Smoking

Re: Smoking

Generally:

1. measure the loads you want to drive (peak watts, Watts*Hours per day, etc.)
2. define the battery bank (typically ~4x your average daily load--2 days of no sun, 50% max discharge for longer life)
3. size the solar array to both support your loads and properly recharge the battery bank (~5-13% with 10-13% being really nice)
4. Then start picking equipment to support your needs.

In this case, you already have equipment. So, we need to hook it up in such away to give you a reliable and safe system that will meet your expectations.

So, what is your hardware:

• Batteries, voltage/Amp*Hour rating, flooded cell/agm/etc. (hopefully deep cycle type)
• Number and brand/model of solar panels (Voc/Vmp/Imp if you have it handy)
• What is the charge controller
• What is the inverter
• Roughly, where will the system be installed (figure out how much sun you will get per day/by season)

In general, I suggest sizing everything to the battery bank (voltage and Amp*Hour capacity). The typical rate of charge of 5% to 13% is a good point to aim for. Less than 5%, you really don't have enough power to quickly and fully recharge the battery bank. Over 13% is a lot of solar panels (expense) and you should have a solar charge controller that supports a Remote Battery Temperature Sensor (it is possible for a battery bank to get hot from high charging current and thermally "run-away"). etc...

Let us know what you have, and possibly how much power you expect to use (a Kill-a-Watt type power meter is great for this job--and handy for understanding power usage in the home and how to best tackle conservation projects).

Enough hand waving on my part--With a list of your current hardware, this will all make a lot more sense as we go through the design cycle.

-Bill

Re: Smoking

techcord wrote: »

2 X 12v Deep cycle 92 amp batterys, they have caps with water in them, that would mean flooded, correct?

Ok--Yep, they are "flooded cell". So you need to check the electrolyte levels about once a month and probably need to add distilled water every couple of months (if everything is going well). Make sure to only fill after a day of charging and don't over fill (or you will have electrolyte spilling out all over your battery top). Make sure to never the the plates be exposed to air.

The "optimal" size of solar array for this battery bank would be (assuming 24 volt battery bank connetion):

• 29 volts charging * 92 AH capacity * 1/0.77 panel+controller deratings * 0.05 rate of charge = 172 watt minimum array
• 29 volts charging * 92 AH capacity * 1/0.77 panel+controller deratings * 0.10 rate of charge = 346 watt nominal array
• 29 volts charging * 92 AH capacity * 1/0.77 panel+controller deratings * 0.13 rate of charge = 450 watt "cost effective maximum" array

2 X Uni-Solar PVL-116 116 Watt 24 Volt panels

I am not entirely sure what the ratings of these panels are... But if this website is correct:

Uni-Solar PVL-116 116 Watt 24 Volt Brand New Flexible Amorphous Solar Panel with MC3 Connectors Maximum Power (Pmax): 116 Watts
Nominal Operating Voltage: 24 Volts
Peak Power (Volts): 30 Volts
Peak Power (Amps): 3.88 Amps
Open Circuit Volts: 43.2 Volts
Short Circuit Amps: 4.8 Amps

They are a bit low in operating voltage (Vmp~30 volts). For a 24 volt battery bank, you should be looking at Vmp in the range of ~35-38 volts (STC--standard test conditions). On hot days and with cool batteries, your array many not generate enough voltage to reach maximum power (i.e., voltage of array falls, and current from array will be less).

At this point, if they are as listed--And you have a PWM charge controller, just put the two panels in series and monitor what happens (i.e., does the battery bank get "quickly" and fully charged).

ProStar ps-30

The Prostar (MorningStar) 30 amp 12/24 volt charge controller is a good controller... However, depending on what your Uni-Solar panel ratings/performance actually is--It may not be the "optimum" controller for this application (if you want to keep the solar panels).

If you keep these panels, the "optimum" performance would be to connect the two panels in series and then use a MPPT type solar charge controller (Maximum Power Point Tracking) to down convert from high voltage/low current of the solar array to low voltage/high current required to charge the battery bank (sort of like how a transformer works for AC voltage/current/systems).

You are sort of between a rock and a hard spot here... A MPPT charge controller that meets these panel specs (two panels in series) would be a full sized 45+ amp MPPT type charge controller because you need one with a Vpanel input voltage of >~100 VDC. And these are not cheap (at least the current brands/models that I am aware of--you might find some less expensive MPPT charge controllers out there--I am not in the solar business).

300w 24v inverter

That is nice--A lot of people try to put 2kW or larger inverters on a "small" battery bank--Yours is sized nicely for your present battery bank (not too large/wasteful of energy).

I live in nashoba OK

Using PV Watts for Fort Smith AK (you can pick which city is closer in weather for your place if Fort Smith is not good). An array tilted at latitude (~35 degrees from horizontal), fixed position would "see" around this many hours of sun per day, by month:

Month    Solar Radiation (kWh/m 2/day)
1      4.13     
2      4.84     
3      5.13     
4      5.67     
5      5.77     
6      5.97     
7      5.85     
8      6.08     
9      5.34     
10      5.07     
11      4.42     
12      3.62     
Year      5.16      

So, if I pick 4 hours per day to cover 10 months or so of the year:

• 116 watts * 2 arrays * 0.52 system efficiency * 4 hours of sun per day = 483 Watt*Hours per day of 120 VAC power

I would like to run two 60w light bulbs 24 hours a day

4 hours of sun would power two*60 watt bulbs:

• 483 WH per day / 120 Watt load = 4 hours per day (ignoring AC inverter tare losses if left on 24 hours per day)

So--Now look at the loads. If you need 2x 60 watt loads to keep eggs warm--Then this system would not meet your needs. It would need to be, very roughly 6x larger.

At best, if you want "light" 24 hours per day:
483 WH / 24 hours = 20 watt average load

Now, two 9 watt LED lights can supply a fair amount of lighting--especially if you get focused LED type bulbs. It all depends on your needs.

But--We also have the problem of the Uni-Solar panels and their less than ideal Vmp output voltage which very likely could negatively impact the output of the above system (as I have guessed at its design).

-Bill

Re: Smoking

How do you want to address the questions of the miss-match between the solar panels and the battery voltage?

We need to know that before we can finish the design.

Unfortunately, there is a lot of miss match right now. Your options:

• You could purchase different brand/model of solar panels (Vmp~17.5 or ~35+ volts) and match your 24 volt balance of system.
• You could put the batteries in parallel and buy a new 12 volt inverter (this MorningStar 300 watt TSW 12 volt inverter is quite nice) and a lower voltage MPPT controller (a bit cheaper than high voltage/power MPPT controllers--but there is not a lot of choices out there for lower power MPPT controllers--For example, if you do not go with more panels is this 15 amp MPPT 12/24 volt controller from MorningStar).

Other than above, it is pretty difficult to make "reliable" system with the components you have at the moment.

If you are trying to optimally use your money--You might have to pencil out several designs and figure out which one offers the best value for your needs.

-Bill

Re: Smoking

The problem is that the Uni-Solar panels do not have the "standard" output voltage(s) used for 12 volt (or 24/48 volt) battery banks and PWM (the less expensive type) of solar charge controllers.

For example, a 24 volt battery bank needs about 29 volts to charge quickly/fully (and around 30-32 volts to equalize charge every month or three). A 30 volt Vmp panel will only output "rated voltage" in fairly cold weather (near freezing). In warm/hot weather, the Vmp voltage will fall by upwards of 20% as the sun heats up the panels (i.e., 30 volts Vmp in STC standard test conditions can fall to near 24 VDC in hot weather). And not have high enough voltage to fully/quickly recharge your battery bank (plus the losses from wiring and controller voltage drops too).

With such a configuration, the battery bank will slowly (or quickly) be discharged over the days/weeks until the batteries are eventually damaged and/or killed (sulfated/damaged from discharging to near zero state of charge).

If you put the two panels in series, the Vmp-array would be around 60 volts Vmp... And you would only have around (35 vmp/60 vmp=) 58% efficiency from your solar panels (i.e., lose almost 1/2 of their output energy because of voltage miss-match).

Unless you change to "12/24 volt friendly" solar panels or use much more expensive MPPT type charge controllers (with your present solar panels in series for Vmp-array of ~60-90 volts), your system will have very poor performance.

One option being changing solar panels, the other is changing to a MPPT type solar charge controller. Larger or smaller versions are available--which depends on your eventual system size.

And if you are OK with smaller inverter sizes (i.e., 300 watt), you could drop to a 12 volt battery bank and use a 300 watt 12 volt TSW AC inverter pretty nicely with your present pair of panels on the smaller MPPT charge controller.

Until you make these choices, wire sizing is not possible.

-Bill

Re: Smoking

It depends, I don't remember the maximum input voltage for that PWM controller. There are PWM controllers with upwards of 125 Volt inputs--but even it if worked, your system would be (on average) only ~58% efficient vs the "100%" of the right panel to battery match...

Note, the overall end to end off grid AC system efficiency of a "properly" designed solar system (from solar panel input to AC power output) is only around 52% (nominal) anyway... Add another 50% loss just on the panels, and you can see it will cut your available power dramatically.

-Bill

Re: Smoking

I should add/clarify--It is not that you cannot ever use those panels for your needs--It is just they are (probably) not optimum. It would cost you more money to use a MPPT charge controller to match the panels to the batteries, or use a cheaper PWM controller and lose much of the energy rating from those panels.

It is one of the major issues that we work with here for many people on an ongoing basis. It is a real pain in the behind and there is, usually, no simple/easy/cheap solution (short of selling your hardware on Ebay/Craig's List and using the money to address your needs).

-Bill