Solar Trailer Build

[mojoe]

Here is the beginning of my build, using a Burley Nomad trailer. As others have noted, one drawback of the Nomad, depending on your use, is the nylon floor. The nylon walls should hold up well, but the floor may wear more quickly. I saw a YT video where someone used a single piece of 1/4 inch plywood, and painted it with a rubber waterproofing. I liked the idea, but thought I'd try corrugated plastic, as one of the YT commenters suggested.

I couldn't find thick, heavy duty corrugated plastic locally, so I bought what they had, and glued three identical pieces together, alternating the corrugations for strength. This gave me a floor that was about 1/4 inch, just like the other guy's plywood, but much lighter. It seemed a little more flexible in the middle than I would have liked, but probably would have been fine with reasonable loads. However, I decided to cut the floor in two, so I wouldn't loose the ability to use the nylon divider that the trailer has. This made the flexibility issue worse. So, back to the store for some angle aluminum (I want to call it angle iron, but it's aluminum)

Attached is a picture of the trailer with the floor installed (minus the cover), and another showing the underside of the large section of floor. Two pieces of aluminum are notched so they rest on the side of the frame, the third is cut short, so it rests on the rear of the frame. The short section of floor doesn't need a center support. I used 3M VHB tape to hold the aluminum, and Velcro to keep the floor pieces from bouncing around. It may look a little rough, but it's the best I could do with a hacksaw and a utility knife. Both sections of floor weigh 40 oz, total. I suspect that this is much less than plywood covered in rubber paint.

Adding a floor does slightly decrease the total cargo capacity, but the front of the trailer is deeper, so you have a hidden storage space beneath that section of floor. I plan on using that space for spare parts, and other items that I will rarely need. Thin items could go beneath the back section of floor.

If anyone is interested, I'll post more pics and info as I build the rest of this project. If that's not wanted, or allowed by the forum, let me know, and I won't.

 

[mschwett]

very cool! an 18" x 32" x 1/4" piece of plywood weighs around 6 pounds, so you saved 3+ lb. nice!!

most of these that i've seen threads about just have big panels mounted (somehow?) flat over the top of the trailer. is that what you're going to do too? would be cool to find a less unaerodynamic approach.

 

[mojoe]

I ordered a Sunpower 110 W semi-flexible panel that is 22" wide by 46" long, and weighs 4.4 lbs. This is 4 " wider and 14" longer than the trailer. I will see how far forward I can move the panel, without interfering with the bike.

I'll have to attach the panel to something (perhaps aluminum or fiberglass sheet) to give it more rigidity. Even so, it will weigh much less than a traditional glass solar panel. I will mount it horizontally, but may tilt it down in front very slightly, for better aerodynamics (sort of like a big spoiler, but not as steeply angled).

I didn't want a sun-tracking panel, as that is more complex, adds quite a bit of weight, and draws power. From my research, during the peak solar hours of the day, the difference between a horizontal panel and one pointed at the sun isn't that great. Of course, when the sun is low, it makes a big difference. Maybe I'll see about making a quick release for the panel, so I can point it when I am parked. It will have to be simple and light weight, though.

I ordered the cargo rack that is made for the Nomad trailer. I'll mount the panel on that. I'm figuring this out as I go.

I would have liked a higher wattage panel, but size was an issue. The 110 W panel won't keep things charged 100% of the time, but it will allow me to ride further without needing an AC outlet.

When I get everything assembled, I'll start with some test rides, to see how much charging I can get with this size panel. When I have some numbers, I'll post them here.

Oh, and for comparison, I have a Priority Current ebike with the extra, extended battery that is part of a rear rack. The main battery in the bike is 504 Wh and the extended battery is 576 Wh. I'm expecting that on a sunny day, I should be able to at least fully charge one of the batteries, while I ride using the other. Like I said, test trials to be done.

 

[mojoe]

I just had a thought about an improvement to the floor. I think I'll glue some of the rubber-like material they use for shelf and toolbox liner to the floor. The stuff has an open weave pattern, and is thin, so the extra weight won't be much. I will still be a few pounds lighter than spray-rubber coated plywood. Other than less weight, I went with the plastic floor because it was inherently waterproof.

Another brain storm - I can save more weight by just using small squares of the shelf liner. I don't need to cover every inch of the floor.

Edit: I compromised and glued strips of shelf liner to the floor. It was easier than doing squares (sometimes you get lazy).

 

[mojoe]

I received the solar panel yesterday, but it was damaged, so it went back today. The box looked OK, but the panel looked like it had been used and abused. I ordered a replacement from another supplier. I don't know when I'll have the new panel.

Today, the Genasun came, but now I have no panel to test it with. I may have the Nomad cargo rack on Friday.

Waiting, waiting, waiting...

Tomorrow, I go shopping for some mounting hardware, and a plastic box to put the electronics in. I'll post a picture when I have it all wired up.

 

[mojoe]

I'm getting tired of going to the local H.D. store for hardware, and finding they are out of what I need. There is no real hardware store locally. So, I had to resort to online, where I had to order larger quantities than I needed.

While I await the replacement solar panel, I hooked things up to do a load test. In the picture, you see the power supply (in the background) feeding the Genasun (half out of frame on the left), feeding a panel meter (center), feeding a DC electronic load (background, right). The power supply is simulating the solar panel, and the load is simulating the ebike battery.

The 110 W panel is rated for 18.8 V @ 5.9 A output, which equals 110.92 W. Of course, the panel won't give me 100% of this. I set the power supply to output 18.8 V, but 6.4 A, which is the maximum it can do. If you do the math, assuming 100 % efficiency, the Genasun should output 54.2 V @ 2.05 A from a 110 W panel. I managed to get the load to draw 2.08 A before the power supply went into current limit, and the Genasun started decreasing its output voltage. The panel meter seems to be quite accurate. Not lab grade accuracy, but more than enough for this use. BTW, ignore the accumulated AH reading, as I had something set wrong on the panel meter.

The panel meter is branded "DROK", and is their part number 200320. It is similar to many other such meters. Most of the ones you will find either use a Hall Effect sensor to measure current, or an external shunt. Most also are designed to measure 100's of Amps. This particular meter has an internal shunt for up to 20 A. Since I only need to measure a bit over 2 A, this is more than sufficient. Also, the high current meters will be less accurate at the very low end, where I am operating.

I let everything run for 20 minutes, to see if heat would be an issue. The panel meter was barely warm to the touch, and the Genasun was hardly any warmer. I shouldn't have a problem mounting everything into a waterproof box. I can always drill a few ventilation holes later, if needed. The box doesn't really have to be waterproof, as I don't plan on using this underwater, or dropping it into a big puddle. It will be housed inside the Nomad trailer. The critical part, the Genasun, is potted, so it is fully waterproof.

This setup will let me monitor the ebike battery while it charges from the solar panel. This isn't ideal, as I will have to keep an eye on things, to see when the battery is charged. Later, I may build a data logger, so I can track things better. That's a project for another day. During my initial testing, I'll just use an action camera, pointed at the panel meter. I will be able to review the video later, to see how long it takes for a full charge. A kludge, but it works.

 

[dblhelix]

I ordered a Sunpower 110 W semi-flexible panel that is 22" wide by 46" long, and weighs 4.4 lbs. This is 4 " wider and 14" longer than the trailer. I will see how far forward I can move the panel, without interfering with the bike.

I'll have to attach the panel to something (perhaps aluminum or fiberglass sheet) to give it more rigidity. Even so, it will weigh much less than a traditional glass solar panel. I will mount it horizontally, but may tilt it down in front very slightly, for better aerodynamics (sort of like a big spoiler, but not as steeply angled).

I didn't want a sun-tracking panel, as that is more complex, adds quite a bit of weight, and draws power. From my research, during the peak solar hours of the day, the difference between a horizontal panel and one pointed at the sun isn't that great. Of course, when the sun is low, it makes a big difference. Maybe I'll see about making a quick release for the panel, so I can point it when I am parked. It will have to be simple and light weight, though.

I ordered the cargo rack that is made for the Nomad trailer. I'll mount the panel on that. I'm figuring this out as I go.

I would have liked a higher wattage panel, but size was an issue. The 110 W panel won't keep things charged 100% of the time, but it will allow me to ride further without needing an AC outlet.

When I get everything assembled, I'll start with some test rides, to see how much charging I can get with this size panel. When I have some numbers, I'll post them here.

Oh, and for comparison, I have a Priority Current ebike with the extra, extended battery that is part of a rear rack. The main battery in the bike is 504 Wh and the extended battery is 576 Wh. I'm expecting that on a sunny day, I should be able to at least fully charge one of the batteries, while I ride using the other. Like I said, test trials to be done.

I did this last summer — a Sunpower 110W on the Nomad rack. I did not find additional support necessary. The POS rack did not fit the Nomad exactly — my biggest problem.

 

[mojoe]

My rack just came today. Thankfully, it fit perfectly. You must have gotten one made on a Monday

As the panel is semi-rigid, I thought about mounting it as you did. However, I thought that the flexing in the wind might cause cracks over time, so I'm going to sacrifice a bit of weight for more rigidity. EDIT: I'll have to re-think this. The weight of 1/4" aluminum sheet is 26.3 lbs. Acrylic sheet is 10.7 lbs. Maybe just some aluminum angle along the sides.

Tell us about your solar setup. Did you use a Genasun controller? How much charge did you get during a typical day? Were you topping off the battery as you rode, or charging a spare battery?

Where did you ride with that setup? Any issues during the trip? I'm a bit worried about theft, when I start doing overnight trips, especially if I stop in town. You can't really secure the trailer.

 

[dblhelix]

My rack just came today. Thankfully, it fit perfectly. You must have gotten one made on a Monday

As the panel is semi-rigid, I thought about mounting it as you did. However, I thought that the flexing in the wind might cause cracks over time, so I'm going to sacrifice a bit of weight for more rigidity. EDIT: I'll have to re-think this. The weight of 1/4" aluminum sheet is 26.3 lbs. Acrylic sheet is 10.7 lbs. Maybe just some aluminum angle along the sides.

Tell us about your solar setup. Did you use a Genasun controller? How much charge did you get during a typical day? Were you topping off the battery as you rode, or charging a spare battery?

Where did you ride with that setup? Any issues during the trip? I'm a bit worried about theft, when I start doing overnight trips, especially if I stop in town. You can't really secure the trailer.

Seattle WA to Wash DC. Plenty of wind, no probs. Genasun, charging spare Bosch battery, no other option. Peak output in July -early Aug but dropped off dramatically in Sept. Biggest issues: crap tires on Nomad. Constant flatting. No theft attempts. Used motorcycle alarm, no locks.

 

[mojoe]

Wow, that's a long trip. How long did it take you? Did you go on the Rail Trails?

Did you manage to get the spare battery fully charged while riding, or did you have to stop and wait? What was the capacity of the battery?

Did you ride back, or did you arrange transportation? It's not like you could call an Uber.

 

[dblhelix]

Wow, that's a long trip. How long did it take you? Did you go on the Rail Trails?

Did you manage to get the spare battery fully charged while riding, or did you have to stop and wait? What was the capacity of the battery?

Did you ride back, or did you arrange transportation? It's not like you could call an Uber.

I live in the DC Metro. My original plan was a round-trip but I got a very late start. When I got to MN, I hopped on Amtrak to get to Seattle. Once in Seattle, I rode out to Olympic Peninsula and officially started my route home in La Push, WA. I did a combination of trails/road but tied to pick up the GART whenever possible.

I was charging 500W Bosch PowerPacks. I also had a 6A ‘fast’ charger along. My panel performed very well — sometimes hit 100W. Over the course of the trip, I’d collect 250W-550W on sunny days. This did not cover my daily riding needs, obvi, and some of it went to charging personal items. Overall, I’d say I covered about 1/3 of my electric demand via solar.

I now own a cargo bike, so I’m redesigning the solar aspect w/ hopefully > 110W. i didn’t like how solar dominated the trailer which left less room for personal items. It’s also yet another spare tube. But for what it was, it worked well enough. Trip home was a little over two months.

 

[mojoe]

I'm still awaiting my replacement 110 W panel, but I was curious to see what higher wattage panel I could find that wasn't "too big". Almost all were very long. It turns out that the SunPower 170 W flexible panel is probably the best choice for size. Rounded up to the nearest inch, it is 32" wide x 46" long. That's 10" wider than their 110 W panel, but only 1" longer. That's 1" wider than my handlebars plus my left mirror. It is quite a bit more expensive, though.

The rated voltage is much higher than the 110 W panel, but rated current is similar. With the higher voltage, it may be more efficient with a boost converter, like the Genasun. The Genasun can handle 9 A (rated for 8 A, but Genasun says 9 A is OK), so both panels are well within the current limit.

If only solar cells were 50% efficient Then I could have a much higher wattage panel that would fit my trailer, and charge my battery in just a few hours. Actually, I recently read a story about some multi-layer cells that were made in the lab with 45% efficiency, and when they made one using real production methods, got 40%. I'm sure that it will take years before it is available to the public. Just like the flying car that I've been promised all my life, and commercial nuclear fusion.

I've already ordered the 110 W panel, so I'll install it on the bike trailer, and see how it performs. The 170 W panel would ideally give about 55% more power than the 110 W panel. Something for me to think about, later.

BTW, let me throw in a few comments about where I bought that first panel. As I mentioned, it arrived damaged, although the box looked fine. I suspected that it was a return, or a reject. That was why I ordered the replacement from elsewhere. Well, it looks like I was probably correct in my suspicions. I just read some comments from others who had ordered panels from Sun Powered Yachts. They also had received damaged and abused panels. When one of the reviewers contacted SunPower, they were told that Sun Powered Yachts was not an authorized dealer. Who knows where they are getting their panels. Fair warning.