off-grid solar system setup help

[Ionelissy]

Hi everyone,

I'm new to the forum and also new to the solar panel systems. The setup is an off-grid system in Romania.

I have 8x 100w mono panels (5,42a-18,51v) and want to get an MPPT controller for them.

how many amps the controller needs to be in order to get the most power from these 8 panels, and what will be that?

and also, how many 200ah deep cycle batteries are needed for this system? ...lets say I will need to use 2kw/day

thanks in advance.

[russ]

An approximate location will help people respond.

[Ionelissy]

added that, thanks.

[Sunking]

The setup is an off-grid system in Romania...
I have 8x 100w mono panels..
want to get an MPPT controller for them.
lets say I will need to use 2kw/day

Let's get the bad new over with first. You will never be able to generate 2 Kwh of usable power per day except for a few of the summer months with a 800 watt panel setup.

Next you did not mention what battery voltage you intend to operate at, but for 2 Kwh per day at:

12 volts 833 Amp Hours
24 volts 416 Amp Hours
48 volts 208 Amp Hours

If these 200 AH batteries you speak of are 12 volt batteries it will take 4 of them regardless of the voltage you intend to run them at.

As for the MPPT charge controller again depends on the battery voltage vs panel wattage. Based on the 800 watts you already have at:

12 volts @ 80 Amps
24 volts @ 40 Amps
48 volts @ 20 amps

Problem is of course you do not have enough panel wattage to support 2 Kwh per day of use except in summer months.

[Ionelissy]

Let's get the bad new over with first. You will never be able to generate 2 Kwh of usable power per day except for a few of the summer months with a 800 watt panel setup.

Next you did not mention what battery voltage you intend to operate at, but for 2 Kwh per day at:

12 volts 833 Amp Hours
24 volts 416 Amp Hours
48 volts 208 Amp Hours

If these 200 AH batteries you speak of are 12 volt batteries it will take 4 of them regardless of the voltage you intend to run them at.

As for the MPPT charge controller again depends on the battery voltage vs panel wattage. Based on the 800 watts you already have at:

Problem is of course you do not have enough panel wattage to support 2 Kwh per day of use except in summer months.

thanks, battery voltage will be 12v.

now I do not understand why, except in the summer I will not be able to generate 2kw? I want to mention that I would need 2kw "cumulated" for 1 day, not 2kw/h for 1 day. For example I would use a TV for 2 hours, PC for 1 hour, a radio and some lighting at night in a 24hour period.... In this case, will I still need 4x 12v batteries? ..Now where I live, I use about 5kw/day, how much panel watts and batteries are needed to generate 5kw/day in a sunny day?

In regards to the MPPT charge controller, I read that the TriSTar mppt 60a can handle max 800w, will that not work with my 8 panels? or should I get 2x 40amp controller?

[russ]

For Bucharest (from http://www.gaisma.com/en/location/bucharest.html)

[TABLE="class: sun-data"]
[TR]
[TH="class: sdlhl"]Insolation, kWh/m

[Sunking]

now I do not understand why, except in the summer I will not be able to generate 2kw? I want to mention that I would need 2kw "cumulated" for 1 day, not 2kw/h for 1 day.

OK you just do not understand the difference between watts and watt hours.

Watts is a micro-second or a moment in time measurement of electric power. For example a 100 watt light bulb.

Watt Hours = Watts x Hours. Or the measurement of electrical energy used over a period measure in Hours. Example how much energy does a 100 watt light bulb use in 10 hours. Answer 100 watts x 10 hours = 1000 watt hour or 1 Kwh.

You stated you want to use 2000 watt hours or 2 Kwh per day or in a 24 hour period. To do that with solar using a MPPT controller, the panels must generate 3000 watt hours per day minimum every day and then some to recover from cloudy days. So in reality they need to generate at least twice what you use. In this case you want 2 Kwh usable so the panels must generate a minimum of 4 Kwh every day of the year.

Now look at the data Russ just printed out for your area. You are looking at the Sun Hours. To generate 4 Kwh per day with 800 watts of panels requires 4000 wh = 800 watts x 5 Sun Hours.

You only have 5 months out of the year with 5 or more sun hours of May, June, July, August, and September. The other 7 months you go dark without enough power. It would destroy your batteries if you tried.

To have 4 Kwh power generated by the panels in December requires a minimum 4000 wh / 1.18 h = 3389 watts of solar panel power. Lets just call it 3400 watts.

So the only setup that works for you requiring 2 Kwh per day year round is:

• 3400 watt solar panel
• 48 volt 80 amp Charge Controller
• 48 volt 200 Amp Hour battery

If you insist on working at 12 volts, you still use the same 4-12 volt, 200 AH batteries, but will need 4 of the 80 amp hour charge controllers to handle 3400 watts of solar panels. You would have 4 separate solar panel systems of 850 watts each with its own charge controller supplying a common 12 volt 800 AH battery bank.

Hope that helps.

[Ionelissy]

OK you just do not understand the difference between watts and watt hours.

To have 4 Kwh power generated by the panels in December requires a minimum 4000 wh / 1.18 h = 3389 watts of solar panel power. Lets just call it 3400 watts.

So the only setup that works for you requiring 2 Kwh per day year round is:

• 3400 watt solar panel
• 48 volt 80 amp Charge Controller
• 48 volt 200 Amp Hour battery

If you insist on working at 12 volts, you still use the same 4-12 volt, 200 AH batteries, but will need 4 of the 80 amp hour charge controllers to handle 3400 watts of solar panels. You would have 4 separate solar panel systems of 850 watts each with its own charge controller supplying a common 12 volt 800 AH battery bank.

Hope that helps.

thanks, that certainly helps,

other questions I have, will a 40a mppt controller be able to charge 500w (from 100w x5 panels) to a 12v 200ah battery? ..I'm thinking getting 2 more panels to make it 1000w and get 2x 40a controller to hook up with 5 panels each, will that do it?

what would be the max power in watts a controller 40a, 50a and 60a can charge a 12v battery, or how many 100w panels I can hook up to a 40a, 50a and 60a controller?

thanks again.

[Sunking]

To determine what the maximum wattage a MPPT controller can handle just take the nominal Battery Voltage x Amp Rating (of the MPPT controller) So let's say you have a 40 amp controller then:

12.6 volts x 40 amps = 500 watts
25.2 volts x 40 amps = 1000 watts
50.4 volts x 40 amps = 2000 watts

It's that easy.