[PB2K]

For working off the grid (central Africa) I am deciding between a solarpanel and a fuelcell
Macbooks no longer have replaceable batteries. An external battery pack / UPS wouldn't provide for longer than 24h of power. So I need a source that is self generating.

I understand that charging isn't possible with the macbook pro15 + solar panel configuration, but perhaps a 11" macbook air+solar panel will work. In optimal conditions the solar panel could generate 40W, which I do not believe to be accurate. It's probably no more than 25W in optimal conditions.

For this I need to know exactly how much power a macbook pro/air consumes.

Is anyone able to provide this information? thanks !

[SierraDragon]

How far off the grid? Will you at least be transported by motor vehicle? If so, use the solar panel to charge a lead-acid battery and run the laptop off an inverter.

[ghporter]

How do you plan to interface your solar cell/fuel cell with the MacBook? Both options produce DC, which means you'd need either a custom DC-powered charger, or have your alternate power system connect up to look like an automotive power system and use a car charger. It is not really effective to expect to use an inverter with a low-power source; inverters are too inefficient to be worthwhile.

Also, are you planning to use the MacBook all the time? As in "never sleeping?" Per Apple's Environmental Report, a MacBook that's "off" while plugged in uses .25W, while one that's asleep uses about 1.0W, compared to one that's on using 5W while idle and up to about 11W while actively in use. This has a strong impact on how much energy it takes to charge the battery. The Environmental Report mentions the standard Apple AC adapter's efficiency as being in the neighborhood of 80-85%, another point to consider.

I'd use a combination of two solar panels charging automotive or lighter sealed lead-acid batteries, and connect them in parallel (both positive terminals connected to each other, both negative terminals connected to each other) to an auto power outlet, and an automotive MacBook charger. Airplane Power Adapters specifically do NOT charge the laptop, so they aren't an option either. It looks like you're stuck with using a third party auto charger (which doesn't need an inverter) or an automotive inverter that would waste a lot of your solar energy as heat.

[Waragainstsleep]

I too would invest in a bigger panel. The PSU for the MBP is rated at 85W so assume it will draw a maximum of about 10-20% less than that with the CPU GPU and both drives running flat out whilst charging the battery.

You can easily get single panels which are rated at 200W these days. Efficient or not, your going to have to use some kind of inverter from the batteries to the Apple charger. Deep cycle lead acid batteries are also the right call.
Whatever panel you go for you should at least get most of its rated power given all the sun it'll get in Africa (Not like the UK!). You just need to try and keep it out the way of the elephants.

[PB2K]

Hi thanks so much, sure there will be generators once in a while but I have been in situations where I was without a powered wall outlet for more than a week. Sunshine is abundant but it's incredibly boring without a computer and I learned my lesson ! if I go for solarpanels I would need this :

solargorilla (perhaps two) I already own one
powergorilla
magsafe airline adapter

It's also possible to have an ipad2 with keyboard. Having two expensive macbooks doesnt really make sense anyhow.

[ghporter]

Remember, Apple says the Airline adapter will NOT charge your computer. And it takes 15VDC, not 12...

[Waragainstsleep]

I was thinking something more like this:

FD200S - 2 x 100W PV Panels + SUN250

[PB2K]

I'm afraid they are a bit too big and not portable

[PB2K]

SPECS of my solarpanel :
Capacity: 500mAh @ 20V: 500mAh @ 5V
Unit Dimensions: 264 x 200 x 19mm
Unit weight: 700g
20V power out socket
5V Standard USB socket

what i remember from physics is that according to the above I do not have 40 Watts but 0.5mAhx20V=20W

[ghporter]

1/2A X 20V = 10W, not 20W. Not so great for running a device that uses at 5-11W while it's running. But if you use that output to charge a battery, the battery can help smooth out your usage and make the solar charger more effective for you.

[PB2K]

pfff 10 W is not enough for anything let me think of a solution

[PB2K]

i Found this on the Hewlett packard website

The Anywhere Solar SystemTM

For Laptops !

Power Conversion Unit Specifications:

400 watt continuous rating with an 800 watt surge provides sufficient power for two laptop computers or one desktop computer with LCD monitor.

Filtered sine wave output does not produce distortion on sensitive electronics.

Built-in transfer switch automatically transfers between inverter power and incoming AC power.

DSP control technology starts complex loads with ease.

Dual AC outlets and hardwire AC connections.

CSA/NTRL certified to UL458 and CSA 107.1

Battery over-voltage and under-voltage protection.

Battery over-voltage and under-voltage protection.

Over temperature shutdown.

Short circuit protection.

Ground fault protection (GFCI).

Dimensions (HxWxD) 3.3 x 7.4 x 13.5” (83 x 187 x 343 mm)

Weight 10.0 lb (4.6 kg)

Solar Charger Specifications:

The solar panel unit with integrated charge controller is rated at 85 watts and in full sunshine will produce up to 17.4 volts @ 5.02 amps. Includes a 1 year materials and workmanship warranty and a 20 year power production warranty. Dimensions are 39.6" x 25.7" x 2.3" (1007 x 652 x 58mm) Weight 18.3 Lbs. (8.3kg) Includes a 15 foot solar power cable and connection instructions.

Battery Specifications:

Universal AGM Battery 12 Volt 110 Amp Hour, maintenance free, valve regulated sealed lead acid battery. 72.75 LBS

Includes The Following Balance Of System Components:

60 Amp class T inverter fuse,
One pair of 5 feet, 6 gauge inverter cables red/black with ring terminals.
18" 6 gauge fuse cable for use in between the battery positive cable and fuse terminal with ring terminals.
Solar charger fuse with holder.
*230 Volt customers please note: The sun will be the only source of power for this 120 Volt Anywhere Solar System. The power cord that is supplied with this system can only pass electricity from a 100/120 Volt outlet, not a 230 Volt outlet.

**Your run time and continuous power rating may vary and is dependent on the internal battery's state of charge. The smaller the load that you are powering, the longer your run time will be.

This is interesting. HP also promises 32.5 hours of battery life with a 9 cell battery for their HP Elitebook (which looks like a powerbook g4 titanium)

A review on youtube says that the 3 cell Elitebook just delivers up to 5 hours.

[Waragainstsleep]

When you say portable....

Are we talking pack it up and carry it by hand or will it be in a vehicle? If you do enough miles it might be easier to charge a big rank of batteries off the alternator.

[PB2K]

It needs to fit inside a normal sized backpack when I check if schools and other buildings meet the requirements to receive a computer room for educational purposes. These locations come in all kinds. Some have no roof, some have no windows and most have no access to electricity, yet.

On a typical day I spend about 3 hours a day inside a car, that is when I should be able to charge my battery the fastest. But the solar option is interesting for the moments in weekends when I am stuck on a compound that has no source of electricity at all.

What I need is a laptop that consumes less power than my current MBP 15". An iPad has a 10 watt powercharger, which is the most promising performance I have witnessed so far. But I prefer a macbook (air) because it is so much smaller. I figured that a 11" MBA and a solargorilla+powergorilla ket might keep me running independent of powersockets.

That's why I am inquiring if the solarpanel (or perhaps two) provides enough power to power this MBA. Otherwise I might choose the iPad2.

[Waragainstsleep]

Is it always the same powerless weekend compound? Is it always the same car?

[SierraDragon]

Double post.

[SierraDragon]

Originally Posted by PB2K 

It needs to fit inside a normal sized backpack... On a typical day I spend about 3 hours a day inside a car, that is when I should be able to charge my battery the fastest. But the solar option is interesting for the moments in weekends when I am stuck on a compound that has no source of electricity at all.

Like I said on March 5th, you could use a solar panel to charge a lead-acid battery when you are not driving. The battery can be recharged by your vehicle while you are driving. Glenn pointed out that inverters are inefficient so you need a converter to provide the voltage/current that the laptop needs.

First you should get a 12 volt battery and appropriate converter and experiment to see how long the laptop runs on a charge. My guess is that simple available-anywhere lead-acid batteries will obviate the need for expensive/bulky solar panels.

Off track simple is invariably the best way to go. Note that the "Solar Anywhere" setup you referenced weighs more than 80 pounds and is fairly complex. For a lead-acid battery setup the converter is only slightly complex and is light enough that you can carry spares.

If you routinely fully discharged the battery you would need more expensive deep cycle batteries, but my guess is one or two 12 volt automotive batteries will suffice. I spend 20 weekends a year in a remote cabin using a single 12 volt battery charged at home. My neighbor at that location has a solar setup on her cabin but she lives there full time all summer and takes the collectors when she leaves.

For transportable on a single vehicle, another friend travels around the country in a van with a solar panel on top charging 12 volt batteries, and domestically that is a great way to go. However in central Africa I would be concerned about too much complexity as well as about theft issues. Only one part of a complex system needs to fail or be stolen to shut it all down.

-Allen

[PB2K]

Thanks Allen i will take it into account !

[turtle777]

(To add to what Allen said.)

Using a (lead-acid) car battery for that pupose is generally a bad idea.
They are not designed for repeated deep-cycle discharges.

HowStuffWorks "What's the difference between a normal car battery and a deep-cycle battery?"

A car's battery is designed to provide a very large amount of current for a short period of time. This surge of current is needed to turn the engine over during starting. Once the engine starts, the alternator provides all the power that the car needs, so a car battery may go through its entire life without ever being drained more than 20 percent of its total capacity

What you need is a lead-acid deep-cycle battery. Those are more expensive than a plain vanilla car battery.

For a few cycles, a car battery might be ok, but you'll prbably kill the battery sooner than later.
Depending on how long you are out there, this might now really be a reliable solution.

-t

[SierraDragon]

Based on my experience improperly using auto batteries for deep-cycle usages (automatic bilge pumps, music for a remote mountain cabin) for decades I would expect a battery charged daily except weekends to last for at least one summer, probably longer. I have always used regular auto batteries because the deep cycle batteries are so expensive and I tend to multipurpose them. I always do try not to 100% discharge such batteries.

The good news is 12v auto and motorcycle batteries are inexpensively available everywhere if you kill it by too much deep cycling. I would test on a motorcycle battery just because they are so conveniently smaller.

-Allen

[PB2K]

my options :
Solargorilla + powergorilla + magsafe airline adapter = for emergency use in the most remote areas (totals 450€)
a magsafe car charger when on the road (70€)
a normal magsafe charger when on the grid (70€)

When I am around the equator I will do a full review and share it with you. I am really looking forward to this experiment.