Portable Solar Charging on the Cheap

I’d be surprised if our popup camper ever sees a campsite with an electrical connection. With just one marine battery, we’re very conservative with the power: All our interior lights are LEDs from superbrightleds.com, for example, and even so we don’t use them much, preferring candles and our lantern instead. The main consumer of power in our case is the heater. On a cold campout, we can get about three days/nights from the battery with judicious use of the heater before it’s down to about 75% capacity. To avoid damaging the battery, I try not to run it down past that.

Options

To get more power, we could add a second battery to the tongue, or even just keep a spare in the back of the tow vehicle. But I didn’t want to drag it around, fiddle with changing it out, or deal with extra tongue weight.

Enter the solar charger. With a small investment, I can now make enough power from the sun in a day to replace all the power we use from the battery the night before.

Rather than mount something to the top of the camper, I wanted it to be portable, so I could move it around. We’ll often want to park in the shade, right? I’d seen portable solar setups with two panels hinged together, and after looking into building such a thing I decided to just buy one ready-made. There are a couple of well-regarded sellers of solar panels on Ebay, and one of them had the perfect-sized portable charger for me: 60 watts total, with two 30-watt panels, pre-wired with a simple charge controller. The controller helps keep the panel from over-charging your battery.

Sizing

How did I reach the 60-watt number? An educated guess. Knowing very little about this stuff, I read a lot, and did some back-of-the-envelope calculations. I figure that we consume roughly 4-6 amp-hours of electricity a day with normal use including the heater. Without the heater it’s much less. On a halfway-decent day, this charger will put out about 3 amps of power, leaving me with a full battery on most days assuming I leave it in the sun for at least a few hours.

I also chose 60w over 80w or 100w because I wanted a compact panel for packing. This setup is only about 21″ x 17″ when folded, a nice compromise between power and space. It can travel on the dinette, while also leaving room for our folding chairs to lay next to it.

Details

The main setup I purchased through this seller on eBay. It came ready-to-go with a charge controller and a simple black zippered storage case for $230.

Here’s the charge controller:

Cabling

First, the easy way. If you are averse to crimping or soldering (by the way, I don’t solder connections where there’s propensity for movement), and you’re looking for a plug and play solution, you can go with off-the-shelf parts:

1. Install a fused two-pole SAE pigtail on the battery, just long enough to hang out an opening in the battery box. These two-pole SAE connectors are pretty common in the motorcycling world.

2. Purchase a 25 foot pre-made cable on Amazon. It’s probably 16awg, but for 25 feet voltage drop won’t be too bad of an issue.

3. For the charge controller, you can get a two-pole SAE connector for the charge controller at radio shack or most auto-parts stores (look in the trailer section). Cut it and replace the cable that came with the charge controller with it to make a connector ready for your cable. With these parts you haven’t crimped a thing and you’re off and running. BUT…

(Now for the better way)

If you want to maximize your charging or get more reach, I recommend 10awg cable. This minimizes voltage drop over distance, which affects how much sun you’re able to turn into electricity. I initially tried 12awg landscaping cable, and it worked, but I could measure the voltage drop easily and I wanted to get the most out of my system, with more reach. So I purchased about 40 feet of 10awg marine wire on ebay. This is stranded, two-conductor wire with a nice thick outer casing. Marine wire is tinned and very flexible due to the many small strands that make up each conductor.

Rather than use SAE connectors as above (which are impossible to find in a kit form or with heavier gauge pigtails, I chose to use PowerPole connectors, which are popular in the R/C modeling field as low-loss connectors. I got mine at Powerwerx. For 10AWG cable you want the 45A contacts, as they’re physically big enough for the cable. You should have a decent crimper too. You can crimp PowerPoles with generic crimp tools, or spring for the TRICrimp or similar tool. The only drawback of these is that they’re not waterproof. But for my setup, they’re fine. Click that first link for some good info. I used some adhesive shrink tubing to help keep thing clean.

For the battery side I made a short fused pigtail with PowerPoles at the end, and a similar non-fuzed pigtail for the charge controller.

Now I just set up the charger, and plug one end of my wire into the charge controller, and the other into the battery connector.

That’s it, just plug it in and put it in the sun for silent, free power. Between simple conservation and the charger, we can now camp as long as we want to. Propane and food (and work) are our only constraints!

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There is one reply to “Portable Solar Charging on the Cheap

  1. shawn hamilton

    hi
    Hope your summer goes well. I’d bookmarked your solar page
    http://www.sebsgarage.com/camping/portable-solar-charger/
    Really liked your writeup and especially the ‘this is where i got this’ details.
    Anyways, the image links are broken. Maybe a folder name change?
    Dont rush for me. haha. I’m a ways off from building, but thought you might want to know.
    so ya, thanks for the info and hope you have a great season
    Shawn

    Reply

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