Will this Off-Grid System Meet the Requirements?

Re: Will this Off-Grid System Meet the Requirements?

Ok, I will make some very general comments first as others will chime in to expand on this...

first test in my book of an existing system is that it has performed up to the design goals, in this case it appears to have but there are a few tests that can be done to confirm its properly meeting those goals... #1 is to check the specific gravity of each cell in that big battery #2 ...is to do a capacity test on the batteries.

At first glance there are a few things that could be improved upon if there are some components lacking but that can be determined after we examine each component and the system performance. more later.

Q1 do you have SGs for the cells after rest with no loads on?
What brand and type battery do they have
What are the charge settings on the Charge Controller?

hyh

Re: Will this Off-Grid System Meet the Requirements?

I'm with Tony on most of this, but you are in a particularly good location for sun, Northern Arizona, and I think even in winter you can expect 5 hours so you might up your multiplier to 5.

I would think you will want a bigger array, and you might just have enough space for it on the same roof.

The type of battery, just the model number will allow us to figure out your battery capacity. If they are golf cart sized (@60lbs look like a big car battery) you are likely near the end of their life cycle, if they are L16's (kinda a double height big car battery size) then you should get a few more years out of them.

It sounds like they have a quality system, Outback was the top of the line in an integrated system and is today for a little while, likely soon to be surpassed by Midnight solar (same people different company). It is expandable though I think you will be close to maxing out the charge controller at 3400 watt array (my thinking on your needs) Outback now has an 80amp charge controller but you might go for maxing out your current MX60, most of the time even with a larger array you won't reach the panel rating and be fine. I think Outback has a Charge controller capacity sizing thing somewhere on line.

As to the Air conditioner, I'd go ahead and add a generator, but do it with your system and have it auto start.

I'd also look into the mini split type A/C likely the most effiecent type currently available if it will work for you.

Also when they added the 2nd inverter, did they switch the septic over to 240V and pair the inverters? I'd bet the pump will run 240 and might be more effeicent that way.

Re: Will this Off-Grid System Meet the Requirements?

Dang 'Coot, have some coffee!

It was for weekend use, and we don't actually know what batteries they have yet. If they are that large, perhaps they are AGM and a 4-5% charge rate might be fine particularly with weekend use and Arizonas reliable sun. Remeber too, that 5 years ago panels were more expensive...

...It's not like they live in Canada, they are in high desert.

Good Morning!

Re: Will this Off-Grid System Meet the Requirements?

Sorry 'Coot, it was the "...Wheel of fortune?..." comment, looked like the installer was actually listening to the client for a change (to me). They wanting something for weekend use but expandable, at a time when panels were more expensive...

If the original poster is still out there somewhere? Did they happen to install a trimetric or similar shunt based battery monitor so we could also get an idea of the current daily use when people are in residence?

Re: Will this Off-Grid System Meet the Requirements?

solarheaven wrote: »

I do not have the SG readings for the batteries, but I can try and get up there in about a week to get those along with the charge controller settings. Whatever the settings on the controller, they will be exactly the same as when the system was installed no one has made changes. However, I am not sure how to do the capacity test that is recommended.

If they are L16 and a flooded battery that someone must add distilled water, to from time to time, they likely are 350-370 amp hour batteries, you'll see 420 amphour, but that is a c/100 rate. While checking your settings you might check wo see if it is set for equalizing every 30 days. I'm unfamiliar with Outbacks system, but if it gives you "a days since last full" or something like that it would be good to know.

solarheaven wrote: »

I have not been able to get model number for the batteries, but they are the L16 Deka Deep Cyle Batteries. I know the Ahr ratings can differ, so I am guestimating at their rating based on the Deka batteries that look the same on the internet.

solarheaven wrote: »

The location does get great sun does a reasonable job even on cloudy days. The mate has shown a reading of 4kw of power collected on cloudy days and over 8kw in the long summer days. They do not have the display to give them more detailed info such as whether they are drawing off the batteries, how much power is used in the day, etc, but I had seen those and thought that getting one added might be a good step in getting a better idea of how the system is handling current loads in relation to the power collected.

I think, again I'm not familiar with Outback, it sounds like your system is working very hard to maintain your batteries. I believe the Outback charge controller only records what current has past through it. 8kw of through put from a 1.6 Kw array is pretty huge, you would expect about 75% of panel rating and perhaps less in summers heat (heat drops voltage) so I don't know how often your reaching full charge. Part of this is likely your 'over sized' battery bank to your array. If your folks have been leaving it during the week perhaps it catches up....

solarheaven wrote: »

They are still deciding what to do with the A/C unit because they are still looking at heating solutions. I know that they have looked at the mini-split systems from a company called Ductless HVAC Supply. Those units have the outside condenser units with the inside handlers. Even with those units, they would plan on running the generator and the units would not likely run long. They would mostly be to take the "edge" off on those hottest days.

To have a healthy off grid solar system there must be waste, but if you add panels and an auto start gennerator, likely you can draw from the array for most of your needs, I hope to be up and running in the Midwest running a couple A/C units with a smaller battery and slightly larger array. I designed it, planning on a 4kw array meeting all of my needs, though I would be willing to moderate my cooling if I wasn't keeping the battery charged.

I don't know how your septic system works if the airator(?) runs constantly or if you could set it to run during the day, while the sun is out (this is called load shifting and allows you to use the solar energy more effiecently since you don't loose the 15-20% storing the energy) As a large load it would be good to know, the what and whens of the septic load.

solarheaven wrote: »

On the inverter, the pumps were not moved to DC. They have the normal AC fuse box and I believe that 2nd inverter is handling only the AC load for the septic system at this time and the rest of the panel feeds from the other inverter.

I don't think anyone had asked if you had moved the pumps to DC, I was asking if, when adding the 2nd inverter if the inverters were paired. Usually you can pair the inverters giving you 240 volts, which is what most homes have coming into them. Large motors like water pumps, and Central air (water heaters and electric dryers, and stoves) run from 240 volts. Often solar electric homes find other ways of doing these things) Inverters can also be run 'stacked' providing 120volts but more wattage or as 2 seperate systems, running off the same battery bank, which might be the way yours is setup.

solarheaven wrote: »

The comment about the expensive panels 5 years ago was correct. The assumption was always that more panels would be required, but to pay that money later when the panels were needed rather than spend even more money at the start. Fortunately, that decision has worked very well since panel prices have come down so much.

That, at least, has worked out very well indeed!

solarheaven wrote: »

I thought of another question in the mean time. The panels are Evergreen 185W panels I believe, but I don't have the specs. So, if more panels are added, are they likely going to need that 2nd charge controller because I won'twon't be able to verify whether the new panels have an amp rating close to the same as the original panels?

You will want to find panels that closely match your existing panels. I search a bit for Evergreen solar pdfs you might want to as well, they had a Spruce line of panels which appear to skip over 185watt, and then ESA and ESE panels The ESA are 12 volt nominal panels and ESE are designed for MPPT only and have higher voltage. I failed to find a 185 watt panel. You will want to match the voltage(VMP) with in 5-10%, also you will want them configured the same, with 9 panels, I'd bet they are in strings of 3. There is also the option to configure strings to match with fewer panels if your current panels are 12 volt nominal panel(around 17.5 VMP)

You might be able to find a receit for them or climb up on the roof and read the back of them, HINT if they are mounted 5-8" off the roof, which they should, you might take a digital camera and reach under to photograph the info sheet on the back.

With your current 60 amp Charge controller, and loosly working backwards, you can handle 60 amps of output, at 48 volts that's 60ax48v(system rating) = 2880 Watts, since the NOCT (normal operating cell temerature) values typicaly run no more than 80% you should be able to handle about 3600 watts of array with out loosing to much current if ever. Outback or your electric inspector may require some derating. So if you can find panels that match pretty close you shouldn't have to replace the charge controller with up to 3600 watts of array.

Here is a link to Outback's string sizing tool.

solarheaven wrote: »

Please let me know if there is any other information I can provide. I will work on getting the other info and will post it as soon as I can.

You did pretty well already, getting a real idea of your loads will be key in designing a system your folks can live with.