For some reason known only to Forest River they put the Zamp solar input jack at a location most distant from the battery. They couldn't have found any place further from the battery. The wires look to be just 12  gauge, which makes a long wire run like that to be a bad setup. Sure you can plug a regulated solar feed that will connect to the battery. But a lot of power is being lost in the long wiring. Solar energy is just too expensive to waste it with a poorly designed feed-in point. 

For the solar system on my 2016 RPod 171 I installed an entrance jack (using power-pole connectors) near the battery and MPPT charge controller. All interconnecting solar feeds are 10 gauge for minimal power loss.

Here are two links to my solar power system as reported on this forum:

Last year my refrigerator struggled to keep up with the 95 degree ambient temperature while boondocking. Inside the refer box, temps were in the mid to upper 40's - not great for food safety. I understand these Dometic refrigerators are good for about 45 degrees below ambient temperature without fan assistance.

So I've added a couple of 12-volt computer muffin fans with baffles to remove the heat being exhausted at the rear of the refrigerator. One or both of these fans can be employed as needed. Since each fan uses around 0.13 amps (1.6 watts) I can leave one running continuously. The second fan can be switched on if needed during the hottest part of the day.

We'll see how this all works. I'll report back to the forum with results as the season progresses.

I can certainly appreciate your viewpoint, Sailor323. That larger wire would help alleviate the problem a bit. I agree that for the 15-25 of 10 gauge wire there wouldn't be a tremendous power loss (maybe 2-3 watts). But there is a significant voltage drop. The overall voltage drop is the sum of all wiring and connector losses between panel and battery. For that reason it is best to minimize the amount of wiring. If the wire run from battery to Zamp port is 18 feet, you can double that to 36 feet, since there are two wires. In choosing that location, Forest River unnecessarily added a lot of wire.  There's no reason the entrance socket couldn't have been closer to the battery. Perhaps there was some marketing reason.

As an example of how much effect that much extra wire causes, one can use the voltage drop calculator in this http://www.wholesalesolar.com/solar-information/voltage-drop - link . Using 18 feet of 2-conductor 10 gauge copper wire with a 100 watt panel (putting out 7.5 amps at 13.3 volts), the voltage drop is 0.34 volt (2.6%). While that by itself is acceptable at less than 3% drop, one must add all other voltage drops caused by other wire and connectors. The overall voltage drop could easily exceed 3%, the standard for acceptable voltage drop. If the drop exceeds 3%, it is best to use larger gauge or shorter wire. So the extra wire does matter.

The power loss in that 18-foot run of wiring is about 2.6 watts (7.5 amps X 0.34 volts).

My MPPT controller is located near the battery on the wall behind the dinette seating at the front of the 171. That location is preferred since the controller more correctly reads the voltage conditions at the battery. If the controller is located some distance away (i.e. at the panel), it can get a significantly inaccurate reading of the actual battery voltage. For proper battery charging, even a tenth of a volt difference is significant.

I don't mean to overwhelm forum members with a bunch of math. But it has been my intent to show the electrical consequences of some decisions we might make regarding implementing our solar power systems. Even if we make some decisions that are not optimum (but perhaps less expensive), things will still work adequately. As long as we don't do something that might cause a fire.

Hi Russ,

My son and I will also be going to GSSP.  We'll be leaving Tuesday evening and staying near Crescent, OR, then the rest of the way on Wednesday morning.  Perhaps we can meet?

Jim

That would be nice, Jim. I'll be traveling from the Oregon coast to the GSSP on Wednesday. It should be easy to find each other. Last year there were only two or three Rpods at the gathering. I'll be parked in one of the rows next to my cousin, who has a Ford travel van with canvas sided pop-up lid. I'll have a Celestron-11 on go-to mount. My telescope is quite modest compared to all the really large telescopes present. But I would be pleased to share what can be seen with all who come by. 

The easy way is to go with the existing setup. And as has been mentioned there would be minimal power loss. You can always opt for installing a more efficient entrance socket at a later time. I tend to do everything reasonably possible to maximize the power reaching the battery - somewhat of an obsession. The SAE connector on the Zamp port is not noted for its low voltage drop compared to Powerpole connectors. Once you start using Powerpoles, you'll never go back to other connectors.

Just be aware of the polarity of the Zamp port. Someone mentioned that it was reversed compared to other setups. Also you'll need a controller somewhere in the line. As can be seen from my other posts, I'm a great fan of high voltage (36-volt) panels and MPPT (Maximum Power Point Tracking) charge controllers. Yes, I'm obsessive about maximum efficiency. This does come at a cost, however. YMMV.

I'll look for you.  Even if we can't park nearby we can still get together ;-)

Jim

Even if you're only using one 37 volt panel under similar circumstances, the 18 volts would still be enough to juice up your battery.

So it's not just efficiency, but also being able to squeeze out some power under not-ideal solar situations.

That is a quite valid way of looking at the overall picture, Tars. But as a certified "techno-nerd" I enjoy fussing with the details. Who knows (LOL). Maybe this summer will be unexpectedly cloudy like "nuclear winter". Then every amp and watt will be important in keeping the battery topped up. Oh Yeah, I could charge the battery with jumper cables from the tow vehicle. But its still fun squeezing every watt out of the solar system.

Good food for thought. Thanks for the insight. 

The biggest problem I find with the higher voltage panels is finding one with suitable small power rating. Many are being made for grid-tied solar systems running 150 to 200 watts or more. I had a spare 185-watt, 36-volt panel from my home solar system. But finding a 120-watt, 36-volt panel took some searching. But the benefits of that panel with a MPPT controller are worth the effort and cost.