First time user, do I need anything else?

joeshmow · July 2019

We are setting up an off grid system in a small 200 Sq Ft. cabin. We are anticipating using 60 KWH per month ( in the condo we moved from we only averaged about 48 KWH per month). I got 4 - 295 Watt Monocrystalline panes, a 60 Amp MPPT charge controller, 8 golf cart 6V - 210 Ahr Batteries, and planning on the Outback FXR3048A instead of the VFXR3648E inverter. Other than wiring is there anything else I would need?

joeshmow · July 2019

As you could probably tell from the stats on the inverter, I plan on running the 8 - 6V batteries in series for a single 48 V bank

Photowhit · July 2019

Well Mr. Shmow, curious where you were living and only using 48 kWhs a month and what your life style was like? That wouldn't support much more than a good size refrigerator.

Do you anticipate using air conditioning?

Will you have gas for heating, cooking and water heating?

So you will have a 210 amp 48 volt battery bank, and live on it/cycle it full time. So you should have enough solar to provide a 10-13% charge rate or 21-30 amps 57 volts or so, or 21x57=1197 watts or 30x57=1710 watts.

Solar panels are rated at Standard Test Conditions, but inn use produce about 75% of that, this is called Normal operating Cell Temperature values (NOCT) So would suggest an array of 1200/.75= 1600 watts to 1700/.75= @1250 watts.

the other question would be where will this system be and will you have enough reserve for the weather conditions. 210amps X 48 volts is about 10 kWhs of storage, of which you should try to maintain above 50% to preserve battery life. So about 5 kWhs of available storage at @1.6 kWhs of use a day should give you about 3 days reserve before needing to start a generator or other backup energy source.

Photowhit · July 2019

BTW - one of the reasons I question your daily use is it would be unlikely to need such a large inverter, if you are only using 1.6 kWhs a day. That inverter could use that much in half an hour.

Other than wiring you will want to use breakers or fuses between the assorted pieces. Midnite makes a nice E-Panel to keep most of these in one place. You should also be careful about the panel type and the charge controller type, 48 volts can get tricky with charge controllers, some having no 'sweet spot' for 72 cell panels and some charge controllers depending on your minimum low temperature. MPPT type charge controllers should have about 30% more voltage coming in than going out. so 72 cell panels fall short of that in strings of 2, but in strings of 3 may produce more VOC to be safe to use.

joeshmow · July 2019

Photowhit thank you for your input. We will be using propane for heating, cooking, and water heating and won't be using A/C for the most part so the 48 KWh is the real amount. Essentially we will use it for a refrigerator, power a single computer, a blender on occasion, and perhaps a small ac/heater unit that uses 1500 Watts and lights. We would only plan on using the ac/heater an hour or two maybe in the hottest part of the summer and coldest part of the winter. We live in Utah at 7000 feet and have quite a bit of sun. We don't even use a microwave. Is it essential that we get a breaker or fuse system or can I just depend on the inverter to regulate that. I thought that's what the low voltage and high voltage features were for.

Estragon · July 2019

You absolutely need breaker/fuse system. Even smaller battery banks can supply 100s os amps into a short, and unlike AC, 48v DC will sustain a fire-causing arc nicely.

To figure out what your pv might be expected to produce in various seasons near your location, you might want to check a site like pvwatts.nrel.gov

At high altitude, you may get a bit better than average pv output.

Other stuff you will/may need; multimeter, DC clamp amp meter, hydrometer for testing battery specific gravity, mc4 extention cables. If you end up with more than two strings in parallel, a combiner box with string breakers. Beefy (eg 2/0) battery interconnect and inverter wire, ideally premade. ~4 gauge wire for controller to battery or buss bars. Good tape or other means of insulating tools used near batteries.

Photowhit · July 2019

Photowhit said:

...So would suggest an array of 1200/.75= 1600 watts to 1700/.75= @1250 watts. 2250 watts

I hope you caught that I screwed up my math, I'd suggest an array of 1600 - 2250 watts.

1500 watts is a huge load, you could do a smaller air conditioner in the afternoon, when the batteries are topped off, but for heating it would often work against you, as the days are shorter and you would most want the heat when it's cold, during the night or cloudy days.

wellbuilt · July 2019

>That is a big inverter to run a small cabin , I have a flex power one system with a vxr3648 a and it uses 50 watts being on with out putting out any power . 1200 watts plus loads the inverter alone uses 35watt per hour . I have 16 GC battery’s @ 215 AHs and use 10 to 15% of my battery power over night and run 3 days before I need to charge with my generator . My cabin is 2600 sf and I use about 200watts per hour and up to 300watts if I turn on every thing I have .

Raj174 · July 2019

@joeshmow
You will need two more of the 295 watt panels. What you have are 60 cell grid tie panels with VMP about 33 volts. These panels will need to be installed in series strings of three. This will give you 90 to 100 volts in to the charge controller. Two panels in series would only provide about 65 volts, not even close to enough voltage to charge the batteries.

As mentioned by the other guys here, there are system loses that have to be considered. Flooded lead acid batteries are about 85% efficient, solar panels, about 80% efficient and the inverter will use about .8 kWh per day. The average flooded lead acid battery solar power system will yield only 50 to 55% of its nominal potential. In my opinion, with six panels and a 210AH battery bank, the system is fairly well balanced even with a 3000 watt inverter. It should provide 4 to 5 kWh on clear days to the loads.

Check out Midnite Solar combiner boxes and circuit breakers, they make good products.

Rick

First time user, do I need anything else?

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