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October 13, 2015 practical

Soak Up the Sun

Or, A One-Month Review of Our Solar Set-Up

Before I get into the details, if you’re just here because you want to know if it works - it works. There are things that we’ve figured out that work really well, but there are also some things we would add/change in the future.

What We’ve Got

Here’s a spreadsheet of the parts we used to connect the pieces of our solar set-up:

Essentially, electricity comes in through the solar panels and gets chopped down to an acceptable flow by the controller (so we don’t flood the batteries and over-fill them). When we need DC power (from the DC sockets - think cigarette adapter for your car - and the LED strip lighting), the power from the batteries goes into a busbar to get sent out to each of the lights/sockets that needs power.

When we’re plugged into AC power (like at an RV park), the battery charger converts the AC power to DC to bring them back to a full charge within a few hours (much faster than with solar panels alone). If we wanted to, we could forgo the solar panels entirely and just charge the RV between parks.

Of note here is that it’s not just the solar panels (how you collect energy) that matter - it’s also the batteries (how you store energy).

My brother Connor did some calculations for us based on our estimated electrical usage before suggesting the parts he did. Our batteries give us 200 amp-hours of stored energy, meaning that if my laptop draws 2 amps (which it usually does), I could charge it for 100 hours just off of the stored energy in the batteries.

These calculations were done assuming we would have an in-line inverter, allowing us to run the AC lights, but we postponed the inverter for later. Instead, we can run really tiny appliances (my mini-straightener and sewing machine, Christian’s soldering iron) off of an inverter that plugs directly into the DC socket, like the kind you might use in your car for laptops.

In the month that we’ve had this solar set-up so far, we’ve been able to boondock’ for over two weeks. We stayed on a residential street in Lebanon, Illinois, for a week and never dropped below 70% battery capacity, even when it was cloudy and rainy. Then we spent a long weekend in Cleveland, Ohio, hopping between Walmart parking lots and a Texas Roadhouse. For these days we didn’t even put out the panels, not wanting to leave them unattended in a parking lot. We were still above 50%. Then we were back at a campground and within a few hours of plugging in our AC the batteries were back up at 99%.

What We Love

The main benefit of having solar panels (and huge honking batteries) is that we don’t have to worry about finding somewhere to plug in each night. We can still see in the dark, store and cook food, stay warm, and charge our devices in the middle of a parking lot or on a street. With our current set-up we can’t quite do everything that we would be able to do on shore power, but it’s pretty dang close.

Also, switching over to DC charging means that all of our devices can be powered by the sun without going through inverters. It doesn’t charge our devices any faster, but it drains much less power from the main batteries than it would if we were double-inverting everything we charged (DC –Go Power inverter-> AC –power brick-> DC).

What We Would Add/Change

I would love to have an in-line inverter for our AC appliances and outlets (powering the microwave, track lights, blender, vacuum, fridge in AC mode, and other appliances). The mini inverter we have works for now for smaller devices but not the bigger ones. This upgrade would be in the several hundred dollar-range, so we postponed it originally.

We’d also love to figure out how to have a one-way connection to the original house battery so it can be charged without drawing power from it for other things. Right now it runs the propane monitor, which is a failsafe that must be on for the fridge to be running off of propane. AKA if the original house battery dies, we can’t run the fridge off-grid.

We didn’t think the little propane monitor could drain the gigantic house battery, but it did when we were parked for a week in St. Louis without running the engine. It didn’t drain completely, but the fridge started warming up and the battery monitor was acting funny. We can prevent this from happening in the future by running the generator or engine for a few minutes if we’re ever parked that long again, but it’d be nicer if it could just steal some power from the solar system instead.

Extra - Propane

Propane is the other piece of the energy puzzle (besides being plugged into shore power). Propane powers our heating elements - the stove, the furnace, the water heater, and optionally the fridge (when it’s not on AC).

We’ve only filled propane once since we left the Dallas area, and that was to go from 1/4 of a tank to 3/4 (the filler said to leave space for when it pressurizes, but Christian thinks he might have been doing it wrong). The half-tank fill was 7.4 gallons of liquid propane, which cost $3.53/gallon for a total of $27.69 for our fill - not a bad first month’s energy bill!


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Fall Foliage, Day 27 - Lake Placid, New York to Smuggler’s Notch (Stowe), Vermont This morning we took our time cleaning and packing up (including vacuuming while we were still plugged in). Then while Christian handled a minor