Despite the terrible weather forecast (rain, clouds, heat, thunder) It’s time to finalize the pack-list and buy the last items, prepare the solar equipment (which should turn up today) and do some test loading and test cycling. Over the last weekend I fitted the baggage to the bike and loaded it up with random heavy items including the new tent, sleeping bag etc. There should be no problem with space or loading weight. I also tested out the tent and it seems OK although some dampness came through from the floor. Is that normal? I’m surprised.

I’ve written the pack-list in Google docs and shared it for everyone so you can always see the latest version. Its organized into sections. Feel free to take a copy for your own use.

View the pack-list here.

I will go through it and weigh each section before I go and add that to the pack-list. Despite the sub 1kg PC, it won’t be a light load! Here’s the list of electronic equipment I’m taking.

12v AA battery charger,12v charger for Nokia phone,12V lead-acid battery (70W/hr),Adaptor cables and tips, Batteries 8xAA for camera, Batteries (2xAA for GPS), Camera case, Camera USB cable, DC-DC adaptor, Digital Camera + 2GB mini-SD card, GPS logger and holder, GPS serial cable and USB-serial adaptor, Li-ion battery (56W/hr), Mini battery tester, Multimeter (voltage, amps, sun, temp), N800 (spare web-access kit), Nokia headphones / adaptor. , Nokia phone (6280) + 2GB mini-SD card, Nokia USB cable, Passive USB mini-hub, Solar panel (25W) +cable kit, Spare mobile phone (voice only), Standard UMPC battery, Torch, Tripod, UMPC (Samsung Q1b) + Extended battery, case + keyboard, USB LED Lamp.

Later today  I should have more details about the solar panel/battery to post. Pictures too.

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.

Thanks to Select Solar UK I received a 15W P3 Solar panel this morning. As I write, it’s out in the garden with 660W/m2 of sun power beaming down on it! Temp in the shade is about 22 degrees.

P3 Folding Solar Panel

Its smaller and lighter than I expected too.

The first test was to measure the open circuit voltage and at about 450W/m2 sun power (I’m using this web site to give me my sun power reading – its very local to me.) it was over 20V. At 650w/m2, its open circuit voltage is about 28v which is higher than I expected.

I connected a AA battery charger with 2 AA batteries in it and it was charging straight away. With 4 batteries I had to wait until about 10:30. I also tried connecting the TabletKiosk PowerBank but it wouldn’t charge until the sun power reached about 650w/m2. I haven’t connected the Q1 yet because I’m missing a connector for a DC-DC converter I will use for protection.

Look at the graph below. Its the sun power from today and I’ve added some notes to it.

Click to enlarge.
A – 2 AA batteries. B – 4 AA Batteries. C – PowerBank

You can see by the wobbly graph that there’s a few clouds around today. Yesterday was perfect and using that part of the graph I can work out how much time there is for a given level of sun power. The sun is at or above the ‘C’ level for 6 hours a day for example. The area under the curve gives us the power too. I’m not going to get my integration maths book out right now but its fair to say that if the sun peaks at 800w/m2 (80% of Panel power) the average is something like 0.7 (RMS?) of (600+(800-600) for 6 hours. Tap tap tap. That’s 75% of 15W panel power for 6 hours….a possible 67W/hrs of power. (average 11w for 6 hours.)

67W/hrs of power is a full power bank or full Samsung Q1 extended battery which is what I think I need every day to keep me going. I might be able to get that down to 40W by being careful with the UMPC but if there are 2 days of clouds, I’ll be out of power.

This is just a preliminary test. I need to do more double checking on this. And don’t forget, its sunny today. The barometer dropped sharply this morning so tomorrow is going to be very different. It will be interesting to see if I can power anything under cloud cover.The other thing to consider is that I’ll be moving on the bike. There will be shady times! The big question is, do I take a risk and challenge and go with the 15W panel or do I take the next step up and go for a 24 or even 30W panel. Like I said, more testing needed!

I’ve put up a gallery of the P3 panel.

More testing going on today and tomorrow.

Thoughts. Should I take a simple sun meter? How much power will I lose through using a DC-DC converter? Should I buy a small multimeter to take with me?