[Q] Portable Solar Panels and the TF101 - Eee Pad Transformer Accessories

Hi,
I plan to disappear into the woods and come back out when I've finished my thesis (more or less). So I'm interested in buying a solar panel to use with my transformer and since people here seem pretty knowledgeable about charging the transformer I thought I would run it by you guys to make sure I do not miss something important.
I've gathered so far that I will need at least an 11v panel.
Also, it seems I need USB 3.0 to charge by USB. Is this correct?
And if I can't get USB 3.0 I will have to modify a 2.0 wire or plug or whatever... I prefer to avoid this
What should I go for in terms og Watts?
Would it be reccommendable to buy a panel with a battery to get a more even current?
Recommandations would be great!

---

Wow, I thought I was the only one that even remotely cared about this!
I have a Goal0 Nomad 7m. It's 12v, and I have had no luck getting it to charge my TF. Do you think it might be because of the USB 3.0 requirement?

---

Great that I'm not alone! Too bad that it doesn't work though...
I got the thing about USB 3.0 from this thread;
http://forum.xda-developers.com/showthread.php?t=1087321
reading it again I noticed this line;
"The Asus charger does need a 3.0 cable extension to work. But with a DIY charger you don't need USB 3.0 cables or connectors."​
So I'm not really sure if it makes a difference whether you use USB 2.0 or 3.0.
Anyway the specs for your Nomad says that it's 5v for USB output and 12v for DC output so I'm guessing that's why it doesn't work with the transformer.

---

Miki T. said:
Great that I'm not alone! Too bad that it doesn't work though...
I got the thing about USB 3.0 from this thread;
http://forum.xda-developers.com/showthread.php?t=1087321
reading it again I noticed this line;
"The Asus charger does need a 3.0 cable extension to work. But with a DIY charger you don't need USB 3.0 cables or connectors."​
So I'm not really sure if it makes a difference whether you use USB 2.0 or 3.0.
Anyway the specs for your Nomad says that it's 5v for USB output and 12v for DC output so I'm guessing that's why it doesn't work with the transformer.
Click to expand...
Click to collapse
You're right!...that actually means there's options. Shouldn't something like this work?
http://www.amazon.com/Portable-Inve...=UTF8&coliid=IUJZFD56YRM5K&colid=HQA2VAAM7MXY
I think I'm gonna have to order this, and give it a shot. I already have the panel & the DC jack, so I might as well.

---

Hey nice find! It seems like it should work, though don't take my word for it. I'm really ignorant of this stuff which is why I started the thread to begin with In any case $22 for a charger sounds fairly cheap.
Let me know if it works or not!

---

Solar panels that put out more than 28W (5V, 2A = 10W + 15V, 1.2A = 18W) would be enough, but then you'd likely want to run it through an inverter to get 110v AC, then the ASUS charger.
Until and unless ASUS comes out with a car charger that would work with the dock, running an inverter to generate an AC signal, then running it through the AC adapter will be the way to go.
Figuring in efficiency losses, you'll probably want 50-75W worth of solar panels for this to work. You can also use a 12v battery as a ballast.

---

FrayAdjacent said:
Solar panels that put out more than 28W (5V, 2A = 10W + 15V, 1.2A = 18W) would be enough, but then you'd likely want to run it through an inverter to get 110v AC, then the ASUS charger.
Until and unless ASUS comes out with a car charger that would work with the dock, running an inverter to generate an AC signal, then running it through the AC adapter will be the way to go.
Figuring in efficiency losses, you'll probably want 50-75W worth of solar panels for this to work. You can also use a 12v battery as a ballast.
Click to expand...
Click to collapse
You don't need 5V and 12V, only 12V. The Asus charger only puts out 5V for non-transformer devices. Don't introduce all the loss from the 110V converter, just charge a 12V battery with a panel(the Asus will draw 18 watts at full charge), then charge the transformer from the battery. Just get a usb extender, cut it, and hook negative to pin 4 and positive to pin 1. I would recommend a 5 Ohm resistor to limit amperage, but it isn't necessary.

---

I'd like to hear how it works out.
I was considering putting some flexible solar panels on the back of the transformer. But with the dock, I've got more than enough power for my needs. Plus, the back of the transformer won't get that much sunlight.
I'm now moving on to trying to put solar panels on the back of my cellphone (Huawei U8800). It's a great phone, and the battery lasts all day, so long as I don't play too many games.
One thing you might want to consider is an external battery pack. They are pretty cheap here in China, and have huge batteries in them. They even have some with built in solar panels. I'm sure you could find one that could recharge the Transformer. Then you could have the battery pack in the sun charging via the solar panel, and you sitting in the shade with the transformer. At night plug the battery up to the transformer to let it charge while you sleep. The transformer with dock should have more than enough battery life to last all day.
If I come across any useful information during my research, I'll let you know.

---

Miki T. said:
Hey nice find! It seems like it should work, though don't take my word for it. I'm really ignorant of this stuff which is why I started the thread to begin with In any case $22 for a charger sounds fairly cheap.
Let me know if it works or not!
Click to expand...
Click to collapse
I bought it! ...and it will be here this afternoon. Thanks to Amazon Prime local delivery .
I'll let you know how/if it works out.

---

philburkhardt said:
I bought it! ...and it will be here this afternoon. Thanks to Amazon Prime local delivery .
I'll let you know how/if it works out.
Click to expand...
Click to collapse
Stuff like that is great for the car, but you're gonna lose SO much efficiency through it, then even more loss from the Asus charger plugged into it. A 15W solar panel should be enough to charge the TF directly. Using an inverter with the asus charger, you'll probably need 50-100W. Just FYI.

---

msticninja said:
Stuff like that is great for the car, but you're gonna lose SO much efficiency through it, then even more loss from the Asus charger plugged into it. A 15W solar panel should be enough to charge the TF directly. Using an inverter with the asus charger, you'll probably need 50-100W. Just FYI.
Click to expand...
Click to collapse
Yup, you're right. No go on charging the TF. Like you said, it will be great for charging things in the car. Just not off my 12W solar panel. I think I'm gonna have to upgrade my panel .

---

philburkhardt said:
Yup, you're right. No go on charging the TF. Like you said, it will be great for charging things in the car. Just not off my 12W solar panel. I think I'm gonna have to upgrade my panel .
Click to expand...
Click to collapse
The real joy of the TF is that it charges directly from 12 volts, so, assuming you have a 12 volt 12W panel, you should go get a 12 volt battery, 4AH(amp-hour) at least. It will be about the size of an old 6 volt lantern battery. Hook the panel to the battery to charge the battery, hook a female usb port to the battery, and hook the TF directly to the female usb port. You'll probably be able to get through a whole night on a 4AH battery + the TFs battery.

---

Great! Lots of useful replies... thanks a lot!
I plan on not using the adapter and use a USB extender the way msticninja wrote, since I don't want to carry or pay for something that delivers 50-100W.
I think I've found the panel I am going to buy. I cannot include outside links until I've posted 8 messages, but you can easily find it by googling "Portable 9x 2.5 W Solar Panel". So 22.5 Watt... that should suffice. That's at 18v * 1.25a.
It seems that all the solutions that comes with a battery are all quite pricey, but then I don't really need some fancy battery do I? Some do-it-yourself solution should be fine as long as the battery is rechargeable, 4AH("at least") and 12v right?
Do I want to reduce the voltage of the solar panel to 12 instead of 18? And should I worry about overcharging the battery?
By the way, is the battery an absolute necessity or is that only if I want to charge during the evening/night?
What I hope to be able to do is; be away from mains for about one week at a time, and use my laptop, say, 8 hours a day. I hope this will be enough...

---

Miki T. said:
That's at 18v * 1.25a.
Do I want to reduce the voltage of the solar panel to 12 instead of 18? And should I worry about overcharging the battery?
Click to expand...
Click to collapse
The Asus charger will put out 15V at most, as marked on the charger itself. I don't think I'd use anything higher than 12V into the tablet/dock. You'd probably want to use some kind of voltage regulator to drop the 18V to 12V.
Without knowing the internal workings of the dock/tablet, I can't really comment more than that.

---

Miki T. said:
Great! Lots of useful replies... thanks a lot!
I plan on not using the adapter and use a USB extender the way msticninja wrote, since I don't want to carry or pay for something that delivers 50-100W.
I think I've found the panel I am going to buy. I cannot include outside links until I've posted 8 messages, but you can easily find it by googling "Portable 9x 2.5 W Solar Panel". So 22.5 Watt... that should suffice. That's at 18v * 1.25a.
It seems that all the solutions that comes with a battery are all quite pricey, but then I don't really need some fancy battery do I? Some do-it-yourself solution should be fine as long as the battery is rechargeable, 4AH("at least") and 12v right?
Do I want to reduce the voltage of the solar panel to 12 instead of 18? And should I worry about overcharging the battery?
By the way, is the battery an absolute necessity or is that only if I want to charge during the evening/night?
What I hope to be able to do is; be away from mains for about one week at a time, and use my laptop, say, 8 hours a day. I hope this will be enough...
Click to expand...
Click to collapse
You will need some sort of voltage regulation to maintain 12V. That's pretty much a requirement for any solar charging system. Panels themselves do not usually have regulation, so the output voltage of the panel is a function of the amount of light the panel is receiving.
This is a really quick search, but this satisfies all the requirements for what you need, and it's only $20:
http://www.amazon.com/Ramsond-SunShield-Charge-Controller-Regulator/dp/B0031FQ1S6
Feel free to search for alternatives, but use that as your starting point for searching.
Another quick search to give you an idea what you're looking for as far as batteries:
http://www.google.com/products/catalog?q=12v+4ah+battery&oe=utf-8&rls=org.mozilla:en-USfficial&client=firefox-a&um=1&ie=UTF-8&tbm=shop&cid=15393345737619657558&sa=X&ei=lq5MTsCGGMSCsgLgivmCBw&ved=0CHIQ8wIwAA
If I made something for myself, I'd use Lithium Ion cells and use a smart lipo charger to regulate the solar panel output, but it needs more research, and will cost more.

---

This will be interesting!
I've ordered the parts - the panel I mentioned, the Ramsond SunShield 12V 8A Solar Charge Controller Regulator that msticninja suggested and a Super Rechargeable Li-ion Battery, 12V 6800mAh. I ordered the panel and the battery off of sunsky. They seem to have very fair prices.
All the parts came to a total of $164, shipping included. Compared to complete sets with the same specs I'd say that's a really good deal, provided I make it work
I'll let you know!

---

Miki T. said:
This will be interesting!
I've ordered the parts - the panel I mentioned, the Ramsond SunShield 12V 8A Solar Charge Controller Regulator that msticninja suggested and a Super Rechargeable Li-ion Battery, 12V 6800mAh. I ordered the panel and the battery off of sunsky. They seem to have very fair prices.
All the parts came to a total of $164, shipping included. Compared to complete sets with the same specs I'd say that's a really good deal, provided I make it work
I'll let you know!
Click to expand...
Click to collapse
Give me a link to that Li-ion battery. If it doesn't have it's own charging circuit, you'll need to get a lipo charger instead of/in addition to the Ramsond regulator. I'll check it out for you.
EDIT: If it's this one: http://www.ebay.com/itm/DC-12V-6800mAh-Super-Rechargeable-Lithium-ion-Battery-/150530536976
it's hard to say, but I think it has it's own charging circuit, because the wall wart included with it doesn't look like a lithium charger. But it does have a charge finished light, so, if the light stays on when the battery isn't plugged in, you should be okay. If the green light only turns on when a fully charged battery is connected, then you might not be fine. Confirm what you're getting by posting a link, and I'll try to make sure. If it doesn't have it's own charging circuit, the battery will explode in a fireball.
EDIT2: This one has it's own charging circuit, and it sounds like it's what's inside the other one I linked, so you should be okay if it's either of these.
http://www.lunershop.com/product_info.php?language=en&currency=USD&products_id=2566

---

Just wondering if something like this would help.
http://www.ioffer.com/i/solar-battery-panel-usb-charger-for-cell-phone-mp3-mp4-147450373?source=eisi
I have no understanding of electricity, except the basic 4th grade stuff. This is a cool project thought. I'm planning on making a 55 paracord strap that will attach to my case and fit like a messenger bag. Having solar panels to charge it and a paracord strap would make the TF a nice camping device

---

SwiftLegend said:
Just wondering if something like this would help.
http://www.ioffer.com/i/solar-battery-panel-usb-charger-for-cell-phone-mp3-mp4-147450373?source=eisi
I have no understanding of electricity, except the basic 4th grade stuff. This is a cool project thought. I'm planning on making a 55 paracord strap that will attach to my case and fit like a messenger bag. Having solar panels to charge it and a paracord strap would make the TF a nice camping device
Click to expand...
Click to collapse
Nope, as discussed before, the TF uses 11-15V to charge, and normal USB chargers/backup batteries only put out 5V.

---

msticninja said:
Give me a link to that Li-ion battery. If it doesn't have it's own charging circuit, you'll need to get a lipo charger instead of/in addition to the Ramsond regulator. I'll check it out for you.
EDIT: If it's this one: http://www.ebay.com/itm/DC-12V-6800mAh-Super-Rechargeable-Lithium-ion-Battery-/150530536976
it's hard to say, but I think it has it's own charging circuit, because the wall wart included with it doesn't look like a lithium charger. But it does have a charge finished light, so, if the light stays on when the battery isn't plugged in, you should be okay. If the green light only turns on when a fully charged battery is connected, then you might not be fine. Confirm what you're getting by posting a link, and I'll try to make sure. If it doesn't have it's own charging circuit, the battery will explode in a fireball.
EDIT2: This one has it's own charging circuit, and it sounds like it's what's inside the other one I linked, so you should be okay if it's either of these.
http://www.lunershop.com/product_info.php?language=en&currency=USD&products_id=2566
Click to expand...
Click to collapse
Fireballs are serious business...
The one I ordered is the blue one. I can't really confirm with a link since I cannot post external links until 8 posts but there shouldn't be any mistake. And it does say the following about it;
With its multi-protective device, the inner circuit pervents the box from over-recharging or over-discharging.​so it should be safe I think...