged for wherever you are going.*

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  20. Thanks for sharing your thoughts on porsche 911 electric car
    conversion kit. Regards

  21. I have a Solargroilla and a dc magsafe adaptor that was sent to me by power traveller and i am trying to charge a macbook book pro 13”. I am just a little confused, how can you use a 12v battery to charge the mac which needs 16 volts???
    And why can’t you Just plug the solar power straight into my mac?

  22. Thanks for the article.
    My setup: McBookAir mid 2010 which requires 14.5V (internal battery=35Wh) + 2nd battery BRUNSTON SUSTAIN 2 (70Wh – 12 or 16v output) + solar panel Brunton 12W + Magic box Hyperjuice / MBA car charger.
    Project: world tour on a bicycle.
    Need: 1hr/day use of the MBA, = 15Wh in the internal batt of the MBA
    prediction: 8hours of sun=>70Wh
    result: 22min (=7Wh)/8hrs of ride in the sun. Meaning 9 times less power than theorically received by the solar panel!

    Q: where do all the energy loss is?
    - brunton batt > MBA batt? :charging a batt from a battery inefficiency?
    - Car charger?
    - solar panel>brunton batt?

    Thank you for your comments
    olivier

  23. I have 3, 15w Solar panels on top of my van producing 45 watts. It charges a 12v battery in 2+ days. My macbook is 85w. It doesn’t last very long. If I get three more panels equalling 90w will it be better. What method can I use to power the computer all day and night if I wanted too.

  24. I have recently bought a 62W solar panel made out of CIGS material and designed to work with Macbook Pro,
    - (CIGS stands for Copper Indium Gallium DiSelenide. It’s the “stuff” that makes our Solar Panels work.)
    - Advertised to work for all Apple MacBooks, MacBook Pro and MacBook Air lap tops – including the 13.3″, 15″ and 17″.)
    - There are two components: the flexible solar panel, the cord, and the magsafe connector.
    I have little theoretical knowledge of wattages etc. – hence inclined to worry. The cause of my worry is as follows:
    I have used the solar powered device on my (7 year old) Macbook for approx. 1 month. This Macbook had, several months prior, been refitted with a new hard drive.
    After approx. one month’s intermittent use, I found that Safari was showing signs of damage (confirmed by Apple Technical Desk). I purchased a new computer. The old computer still works in other packages such as Pages, etc.
    What I am concerned about – is the damage due to the use of the solar powered device or due to age of computer or even some other factor. I have read on the internet that directly charging your computer this way could lead to damage.
    I ask due to the amount of knowledge you appear to have on the subject and would much appreciate any time you could put aside to answer this question.

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