It looks like Voltaic will be releasing a 14w solar panel bag, a huge step up from their, largely useless, at least for UMPCs, 4W bad. I hope its not a typo as the three-panel setup look exactly the same as before.

If it really is 14W then I’m interested. Well almost. The design is a little on the ugly side and the price of $559 means I could actually buy a stack of spare Li-ion batteries that, charged, would run a UMPC or one of the new Menlow-based MIDS showing up at CES for a few weeks or more!

This story is from CNet and the author mention in the article that they will be running a story about solar laptops soon. That should be interesting and one to look out for.

Thanks to Matt for the tip.

It’s nice to see that someone else is as tech mad as me! Scott, currently residing in Cubicle 13, has decided to get out of the rat race for 18 months and he’s taking a UMPC and Solar panel with him.

18 Months! 6 months of that will be on the Appalachian trail!

Scott is taking the ac-inverter route with his solar solution so it will be interesting to see how he gets on. He doesn’t set off for another 78 days so there’s time to get the kit in order!

His first tech task was to buy the Raon Digital Everun that he’s planning to use and get it protected in some way. He’s currently testing out a modified OtterBox.

I’ve promised to help out with the testing. I’m just about to go outside and plug my Raon Digital Everun directly into a solar panel as a test. Luckly I have a spare power board for it so if I get any of that magic smoke, I should still be OK!

Scott’s blog was: Escape from Cubicle 13

Last Thursday I spent a lot of time analyzing exactly how efficient my charging solution was with a real-life test. What dropped out was a rather poor picture of how inefficient the whole solar charging setup was. From over 1.2KW hitting the area of my solar panel I managed to use about 19W. That’s a 1.5% efficiency rate and its amazing that I was able to do anything with it!

Take a look at the diagram again below. it shows the loss-points along the route from the sun to the UMPC.

More efficient UMPCs?

Of course! Any improvement in efficiency here would help. Currently a good average is around 9W and if this could be reduced to 6W average, it would be a major improvement.

Bigger battery life?

No. For my tour, the battery life or battery capacity was really not an issue. 50W/hr per day total capacity (via two battery packs; one that can be used and one that can be charged, is ideal.)

Solar Panel improvements.

From 1.2KW that hit the panel, only 660W hits the solar cells and those cells are only around 8% efficient and this is the first place we can look for improvements.

Current top-end production solar panels are 22% efficient but these are hard panels. To get the equivalent of 25W power you would need a hard panel of about 35x35cm plus frame. Lets say 40cmx40cm in total area. By using a hard panel of this size I could have actually put one on the front and one on the back of the bike to achieve a much more powerful solution. Finding a 40x40cm high efficiency panel might have been difficult though and probably less rugged. There could be a weight consideration too. Given the space restrictions on a bike, I think that a hard panel solution might have been better. In the campsite it wouldn’t have made much difference. The foldable panel was light and small and there should be no need for more than 25W of max power.

Battery tech and charging methods.

There’s a lot that needs to be improved here and the improvements can be achieved through a combination of process and of technology. What follows are the most important issues.

Lead-acid out!

The lead-acid battery proved to be a hindrance more than a help. It was heavy. It had no charge level indication and at low charge levels it couldn’t deliver enough current to drive my DC DC converter or even charge the AA batteries. In short, I didn’t use it much at all and I would drop it from my kit list if I did it again.

Li-Ion problems.

I knew that charging a battery just to have it charge another battery would be inefficient but I didn’t realize that it could be so bad. For example, the Li-Ion battery pack I have (Tekkeon/Tablet Kiosk MP3400) appears to lose about 25% energy through the input and Li-Ion charging stage. That is, you have to pump something like 20% more energy into it than it can store. But that’s not the whole story. The voltage conversion process on the output stage kills another 20% of the energy! From input to output you’re losing a shocking 40% or more energy!

But there’s another problem too and i’ve mentioned it before. The charging of Li-Ion batteries occurs at a fixed rate which means however much energy you have available and however quickly you could feed it into a Li-Ion battery, it won’t take it any quicker than its designed for. The MP3400 takes about 15W (about 0.8A at 19V) of energy to charge it and even if I attached a panel capable of delivering 50W, it would still only take 15W wasting a huge amount of available energy.

This last problem is the one that needs attention when designing a solar charging solution. I have detailed some possible solutions at the end of this article.

Direct charging UMPCs from solar.

One thing that I found annoying was that the only was I could charge my UMPC battery safely was to charge it from the Li-Ion battery. Obviously this is inefficient for the reasons mentioned above but why can’t I charge the UMPC direct from the solar panel? The main problem is that the DC input circuitry on the UMPC is an unknown factor. There’s no way to tell if there is over-voltage protection or whether it will charge a through varying input voltages and its just too much of a risk to try it out. When the DC input on the UMPC is broken, so is the UMPC! I also though about trying to charge the UMPC battery on its own but there’s no standard in connectors or charging currents and voltages so unless you want to build your own charging circuit, this isn’t possible (with the one exception of the OQO Model 02 that has an external battery charger.) I don’t really see this changing much on UMPCs in the near future though. There’s no real reason to increase the complexity of the DC circuit just because Chippy and a few others wish to use solar panels!!

How to improve the solar charging process today…

The Sunlinq 25w panel and Tekkeon MP2400 battery pack is an easy option, readily available and relatively cheap. It works, and if you use the tips above, it can be quite succesful but there are further improvements that could be made, especially if you have the time a flexibility to adjust your solution as you go. Lets assume the lead-acid battery option is too heavy and will not be used.

Ideally you will have the flexibility to add load and add solar capacity as conditions vary. This requires multiple smaller solar panels and multiple smaller Li-Ion batteries that can be set up in different situations. This is currently the only way to provide the most efficient charging solution. Buy multiple slow-charging (500mA for example) Li-Ion battery packs that can be stacked in parallel as energy availability increases.  You will need a voltage regulator on the output of the solar panel and this will need to match the input voltage of your charging solution. Preferably 12V. Fit an ammeter and voltmeter to the output of the voltage regulator so that you can monitor load and voltage. This all takes a lot of time and effort though and for most people its not worth the trouble. Ideally you would have a smart charger that does the monitoring and switches in Li-Ion packs as current availability increases. I have not seen such a solution yet and this, along with some more advanced solutions is what I’d like to see in the near future.

…and in the future.

How about a Li-Ion battery pack that has three levels of charging speed. Low, Med and High. These can be manually adjusted to match the energy available. Ultimately you would have a Li-Ion battery pack that self adjusts to the input current available. I have seen a few advanced components that claim to be able to do this but have never seen a consumer product that is able to do it. If you can get vari-charging Li-Ion batteries then there is really no need for the heavy lead-acid battery at all.

Finally, I’d like to see more UMPCs that have an external battery charger with good, efficient circuitry, over voltage protection and a wide range DC input voltage. Currently there are very few options here.

I’ll be watching this space carefully from now on and I hope that it won’t be long before I can report about new solutions to the issues of solar power and battery charging.

When I did my first tests and calculations about the use of solar power to drive a PC I was quite amazed at the inefficiency of the process and today’s ‘laboratory conditions’ test proves just how much room for improvement there is. It’s thanks to devices like UMPCs that this is project is at all possible because I really doubt it would have worked with even a ‘power saving’ notebook PC.

Today I stayed at the campsite and put the Solar panel and Li-Ion battery through a 3 hours test. Its was a cloudless day with a very thin haze, 22 degrees centigrade and for reference I’m located at about 50 degrees north and 7 degrees east. The date is the 30th of August which is heading towards Autumn here in Germany. The test was done from 11:00 – 14:00 and I took the empty Li-Ion battery and charged it with the solar panel for 3 hours.

I estimate that about 1.2KW of energy hit my 7000 cm2 panel with about 660W falling on the Solar cells (3500 cm2). After conversion to electricity it created about 50w/hr of energy. Of that, about 40W was taken by the Li-Ion battery because it only uses a fixed current and voltage. It won’t adapt to the power available. Due to input voltage conversions and charging losses, this left me with an estimated 30W of energy and after taking this through yet another set of voltage conversions and charging process, left me with a rather poor 18W of power. Of course this is enough for a few hours of work but isn’t it incredible that so much power is wasted (or rather passed back as heat!)

I spent the rest of the afternoon trying to work out how this process could be improved and I’ve come up with a list of ideas that could help. I’ll talk though them in the next post but right now I need to put some more cream on the back of my legs because through all the concentration I forgot about the sun and I’ve burned the bit right behind the knee. That’s going to be really enjoyable tomorrow when I make the 70km dash to Bonn.

Here’s a diagram I created quickly on the Q1b. Hopefuly it makes things a bit clearer. How would you improve the architechture?

I don’t really understand why I didn’t try this before. Its simple. its recommended and it works. Have I been too focused on flexibility why simplicity could be the answer?

I was speaking to Chris from Euro-Line, an importer of consumer solar products and he highlighted a document that I’d already seen. I took another look and staring me in the face was a recommended and tested solution using equipment that I already have. Its the same setup that I tested with the P3 panel. Just plug the panel into the Tekkeon MP3400 and wait for enough sun. You might remember back in the early posts that this is how I found out that Li-Ion charging solutions where not so efficient and how it set me on the path to research a more flexible solution.

With the ’12v’ 25w Sunlinq panel I have I assumed that a 12V output wouldn’t drive a 19v input and after looking at the diagram again I though ‘why are they recommending this solution? It shouldn’t work.’

Image taken from GlobalSolar.com PDF here.

Looking more closely at the specs of the panel, its clear now why it works. The 12 panel isn’t strictly 12V. The voltage varies according to the load and in fact with an open circuit the voltage is way up over 20 volts. However, with a load of around 800mA, the charging current for the power bank, the voltage sits nicely at around 20V. Tada!

With a 25W panel, 800ma at 19V is reached at around 60% sun power. On a clear summer day here, the sun is over 60% power for around 5 hours between 11 and 4pm. The charger needs 4 hours to load up 56W of energy.

Now here’s an idea. Between 12 and 2, the panel is producing 40% more energy than the Li-Ion battery is taking. Can I mop that up with a lead-acid battery?

Testing continues…

In a recent comment here, someone asked why the Lead-Acid battery was needed. Its probably not too clear in the video why I use it so I reproduce my answer (which comes from the best of my knowledge!) here.

There are two main problems with charging Li-Ion batteries from Solar panels.

Firstly, Li-Ion batteries (in notebooks and battery bank) charge using a constant current (stream) of power. For common notebook batteries and battery banks such as the Tekkeon MP3400, this is around 1A. A lot of the 12V portable solar panels only reach this power at high sun levels meaning you can only use them for a few hours mid-day. In fact a 12W panel might not be enough to even start the charging process. Secondly, if you have a huge panel that could deliver, say, twice as much power as needed, its not used. Only the power needed is taken. The rest is wasted.

These two problems can be overcome at the expense of weight with a lead-acid battery.
L-A batteries are more flexible. You can charge them with a trickle and also with a higher charge rate. They are much more suited to pairing with a solar panel. The problem with this solution is weight. Small 12v L-A batteries are over 2KG in weight!

What’s needed is a flexible Li-Ion battery charging solution. Currently there are no products on the market that can archive this but I’m searching hard!

In summary there are 2 solutions.
1 – Get a panel powerful enough to charge a Li-ion battery at 70% of its rated output. For example, a 25W panel and the Tekkeon MP3400 Li-ion battery. This will give you about 4 hours of charge time on a sunny summer day.  (Mid-Europe) This should be enough to completely fill up the Li-ion battery.
2 – Go for a heavier solution with a L-A battery and give yourself more charging flexibility.

Encouraged by yesterdays progress with the solar kit, I spent most of today finishing off the wiring and packing it all into a plastic box. I then paired down my kit list somewhat (out goes the Nokia N800 and spare mobile phone, two pairs of underwear, one of the t-shirts, the multimeter and a pair of trousers) and loaded everything up on the bike to see what sort of weight I was dealing with. The total wight of the bike and kit together (that’s biking, camping and computing gear) comes to 55KG. I have some food and bits and pieces to add to that so lets call it 60KG. Considering the bike weighs 25Kg that means I’m going to be carrying a 35Kg office. I took the bike for a ride and it seems pretty stable although I am a little worried about brake failure. I only have a back-pedal brake and while its very good I’m in serious trouble if it fails. I’m thinking about getting front brakes fitted this week. I also notice a small S in the back wheel. Its out of alignment and I hope that it can be brought true again by a local bike shop. If not, I’m probably in trouble and might have to switch bikes. I don’t want to do that as I really like FK398. Its been a work horse for 4 years and it deserves to be in the tour. It also looks great. I love the retro style.

 
About 90% loaded. The Kronan feels OK to ride with 35KG on it.

Another problem I really need to think about is the positioning of the solar panel on the bike. I can easily deploy 50% of it across the rear baggage but that’s not really going to be enough. I should have tried to find two separate 12W panels and mounted them front and rear but its too late for that now and I’ll have to work round it. In this part of the world, the sun gives you about 4 full-power hours per day. With a 50% deployment of the panel, that’s only 48W/hrs. Short of the 60W/hrs I think I need per day. However, what I could do (and I really like the sound of this idea) is take a 2 hours working break between 12 and 2. This should give me close to 50W/hr of energy assuming the sun is shining. Outside these hours I might pick up another 10-20 w/hr so that’s 70W/hr of energy from the panel in a day. It looks like its possible and I will test the theory this week.

Under the seat is the battery and electrical kit. It weighs something like 5KG but packs an 80W/hr lead-acid battery and a 56W/hr Li-Ion battery. Enough to take a full days energy from the solar panel. 

There’s about 5KG going on the front rack. Its not attached to the forks so doesn’t affect steering as much as panniers would. I’m thinking of using it as a computer table in the evening but I can’t find a good enough stool. 

Mounted on the front handlebar are the Garmin Etrex GPS logger and a Plexiglas map holder. I will get some rain covers and more straps for the equipment. The Q1b UMPC sits in the right hand pannier its its organizer case and wrapped in clothes. I will have to be careful about making sure the device is in hibernation before I ride. If its in standby and then goes into hibernation it will have to start-up the disk. I don’t want that to happen while I’m riding as it could be fatal.

The new tent has arrived, the bike baggage, and finally, some warmer weather so I’m taking the chance to test things out in the garden. My daughter is nearly asleep in the tent and I’m perched outside with the Samsung Q1b and organizer pack resting on one of my panniers, a clip-on LED lamp a paraffin lamp and a bottle of Germanys best beer!

This is the perfect time to be writing because its dark and you only need the minimum of backlight on the UMPC. As I write this with WiFi on, I’m taking between 6.5 and 8.5W on the UMPC. Its also wonderfully quiet.

Behind me, in the spare bedroom, I have started to lay out everything I need for the tour. I’ve written the pack list and there are only a few more things to buy before I’m ready to go. I hope it all fits into the panniers I bought for the bike which, incidentally, is going to be the blue Kronan.

A few things that haven’t turned up yet are the Lead-Acid battery and the solar panel. They should be here on Monday which will allow me to build the frame that the panel and battery will sit in on the back of the bike. I’ve ordered a could of panel meters too because I want to see what sort of drain each component puts on the panel.

One thing I was a little disappointed to find out tonight is that in theory, DC-DC conversion will cost at least 25% of my energy. That’s rather a lot to be wasting just to transfer energy, especially if I charge the Li-Ion battery from the 12V lead acid battery. I could lose an hours computing time just in that process.

I’ll finalise the packlist (V1.0) in the next few days and post it up. I’m also planning to do a video overview of all the equipment I’m taking, a picture-set of the bike and the charging setup and as many other images as I have time to take. The 9-day forecast is looking OK (not perfect, but OK) and so I’m quite confident that the tour will start at some point next weekend.