Note: this post is slightly technical. Feel free to skip any sentences that have numbers in them 🙂
During our Quartzsite boondocking experience we were able to live completely off the grid for two weeks, but we found there were a few times when we had to run the generator to keep our batteries charged up. Most days were sunny, but there were a few with high thin clouds, plus during January the sun angle is very low. Combined, this meant that our Trimetric battery monitor told us we were only getting back to maybe a 90% charge by the time the sun went down.
I also had noticed that most of the boondockers around us had pretty substantial solar setups. One fifth wheel across the “bar” from us had in excess of 1000W of solar power. Our single little 160W panel was feeling weak in comparison.
(Tech note1 : these panels are rated at just over 9 amps at a maximum of 17.5 volts. There are losses in any solar system, such as those caused by temperature, resistance in the wiring, and inefficiencies in the solar controller. The controller essentially takes the power from the panels and presents it to the battery in a controlled voltage, so that you get the most out of the panel while not overcharging the batteries. We have a very good, although run-of-the-mill Pulse Width Modulated solar controller that essentially throws away the difference between the solar panel voltage and the charging voltage, which varies between 13.6 and 14.4 volts. That means you max out at maybe 130W and lose 20% or more of your precious power. Fancier Maximum Power Point Tracking [MPPT] controllers convert that wasted voltage to power, but they are more expensive. If we have some spare change lying around next year we may consider this upgrade, but it probably isn’t necessary.)
I had mused to Maureen that maybe we should consider beefing up our panels. Because of the presence of hundreds of thousands of potential customers, there are several businesses in Quartzsite that compete against each other, so I knew this would be an ideal place to get the work done. In anticipation of maybe someday getting this done (“way, way in the future” is the inside joke Maureen and I have for something that may happen sooner than later), we had solicited recommendations for a good solar shop from fellow RVers and then stopped by a few to see what they were like.
One that stood out to us was Discount Solar. For one thing, they carried the exact same panel as the one the factory had installed. The pricing was attractive. They had a clean, organized shop (some of the places we saw looked a bit like an electronics flea market). And they seemed to know what they were talking about. We had planned to come back through Quartzsite on our way back from the west coast in March, so I told the folks at Discount Solar that maybe we would make an appointment to add the panel then.
When we came back to Quartzsite from our Chicago visit, we left Phoenix and stayed one night at the 88 Shades RV Park instead of boondocking, so that we would have access to cable TV – it was, after all, the night of the Super Bowl! – and there were no other over the air TV stations to be had in Quartzsite.
We had planned to head west the next morning and set up camp in Joshua Tree. Upon reviewing our reservation (which I had made 3 months ago in November), I realized that the campsites in Joshua Tree are dry camping only – no hookups. After this had sunk in, Maureen surprised me by suggesting that we should try to get our additional solar panel installed the next day, as we would be able to use the extra power during our week of dry camping.
So I got on the phone with Discount Solar as soon as they opened on Monday. They had appointments for the morning, but said they would be able to squeeze us in at about 1:00. During our prior conversation they had estimated the work as about a 1½ hour job. So I thought “great, we’ll be on the road by 2:30 and at our campsite by 5:00 – before sunset.” Well, it didn’t quite work out that way.
One reason the work took longer than expected was that it was more than just slapping another panel on the roof. First, I wasn’t happy with where the existing panel had been placed by the factory. It was next to the air conditioner, which meant that through mid-morning or even mid-afternoon, shadows would creep across the bottom of the panel. This may not seem like a big deal, but even the slightest shadow can reduce the power output by half. I had found out in Quartzsite that the 1” shadow cast by our cell booster antenna pole had a similar effect. So I wanted the panels moved to as shadow-free a position as possible.
Another issue was that the existing panel did not tilt, and in mid-winter this can mean giving up 30% or more power. I had researched adding a tilting kit to our existing panel, but the available ones seemed expensive and poorly designed, relying on flimsy wingnuts, and retaining the awkward, difficult-to-reach attachment point on the bottom of the panels. Discount Solar’s recommendation was to unscrew the old brackets and toss them away, and I agreed.
Lastly, we discovered that the factory had used 10 gauge wiring between the panel and the power distribution panel. That’s not horribly thin, but by adding another panel we would be doubling the amount of current flowing through these wires, and every amp was precious; I didn’t want to lose any to resistive losses. So I OK’d an upgrade to 8 gauge wire.
When our technician finally got up on the roof, he took one look and suggested moving both panels to the front of the roof, on either side of our Maxxair roof vent, where shadows would not appear except very early or late in the day. I was concerned about moving that much weight forward (we are close to the maximum hitch weight on our Jeep), but after feeling how light the panels are, I agreed to this placement.
The tech pulled out the old wires, fished the new wiring in its place (neatly tied down in several places and leaving slack for tilting), mounted the new and existing panels with tilting kits, sealed everything up with Dicor and ran a shade test to make sure both panels were putting out power. It sounds simple, but done right it is tedious work. I was pleased with the workmanship.
The previously scheduled job had run into some unexpected problems, so work on our project didn’t get started until 2:30, and it turned out to be more like a 2½ hour job instead of 1½ . That meant we ended up driving through Palm Springs, climbing the twisting mountain road up to Joshua Tree and setting up, in the dark, while hungry. It was a long day. But still, it was really good of Discount Solar to fit us in – they had to pull a technician off another job and move work around to get it done.
Was it worth it? I am delighted with the results. Before, we were lucky to have 4 amps (at max 14.4 volts) charging for a few hours during midday. Now, even without the panels tilted I am seeing well over 8 amps by mid-morning and the batteries are usually fully charged by noon. I expect as the sun climbs higher in the sky during the spring we will see even higher output.
(Tech note 2: We have 220 amp-hours of Absorbed Glass Mat (AGM) batteries. Due to weight limitations, we probably can’t add any more [unless we went to lithium-ion batteries, which are the leading edge in RV power supply]. In sizing a solar system, you want your batteries to have enough capacity to handle whatever your daily usage is, especially in the evening, when they aren’t being charged. In practice you don’t want to go below 50% charge, because this can damage the batteries. So that means we have about 110 Ah of available capacity. While I haven’t done a complete energy audit yet, our Trimetric battery monitor keeps track of the amps going into and out of the battery, and we typically don’t go below 80% charge by morning. That means we are running about a 22 Ah deficit by the time the sun comes up. You want your solar panels to comfortably be able to make up for that deficit during the day. With 8 amps coming into the (non-tilted) panels with weak winter sun, we are now charged up in about 3-4 hours. That gives us plenty of cushion for cloudy days or for adding more power consumption at night, say a slow cooker or satellite TV receiver. The key is to balance power and storage.)
Next winter we will be able to tilt the panels and capture whatever weak sun is available. Knowing we have more than doubled our solar capacity means we can be comfortably off the grid – literally – and that brings peace of mind. Now if there was just a way we could make our own water, just like in “The Martian”!