Please help me design my system please please please

I'm trying to design a solar system, but I'm just getting more and more confused. I feel like I just need to see examples of complete systems or to have someone just tell me what to buy

I live in a small off-grid home that currently has 2 mismatched solar panels, a 1500w/3000w Flamezum inverter, a Pow-keeper 1240 charge controller, 3 Mighty max ML 100-12 batteries.
I live in a super sunny area with no restrictions on solar.
I am open to starting from scratch with the system and my budget is 4k.
I won't need much.

Always on items:
Internet 40w
Fridge/freezer (open to suggestions)
Water pump max draw 17A- intermittent use
Heat lamps/thermostats for 3 reptiles

Sometimes on items:
27" LCD tv
Laptop
Record player
Circular saw
Small vacuum
2 fans
2 lamps

NO microwave
NO toaster
NO A/C

michileigh87 said:

Always on items:
Internet 40w
Fridge/freezer (open to suggestions)
Water pump max draw 17A- intermittent use
Heat lamps/thermostats for 3 reptiles

Click to expand...

40W x 24h = 960WH
Refrigerator we usually use 2000Wh per day

Water pump... 17A at 120V?
5 minutes per day:

17A x 120V x (5/60 hours) = 170Wh

Heat lamp 40W? x 24h = 960Wh

Just your always on = 4090Wh per day

Lets say 5h sun summer, 3 winter:
4090Wh / 5h = 818W solar array operating at 100% (~1200W panels realistically)
4090Wh / 3h = 1363W solar array operating at 100% (~2000W panels realistically)

Running off batteries for 19 non-sun hours:
4090Wh x 19/24 = 2340Wh battery (double that for 50% usable lead acid batteries)

2340Wh / 12.8V nominal = 182Ah (364Ah lead acid) just for your always on estimates

Another way to approach this is to install an off-grid friendly "expandable" system, in these phases:

1. reduce your loads where possible, as power saved at this stage makes the rest of the system work better. Turn off internet at night (simple power switch or power strip, in front of all internet gear). Turn off fridge/freezer on a schedule (8 hours during overnight sleeping), or whatever works for you; place frozen water bottles in fridge to help out.

2. put in site propane (if you don't have it already), and a propane generator, like the Westinghouse igen series (up to the size you can afford)

3. install an AIO inverter (off-grid model), LiFePO4 batteries, and inverter-generator
- 24v 3000w or 4000w AIO (MPP or whomever's)
- 2x 12v300ah LiTime batteries (adjust this to any 12vXXXah batteries from LiTime)

4. install solar panels (300w to 500w, of anybody's make), up to about 75% or so of what the inverter can take in. the manual should be able to diagram/explain how many panels, of what size, in what pattern that you'll be able to use.

Buy all solar gear from a well-known vendor, such as CurrentConnected or equivalent; they'll help you make sure everything plays well together, and you won't pull your hair out in endless calculations. Buy the igen from home depot or lowes or amazon.

While sitting down with your budget and the above, you can hopefully determine if you can eke out a 48v system (inverter & batteries), but that will drive costs up a bit (48v inverter, 4x 12v batteries, or 1x 48v battery). But, it is possible the 24v will see you through.

The propane generator is there for two reasons: a.) a backup, in case of long stretches of clouds, or other unknown winter problems (this is colorado, after all), and b.) as a way for you to power on the generator (remote key fob) and run spot loads, like vacuuming, etc., and the generator will still top off the batteries. If you aren't on propane, get a small site tank by any of the propane suppliers in your area ... this way, there is no fuel mess.

Try to time your daily activities (breakfast, lunch, dinner) with small generator runs, and you'll avoid drawing down the batteries for those, while handling the large loads (vacuum, water pump, etc.) ... you can best figure out this stuff with your lifestyle. Such a scheme should easily allow the battery-bank to carry always-on loads through the night.

Notes:
- Generator can be placed into a "quiet" enclosure (youtube vids) so you don't really hear it, although the igen's are already pretty quiet.
- battery-bank can be expanded with a 2nd set of 12v matching batteries, in parallel, for more run-time.
- At the end of the new project, sell off all the old stuff, and apply towards costs.
- could have propane indoor heaters, as another form of backup; could have other propane devices, like cookstove, etc.

Hope this helps ...

Budget of $4K should give you an adequate system.

Example: AIO 3kw, 24vDC, 450Voc $400-500
Panels: 1600-2000w that the Vmp of panels wired in series is at least 120vDC. Depending on new or used the price will be $500-1,000.
24vDC LiFePO4 100ah 2-3 of them at $400-500ea.
The rest of your funds will be spent on panel mounts and proper wiring up components.

What that gives you is AC output of 120v and 25 amps to run and start loads. It gives you 8kWh to 10kWh worth of power from a sunny day on average. Your batteries will provide 100ah by 25vDC=2.5kWh if 2 of em wired in parallel 5kWh storage and so on.

50ShadesOfDirt said:

While sitting down with your budget and the above, you can hopefully determine if you can eke out a 48v system (inverter & batteries), but that will drive costs up a bit (48v inverter, 4x 12v batteries, or 1x 48v battery). But, it is possible the 24v will see you through.

Click to expand...

Okay so for the inverter, panels, and battery, what do you think about these (probably 3 panels?):

Look in resources.. https://diysolarforum.com/resources/

There are one line drawings and a lot of things to help you. The AIO manufacturers all have sample systems layed out.


Study simple off grid diagrams and you can use most to get ideas.

I couldn't imagine using a 30aH battery in a system, even though it's a 48v model ... the smallest I'd go is 48v100aH. Not sure why you'd want a 30ah battery (one at $700?), but it would take lots of calculations to see if it would serve your needs, and, that 30ah battery is probably "special-purpose", and not a general purpose battery typical for a battery-bank. What you may be bumping up against is the battery-bank configuration.

If 24v inverter, and using 12v batteries, then you need minimum 2x 12v100ah batteries (2 x $300 for SOK) for an initial battery bank. variations:
- 1x 24v100ah (or 200ah, or ..,)

If 48v inverter, and using 12v batteries, then you need minimum 4x 12v100ah batteries (4 x $300 for SOK); keep in mind that at 4x 12v batteries, you can't easily grow the battery-bank. variations:
- 1x 48v100ah, most likely a rack-mount for around $1200, and 1x 48v battery-bank easily grows with more of same battery

I would tend not to buy used panels, as you are buying someone else's problems. I'd keep casting around for new panels that fit the inverter's panel specs.

I'd set aside X amount of money from your budget for the 48v inverter ($600 or thereabouts), then Y amount for minimum 100ah batteries ($1200, or thereabouts) to make up your battery bank, and set aside some small amount for cabling, bus-bars, fuses, etc., and finally, whatever is left over, I'd apply a Z amount towards new solar panels.

Talk with the folks at currentconnected, & have them give you a parts list and diagram ... you can go back and forth with them on variations, until you find just the right mix of items that make you and your budget happy.

Hope this helps ...