When I first mounted the rooftop solar on my Odyssey Camper, it was with the intent that I would buy a second panel at a later date.
I used the original panel from my solar generator DIY and built a roof rack to hold it. When I assembled it, I left a space for a second panel of the same size. If you missed the original van roof solar DIY, you can check it out here.
When I mounted the solar panel in May of 2018, I had already been looking for a second panel, for six months. It seemed that the “Eco-Worthy” brand panel I purchased was no longer made.* So, since May I’ve been trying to find something that is the same size but haven’t found anything that would fit the space I left in the frame. With RTR 2019 getting close, I figured I’d better try something different. So, I bought a Renogy 50 W panel and added it to the frame (more info below the video).
I’m sure I have said something disparaging about Renogy in the past because until recently, I found their panels to be way overpriced. I also think that their other components are priced too high. However, my experience with this panel has been a positive one and has led me to experiment with one of their charge controllers and I’ll tell you how that goes, in the future. Sometimes a product IS actually worth the higher price (but not Yeti, that stuff is a rip-off 😉
Having the Renogy next to the Eco-Worthy panel let me compare the two and I found something interesting. For the same amount of light, the Renogy panel output was between 3 and 4 volts higher. In full sun, the Renogy put out 22 Volts and the Eco-Worthy puts out about 18v. Both panels are monocrystalline even though the Eco-Worthy might look like a polycrystalline solar panel in the photo. Under a cloudy Michigan-in-December sky that would depress even someone from Seattle, the Renogy put out 16 volts and the Eco-Worthy put out 12V. Remember, solar panels are rated on wattage, which is voltage times current (W=V*A) so two panels with different voltages can still put out the same amount of power if the current output is also different. So why does the higher voltage matter?
The job of the solar charge converter is to manage the charging of the batteries. It does this by lowering the voltage from the panels to somewhere between 13.5V and 16V depending on where it is in the charge cycle and the type of battery (it also controls other facets of the charging cycle, but I won’t cover those here). However, it does not RAISE the voltage from the panels. That means if the voltage from the panel falls below the level of the battery, the charge controller does not function. So on a cloudy day, my old panel was not charging at all. However, the new Renogy panel was still powering the charge controller and keeping the batteries topped off even on this off-yourself Michigan winter day. Granted, if the batteries needed serious charging, the output from even the Renogy panel would not have been enough, but being able to keep the batteries at full charge is definitely worth the extra $20 I paid for this brand-name panel.
The new solar panel was about 1.25″ wider so I had to spread the frame rails a bit. I then used some one-inch standoffs to fill the space between the old panel and the rails. Unfortunately, I also had to drill the uni-strut to move the panel over to the side (it used to be in the middle) so the whole project ended up taking about 3 hours instead of the 1 hours I was expecting. But, I like the results. In the future, I will probably use a second Renogy panel and move the old panel to the roof of my garage. There it will keep the batteries topped off when I’m not on the road.
There is a link to this Renogy panel in my Kit for the DIY solar generator.
Thanks for reading!
*Note, I now believe that a lot of the “off” brand panel sellers are actually buying surplus panels and framing them in China (where most of these, are made) without concern for size standardization. They just buy the sizes they can get. There’s nothing wrong with that, but if you go the off-brand route, be sure to grab all of your panels at the same time.