Tons of easy questions for you guys

**Mike90250** · 02-25-2016, 12:32 AM

1. Mttp seems to be the best choice when you live in Canada and obviously want to max production but I am scared it would require a lot of knowledge and programing. Is it really?

(it's MPPT)

Then maybe you need to read through the stickies in the Off-Grid sections. You got to get a better handle on things before you design and buy anything.
The software for Morningstar and Midnight controllers is pretty simple, once you understand what your batteries NEED (controllers come with basic generic settings) and how you need it modified.
Morningstar is absolutely silent, the Midnight has 3 cooling fans. Inverters nearly always have a cooling fan that comes on at >40% loading

Cooking - Propane is your friend. Using batteries requires a huge inverter, and at least a 24V system much larger amperage than you would normally need. But induction hot plates are about 90% efficient - at least 2x what a thermal resistance heater would be. The only losses are in the AC inverter (must be pure sinewave (90%) and the electronics in the cooker (95%)

More than 20' of DC wiring and you should convert to AC, the expense of using heavy copper wire, rarity of DC rated switches and light sockets, overwhelm the convenience of the 12VDC cage.

**KhellQc** · 02-25-2016, 02:01 PM

yeah propane makes sense, and winter I ll have a wood stove. Im still not sure about the lighting, Putting it on AC wouldnt be a big deal but if I went the dc way I ll end up over heating my LEDS.

I did more research and will keep doing more. I still need answers to stuff I cannot find myself. Most of them are listed a the top, like
Panel 2 & 3
Controller 2 & 3
Inverter 1

And now I have a new one regarding controller. I did new Calculation and the system would be 2kw and then I used 4 different Calculator to figure out how to set out the array and the proper controller. Ive looked at midnite classics 150 200 and 250 / also TSMPPT 45 and 60.

First everytime I use their calculator they say :

here on the 45 @ 24v

Maximum Nominal Solar Input Power exceeded for this controller. Controller output current will be limited, reducing power harvest below Maximum Power Point levels. Full output of array will not be realized. No risk of damage to controller in this configuration.

1 Module	290	580	870	1160	52.97	150.00	30.39	30.00	40.91
2 Modules	580	1160	1740	2320	105.94	150.00	60.78	30.00	81.83

then on the 60 @ 48V

2 Modules

105.94

150.00

60.78

60.00

81.83

but everytime if I add up the Vpm of each panel I bust the max tolerated by the controller. What am I doing wrong here

---------------------------

Also to add to the confusion, some calculator make me get 7-8 300w pannels and others 4 100w but with 9 100ah batteries

**Mike90250** · 02-26-2016, 06:49 PM

Don't buy stuff yet. Before you size the controller , how did you come up with the daily usage. ?

I'll quote the famous Sunking about sizing the PV for the batteries, THEN you chose a controller. A large 12V system may need $1300 of controllers, where a 48V system needs only $600 for the same watthours of harvest, As voltage goes lower, the amps increase.

Originally posted by Sunking

You must know two data points before you start.

1. Daily Watt Hours
2. Solar Insolation for your location in the shortest winter months.

From those two data points everything is calculated. First determination is what battery voltage you will be using. For battery voltage anything below 1500 watt hours can be 12 volts, although 12 volts is very inefficient, expensive to implement, and can only input up to 1000 watt Solar Panels.

So let's run an example. Say you need 3 Kwh per day and in January your Solar Insolation is 3 hours. First try 24 volt battery. For the battery size AH = [Daily Watt Hours x 5] /Battery Voltage], so [3000 wh x 5] / 24 volts = 625 AH..

Panel Wattage = [Daily Watt Hours x 1.5] / Sun Hours, so [3000 x 1.5] 3 = 1500 watts.

Now for the MPPT charge controller Amps = Panel Wattage / Battery Voltage, so 1500 watts / 24 volts = 62.5 amps.

Lastly you need to do a sanity check for the batteries as batteries, FLA Batteries, have a window of charge current they can accept of C/8 to C/12 where C = the AH capacity, and the number is Hours. We determined it would take a 625 AH battery. To make that battery happy means we must charge it with no less than 625 AH / 12 hours = 52 amps, and no greater than 625 / 8 = 78 amps. So the range is 52 to 78 amps for a 625 AH battery. We calculated 62.5 amps @ 1500 watts. We have a perfect C/10 charge current.

So the answer to your question is do the math, do it correctly, and everything works out just right.

**Sunking** · 02-26-2016, 08:31 PM

Quit worrying about panel voltage. You will be using inexpensive Grid Tied Panels and MPPT CHARGE CONTROLLER. You can charge a 12 volt battery with 120 volt panels. Higher the voltage the better off you are within limits of the controller. You are not even remotely close to buying anything yet. You have not done your fist steps. Read these and come back with questions. But you had better nail your daily watt hour usage and solar insolation. Otherwise you will fail and waste your money. Once you fin dout what it really takes, you may decide to go a different route. I will tell you are looking a 5 digit$.

Off-Grid Design
Battery Tutorial.
Inverter/Battery Size
Are you sure you want off grid
WTF Battery Tutorial.
Kill your battery

Plus the dozen other stickies.

Tons of easy questions for you guys

Tons of easy questions for you guys

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