diy solar

diy solar

Hello, new guy here with questions.....

Ivel

New Member
Joined
Aug 11, 2020
Messages
25
I'm new here and new to solar.

I would like to install a system on my home in case, heaven forbid we are truly in the end times and the grid goes down, or best case the power goes out for a few days.

My golf cart has six 6 volt Protron 2000 batteries in it. My thought is building an enclosure for the batteries on the outside of my house behind my electrical panel, run a conduit through the wall, mount the controller, inverter and whatever else in required on the wall. I would like install a manual transfer switch between my electric panel and the shore power/battery power.

I need to know if the batteries i have will work and if so for how long and how much power will be available, how many and what kind of solar panels, controller, inverter, any other pieces and parts I would need, if this is a dumb plan and if so what would I need to do different.

I'd like it to be capable of running at least a fridge, freezer, coffee pot, a light or two, tv, dvd, charge two phone and two laptops and the washing machine once a week or every other week. Any thing else would be great.

Am I dreaming big here, am looking at a really expensive system ?

Fire away but be gentle, I'm out of my wheelhouse here.

TIA, ivel.
 
Forgot to add these...
 

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There are great resources, including some system "blueprints", on this forum, just search on some common terms. There is also a spreadsheet that you can use to total your loads and figure out your needed capacity, which is the first thing you need to do. How old are those batteries, and have they been cycled a lot?

If your loads will always be small, say a maximum of 3,000 watts, building a 12v system would be ok. If you want to use the batteries you have, they would work well for a 12v system by arranging them into 3 groups of 2 pairs, with each pair in series. Then connect the 3 series pairs in parallel, giving you 12v and "about" 3x175=525 amp-hrs capacity. (See last paragraph though.)

A 24v system would provide more flexibility for future expansion, and especially if you don't need to power 12v appliances, would be a good choice. The down side of building a 24v system is that you can't configure your six 6v batteries efficiently for 24v. You would only use 4 of the 6 batteries, or you'd have to buy 2 more so that you could put two groups of 4 in series, then parallel the two groups. One group of 4 would give you about 175 amp-hours (but you'd be discharging the batteries at half the rate of a 12v bank, so their "charge" would last about twice as long). Two groups of 4 would give you 350 amp-hrs or so. For comparing capacities, it's best to use watt-hours, so you don't have to worry about voltage. So, e.g.

12v and 525 amp-hrs => 6,300 watt-hrs (using 6 batteries)
24v and 175 amp-hrs => 4,200 watt-hrs (using 4 batteries)
24v and 350 amp-hrs => 8,400 watt-hrs (using 8 batteries)

These batteries are lead-acid, and can only be discharged to about 50% or they will quickly degrade. So, for an "actual usable" capacity, cut all the amp-hour and watt-hour figures above in half.
 
I'd like it to be capable of running at least a fridge, freezer, coffee pot, a light or two, tv, dvd, charge two phone and two laptops and the washing machine once a week or every other week. Any thing else would be great.

210Ah at 24V (can't use 36V), is 5kWh assuming the batteries are still in good shape. If you've fully charged them after every use, they might be good. That gives you 2.5kWh of usable without excessive battery damage.

A typical fridge is about 2kWh/day fully loaded, so you'd have that covered with a little extra. To @Fred S point, you really need to add up those loads. That's link #1 in my sig. You also need to see how much solar is available in your area via link #5.

1000-1500W of solar will be enough to keep that battery charged in most cases.

Once you've done the energy audit, you can really zero in on what you need.
 
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