Portable solar charging system for kayaking and adventure December 4, 2013 – Posted in: Equipment
On my first longer sea kayaking adventure, when I was paddling solo from Slovenia to Greece, a little bit more then 1400km, my father and I designed and built a very simple and effective solar charging system that was powering all my electronics. It includes my laptop, mobile phone and GPS.
The system is really simple and anyone with a screwdriver and basic solder kit can make one from home.
-Flexible waterproof solar panel.
-Waterproof cable gland.
-12V charging controller.
-12V AGM battery.
-12V female socket.
-Adhesive heat shrink crimps.
Flexible waterproof solar cells
This is the most expensive part of the system. If you want something versatile, I would advise you to look for rollable cells such as PowerFilm, from 10W and up, depending on your deck size.
Waterproof cable gland
The waterproof cable gland ensures that the cable can pass through the side of the box and still leave the box waterproof. I personally prefer Index marine cable glands, but any good brand will do.
Charging controller 12V
You can buy the smallest 12V controlleron the market, as the current from the solar panels will be low (definitely less then 10A). If you can afford, go for a MPPT regulator and you will get a few more % of efficiency out of it.
12V AGM battery
The tricky part is to determine how big the battery should be. I used the 10Ah AGM deep cycle and didn’t have any problems with it. The battery is very “tough” and it works even if you discharge her to 20%. But you will get a much longer lifespan out of the battery if you don’t go below 50%.
12V female socket
Use any of the standard 12V female sockets.
For the waterproof case I first used Peli case, but that was an overkill in many ways. It’s too heavy, bulky and expensive. That was my first real adventure and I wanted to have all the hardcore heavy duty grade equipment. But the reality is that for sea kayaking and other adventures, lighter solutions work better. Now I only use the simple transparent 4 clip waterproof boxes from Lock&Lock (designed for food storage) that you can buy in any supermarkets. I never had any problems with such cases.
Tinned copper wires are the number one choice for the marine environment. Tin doesn’t corrode (doesn’t get oxidized) and thus helps the wire to last more then 5 times as longer than a normal copper wire.
Adhesive heat shrink crimps
The most exposed part of wiring are the connectors. Always use adhesive heat shrink crimps that will keep the moisture out of the vulnerable part (the joint between the wire and the crimp). Check here how to work with heat shrink terminals.
How much power will you get?
That depends on where you will paddle and how you will position the panels. As a rule of thumb, on a average day (mostly sunny, with clouds in between), from a 15W solar panel on your deck, you will get minimum of 2.5Ah (Europe in summer). If we put that into perspective, this is around 1.5h of laptop time each day. You can improve that by changing the location of the solar panels during the day. For example moving them from the rear deck to the front, if you are paddling in the direction from E to W, or the opposite, if you are paddling from W to E.
1. Fix the cable gland to the box
Take the measurements of the cable gland and drill suitable holes on the side of the waterproof box. Put the cable gland on it’s place and use Sikaflex (or similar, but not normal silicone, as it won’t last long) to seal the bottom of the cable gland to the box. Detailed instructions are found here.
2. Connect the 12v socket to the controller
Usually the 12V socket comes with a wire already attached to it. Cut the wire to a suitable length and put adhesive heat shrink crimps to the end of the wire (to both + and -). Connect the wires to the controller. On the controller the output is usually marked with a light bulb icon. The red wire goes to +, black to -.
3. Connect the battery to the controller
Cut the wire the the suitable length and attach the appropriate cable glands to both ends. Connect the + and – to the + and – of the controller. The inputs to where you should connect are usually marked with a battery icon. But check the instructions to be sure.
4. Pass the solar panel cable inside the box
When cutting the appropriate length of the solar cell cable, keep in mind the setup that you will usually use for charging. For example you can put the solar panel on the rear deck of the kayak and the box behind your seat. Cut the length of the cable appropriately and better leave a few centimeters more then needed. Pass the cable from the solar cable through the cable gland to the inside of the box.
5. Connect the solar panel to the controller
Connect the + and – wire of the solar panel to the input of the charging controller (usually marked with a solar cell icon).
6. Fix the controller and the battery to the side/bottom of the box
Use glue or Sikaflex to attached the battery and the controller to the box. So they won’t move when you rock and roll in choppy sea.
7. Spray all the contact with WD-40 or similar
The longer you can keep the salty moisture out of the box, the longer it will last. Before every trip, spray all the metal parts with WD-40 or any other water-displacing spray suitable for electronics.
Can I make the cable, from the solar power to the box, detachable?
Yes, I would advise you to do so, as the box(with the battery) will be more portable. You can use waterproof connectors to make the cable detachable. But bear in mind that you are putting a weak link in the system.
Can I use a LiFePO4 battery instead of AGM?
You can, but you also need to use a controller that is suitable for charging lithium-ion batteries. You can buy a smaller LiFePO4 as they can be discharged deeply without harmful consequences.
What is the most important factor (that you have under control) that determines how much electrical energy the solar cells will produce?
It’s the angle on which sun rays fall on the solar panel. Ideally the panel would always be perpendicular to the sun rays (in which case the panel would capture the most sun). The panels should face true north if you are in the southern hemisphere, or true south if you are in the northern.