What is the best way to connect 6x 200W solar pv?

Photowhit said:

The chart you have pictured shows the wattage for the system voltage, yes, 12 or 24 volt battery bank.

General rule is, for a PWM charge controller, set them up for the system voltage, If the 200 watt panels have a VMP of 17-19 volts, they are designed to charge a 12 volt battery bank, and they should all be in parallel with each other. If you are using the same panels to charge a 24 volt system they should be 2 in series strings and 3 strings of 2 in parallel.

If they have  VMP of 34-38 volts then the should all be hooked u in parallel to charge a 24 volt battery bank, with a PWM charge controller.

If they have a VMP of 20-33 volts they are pretty much designed to be used with a MPPT type charge controller, in which case they tend to be most efficient with a VMP closest to 2x the system/battery bank voltage.


Your question would be more straight forward if you provided the vmp of the solar panel. They come in all 3 of the above ranges!

BB. said:

Forget your 5 series + 1 series setup... It will not give you very effective output power... More or less, it would be roughly equivalent to 1+1 in series. 4 of the panels are completely wasted.

When placing panels in series--Your want each panel to have the same Imp (current maximum power rating). If panel A outputs 5 amps, then the series connected panel B would also be rated at 5 amps. If you had a 25 amps 5 panels parallel in series with a 5 amp panel, then the 5 amp panel will limit the total current through the string.

So in your example with 2series * 3 parallel strings... That would be very nice for your SE/South/SW facing array. We call it "virtual tracking". Lead Acid batteries really "like" getting charged for many hours per day--I.e. charging 7% rate of charge for 10 hours per day is better than charging at 14% for 3.5 hours per day. Your total power per day is less from a virtual tracker vs all panels facing south, but it is (many times) cheaper to have a larger virtual tracker than to go to the expense of a smaller array + physical tracker (hardware, motorized actuator, controller, large steel pole, large concrete base).

More or less, it usually works out that PWM works cost effectively for smaller systems of 400 Watts or less. And MPPT work out for systems with 800 Watt or larger arrays. Note with PWM controllers you need "24 volt array" (really Vmp-array~36 volts) and a 24 volt batttery bank (or 12/12, 48/48 volt)... An MPPT type charge controller lets you work with Vmp-array that is >> battery bank voltage so you can put the array a longer way (100's of feet) from the battery shed (high voltage array/low current--MPPT controller "efficiently down converts" to low voltage/high current needed to charge the battery bank).

Rather than get too bogged down in "what ifs" and generic system design rules--Do you have an idea of what loads you want to support (maximum Watts, Watt*Hours per day, time of day of power usage (night or day)). Where the system will be installed (nearest major city)? Full time off grid or weekend/summer use?

It is less confusing to design to your needs, vs talking about general design principles. Many times, the solutions end up being different (1,000 WH per day 12 volt system vs 3,300 WH per day and 24 or 48 volt system that has an electric refrigerator and a deep well pump).

Once you know your loads--We can then help you with a couple of paper designs to see what works best for your needs (12/24/48 volt, PWM or MPPT controller, etc.).

-Bill

BB. said:

600 Watt--Is that a 600 Watt inverter or a 600 Watt solar array? What is the DC bus voltage for your AC inverter?

Generally, if we are starting with loads, a 500 Watt*Hour per day system (roughly 250 Watt of solar panel(s)) is enough to run a laptop a few hours per day, cell phone charger, LED lighting, small LED TV, etc.

A 1,000 WH per day system--More laptop usage, RV Water pump from cistern--Pretty much a "comfortable" amount of power--Excluding a refrigerator.

Add a Honda eu2000i (1,600 watt genset) for bad weather/running a larger load (saw, recharging battery bank during bad weather) plus 10-20 gallons of gasoline with fuel stabilizer (change out fuel every 6-12 months) and you are set for 5-10 days of emergency backup power (and enough to run the refrigerator 12 hours per day--even if your solar system is too small).

A 3,300 WH per day system--Pretty much an almost normal "electrical life" in a very conservation minded home (refrigerator, add deep well pump, clothes washer, etc.).

Of course--All of this is dependent on your energy needs (power usage is a highly personal set of choices--What works for me, may not for you).

1,000 WH per day or less--A "small" solar power system.

3.3 kWH per day--You are in the middle of solar power--The refrigerator really pushes the solar power system larger.

Note--There are choices here too... An Energy Star rated full size fridge can be very cheap to buy and maintain--But you need a good size solar power system to power. A DC refrigerator may be 1/2 the cubic foot storage and 3x as expensive--But you can get away with around 1,000 WH per day system.

Similar if you have a well pump... A "cheap" induction motor 240 VAC well pump (1.5 HP)--Need a good size solar system to manage the starting surge current. Get a "solar friendly" well pump for a lot more money, but almost no surge current--And some (of the more expensive models) will run directly from solar panels (pump when the sun is up) or even from a 48 VDC battery bank.

Lots of options and choices... I suggest that you try several paper design (paper is cheap and easy to change)--And see what best meets your needs--And, if you are interested in saving money--Conservation is your first choice. Insulation, Energy Star appliances, LED lighting, etc. is almost always cheaper than building out an off grid power system to power them.

Grid Tied Solar--It is getting towards the end of its government subsidies (in my humble opinion). Today (or at least yesterday)--A GT system could drop your electric bill to $5 per month.

In the future (next few years to next decade)--A GT power system may only be able to knock 1/4 to 1/3 off of your power bill (for many reasons--This is what makes "economic sense" to utilities and customers at large). And going off grid--It is not unusual for that power to cost your $1 to $2+ per kWH or almost 10x your utility power costs--So, again, conservation is critical here. I do not want to "spite" my utility by driving my electrical costs up by a factor of 10x.

A great little tool to understand your power needs is a Kill-a-Watt type power meter. Just plug your loads in (one at a time, 120 VAC max 15 amps) and see where you are spending your money (and where conservation makes the most sense). With the meter and a bit of math (spread sheet)--It really brings home how cheap power power is today.

-Bill

BB. said:

One part missing--How many hours per day do you want to run each load (5 hours fans, 5 hours LED, 6 hours TV, etc.)?

-Bill