Tag Archives: inverter

photo of the solar system with A new AGM battery

A Solar Upgrade for the Teardrop Trailer

Teardrop Trail: June 4, 2017

In the last few months, I’ve been working on a larger solar system to pump water at the ranch. We live out in the Texas Hill Country and occasionally experience power interruptions, and I wanted to use solar power to improve our emergency preparedness. The experience of designing and building that system led me to rethinking the teardrop solar system.

A New Battery

photo of Cutting a hole for the data display

Cutting a hole for the data display

Two 100-watt solar panels provide enough power to meet our modest camping needs, but I felt the battery could be improved. We were using a marine battery, but it was a compromise between high starter current (which we would never use)  and deep-cycle power for camping use. An Absorbed Glass Mat (AGM) deep-cycle seemed a better match. I ordered an Optima D34M Blue Top that could supply up to 55 Amp/hours of power and fit into the modest available space.

And a way to measure it

photo of The new data display

The new data display

Of course, fully discharging any lead-acid battery will shorten its life and normally one leaves at least a 50% charge. How do you know when you’ve reached 50% remaining power? You can estimate from the battery voltage, but measuring power directly would be best. That led to the second upgrade; a digital energy meter. It shows voltage, current and power, as well as the total power in watt/hours consumed since the last reset. Using the Optima battery as an example, I could use up to 330 watt/hours of power ((55 amp/hours / 2) * 12 volts = 330 watt hours) before it was wise to recharge.

Electric Kettles for Camping?

Finally, we enjoy electric kettles for heating water, and they’re perfect for camping. In many campgrounds, shore power is available and we can heat water for tea, coffee and washing up with ease. Would it be possible to use an electric kettle on solar power?

photo showing solar system With 1000 watt inverter installed

With 1000 watt inverter installed

Researching electric kettles and hot pots I found one model that only used about 1000 watts. A lot of power, but within reach of a not-too-expensive 12-volt to 120-volt inverter. It looked like fun to see if I could make it work, and I ordered an inverter and the necessary wiring to hook it up. Besides; the same inverter could be used to power a Crockpot or Slow-cooker — something we’ve already shown is practical.

The picture tells the story. The new battery, inverter and hot pot were connected and did indeed heat 12 ounces of water to boiling. It used 164 watt/hours of energy as measured by the new digital meter — about half of the available battery storage. Not too practical, but a fun experiment!

photo of Solar chili complete

Solar Chili

Making good food with limited resources has always been appealing to me, and camping presents a perfect challenge. I still enjoy cooking over an open campfire, but solar power presents a new opportunity to make great food with simple tools.

photo of the Solar-powered system in the galley

Solar-powered system in the galley

With the addition of a slow-cooker to our galley and the upgrade of the teardrop’s solar power system, I began thinking about combining the two. Marilyn’s recipe for “Teardrop Pork Chops” proved we could have dinner ready when we got back to camp in the evening. I wondered if the solar system could effectively power the slow-cooker. Some quick measurements with the “Kill-a-watt” meter showed power usage for the 1 1/2 quart cooker to be well under 100 watts — even on the “high” setting. The “low” setting only consumed about 65 watts. With our 200-watts of solar panels and adequate sun, it should work fine. What to cook for an experiment?

Slow-cookers have always worked well with bean dishes, in fact, they were invented for cooking beans. The combination of low temperatures and long cooking times guarantee tender beans that retain their shape and texture. Chili is an iconic bean dish, and what could be better after a day of camping fun?

Solar Chili

Cooker: 1 1/2 quart oval, powered by a 300-watt Bestek Inverter plugged into a 12-volt, 200-watt solar system
Settings and Cook times: HIGH for 2 to 2 1/2 hours, then LOW for 8 to 9 hours

1/2 pound dried pinto beans, cleaned and soaked overnight and drained
2 cloves of garlic, peeled
1/2 pound of course-ground lean meat, beef, pork or turkey
1 medium onion, chopped
3 ounces of tomato paste or puree
1 1/2 tablespoons of Dixon medium hot (or other high quality) chili powder
1 tablespoon ground cumin
1 teaspoon salt (or to taste)

For serving:
Shredded sharp cheddar cheese
Chopped fresh tomatoes
Chopped green onions
Warm cornbread or saltine crackers

photo of Starting the beans and garlic

Starting the beans and garlic

Put the soaked and drained beans and whole garlic cloves in the slow cooker, adding enough water to cover. Cover and cook on HIGH until tender but not mushy, 2 to 2 1/2 hours. Drain and discard the garlic.

photo of

All ingredients cooking

Meanwhile, brown the ground meat and onions in a large skillet and drain off the fat. Mix the meat, onions, partially-cooked beans, tomato paste, chili powder and cumin in the slow-cooker. Add enough water to cover and stir. Cover and cook on LOW for 8 to 9 hours, stirring occasionally. During the last hour, season with salt. Serve with toppings and warm cornbread.

photo of a solar dining experience

A solar dining experience

How did we do? Using the measured slow-cooker wattage on high and low settings, a little quick math showed a total power consumption of about 750 watt-hours — within the production capacity of our 200-watt solar system on a sunny day. With the skillet-baked cornbread, all the fixins’ and a glass or two of wine — delicious.

 

photo of 100 watt monocrystalline replacement panels

The Teardrop Gets a Solar Power Upgrade

Teardrop Trail Log: September 20, 2016

photo of MC4 solar branch connectors

MC4 solar branch connectors

After the unfortunate incident with the solar panel on our way to the Red Power Roundup, we were able to use shore power for the remainder of the trip. Disappointing, but not a show stopper. We had already determined that a single 100-watt panel was not enough for our needs, so I was planning an upgrade anyway. With a trip planned in late September, it was time to act. I ordered two new 100-watt panels, MC4 combiner connectors and additional MC4 crimp-on connectors. This would double our previous power capacity and allow for daytime use of a couple of small appliances including a crock-pot and solid-state cooler.

photo of Aluminum bar seals leading edge to teardrop

Aluminum bar seals leading edge to teardrop

Analysis of the incident and the remaining parts of the old panel made it clear that wind entering the leading edge had repeatedly flexed the panel causing it to fatigue and ultimately fail. It seemed to me that sealing the leading edge to the teardrop roof with a rigid mount would prevent this type of failure in the future. A trip to Home Depot secured an aluminum strip, and by drilling holes that matched the existing screw mounts, I could seal the leading panel to the teardrop skin. The leading panel then overlapped the other panel so it was also sealed to the wind.

photo of volt meter showing 13.2 volts

The new panels began working immediately

Once installed, the panels began producing power immediately. Although we currently only have about 80 Amp-hours of storage, the two panels can easily replace the day’s power use with 10 to 12 amp output in full sun. Also, by adding a 300-watt inverter, we are able to run a 1 1/2 quart crock pot during the day with power to spare. The next upgrade will be a larger battery.

The Ambassador was ready for a trip to Bob Sandlin State Park.

photo of solar panels on teardrop trailer

The panels overlap like shingles

photo of mounted solar panel

Solar Power on the Teardrop Trail

In an earlier post, we described a simple solar system for the our teardrop. With only a 15-watt capacity, we needed to upgrade and did so last year. We’ve gotten some questions about our solar power installation on the teardrop, and I wanted to share what we’ve done. This a work in progress, but during our recent Big Bend trip, we never hooked the trailer up to shore power (aka 120 volt hookups) and used solar power almost exclusively. It’s important to state our goals however, we didn’t intend to replace shore power. Instead, we wanted to extend the practical range of our trailer, making it possible to use primitive campsites for days at a time. This is where solar power can really shine (pun intended) on a small trailer.

There are several elements to a solar system. At minimum, a solar panel, a storage battery and some kind of charge controller are needed. Additions include 120/240-volt capabilities like battery chargers and inverters. Our system is almost exclusively 12-volt. With it we run lighting and have the ability to charge multiple devices such as smart phones, tablets, a laptop and digital cameras. We even have the ability to run a few high current 12-volt appliances like an electric tea kettle intermittently. Our trailer has a 7500 BTU air conditioner (this is Texas after all), but that must be run on shore power.

photo of battery, charger and charge controller

Charge controller in place

Broadly speaking, there are two types of charge controllers: Maximum Power Point Transfer (MPPT) and Pulse Width Modulation (PWM). Both have their advantages, but a PWM controller won in cost and efficiency for our particular application: hot, sunny climates and systems of 170 watts or less.  An article with a more complete comparison may help with your decision.

Here’s what we ended up with:

  • Renogy® 100-Watt Monocrystalline Bendable Solar Panel (update: no longer available, but this panel is similar)
  • Renogy® 10-Amp PWM Solar Charge Controller (update: no longer available, but this controller is similar)
  • Interstate Group 27 Marine Deep Cycle/Starting Battery (available from Costco)
  • Jensen JMP-800 75-Watt Power Inverter (plugs into a 12 volt outlet for occasional use)

Fortunately, our trailer was built with dual wiring: 12 and 120-volt. There is 120-volt power in both the galley and interior, and a 12-volt outlet is available in the interior. I added a 12-volt feed into the interior cabinets to power a Ten-Tec Triton II amateur radio. Most of the installation work involved mounting the solar panel on the trailer’s roof. The charge controller was mounted in the galley storage adjacent to the battery. The trailer was already equipped with a small charger, and it charges the battery when we’re hooked up to shore power. The solar panel can be removed from the roof and located away from the trailer using an extension cord. This way, we can park the trailer in a shady spot while the panel is located in the sun. The photos show the mounting screw installation process.

photo of Incandescent Bulb

Incandescent Bulb

The trailer came with 12-volt automotive light fixtures and incandescent bulbs.

photo of LED "corn" lamp

LED “corn” lamp

These were replaced with LEDs resulting in a 75% power savings. As I mentioned, it is a work in progress, and I would like to add a second panel. There’s room on the roof, and that would double our capacity.

photo of Mounting the panel

Mounting the panel