Solar Suitcase & OEM system?

[Blue~Go]

deppstein: I had forgotten about your clever panel storage theme - nice one! I don't have the tire there anymore, but my install would not have been as slick as yours since my "tire locker door" opens the opposite way (Chinook changed the hinge location on many of the doors at some point, so they all open opposite).

Scott: I agree on the not setting up/breaking down. Heck, I sit on the back step and forego the chair - that's too much of a commitment I think adding roof panels to my setup will be perfect for me, because at least 50% of the time I won't need to deploy the ground panels at all. But then I will have them for shady spots, winter sun angle, etc. Many times it's no problem to put them out (but other short stops I'd prefer not to).

My charge controller from Renogy seems very adequate, programmable to set voltage boost, absorption and float values...equalization values also, but Windy Nation says do not use equalization for these AGM batteries. I will program the controller to Windy Nation recommendations.

Are your batteries made by Windy Nation? If so, then doing what they say is a good idea. If not, I'd recommend seeing what the battery mfgr. recommends. In my case, with Lifeline AGM batteries, there are times they recommend equalizing (which they call "conditioning"). Not something I do often, but definitely in the arsenal.

The controller did arrive with a temperature sensing unit, but I did not install it...would have had to drill another hole in the floor and try to route the very thin wire. Not sure if this is necessary if I'm not allowing a high voltage equalization charge, but will research this more. Worse case scenario is removing that pillar etc. and trying to fish the delicate connector through.

You absolutely, 100% want to install that remote temp comp with any lead acid batteries (which includes AGM). That is used EVERY DAY to deliver the correct voltage to the batteries in the absorption charge stage. Very important. I'll give you an example from my setup: First of all, I have the "best" situation in that my batteries are under the couch (not outside where temps vary more) and the solar controller is literally 3/4" away on the other side of a battery box board. Closest possible temperature situation. BUT, those batteries are a large mass. The underneath of my couch area is not 72º all night, especially in cooler weather. So very often when I'm in absorb (say around 10 a.m.), the controller will show that it is at 75º, and the batteries (at the end of the temp comp probe) will be at 55º. Now imagine the difference if your batteries are outside and the controller inside!

The deal is that the batteries want, let's say 14.4 volts in absorb. BUT, that is at 77ºF. Every degree lower that the batteries are from that, they want more voltage to be the equivalent of 14.4 at 77ºF. Any amount above 77º and they want less voltage to be the equivalent.

So with no temp comp you buy the panels, do a good install, take care to avoid voltage drop in the wiring, buy a good MPPT controller, and then kind of throw it all away because without on-battery temp comp your voltages will only be correct when both the controller and the batteries are at 77ºF. I bet that happens once in a blue moon.

In short, absolutely mount the on-battery temp comp! Also, find out what the actual battery mfgr. wants for charge voltages and durations, and go with that. If your battery mfgr is light on information, and you want to know more, have a look at Lifeline's free "battery manual" which explains it all in detail, in an easy to understand manual. While the exact voltage numbers another company wants might be slightly different, the principles are the same. Knowledge is power (literally in this case ).

Cool that you have got it up and running! I you want to share any photos, I know we'd all enjoy them.

PS: Good on you with the pillar!

[chin_k]

I'm curious if roof mounted panels increase or reduce heat gain in the coach?

It will keep the rig cooler. If you want your panels to work well, and last longer, you should keep some air moving underneath. A hot panel is a unhappy panel.

As for the start battery, I have three alternatives, I guess. The first one is what you suggested, using a manual switch. Then there is the solenoid like the SurePower, or the BlueSea, and then the dual battery controller. I may do the manual route, but I need to decide the option before ordering the controller.

[Blue~Go]

I did some experiments a while back. In my case I was mostly trying to figure out how close I could put the panels to the roof, without sacrificing too much of their efficiency to heat (edited to add: panels work better when they are cooler).

I did this on a day of about 80-85ºF, in direct sun. It was May, so at noon the sun was reasonably overhead. I set up a couple of solar panels on the roof, and used various blocks of wood to keep track of the height. I used an IR handheld thermometer and measured the underside of the panel surface, the roof surface under the panel, and the inside ceiling surface (although that last would not be very accurate unless you waited quite a while). I also measured the "plain" exposed roof for a comparison point.

In a nutshell I found that 1-1/4" off the roof (to the bottom of the solar panel frame, so there is another 1-1/4" or so to the actual bottom of the panel surface) was about as low as you could go without trapping excessive heat beneath it. 1-1/2" would probably be better. But below 1-1/4" I found the surface of the roof and the underside of the panel getting much hotter than if there was more space. I don't remember the numbers anymore but just the takeaway.

So kind of reverse-engineering this, I would think that with the panel frame bottom at least 1-1/2" off the surface of the roof, you would probably end up with a slightly cooler rig, due to shading. OTOH, if the panels were less than 1-1/4" off the roof, you'd probably reduce their efficiency a fair bit and also heat up the rig more (the roof surface got hot at those lower heights and that must transfer through)

Ultimate would probably be complete coverage of the roof with panels like 4" up. Probably not going to happen on our Chinooks though.

[Scott]

I'm curious if roof mounted panels increase or reduce heat gain in the coach?

It will keep the rig cooler.

Please explain.

[chin_k]

I'm curious if roof mounted panels increase or reduce heat gain in the coach?

It will keep the rig cooler.

Please explain.

It is just some observation I have, unlike Blue who actually do the measurement. The important think is that when you use the panel as shade, make sure there is enough air space between the panel and the top of the rig. Also, if you use the electricity from the sun to run a heater, then it will increase the heat gain. I think the fact that you will purposely look for good sun exposure to get the panel working kind of make it feel like the solar panel is making the rig warmer. In reality, the shade the panels provide will keep the rig cooler than park your bare rig under the sun.

[Scott]

Gotcha.

Okay that makes sense. Experimentation wasn't really an option for me because the brackets I bought predetermined the height. The bottom of the panels is a little less than 4 inches from the roof. Unfortunately, my Renogy panels have an aluminum perimeter that is perfectly designed to trap in hot air. I guess I could drill a bunch of holes all the way around to increase airflow without compromising structural integrity. But that would not be a small task...

[Blue~Go]

At 4" I think you'll have better cooling air than most.

I guess I could drill a bunch of holes all the way around to increase airflow without compromising structural integrity. But that would not be a small task...

Also, I don't know exactly which panels you have, but many that I've seen, the vertical "sidewalls" are actually two thinner layers of aluminum with about 1/8" of air in between. So with holes you'd have water and dirt getting in there. "Now where are all these mosquitoes coming from?"

Edit: Oh, maybe you meant around the bottom lip, which is usually just one layer of aluminum. Never mind! I don't think it's necessary though (there, just saved you some work).

[chin_k]

I don't think the little holes going to work that well. One 1" hole is much better than four 1/2" holes. I would just leave the panel the way they are. A slight tile in the panel in this case will help the heat a bit, since the air can cool it off by convection.

[danesk]

You absolutely, 100% want to install that remote temp comp with any lead acid batteries (which includes AGM).

In short, absolutely mount the on-battery temp comp! Also, find out what the actual battery mfgr. wants for charge voltages and durations, and go with that.

Blue-Go,

Now I must take back all the nice things I said about you in a previous post, since you had to convince me to remove that pillar again to install the battery temperature sensor. Additional reading into my battery manufacturer website (WindyNation) verified the need.

Seriously, thanks for the excellent discussion on the benefits of the sensor; removing and reinstalling the pillar went much faster this time since I knew the workflow. I drilled a new hole in the floor for the sensor connector and wire, and also a new hole in the battery compartment. All new wires were encased in surrounding silicone. I will keep an eye on these to be sure the silicone is protecting from chafing. Still waiting for the gland to arrive for routing the panel wires through the roof - hopefully Thursday .

I will attach a few photos so any prospective Chinook solar installer will have some visuals. Thanks again for your detailed information!
(click on photos for proper orientation and enlargement)

Pillar partially removed - access gained to work area

Magazine rack and bed side panel removed

Wires run through floor (difficult to see)

Wires from below into battery box

[chin_k]

Nice, Dan!

Oh, I'm too lazy to search, but is there any specific instruction to remove the pillar? I am ready to do this soon.