December 13, 2019

A Home for the Solar Battery Bank


After we got the batteries, we needed a home for them. Dan planned to build a box, until he took a closer look at an old box that we already had.


This was left in one of our outbuildings when we bought the place. We've used it to hold kindling over the years, but when Dan measured it, he discovered that it would work for a battery box. It's just large enough to house our six batteries, the charge controller, and the circuit breakers. All it needed was reinforcing, a base, and some paint.


The base is repurposed too. It was originally the form Dan made for pouring the concrete pad for the outdoor laundry tubs.


We had already chosen the location.

Photo from "Burying the Solar Cable." See
that post for why this is a good location.

The cable was buried in a conduit under the driveway. To run them into the box, Dan used vertical PVC pipe and two elbows the same way he did at the solar panel end.



The last step was to build a cover. This was made from scraps of lumber, plywood, metal roofing leftover from the carport project.


It still needs some paint and vents, but other than that it's ready.

December 9, 2019

Digging Out the Old Swimmng Pool

One of the items on our winter project list was to dig out the old swimming pool. We had no idea it was here when we bought the place. It was our next door neighbor who told us about it. He remembered swimming in it when he was a kid. It was filled in some years later and so overgrown that we really weren't sure where it was. I finally found it when I cleared back the overgrown brush behind the carport. That was almost ten years ago.

Photo from March 2010. It measures 11 feet by almost 24 feet.

We've pondered what to do about it from time to time. We definitely have no interest in using it for swimming. Dan's mentioned a cistern and we've also wondered if we could somehow convert it to a root cellar. But it was hard to make plans without knowing exactly what it looked like. And of course, there was no telling what kind of condition it's in. For that we'd have to dig it out, so Dan rented an excavator to do it.




The last of it was done by hand. Sam helped.


The shallow end is 3 feet, the deep end is 6 feet.


In the above photo, the board on the bottom marks the location of a possible wall for a root cellar. The slope would have to be dealt with, and it would need to be built up for a roof. The other question is what to do with the rest of the space.


Another option might be to use it as a cistern for rainwater. There are cracks in the walls so it would need to be lined, then need a cover and a pump.

We're still busy with the solar project, but at least we know what we're dealing with. Obviously, it can still hold some water, so we'll have to come up with a plan one of these days!

December 5, 2019

Solar Pantry Project: Batteries

Continued from "Burying the Solar Cable."

Step by step we're making progress toward getting our freezer (and maybe a chest fridge) on solar. Each step has presented challenges! Choosing batteries, for example. Solar panels only produce electricity in the sun, so batteries are a necessity to keep things running when the sun goes down. However, there are so many choices. Here are the factors we looked at and how they influenced our decision.

Flooded lead acid batteries. Of the various kinds (flooded, sealed, lithium), these are the most economical. Considering this is our first solar set-up and it's possible we'll make some learning mistakes, it makes sense to keep it affordable. Life expectancy for this type of battery is only about five years, and they do require maintenance and need ventilation. But also, we can buy them locally, another plus.

Local availability. The reason for this is simple—shipping costs! Shipping for batteries starts at $250 to $350. Because of our budget, it makes more sense to buy locally. But also, if there's a problem it will be easier to return them to the store rather than ship them back.

Deep Cycle. These are different from car (cranking) batteries. In a vehicle, the battery has to supply a brief high demand to get an engine started, i.e., rotate the crankshaft. A cranking battery is built to bear a high load for a short duration. Deep cycle batteries are built for a low continual draw with repeated discharging and recharging.

6-volt batteries. We took this recommendation from our go-to book, Prepper's Total Grid Failure Handbook (my book review here.) They are similar in size to 12-volt batteries, which means they are more heavy-duty than their 12-volt batteries and should last longer.

Amp-hours (AH). Starting batteries list cranking amps, while deep cycle batteries list amp-hours. This isn't a specific time measurement, because factors like temperature make a difference. Basically, the higher the AH, the longer the battery can last before it needs recharging. Of course, the higher the AH, the higher the price.

Weight. Three popular sizes of batteries for solar battery banks are golf cart (GC), L16, and fork lift (industrial) batteries. The L16s and industrial batteries offer the highest amp-hours, but are heavier (and more expensive). In general, golf cart batteries typically weigh less than 100 pounds, L16s weigh more than 100 pounds, and industrial batteries weigh 800 pounds or more. Handling them is a consideration!

After weighing our choices, we decided that golf cart batteries would best meet our needs and our budget. We ended up with two options, both are the same size (GC2), weight (65 pounds), and AH (235).
  • Duracell from the battery chain store. $133 each + $21 core charge = $154 per battery
  • Rolls Surrette from a small business. $130 each + $16.67 core charge = $146.67 per battery

Price plus brand reputation determined our choice:


My original estimate was four batteries, but we were able to get six for $880. And that still keeps us within our original budget of $1500!

How much energy will these actually give us? Well, do you remember my explanation of series versus parallel wiring in "Wiring the Solar Panels?" We'll apply that to our battery bank, connecting some in series and some in parallel.

Blue - series connection, neg to pos. Adds voltage. 6v + 6v = 12v
Green - parallel connection, neg to neg & pos to pos. Adds amperage.
235 amp-hours + 235 amp-hours + 235 amp-hours = 705 amp-hours

This set-up will give us a 12-volt, 705 amp-hour battery bank. We need less than 1000 watts, so 12 volts will work well for us. If we wanted much more than 1000 watts, we'd need a 24-volt system, or even 48 volts for higher usage.

Hopefully, 705 amp-hours will give me a two-day back-up if the skies be dark and sunless. That's a definite possibility, especially this time of year. In that case, the options are plugging back into the grid or finding an alternative way to recharge the batteries (like a generator—something on Dan's wish list!) Adding more batteries at a later date is not an option. This is because the batteries in the bank need to age together, with the same number of discharges and charges. Adding new batteries would create an imbalance that would cause more problems.

Next step is building a box for them. While Dan's working on that, I'm figuring out cable sizes and DC circuit breakers. We're getting closer!

December 1, 2019

Winter Project List

In the past we've always done an annual goal list. I post it on January 1st and wrap up the year with a review post on how well we met those goals. This year, we seem to have fallen into a different pattern. Maybe it's because Dan is retired now, or maybe it reflects a shift in the kinds of project we do. Mostly, I think it's because our lives are more in sync with the seasons; everything seems to revolve around that. Everything we do fits into the pattern of the agrarian cycle I've blogged about.
  • Spring: March, April, May - season of planting
  • Summer: June, July, August - season of growing
  • Autumn: September, October, November - season to harvest
  • Winter: December, January, February - season of the hearth

This year we've started doing quarterly project lists instead of an annual one. The other day, we got out our notebook and made a winter project list. Here's what's on it.

  • build battery box
  • install batteries
  • connect batteries
  • move freezer
  • new chest freezer → convert to chest fridge
Garden
  • dig two more swale beds
  • cover and mulch main aisles
  • do something with that weedy corner!!!
Workshop
  • fix the back gutter → rain tank?
Trees
  • cut old pecan tree in the goat corral
  • cut down dead dogwood in front yard
  • limb out trees shading pasture
  • cut and remove fallen pines
  • chipping
Fencing
  • better (stronger) subdivision of buck pastures
  • start repair in browse areas
House
  • front porch trim
  • finally replace windows in front bedroom
Root cellar?
  • where?
  • dig out old swimming pool & evaluate
  • form a plan
Greenhouse?
  • where?
  • monitor winter sun in potential locations
  • dig out crepe myrtles 
  • cut back bushes

We prioritize and choose projects according to the weather. But winter can go either way for us; it can be either mild or miserable. There's no way to predict that, so except for finishing the solar pantry project, everything else on the list is flexible. Still, it's nice to have a written list of things to do in case the weather is cooperative. Dan, especially, is not one to sit around, so I suspect quite a bit of this will get checked off no matter what the weather does. 😀

Winter Project List © December 2019