Our last trip was to North Carolina to the BMW RA rally and Great Smoky Mountains National Park. It was also the shakedown trip for our new NovaKool compressor refrigerator. The shakedown was not much of a success.
The NovaKool is great on the road, since the alternator provides plenty of power, but it was draining the batteries when stopped. It seemed to have about a 50% duty cycle and drew a bit over 4 amps when running. That's about 50 amp-hours a day just for the refrigerator. The batteries have 150 amp-hours capacity. Add in the lights, pump and vent fan and two days was all we would get before the batteries were essentially flat. This required long periods of charging bring them back up to charge. The only way to do this way by running the engine for a couple of hours, as the generator (or plug-in 120V AC) only powers a 5 amp charger—that's 15 hours of charging time for a half dischaged battery bank.
Needless to say, that was not going to be acceptable if we expected to spend any sizable time without being plugged in. The choices were to abandon the compressor refrigerator idea or find another power source. Ellen was all for selling the new fridge and going back to propane, but that wouldn't solve the original problem—no refrigeration while on the road. We have been unable to keep a propane refrigerator cold while driving, DC didn't keep it cold and the propane flame would blow out at any speed over 50 on in a crosswind.
The other possibility was a solar panel. I pushed for this option, with the justification that, even if it wasn't completely successful, we would still end up ahead since we would be much more self-sufficient anyway and we could take it with us if we sold Speedy in the future. We went that route.
A great deal of research followed. I wanted to get as much as I could on the roof without adding any massive infrastructure and we wanted to minimize the cost (We could easily spend thousands having a professional installation covering the entire roof). We decided that we could do it ourselves.
We seem to have found a cost-effective and relatively powerful way—a large panel. Many RV installations have multiple panels in the 100 watt range, but it turns out that larger panels have a much lower cost per watt. So, it was off to find the largest that would fit.
There is a place called the altE store, which it just happens to be located in Hudson, MA and they had great prices on larger panels, as low as 92 cents/watt. 100 watt panels were multiples of that. The least expensive panel was about 260 watts, but unfortunately it was too long. The space we have between the roof vent and the end of the van is just over 50 inches. Almost all the panels over 200 watts were 54 inches long. They are designed for large arrays and that seems to be a standard length. I toyed with the idea of an overhang, but it seemed like asking for trouble.
There was, however, a 215 watt Kyocera panel that was being offered at a great price. It was just 50 inches long—perfect. We went with that. In addition to the panel, we needed a power controller, mouting feet, wiring and some kind of monitor. Since it is a 20 volt panel and the batteries are 12V, an MPPT controller was required. These are a little more expensive than the controllers used for smaller 12V panels, but are also more efficient. We went with a TriMetric monitor, which gives us a complete picture of all the power put into the system and all power drawn out, so we can see state of charge of the batteries at all times and also determine what the various loads are. We were able to just drive up to altE and pick it all up, saving quite a bit of shipping expense.
We chose to use an adhesive foot system to attach the panel to the van. We wanted to avoid putting holes in the fiberglass roof. 3M makes a tape which is very strong. Its primary use is to hold up metal signs such as store names and logos on the sides of buildings. One of the largest professional RV solar installers uses this technique and claims that they have never had a failure. Fiberglass is an ideal substrate. We went with larger feet than they use and more of them, six rather than four. We also backed the adhesive up with a bead of 3M 5200 adhesive caulk (used to glue boat hardware on) around each foot.
After getting all the parts, it took about a week to install it. The hardest part was figuring out how to run the wiring. The monitor wire had to run from the batteries, on the left side in the rear of the van, to the wall with all the switches and gauges. on the right side near the front of the van. The other challenge was running the wiriing from the roof, on the outside, to the electrical wiring area near the batteries, on the inside—without drilling a hole in the roof. Both were solved, but it took a while to do it.
With a little bending of the feet to match the curve of the roof, the panel was fitted to the roof. This was probably the most stressful part, as you get only one chance. Once the tape sticks, it doesn't move. With a lot of help form Ellen, we made that happen. Then we plugged it in.
In bright sun, I've seen it putting out over 12 amps into the batteries, In shade, on the other hand, it might be one amp. But, in the few days we've tested it, it has been able to recharge the batteries when the refrigerator is full and running and set to less than 40° F.
The test will be our current trip, with several days sitting in the woods using lights, pump and fan as well as the refrigerator.
We'll see.
No comments:
Post a Comment