Installing Off-Site Watering Setup

[Naptown]

Yes you can
However there isn't really a solar charge controller made for those so it would be something custom
Second you would be drastically increasing your battery costs.
The least expensive battery chemistry is lead acid.
High Energy density isn't really an issue with solar.

Did you re run the calculator using the revised watt draw of the pump?

[Sunking]

Here's another possibility for my batteries: Perhaps LiION?

From what I've read so far, they have a MUCH higher energy density than FLA's or AGM's, and can be discharged past 60% safely. .

Yes they do have much higher energy density, but so what? That is only important for motive power where weight is a concern.

A mid quality FLA battery that will last you 3 to 5 years cost around $175/Kwh. A mid quality 2 to 4 year AGM around $225 to $300/Kwh. A very low end 1 to 2 year LiPo around $500/Kwh and a high end 5 year Lithium Titanate used RE power in substation is around $1000/Kwh. Not even utility companies use them, Why would you spend $1000/Kwh when you can get the same for less than $200/Kwh?

In addition to be being cost prohibitive, there is no charge controllers out on the market for lithium chemistry except for the RC (Radio Control Toys) market which is a motive power market. No one makes them yet because lithium is still too expensive and thus no demand. It would be a custom design.

[OregonSolar]

OK, so scratch that idea.

So far, my estimated cost per system is about $900. here is my list, it may be a little on the low side of the energy ratings but I can live with it.

STATS:
Solar panel 24 volt 240 Watts 10A: $210
Pump 3GPM @ 3A 24Volt: $100
Charge Controller Morningstar Prostar PS-15 $95
Two 175Ah 12V deep cycle FLA batteries: $240x2=$480
TOTAL COST: $885

Run time per day, not counting longer Summer hours: 6HR


I know its a PWM charge controller and that's probably not enough panel for the charge controller. But at this point, it's either a better charge controller or a bigger panel, and I'm already getting a little big on the panel as it is. For a MPPT option in the charge controller department is a SunSaver SS-MPPT-15L. Would this controller be a good choice or do you have another preference? With this model i'll be slightly over my preferred cost of $1000.

CORRECTION: I really need to go up to a 200Ah battery, don't I. The calculator says so.

ANOTHER EDIT: And I assume a FLA would be a good system for this? I'm not sure if a FLA or an AGM would be better, but I'm leaning towards an FLA simply for lower price and I don't need the higher charge current.

[Sunking]

OK I see problems maybe. Are you running the system at 12 or 24 volt battery. If 12 volt you must use MPPT. If you intend to run at 12 volts with a 36 volt solar panel (24 volt battery panel), that PWM controller will turn your 240 watt panel into 87 watt panel.

Once you get above 200 watt panel wattage MPPT is less expensive. There is two reasons for this.

1. With MPPT you can use higher wattage, higher voltage, much less expensive Gri Tied panels. Grid Tied panels are 1/2 the cost of battery panels.

2. is efficiency and power. It takes a 300 wat panel with PWM to make the same power as a 200 watt MPPT.

What you have done is made the same mistake most make. You only looked at the cost of the controller, rather than the project. I can buy a 200 watt GTI panel and a MPPT controller for less than you can by 3 watts of battery panels and a PWM controller. Not only that but I get to save on installing 1 single panel with less and smaller wiring. 300 watt s of battery panels is at least 2 panels with twice the hardware and more and large wring. It would cost you $1000 all together with PWM, or $700 with MPPT.

[OregonSolar]

OK I see problems maybe. Are you running the system at 12 or 24 volt battery. If 12 volt you must use MPPT. If you intend to run at 12 volts with a 36 volt solar panel (24 volt battery panel), that PWM controller will turn your 240 watt panel into 87 watt panel.

Once you get above 200 watt panel wattage MPPT is less expensive. There is two reasons for this.

1. With MPPT you can use higher wattage, higher voltage, much less expensive Gri Tied panels. Grid Tied panels are 1/2 the cost of battery panels.

2. is efficiency and power. It takes a 300 wat panel with PWM to make the same power as a 200 watt MPPT.

What you have done is made the same mistake most make. You only looked at the cost of the controller, rather than the project. I can buy a 200 watt GTI panel and a MPPT controller for less than you can by 3 watts of battery panels and a PWM controller. Not only that but I get to save on installing 1 single panel with less and smaller wiring. 300 watt s of battery panels is at least 2 panels with twice the hardware and more and large wring. It would cost you $1000 all together with PWM, or $700 with MPPT.

It is a 24V system, 24 volt battery, 2 175Ah (upping to 200Ah)12V batteries in series for 24V. But one thing to clarify: What is the difference between a GridTie panel and a Battery panel? Aren't they all solar panels?

You've convinced me. I have a 240Wpanel; i'm going with MPPT.

[Naptown]

Panels made for batteries generally will have a cell count of 36 for 12v and 72 cells for 24v
That said there are a lot of 72cell grid tie panels out there.
However you are still losing a good bit with a PWM controller. Roughly a third
You will need a minimum of 72 cells to charge a 24v battery efficiently.

[OregonSolar]

Panels made for batteries generally will have a cell count of 36 for 12v and 72 cells for 24v
That said there are a lot of 72cell grid tie panels out there.
However you are still losing a good bit with a PWM controller. Roughly a third
You will need a minimum of 72 cells to charge a 24v battery efficiently.

What relation does the cell count have? Does it really matter?

Already decided: changing to a MPPT.

[Naptown]

Cell count is directly proportionate to voltage. With the exception of amorphous panels.
Generally a single cell will produce .5 volts at max power and .6 volts open circuit.
Doesn't matter how big the cell is a 1"
Cell will be the same voltage as a 6" cell however the amps and watts will differ

[SunEagle]

What relation does the cell count have? Does it really matter?

Already decided: changing to a MPPT.

The more cells you put into a series circuit the higher the max power output voltage of the panel. A 36 cell panel usually yields about 18 Vmp. A 72 cell panel yields about 36 Vmp. A 36 cell panel is called a battery panel. A 60 or 72 cell panel is called grid tie.

[OregonSolar]

Cell count is directly proportionate to voltage. With the exception of amorphous panels.
Generally a single cell will produce .5 volts at max power and .6 volts open circuit.
Doesn't matter how big the cell is a 1"
Cell will be the same voltage as a 6" cell however the amps and watts will differ

OK, I see now.

A panel need a certain amount of head voltage to charge a battery. So a 24V grid-tie panel might only put out 25 or 26 volts while a battery panel will putout 30 volts, which is enough to actually put some current into the battery.

So it's kind of like trying to fill a tire to 40PSI with a compressor that's only putting out 50. You'll eventually get the tire full, but it's going to take a looooooongtime when it starts to get near full.

The panel I'm looking at says a Vmp of 36V. Even though it is marketed as a 24V panel. Time to change...

[Naptown]

Most of the 200-270 w panels are going to be 60 cell
Once you get to 300 with a few exceptions they will be 72

[Naptown]

OK, I see now.

A panel need a certain amount of head voltage to charge a battery. So a 24V grid-tie panel might only put out 25 or 26 volts while a battery panel will putout 30 volts, which is enough to actually put some current into the battery.

So it's kind of like trying to fill a tire to 40PSI with a compressor that's only putting out 50. You'll eventually get the tire full, but it's going to take a looooooongtime when it starts to get near full.

No a 24 v panel will put out about 36 volts.
Battery voltage x 1.5

[OregonSolar]

No a 24 v panel will put out about 36 volts.
Battery voltage x 1.5

Makes sense now. So a 36V system (however odd and wierd) would require about a 48V panel setup, so on and so forth.

Understanding Dawns!
Sothe panel I already have picked out will be Perfect.

[Sunking]

The panel I'm looking at says a Vmp of 36V. Even though it is marketed as a 24V panel. Time to change...

That is a 24 volt battery panel. 12 volt solar panels are 36 cells in series with a Vmp = 18 volts. 24 volt battery panels are 72 cells operating at 36 volts and can also be used as Grid Tied. 30 volts is not quite enough for a 24 volt battery system.

OK your panel with PWM will generate 160 to 170 watts at the battery. Same panel with MPPT up to 230 watts.

[Naptown]

Now here is where the pwm vs mppt part comes in
In your case that 240w panel at 36v
Will produce about 5 amps
With PWM amperage in= amperage out so with a pwm controller you have a charge current of about 5 amps
Now move to an mppt and things get different
Watts in = Watts out - about 5%
So 240 watts in = 240 watts out - 5% = about 228 watts out
228/24 is just under 10 amps
Enough to keep a 100ah battery very happy