Jump to content

Solar Power Setup Questions


musingloudly

Recommended Posts

musingloudly

Hi Guys,

 

I noticed that there are several in the forum knowledgeable on the subject matter and was hoping to get some help having very little background on solar power in general. 

 

Current setup:

 

1 100watt solar panel

1 120watt solar panel wired in parallel both mounted on rooftop (2 story house) with no obstructions

1 solar charge controller 20Amp 

3 70Ah deep cycle batteries also wired in parallel

1 300 watt pure sine inverter

 

Even at peak teams (where I perceive the sun to be at its brightest), the peak values I have seen via the interface in the charge controller is 12.6V at 9 something amps. Is this normal? BTW, when I was just using a 100watt panel, the maximum readdings would be 12.2 or 12.3 at less than 3 amps. I wonder whether my initial panel was busted or something. 

 

I wonder if I could get better voltage and current if I move the charge controller closer because the current setup I estimate to be wired more than 30 feet with gauge 12 wire. 

 

Comments for improvement, what can I do better? 

 

 

Link to post
Share on other sites
  • Replies 35
  • Created
  • Last Reply

Top Posters In This Topic

  • Paul

    14

  • musingloudly

    10

  • thebob

    3

  • AussieLex

    3

Top Posters In This Topic

Popular Posts

The first thing I see wrong here, is your voltage drop from running 12ga wire a distance of 30 feet. Also, is that round trip, or one way? You need to keep your voltage drop under 3%.     The sec

Sorry about that. I am still not 100% after being ill. I meant to write that MorningStar controllers are built to US Specifications.    However, the Midnite Kid is manufactured in the US. Other cont

Paul,   Your comment prompted me to search and this is what I found. If the chart below is accurate, I am discharging my batts way too low. Until I am able to add some panels, I will likely take out

Posted Images

Knowdafish

1) When you think the output should be at its peak are the panels clean and facing directly into the sun and not at an angle? Even a slight angle will affect their output. 

 

2) Are all of your connections clean and tight? 

 

3) All of your batteries are in good condition, and if wet (not gel) are all full of electrolyte? 

 

4) Stepping up to 10 gauge wire or even doubling up with the 12 gauge wire you now have will give you a little bit of a boost, but not much. 

 

5) What brand charge controller do you have? It seems to be limiting your charging ability also. Your charging voltage should be higher. 

 

6) What is the output voltage of each panel if you check them separately before they hit the charge controller? 

 

I suggest you comb this guys website if you really want to get the most out of your set-up. He lays it on the line and is completely honest when it comes to solar panel systems.

  • Like 1
Link to post
Share on other sites
Paul

The first thing I see wrong here, is your voltage drop from running 12ga wire a distance of 30 feet. Also, is that round trip, or one way? You need to keep your voltage drop under 3%.

 

DC_wire_selection_chartr.jpg

 

The second thing I see here is, your charge rate for these panels is about 5%. It should be closer to 10%, which would mean you need an array closer to 400 watts. Here is the formula:

 

210AH x charge rate ~14.5vdc / .77 (percent efficiency of the array) X (rate of charge) .10 = 395 watts (solar array size). So, you should be closer to a 400 watts array to charge 210AH of batteries.

 

The first thing I would fix here, would be to add more panels to the array, keeping them as close as possible to the same rating.

 

The second thing I would fix here, would be to shorten that distance, if at all possible, and as much as possible. If not, go with some serious larger cable from the panels to the controller. 

 

This is a diagram of my current array:

400_watts_array.gif

 

Note cable sizes.

Panel distance for the array is only 4 meters from the fuses, and just a few centimeters from there to the controller. Batteries are 1.5 meters from the controller, total.

Edited by Paul
  • Like 3
Link to post
Share on other sites
musingloudly

1) When you think the output should be at its peak are the panels clean and facing directly into the sun and not at an angle? Even a slight angle will affect their output. 

 

The roof is angled and therefore the panels are angled as well. 

 

2) Are all of your connections clean and tight? As far as I can tell, it seems like they are okay. 

 

3) All of your batteries are in good condition, and if wet (not gel) are all full of electrolyte? Batteries are full of electrolyte. Dont know how to tell if they are in good condition. They have been in use for at least 3 months never going below 11.5 volts I estimate.

 

4) Stepping up to 10 gauge wire or even doubling up with the 12 gauge wire you now have will give you a little bit of a boost, but not much. 

 

5) What brand charge controller do you have? It seems to be limiting your charging ability also. Your charging voltage should be higher. 

 

it's the epsolar viewstar vs2024N.. Link here ... http://www.solarguru.com.au/Special-Sales/c89/p528/EPSolar-ViewStar-VS2024N-Solar-Charge-Controller-(12/24V)/product_info.html#.U18ECvmSyAg

 

6) What is the output voltage of each panel if you check them separately before they hit the charge controller? Not exact here but the 100watter was giving about 15 something volts and the 120 watt was giving out about 17 or 18volts

 

I suggest you comb this guys website if you really want to get the most out of your set-up. He lays it on the line and is completely honest when it comes to solar panel systems.

 

Thanks.. I'll take a look at this.

Edited by Paul
separated reply from quoted text.
Link to post
Share on other sites
musingloudly

The first thing I see wrong here, is your voltage drop from running 12ga wire a distance of 30 feet. Also, is that round trip, or one way? You need to keep your voltage drop under 3%.

 

attachicon.gifDC_wire_selection_chartr.jpg

 

The second thing I see here is, your charge rate for these panels, just is about 5%. It should be closer to 10%, which would mean you need an array closer to 400 watts. Here is the formula:

 

210AH x charge rate ~14.5vdc / .77 (percent efficiency of the array) X (rate of charge) .10 = 395 watts (solar array size). So, you should be closer to a 400 watts array to charge 210AH of batteries.

 

The first thing I would fix here, would be to add more panels to the array, keeping them as close as possible to the same rating.

 

The second thing I would fix here, would be to shorten that distance, if at all possible, and as much as possible. If not, go with some serious larger cable from the panels to the controller. 

 

This is a diagram of my current array:

attachicon.gif400_watts_array.gif

 

Note cable sizes.

Panel distance for the array is only 4 meters from the fuses, and just a few centimeters from there to the controller. Batteries are 1.5 meters from the controller, total.

 

 

The approximate 30 feet is one way. Would I get some gains if I moved the charge controller closer to the solar panels and lenghten the cable from the charge controller to the battery bank? I would have a difficult time moving the battery bank given the space situation.

 

I'll see options on where to mount the other panels given the space situation (subdivision layout). The computation you share shows that my current panels cannot optimally support the battery bank. 

  • Like 1
Link to post
Share on other sites
Paul

The approximate 30 feet is one way. Would I get some gains if I moved the charge controller closer to the solar panels and lenghten the cable from the charge controller to the battery bank? I would have a difficult time moving the battery bank given the space situation.

 

For voltage drop, ALWAYS calculate for total distance, not one way. So, yes, you have serious voltage drop over 60 feet, running only #12 wire. For those two panels, you should be running at least #6, preferably #4 wire that distance.

 

Wire distance is wire distance. So, you just need to shorten the wire run wherever you can. Moving the controller closer to the panels, without shortening the distance will not help, as far as I know. 

 

 

I'll see options on where to mount the other panels given the space situation (subdivision layout). The computation you share shows that my current panels cannot optimally support the battery bank.

 
Absolutely correct. You only have a number of hours, typically 4 to 5, during the day for the panels to charge your battery bank. During this time, the system needs to be able to go through all stages of charging. I am under the impression you are running a PWM controller. Here are the stages for that type of controller:
 
charging.png
 
The panels have to be able to charge your bank, equalize the bank, and go into float all before the sun goes down. So, it is important to have an array sized large enough to be able to do this for you, and on a daily basis. Also, if you have a bit more from the array, you can draw off the panels during the day without using any power stored in the batteries.  
 

 
Also, something that has not come into the equation, DOD (Depth of Discharge). How low you are taking those batteries at night. Keeping them from being drained no more than 50% is good. But, if you can keep the DOD under that it will be even better. That will allow your batteries a much longer life span. Of course, this all depends on your load requirements when the sun isn't shining. 
Edited by Paul
Link to post
Share on other sites
Paul

GENERAL ADVICE: A quick way to determine about what you need to charge a given bank of batteries, is to take 10% of their 20 hour AH rating. In your case, 210AH X 10% = 21 amps. If you can size your array to have 21 amperes available for your batteries, you will be doing well.

  • Like 1
Link to post
Share on other sites
musingloudly

Paul,

 

Your comment prompted me to search and this is what I found. If the chart below is accurate, I am discharging my batts way too low. Until I am able to add some panels, I will likely take out a battery to keep my system at 140Ahs which would allow my current panels to keep it charged a bit better. 

 

State of Charge

Sealed or Flooded Lead Acid

Gel battery

AGM battery

100%        75%     50%       25%     0%

12.70+      12.40    12.20    12.00   11.80
12.85+      12.65    12.35    12.00   11.80

12.80+      12.60    12.30    12.00   11.80

Edited by musingloudly
  • Like 2
Link to post
Share on other sites
Paul

If this system is primarily for back up and if you have mains power at this location, you can also get a battery charger to help top up your bank. Just a thought. That is, until you can add additional panels to the array. 

Edited by Paul
  • Like 2
Link to post
Share on other sites
thebob

You need a 2 position isolator switch so you can switch each of the batteries in or out. Charge them on alternate days, and still have 2 ready incase of prolonged brownout.

Link to post
Share on other sites
Paul

You need a 2 position isolator switch so you can switch each of the batteries in or out. Charge them on alternate days, and still have 2 ready incase of prolonged brownout.

 

That is certainly a possibility as well. Just use a marine, dual battery bank switch. 

  • Like 1
Link to post
Share on other sites
  • 4 weeks later...
musingloudly

UPDATE: Still not been able to add panels to get to the ideal wattage number of at least 10% to support my 210Ah battery bank given that I have not found a practical location for the solar panel. I've redirected money instead to buying 12v fans. 

 

My typical usage from Monday to Friday are as follows:

 

2 pcs 12v lights 5 watts - ~12 hours use

3 pcs 12v lights 5 watts - ~ 3 hours use

1 pcs 500 watt inverter driving a ~90 watt LED TV and the Skycable box ~5 watt for ~5 hours day (2 hours morning and 3 hours at night)

2 fans 12v 15 watts ~ combined total of 12 hours use 

 

results to the battery bank use as follows:

 

Typical rating at sundown (6pm.) is 13.0v to 12.9v and by the time it gets to 6 a.m. I am at 12.5v.

 

The system is holding for now at not discharging below 75% which should be good for the longevity of the batteries. 

 

I've been monitoring this for about a week now and the numbers seem to be holding firm. 

 

The last time I did the math I figured this would save me about 500 to 600 pesos a month at 10P a killowatt

  • Like 1
Link to post
Share on other sites
Paul

 

 

The system is holding for now at not discharging below 75% which should be good for the longevity of the batteries. 

 

Sorry for the late reply. Are you saying you are only using 25% of the total battery bank capacity? Or, are you saying that you are depleting all BUT 25% of the battery bank capacity? 

I believe you are saying that DOD (Depth Of DIscharge) is 25%, leaving 75% battery capacity?

Link to post
Share on other sites
musingloudly

Sorry for the late reply. Are you saying you are only using 25% of the total battery bank capacity? Or, are you saying that you are depleting all BUT 25% of the battery bank capacity?

 

I believe you are saying that DOD (Depth Of DIscharge) is 25%, leaving 75% battery capacity?

You are correct Paul. By six am myvoltages still read 12.5 which means ive only used up 25percent of my battery. Again basing on the charts above

  • Like 1
Link to post
Share on other sites
Paul

Were you ever able to look into this? 

 

 

 

I'll see options on where to mount the other panels given the space situation (subdivision layout). The computation you share shows that my current panels cannot optimally support the battery bank. 

 

I ask, because I was wondering have you considered adding additional panels?

 

Or, have you considered a charger to supplement the batteries?

 

Also, once per week or so, I would take the batteries down to 50% and let them charge back fully, a good solid charge by the panels (or alternative charging system). But, I would divide the bank to do this, due to the limits of the solar array. 

It's great that you are keeping an eye on the specific gravity, by the way. I don't do that as often as I should.

  • Like 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use, Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue..

Capture.JPG

I Understand...