Solar power on a motorbike

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This idea of charging the battery on my motorbike with a solar panel is one that comes and goes. Because idling the GS and going nowhere is an insensible use of fossil fuel and a terrible strain on an air-cooled engine, the solar panel idea comes about most strongly while I’m stationary for a few days. And then it abruptly goes away once I’m traveling again. It goes away for a very obvious reason.

The bike’s 720-watt alternator can produce more than 50-amps an hour, which is quite sufficient at powering the bike and charging every battery I own at once! Compare this to the solar panels on the market that fill the trickle-charging motorbike/tractor/RV niche. These panels range in size and materials; those sized for convenient use and permanent exterior mounting on a motorbike are rated at 5 watts and less. Larger rolling and folding arrays produce 20, 30, and sometimes as much as 60 watts an hour, but these panels would consume a great deal of valuable storage space and involve packing and unpacking to use.

Without getting bogged down on acceptance rates, ideal charging conditions, and the overhead of the bike’s equipment, the alternator will produce in a minute what takes a 5-watt panel two and a half hours to produce. Realistically, the ratio is closer to 1:5 given a typical bulk charging rate of 2 amps an hour for a motorcycle battery. Still, any day I ride for at least an hour is a day I can top off the motorbike’s battery and recharge everything else, and thus out goes the idea of a solar panel.

Then I find myself camping for a week alongside a beautiful waterway in California or in the high mountains of Colorado with no need to ride except to recharge a laptop, a camera, or even my USB-powered beard trimmer. And considering the convenience of having a panel permanently mounted to a pannier, always ready to contribute a few electrons to my power-hungry millennial needs, the idea of a solar panel burns brightly again.

The idea has done just that during my extended stay in Texas. After seeing a panel in action and measuring its results, I’m ready to pull the trigger and install one of my own. It’s easier to balance cost, efficiency, and build quality now. Two years ago, I would only consider the expensive folding/rolling arrays produced by PowerFilm. Their build quality and power output were unmatched, but their size was prohibitive for permanent installation on a bike. Since then, the cost of compact solar components has decreased considerably and their power output and build quality have increased. For less than $200, I will have a solid, power-producing panel permanently mounted to my top case.

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I’m using existing holes in the top case and running an electric wire externally to minimize the permanence of this setup — just in case I change my mind later. The panel bolts onto two aluminum bars, bent to accommodate the fasteners.

The cutting is fairly straight forward, but the bending is a challenge. I carry a hacksaw blade; I do not carry a hydraulic press or a vice. It’s time to improvise one out of the PegPacker hardware.

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My initial readings are very promising. The panel produces a steady 0.3 Ah unregulated in full sunlight. The charge controller regulates the voltage to meet the battery’s needs (for example, 0.03 Ah in float mode). When I put a load on the battery, the charge controller goes into bulk mode and delivers the full current of the panel to the battery.

A few finishing touches to the wiring and mounting remain. Overall, I’m pleased and excited to see how this performs on the road.

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Do you use a solar panel on your bike, boat, RV, or truck? Share your experience in the comments!


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