Thoughts on this system

Yes, those loads are pretty small at this time... However, we also need to know the hours per day of usage. A Kill-a-Watt meter can make these measurements much easier:

http://www.solar-electric.com/kiacpomome.html

Knowing Watts is like knowing Miles per Hour... Without knowing the time, we really cannot estimate how much fuel (energy or Watt*Hours) you are using:

8x 9 Watt LEDs * 5 hours per night = 360 Watt*Hours per day
2x16 Watt LEDs * 12 hours per night = 384 WH per day
41 Watt TV * 5 hours = 205 WH per day
36 Watt Sat Box * 24 hours per day (if not turned off) = 864 WH per day
23 Watts * 24 hours per day (inverter just turned on) = 552 WH per day
===============================
2,365 Watt*Hours per day

My guesses above--But that is not a small amount of power for an off grid cabin (no refrigerator, no cell phone charging, no water pumping, etc.).

You have 3x 320 Watt solar panels (hopefully in series)--How many hours of sun per day for "break even":

• 2,365 WH per day * 1/0.52 typical off grid system eff * 1/960 Watt solar array = 2.5 hours per day of "sun"

Ok--From that point of view, assuming my numbers are anywhere near accurate (or over estimating power usage), you should have enough sun to keep up with the loads you have (except winter for most regions).

If you can let us know where your cabin is located (roughly, near what major city)--We can look at the sun for your location.

The other thing we like to do is size the solar array for the battery bank. Large battery banks need larger solar arrays for proper charging. 5% to 13% is what we start with. 5% can work OK for an off grid weekend/seasonal cabin. 10% or more is better for a full time off grid home.

• 225 AH battery bank * 59 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge =862 Watt array minimum
  
• 225 AH battery bank * 59 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 1,724 Watt array nominal
  
• 225 AH battery bank * 59 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 2,241 Watt "cost effective" maximum array

So--You are >5% minimum array (960 Watts for your system)--That looks OK for weekend/seasonal usage. At this point, a 48 volt system is pretty large for your needs--But if you plan on building out (adding a second string of batteries, more solar panels, more loads), you will have a very capable system (suggest ~3,300 Watt*Hours per day as an efficient off grid cabin/home with refrigerator, well pump, clothes washer as a starting point).

Your thoughts?

-Bill

String inverter--I guess I would call them "Micro Inverters" (a smaller 200-300 Watt Grid Tied inverter per panel connected to AC utility power).

Normally, I would not use them, however, it is possible--You get an Off Grid inverter designed to work with GT inverters "back feeding" the Off Grid inverter (yes, in many cases, you can push power "backwards" through an off grid inverter and actually recharge the battery bank).

This is not a "simple" setup. If you have the wrong type of off grid inverter, it is possible to overcharge the battery bank and cause the batteries to fail or even catch fire. You need some way to turn off the battery charging. You can put a dump controller on the battery bank (like used for a wind turbine). You can have a battery charge controller that turns off the AC power to the GT inverter strings. Or, you get an Off Grid inverter that can change its output frequency (50 Hz +/- 1.0 Hz or more)--then the battery is full, the OG inverter goes to 51/49 Hz which causes the GT inverter to shut down.

-Bill

Many inverters have the ability to connect both to the AC Mains (or backup AC Generator) and charge the battery bank--And their output will take energy from the AC input (if present) or energy from the DC Battery bank.

Many times, the AC inverter-charger is actually a pretty nice battery charger--Very configurable to meet your needs vs the (usually) low technology AC battery chargers that most people find.

Some of the modern Inverter-Chargers have some very complex operations/options. One of the neat things that some inverter-chargers do is "generator support". You can have a 3 kWatt AC generator running a 6 kWatt AC inverter--When your generator is running, it will charge the battery bank (if no loads). As the AC loads increase, the power is redirected from charging to supporting the AC loads. And, if the AC loads are larger than the AC generator's rating, the AC inverter starts taking battery energy to "support" the AC loads (makes the AC generator look like it is much larger).

-Bill