Why Solar?

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 As my demand for more hours of more watts increases, I found I need to expand my solar setup. Watts = Volts x Amps, so the more Watts I need to consume, the more amps my 12 volt system needs to push out.  

 That's problematic, because more amps puts a lot of heat and stress on my wiring. It wastes more energy, and increases fire hazards. Not a good solution around temperature sensitive batteries and equipment.

 So to keep amperage requirements reasonable, I'll need to increase system voltage. Fortunately, that's not too hard.  Wiring batteries in series instead of in parallel will increase the voltage. So two 75 amp hour 12 volt batteries in series results in 75 amp hours at 24 volts. Four 12v batteries in series is 48 volts. Match that with a 48 volt compatible charge controller and inverter and you're good. Almost.

 There is the "water won't flow uphill" problem with electricity. In order to get energy to flow into a 48v battery array, you need a source greater than 48 volts. The 15 - 20 volts coming from the 100 watt solar panels is fine for a 12 volt system, but it won't budge the charge on a 48 volt system.

To get that done, I'll need to connect the solar panels in Series. Not a problem in and of itself, but I will want more amps coming into the system to charge the batteries all the way during short daylight winter days. I'll solve this by having six panels. I'll make two sets of three connected in series, and then I'll connect the two sets in parallel and run that to the charge controller.

 I'll do the same with my battery array. It will take four 75ah batteries to get to 75ah at 48v.  By my calculations, my compressor, pressure washer, and air conditioner will demand 4500 watts from my 5K Watt inverter at peak usage. At 48 volts, 4500 watts will suck up about 94 amps (figure 100 amps to include motor startup costs).  This means my 75 ah array gives me about 45 minutes of power at that level. If I had 150 ah, I could get 90 minutes of having everything on.  

 Realistically, I'll probably want to sustain 3000 watts, which is the air conditioner, lights, a mini fridge, portable battery chargers, and occasional power tool use; about 65 amps per hour at 48v.  

Now, when planning battery capacity, having a 75ah array does not give you 75 actual amp hours. With lead-acid batteries, even deep discharge batteries, you're really only supposed to discharge to 50% of total capacity to get maximum lifetime out of your batteries.  So we'll need to take that into consideration.

An array of 150ah is a good start, but ultimately,  I'll want to connect three groups of 48v 75ah batteries to get 225 amp hours @ 48 volts, or ~115 usable amp hours.  3000 Watts divided by 48 Volts is 62.5 Amps, so 115 usable amp hours gives me 115/62.5 or just under 2 hours of 3000 watts continuous usage, not including any solar replenishment taking place during the day.  I'll probably be running 8 panels by the time I get to three sets of batteries in parallel. Good thing panels are less than $100.

 I've taken the Nature's Generator all-in-one portable unit offline so I can use it elsewhere, and am running the entire building from my primary configuration. 

I have re-configured the solar PV panels that had been feeding the portable unit into a pair of three panel arrays (6 panels total), that I am connecting to my primary configuration using a separate charge controller.  

 Why a separate charge controller?  Charge controllers work best when dealing with similar inputs. The larger controller on the bottom is running two parallel arrays of four panels in series, all facing South.  Adding East facing arrays that have three panels in series requires a second controller that can optimize for these new arrays, which is exactly what the smaller top controller is doing.  

So how do the batteries and controllers not get confused with two charge controllers sending power at the same time? While one controller is bulk charging, it would be counter-productive (even potentially damaging) if the other controller was in float-charge mode. Fortunately, Victron Charge Controllers have this neat feature wherein the two controllers can talk to each other and coordinate their charging modes, so my battery banks remain well cared for and not at all confused.