Chinook RV

I also purchased the Renogy Compact for the reduced width (but without them being much longer). They measure 19.5" wide in reality (I have them on hand). That inch and a half (or so) less in width is really nice for our ~18" cake tier.

One note (which you may already have taken into account) is that because they are only 16 volts (most nominal 12 volt panels are at least 17.5 volts) you may want to run them in series (that's what I'll be doing). That does require pairs (or even multiples at any rate).

If not, just be aware that you have even less voltage to lose than with 17.x panels. If you are using a PWM controller, I think just reduce voltage drop as much as possible (which you'll be doing anyway I imagine). You can easily see absorb voltages up to 15 volts with temperature compensated charging when your battery bank is below 60)F. I'm more familar with MPPT controllers and with those you can make good use of a voltage "head space" so a slightly higher voltage is useful. I'm making some assumptions for PWM. I think they just switch on and off to make the correct voltage? Maybe someone else here knows more about them.

BTW, the "super efficient" panels (which are good panels, I have Eclipses as my ground panels) doesn't mean they work any better by my understanding. What it means is they are physically smaller for the 100 watts (or whatever the panel is rated at). You don't get more than 100 watts with a "super efficient" 100 watt panel; you just get a smaller footprint for that 100 watts. The cells are more efficient so can be smaller.

For example, the Solarland SLP 070's which are somewhat attractive due to being 13" wide, are not a very efficient panel. They are nearly 60" long (58.x"). 13 x 58 = 754 square inches. So that's 10.77 square inches per watt. Now take the Renogy Compact 100 watt. 19.5 x 42.5 = 828.75 square inches. So that's 8.28 square inches per watt. Obviously that's a big difference. Whether it matters or not depends on your real estate. For me, the SLP-070's were out because the very most I could fit would be three, and that would pretty much use up my roof for only 210 watts. Boo.

BG

PS: AM Solar has a custom Zamp panel that is just about the same size as the Renogy compact but 19.5 volts. However they are $250 apiece. For me the 16 volt is perfect because I don't have any worries of too much voltage with them in series pairs (32-36 volts is more convenient than 39-44 or so).

Yes, a PWM just switch on and off quickly (maybe a few hundred Hertz). The duty cycle is the % of time the pulse is on. By changing the duty cycle, it changes how much energy is sent to the battery.

I almost step on the PV when I was on the roof yesterday. I don't think any PV is actually strong enough to be stepped on. I wonder if it is practical to put them on the rack so that the panels can be tilt out of the way. This feature will enable the panels to tilt to the south for better output, if the rig is stationary. But the first and second benefit maybe not worthwhile if the mount is too complicated.

They can actually be tilted somewhat (to the outside) even with a nice snug and low mounting because they can go over the edge a bit. If you mount them snug to the upper tier then they can't tilt to the inside.

(Speaking of snug, I did some tests with panels, blocks of wood, and an infrared thermometer. Leaving a 1-1/4" inch gap under the bottom of panel frame (between it and the roof) was a good logical point. Less than that caused the roof and panel to get warmer (less efficient for panel and could transfer heat to inside). More than 1-1/4" was even better but I mean that was the first point that seemed like a good compromise to me. Any less trapped more heat.

I have decided not to make my roof panels tilting for solar function. I will be able to tilt them outboard for servicing the wiring or cleaning the roof, but I mean I won't use that for sun gathering. For me it's much easier and more efficient to use ground panels that way. Not only can I tilt them perfectly, I can also aim them just right and/or put them in the sun (while I lounge in the shade).

I also like to be able to get a move on if necessary (without tilted panels on the roof). And although I will (and do) hop up on the roof reasonably often, I don't want to have to do it just to tilt and un-tilt the panels.

Back when panels were much more expensive, I felt differently; at that point buying two more for ground panels would have been a large cost.

That's not to say everyone would or should do it my way - just mentioning how my usage has evolved.

Blue;
I don’t want to comment on things above my pay grade because I have no idea what I’m talking about but the Renogy site shows the original size "New Edition" 100W panels Optimum Operating Voltage (Vmp) as 16.4V and the new "Compact Size" panels Optimum Operating Voltage (Vmp) as 17.9V. Am I correct in assuming I should run mine in parallel?....Dano
https://www.renogy.com/renogy-100-watt- ... w-edition/
VS.
https://www.renogy.com/renogy-100-watt- ... ct-design/

Also, does anyone have a recommendation for an inline fuse size before the charge controller? They have a 20amp or 30amp available, plug and play and it seems wise to install one. Thoughts?

I agree that the pay off for tilting it probably not going to have a big pay off. Back in the old days, it is even economical to have the panels on heliostat to follow the sun. Right now, the panels are so cheap that people just mount them fixed and forget about optimize for the extra 10%.

One excellent solution that both improves the aerodynamic and to deal with the heat is to mount the panels under the chassis...

I'm dumping the solar in favor of a nuclear reactor I'm building. It will replace the old Suburban LPG furnace. Not only will it provide unlimited power, but it should emit a decent amount of interior heat as well (radiant or radiation?).

Dano wrote: March 5th, 2019, 9:50 am Blue;
I don’t want to comment on things above my pay grade because I have no idea what I’m talking about but the Renogy site shows the original size "New Edition" 100W panels Optimum Operating Voltage (Vmp) as 16.4V and the new "Compact Size" panels Optimum Operating Voltage (Vmp) as 17.9V. Am I correct in assuming I should run mine in parallel?....Dano
https://www.renogy.com/renogy-100-watt- ... w-edition/
VS.
https://www.renogy.com/renogy-100-watt- ... ct-design/

Because of the odd nature of our solar panel configurations on the roof of the Chinook, I would always recommend wiring the panels in parallel. A major deficiency in Series operation is that partial shading of any part of a single panel affects the performance of all the panels in series. Because of shading from the AC or upper tier and the shading determined by where we park, you will not see 100% solar exposure on all panels except at noon on a sunny day parked out in the open. In a parallel configuration, you are much more likely to get as much as each panel can contribute in a marginalized situation. To me, that would outweigh the advantage of series operation, which is higher voltage and theoretical savings in transmission loss.

Thanks Clay! Any thoughts on an inline fuse size? 20 amp? 30amp?

Dano wrote: March 5th, 2019, 10:47 am Thanks Clay! Any thoughts on an inline fuse size? 20 amp? 30amp?

Either one is sufficient. Your controller is rated for 30 Amps (about 400W of solar), so 30 would be the max size you should use. There is also an inline fuse at the battery for the solar input, which is only 7.5Amps from the factory, which was designed around the single 50W panel. You need to put in a higher value to handle your expanded configuration. I put in a 20Amp. The most amps I have ever seen on my 150Watts of panels has been about 9Amps, so I did blow the 7.5 Amp fuse once. It felt good, kind of like getting a speeding ticket for going 80 mph in a Volkswagen! Typical throughout a sunny day is about 1.5 to 3.5 Amps. (And I am parked out in the open in my driveway in sunny Southern California, but the panels are on the north side of the Chinook.) My trusty little 50W flat panel on top of the air conditioner is never shaded, however, since it has the uppermost level of the rig.