An open community 
of Macintosh users,
for Macintosh users.

FineTunedMac Dashboard widget now available! Download Here

Topic Options
#49371 - 07/06/18 10:02 AM Ever charge a laptop with a solar panel?
deniro Offline
Temp Banned

Registered: 09/09/09
I've read about portable solar panels, such as the Anker, that claim to charge laptops. Anyone every try one?
_________________________
OS X 10.11.6
iMac 21.5", Mid 2011
2.8 GHz Intel Core i7, 24 GB
AMD Radeon HD 6770M
Using Apple computers since 1980

Top
#49389 - 07/07/18 09:14 AM Re: Ever charge a laptop with a solar panel? [Re: deniro]
Ira L Online


Registered: 08/13/09
Loc: California
I would first do the math—what are the demands of the battery to charge and what can the panel produce?
_________________________
On a Mac since 1984.
Currently: 27" iMacs, Macbook Air, macOS 10.14.x,; iPhones, iPods and iPads galore!

Top
#49394 - 07/07/18 12:04 PM Re: Ever charge a laptop with a solar panel? [Re: Ira L]
joemikeb Online
Moderator

Registered: 08/04/09
Loc: Fort Worth, Texas
I have not used one myself, but from what I have read on RV and camping forums and magazines solar panels such as the Anker are adequate for charging an iPhone or iPad if they are left on charge pretty much from down to dusk.

The Anker charger puts out a MAXIMUM of 3 Amps (15 Watts) to each of 2 ports and is marketed for use with smart phones and tablets. The lowest powered laptop power adaptor Apple produces is 45 Watts and current MacBooks and MacBook Pros use 60 to 87 Watt power adaptors.

While I have not used portable solar panels I do have 45 permanently installed on my roof and they typically reach their peak output only 1 or two hours out of a typical day and the drop off in energy production on either side of that peak is steep. Let a cloud drift by and the output can easily drop to zero. So unless you are constantly chasing the sun with a portable solar panel the average output will probably be significantly less than half of the peak. You can buy solar panels at RV and camping stores that are capable of putting out 60 to 120 Watts, but those are mostly made to mount on the roof of your vehicle and are not conveniently man portable. Generally they will also require additional electronics to make the energy produced usable.
_________________________
joemikeb • moderator

Top
#49405 - 07/10/18 09:15 AM Re: Ever charge a laptop with a solar panel? [Re: deniro]
Virtual1 Online


Registered: 08/04/09
Loc: Iowa
Originally Posted By: deniro
I've read about portable solar panels, such as the Anker, that claim to charge laptops. Anyone every try one?

I've got a reasonable amount of experience with solar. First things first: solar does NOT provide a lot of power, unless you have a big panel.

As an example, there are some USB power banks with solar panels on them that actually discharge the battery while in the sun most of the time, because the charging electronics draw more power than the panel produces, in all but the brightest of sun. Don't bother with anything less than a square foot of cell area.

Second, USB devices are easier to charge because they use low voltage DC power. The optimum arrangement is to get a decent capacity (10,000mAH) battery bank (I prefer Kmashi, <$20 shipped from Amazon) and use a fair size solar panel to charge that. Then use the bank to charge the device. You'd be correct to point out that converting power once instead of twice is more efficient, however it's not often convenient to leave your device by the panel. Fill up the bank whenever the sun's available, and use the bank to refill the device when needed, including when it's dark or you're on the move. (or using your device) Plus, if your panel is putting out 15w and your phone can only draw 10w at a time, you are throwing away 5w of power by charging your phone directly. You want that to top into your bank for use on another recharge later when the sun's not out.

I got a killer deal last year on one of these, I think I paid $60 for it.
https://www.amazon.com/StrongVolt-SV-18WFLDBLK-Strong-Solar-Charger/dp/B00XM7OIO2
This is the sort of thing you want at the minimum - 18 watts of tri-folding panels. Anything less than 18w is a waste of time and space. Don't save and get two panel. Make sure the panels are big.

I also bought several SUAOKI 20W Solar on sale a few years ago for about $35 ea. Sold them to friends who where very grateful to have the deal. https://www.ebay.com/itm/292591224226

Both put out about the same power, so the Suaoki are definitely a better deal. They are almost useless when slung on the backpacks as often shown. Lay them out so they are directly facing the sun for best output, angle is very important and 30 degrees off can cost you half your output power. This means they need to be adjusted several times during the day if you've got a lot of charging to do.

Kmashi banks are holding steady on price and are good quality. https://www.amazon.com/KMASHI-10000mAh-Portable-Power-Output/dp/B00JM59JPG


Charging laptops is more difficult because they all have their own custom DC ports, convert down to a wide variety of DC voltages, can be very picky about the power they receive, and usually end up being more convenient to just use their 120VAC adapter pack to charge from. This not only makes conversion less efficient, but adds another step in the process. A substantial panel will be needed to charge the higher capacity battery also.

Here's my suggested "kit" for laptops:

panel: https://www.ebay.com/itm/372060104057 (I own two, they work VERY well and are light and semi flexible, BIG plus for portability)

charge controller: https://www.ebay.com/itm/273205062626 (there are many out there, get one that's "MPPT" and has an LCD display) I've got several controllers and they all work more-or-less equally well.

Then find your car battery of choice. junk yards get $22 or so for a good used car battery. ask for the largest one they have available, there's no difference in price! You can skip the battery and lighten your load, but charging will be spotty at that power level without a battery to buffer the power. At least get a small lawn tractor battery.

I don't have a preference for inverter, but you should get one rated 300w because of how over-stated their ratings are. 150w inverters will likely overheat and run inefficiently at the full 70w draw from a MacBook pack. Here's an example I spotted, though I have no experience with this specific one: (ymmv) https://www.ebay.com/itm/201941981951 - "pure sine wave" look better and are, but you don't need that and it makes the inverter less efficient, at a time when power is a valued resource.


Watch for deals on solar, they do pop up from time to time on Amazon and Woot. (Black Friday is coming up too)
_________________________
I work for the Department of Redundancy Department

Top

Moderator:  alternaut, cyn