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.

Tonight I’m doing what I’ve been doing most night for the last few months – researching solar power and solar notebook/laptop solutions. Tonight the Google search subject is expeditions. I figured that these guys must have solar computing pretty much sussed by now but I’m struggling to find a solution that can improve on my, ‘draft’, solution.

For a start, many of them are using lead-acid batteries, the most dense battery solution around. Is it because they are cheap , rugged and flexible I wonder? Why aren’t they looking at lighter Li-Ion solutions? And then there’s the panels.  All the expedition panels I’ve seen have been non-flexible  solutions. Is this because  the efficiency is  better than the flexible (CIGS) solar  solutions? That’s actually quite likely and I’m wondering if I would have been better off with a solid panel solution, especially after I just spend two hours making a frame for my flexible solution!

The biggest shock came when I looked at the PC solutions though. None of the websites I’ve looked at  attempt to  advise on  the  most  efficient laptop solution. Those that do seem to be incredibly out of date. “Laptop computers consume between 15 and 30 watts of power (some as much as 60 watts)” said  one.

It makes me wonder weather I could actually help some of  these expeditions.  I wonder what they  are using the notebooks for? Is it just  emails, logging, weather, mapping solutions, inventory management? If so then I think a UMPC could really help.  Not only  are they much lighter and smaller than your average notebook (1/3rd the weight  which could  save 3-4KG for  an expedition that  is taking two notebooks.)  but the excellent power efficiency would mean knock-on savings  with battery weight and solar panel size.

If you’re responsible for the PC solution on your expedition, please let me know what your set-up is and what you’re planning to use it for. I think I might be able to help you cut your weight or increase your computing time. For example, the very efficient VIA C7-based Samsung Q1b, retro-fitted with a solid state disk drive could average less than 9Watts of  power and give expedition team members enough time for a lot of extra emails home!

After I’ve finished the solarumpc tour I’m planning to take the knowledge gained, continue to add to it and then try and design an ultra-efficient solar-computing solution. Well at least I’ll try! I have been speaking to Select-Solar about this and they’re also keen to find out more. Maybe together we can take solar computing to the next level and make it available in a cheaper, lighter and more efficient package. I think that Ultra Mobile PC’s are going to be an important part of it because battery and solar technology seems to be advancing very slowly compared to the efficiencies of Ultra Mobile PC’s

Digital Donkey image courtesy of Alex Papadimoulis.

Technorati Tags: expedition, solar, notebook, pc, adventure, umpc, camping, backpacking, outdoors

It was an early start yesterday. 0445 rise and bus at 0530. 5 hours later after three trains and another bus I arrived at InterSolar 2007 in Freiburg, Germany hoping to find out how I could improve the UMPC Solar kit at Europe’s biggest solar expo. Unfortunately, there wasn’t much there for consumers at all. It was all 200w, $1000 panels and huge thermal heating set-ups. I saw one company that was selling the Voltaic Solar Backpack but I’ve already assessed this product and at 4W max output, its not powerful enough. I was rather hoping to see someone with the Reware Juicebag which, at 6.3W is much more useful.

Actually the most interesting thing that happened yesterday, apart from some awesomely stormy weather, was that the train journey took me on the Rhein route south to where I will start the Solar UMPC tour. Its a gorgeous route. Lovely scenery and I saw loads and loads of great Rhein-side restaurants and camping sites. I’m looking forward to the tour more than ever!

One bit of relevant news from yesterday which came through RSS and has spawned another bit of research was that Sanyo have broken the record for a production solar cell. We’re up to 22% now. In theory, the cell on the left here, a 10x10cm device, should be able to generate over 2W. 100cm2 is about the same area as the face of a UMPC. 4W is the target average power consumption that Intel have set for devices based on Menlow, their UMPC platform for 2008. The interesting thing that I’ve found out is that this cell (or at least the previous version of it) appears in the Sanyo Eneloop solar charger. The charger houses a Li-Ion battery which can store enough energy to charge 4x2000mah batteries. That’s about 10W if my maths is correct. The only problem is the quoted 6 DAYS charging time for the internal Li-Ion battery. I suspect that the cell isn’t exactly being used that efficiently because as I said before, that 10×10 cell should be able to kick out 2W, enough to charge the batteries in a few full days of sun. This little bit of tech will set you back over $150. Eek!

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.

Lesson number one in the Solar-UMPC project is that the weather is chaos and if you live in mid-northern Europe, you can’t rely on it as a source of instant energy. You’ll see how I’ve had to adapt my solution in my first Solar UMPC video. In the video I present the solar charging and storage setup that I’ve decided to use for the tour. Its based on the fag-packet drawing I did a few weeks ago after deciding that Li-Ion batteries weren’t really the best solution.

I’ve introduced the lead-acid battery as a buffer and despite the 100-year old technology and 2.6KG weight, provides the perfect stabiliser to the whole architecture.

A quick rundown of the equipment I’m using (mostly bought from my home country, Germany.)

• Sunlinq 12v / 25W foldable solar panel.
• Sonnenschein 12v / 6.6Ah lead-acid battery.
• Solar charge controller. 12v / 4A
• Samsung Q1b UMPC.
• TabletKiosk MP3400 Li-Ion battery pack.
• Voltcraft dual-mode 12v battery charger.
• Voltcraft 12v DC-DC adaptor.

More pictures in the gallery here. Many thanks to SelectSolar for their help in preparing this solution.

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.

I’ve just had a nice conversation with my energy advisors, Select Solar, about some of the issues I’ve seen with the tests I’ve done so far.  The main problem being that Li-Ion batteries will not trickle charge. They require a certain level of stable voltage/current before they start to charge and this wastes the possibility of charging a battery at lower sun power. In fact, on a hazy day or with light cloud cover, the sun power might not actually go above 70% and you have no chance to charge anything. This could be  major problem and I’ve decided to try and address it.

A solution to this problem, as I mentioned before, is lead-acid batteries. These are the type you will find in your car and are a tried, tested, reliable and relatively cheap solution. The problem is that they are also extremely heavy – at least 400% of the weight for like-for-like power storage. They also operate at 12v which means voltage conversions (and more electronics and power-wastage) in order to operate the UMPC.

The decision I’ve made is to buy a 70W/hr 12v lead-acid battery (2200g) and to try and use this as a charge buffer. Here’s a little sketch of the planned set-up.

The idea would be that I connect devices to the lead-acid battery as the solar power increases during the day. For example, I might add a couple of AA batteries or my mobile phone in the morning. At mid morning I might replace it with the Li-On battery and during the peak hours I could re-attach the AA battery charger with 2 or 4 batteries depending on sun power.

Two problems I can see here:

• How do you know the charge on the lead-acid battery?
• Will the lead-acid battery be able to feed up to 1.5 Amps?

There’s only one way to find out. I’ve just put an order in for a 70W/hr lead acid battery and charge controller along with some fresh AA batteries, a powerbank tip adaptor for the Samsung Q1, a 12v charger for the mobile phone and something I’ve always wanted, a flexible USB LED-lamp!!!

Later today I will probably be ordering the solar panel. I won’t be using the P3 Panel as the only advantage with that was that it could drive 19V into the PowerBank. Now that I’m going for a 12V source solution I’m going to be looking at the 25W version of this Sunlinq panel which is the same price as the 15W version of the P3 panel. There’s a risk that its going to be too big for the bike at 1m long but even if I fold 25% of it away, its still going to give more power than the 15W panel and during mid-day pause and work sessions I hope to get the full 25W out of it.