i need expert installers advice on my streetlight system sizing

[pettral]

hi guys, i am a little new to this forum so permit my naivity.

i designed a solar streetlight system as follows; solar module=2pcs 80w, battery=100ah, LED lamp 30w, charge controller=12v/20a
however i realize that the light comes on as it should (around 7pm) but goes off by 3am instead of it lasting till daybreak (6-6:30 am).

i used suntech panels and emel (a good brand here in nigeria) batteries so i dont think it is a question of the batteries not getting fully charged.

i am still at a loss as to what could be responsible for this. expert ideas will be appreciated

thanks.

mod note - the duplicate post was deleted - please just post a question in one thread

[Sunking]

hi guys, i am a little new to this forum so permit my naivity.

i designed a solar streetlight system as follows; solar module=2pcs 80w, battery=100ah, LED lamp 30w, charge controller=12v/20a
however i realize that the light comes on as it should (around 7pm) but goes off by 3am instead of it lasting till daybreak (6-6:30 am).

i used suntech panels and emel (a good brand here in nigeria) batteries so i dont think it is a question of the batteries not getting fully charged.

i am still at a loss as to what could be responsible for this. expert ideas will be appreciated

thanks.

mod note - the duplicate post was deleted - please just post a question in one thread

The problem is your panel wattage and battery are a bit undersized. If you have discharged your batteries several times they are likely pretty much toast.

Battery capacity needs to be 150 AH.
I assume you have a PWM charge controller? Assuming your winter sun insolation is 3 hours the panel wattage needs to be 240 watts. Are you sure your LED is only using 30 watts total? Have you actually measured it? Many of the LED's out on the market use up to twice as much as their rated power when driver power is included.

[russ]

You need to check the current draw with an amp clamp.

[pettral]

The problem is your panel wattage and battery are a bit undersized. If you have discharged your batteries several times they are likely pretty much toast.

Battery capacity needs to be 150 AH.
I assume you have a PWM charge controller? Assuming your winter sun insolation is 3 hours the panel wattage needs to be 240 watts. Are you sure your LED is only using 30 watts total? Have you actually measured it? Many of the LED's out on the market use up to twice as much as their rated power when driver power is included.

Thanks for the enlightement. However i still have some questions.

I based my calculation thus: a 12v/30w lamp will consume 3A/hour which comes to 36AH in 12 hours (7pm-7am) and a 100AH/20H rating should be able to supply 5A for 20 hours. This i reasoned should leave the battery discharged by only 40%. So which part did i get the assumptions wrong?

Yes i used a pwm controller, do you have a better suggestion especially to compensate for the undersizing?

How did you arrive at the 150 and 240 for the battery and panels respectively?

Pls what does insolation mean?

In this part of the world we do not experience winter, all we have is the rainy season (may-oct) and dry season (nov-apr). The latter is when the sun is at its highest with temperature as high as 34degrees.

Lastly, how do i measure the led lamp? I dont have amp clamp, can i use a multimeter to test it?

Sorry if the post is too long but i will appreciate some explanation. Thanks.

[inetdog]

Thanks for the enlightement. However i still have some questions.

I based my calculation thus: a 12v/30w lamp will consume 3A/hour which comes to 36AH in 12 hours (7pm-7am) and a 100AH/20H rating should be able to supply 5A for 20 hours. This i reasoned should leave the battery discharged by only 40%. So which part did i get the assumptions wrong?

Yes i used a pwm controller, do you have a better suggestion especially to compensate for the undersizing?

How did you arrive at the 150 and 240 for the battery and panels respectively?

Pls what does insolation mean?

In this part of the world we do not experience winter, all we have is the rainy season (may-oct) and dry season (nov-apr). The latter is when the sun is at its highest with temperature as high as 34degrees.

Lastly, how do i measure the led lamp? I dont have amp clamp, can i use a multimeter to test it?

Sorry if the post is too long but i will appreciate some explanation. Thanks.

Longer is better than too short with not enough information.

To measure the LED drain, if your multimeter has a 10 Amp DC range, you can put the meter in series between a 12 volt source and the LED unit. Make sure you understand how the high amp range on your meter works before you try this.

Insolation is the technical term for how much sunlight. It will be more or fewer hours depending on the position of the sun in the sky, and it will be greater or smaller depending on the weather. Rainy --> zero, thin clouds or haze maybe as good as 50%., etc. The online sites will show the the "standard hours" worth of sun you get per day including average weather.
If you are lucky you will get 70% or more of the product of the nominal power of the panels times the number of solar hours each day.

For steady use, it is best not to draw the battery down more than 20 or 25%. That is why the 150 AH battery.
One possible reason that your current system is running the battery down after only 8 hours is that it is never being fully charged. (More about that later.) If you can test by charging the battery fully using a mains charger, you can see if this is part of the problem.

To recharge the battery, you need to put as much as 150% as many amp-hours back into it as you took out. That is based on the chemical efficiency of the battery. In addition, you will lose some energy because you are using a PWM charger. How much depends on what the actual output voltage of the panels is. I would expect somewhere around 20 volts if they are designed to work directly with 12 volt batteries. So 160 watts will be only 8 amps. If you used an MPPT controller, you could get as much as 12 amps, but it would probably be cheaper to buy another panel (making 240 watts.) That would give you 12 amps with your current PWM controller. If you get 5 standard hours of sunlight per day, you will get 60 AH, and you need about 54 AH to make up for the 36 used. But the battery will not continue to accept 12 amps as it gets closer to full charge, so you may still be short on panel power and time.

[pettral]

Longer is better than too short with not enough information.

To measure the LED drain, if your multimeter has a 10 Amp DC range, you can put the meter in series between a 12 volt source and the LED unit. Make sure you understand how the high amp range on your meter works before you try this.

Insolation is the technical term for how much sunlight. It will be more or fewer hours depending on the position of the sun in the sky, and it will be greater or smaller depending on the weather. Rainy --> zero, thin clouds or haze maybe as good as 50%., etc. The online sites will show the the "standard hours" worth of sun you get per day including average weather.
If you are lucky you will get 70% or more of the product of the nominal power of the panels times the number of solar hours each day.

For steady use, it is best not to draw the battery down more than 20 or 25%. That is why the 150 AH battery.
One possible reason that your current system is running the battery down after only 8 hours is that it is never being fully charged. (More about that later.) If you can test by charging the battery fully using a mains charger, you can see if this is part of the problem.

To recharge the battery, you need to put as much as 150% as many amp-hours back into it as you took out. That is based on the chemical efficiency of the battery. In addition, you will lose some energy because you are using a PWM charger. How much depends on what the actual output voltage of the panels is. I would expect somewhere around 20 volts if they are designed to work directly with 12 volt batteries. So 160 watts will be only 8 amps. If you used an MPPT controller, you could get as much as 12 amps, but it would probably be cheaper to buy another panel (making 240 watts.) That would give you 12 amps with your current PWM controller. If you get 5 standard hours of sunlight per day, you will get 60 AH, and you need about 54 AH to make up for the 36 used. But the battery will not continue to accept 12 amps as it gets closer to full charge, so you may still be short on panel power and time.

Thanks for the response.
My multimeter has the 10A range so i will use it in testing but in doing so do you mean that i should put on the LED lamp and then connect the POSITIVE of the meter to the NEGATIVE of the DC load output of the controller and vice versa? The reason i asked is that all the test i have carried out with it has been by connecting in parallel.

Which online site(s) can i get the standard hours worth of sun for my country?

are you saying my calculation on the led lamp is correct only that i need a bigger sized battery for a shallower DOD? I would like to know so that i dont 'throw away the baby with the bathwater'

Also, i will try the option of using a mains charger and let you know how it goes next week. could the charge controller be responsible for the battery not being fully charged?

Yes the suntech 80w panels are rated 17v/4.8A. However, when i connect them in parallel and measure, i get between 19.5v and 22v so lets say 20 on the average and the amps comes to between 9and 10 at full capacity. So will it be okay if i go for mppt charge controller instead of buying another panel? This is because the system is on a pole and an extra panel means a reconstruction of the solar frame.

Thanks.

[russ]

For your area's insolation try http://www.gaisma.com/en/

You need to measure the actual current draw of your lamp with any driver included.

[inetdog]

Yes the suntech 80w panels are rated 17v/4.8A. However, when i connect them in parallel and measure, i get between 19.5v and 22v so lets say 20 on the average and the amps comes to between 9and 10 at full capacity. So will it be okay if i go for mppt charge controller instead of buying another panel? This is because the system is on a pole and an extra panel means a reconstruction of the solar frame.

Thanks.

You will have to make the choice between the extra cost of an MPPT charge controller to get less than 50% more power and the cost of adding a panel and reconstructing the frame to get a full 50% increase.

[Sunking]

I based my calculation thus: a 12v/30w lamp will consume 3A/hour which comes to 36AH in 12 hours (7pm-7am) and a 100AH/20H rating should be able to supply 5A for 20 hours. This i reasoned should leave the battery discharged by only 40%. So which part did i get the assumptions wrong?

You need to design for 20% discharge per day and forget about Amp Hours use Watt Hours. 30 watt x 12 hours = 360 Watt Hours per day needed. For 5 day reserve capacity or 20 % DOD is a capacity of 1800 watt hours. 1800 WH / 12 v = 150 AH @ 12 volts

How did you arrive at 240 watts?

I made 2 assumptions. 1 you used a PWM controller which is only 50% efficient. That means the panels have to generate a minimum of 720 Watt Hours per day. I then assumed Your minimum Sun Hour Insolation is 3 Hours. 720 Watt Hours / 3 Hours = 240 watts.

You need to nail down two points of data. Exactly how much power your LED actually uses, I would bet it is more than 30 watts. Measure the current it uses. Next peice of data you need is you rareas shortest month of Insolation in SUN HOURS.

[russ]

Insolation in ''Sun Hours'' - This is a widely used though flaky number.

Insolation is measured in watts/m2/day

Typical summer sun may be in the 800 range occasionally hitting 1000 for a few minutes to an hour at solar noon. - maybe 7,000 watts or 7 sun hours
In the winter you will receive a fraction of that - maybe 2,000 to 3,000 watts meaning 2 to 3 sun hours

[Naptown]

Insolation in ''Sun Hours'' - This is a widely used though flaky number.

But the most widely understood and stated insolation value used anywhere.
Pro's know the actual, Most here do not. Since they actually mean the same thing what is the difference. Using the number stated in calculations ends at the same sum. Why is using 5 sun hours any more flaky than using 5KW M²/d\. They both mean the same thing one is easy to understand and one can create confusion.

[russ]

But the most widely understood and stated insolation value used anywhere.
Pro's know the actual, Most here do not. Since they actually mean the same thing what is the difference. Using the number stated in calculations ends at the same sum. Why is using 5 sun hours any more flaky than using 5KW M²/d\. They both mean the same thing one is easy to understand and one can create confusion.

In industry you learn the terms of that industry to avoid confusion. Otherwise each plant in that industry would have it's own terms and plants around the world would not be able to talk to each other. Terms are normally scientific or engineering terms - watts/m2/day is just that.

I have accepted the term as used with solar but as far as I am concerned it is about like calling a duck a goat to make it easier for newbies.

[pettral]

thanks guy for all your replies and suggestions. i tested the the lamp was about 36 watts when i tested it. also when i visited y http://www.gaisma.com/en/ i discovered that the shortest month of insolation for my region (july) is 4.06kW/m2/day. it is at 4.58this month.
how does that affect my calculations?

thanks.

[Sunking]

thanks guy for all your replies and suggestions. i tested the the lamp was about 36 watts when i tested it. also when i visited y http://www.gaisma.com/en/ i discovered that the shortest month of insolation for my region (july) is 4.06kW/m2/day. it is at 4.58this month.
how does that affect my calculations?

thanks.

It means you need :

220 Watt Panel
12 volt 180 AH Battery
20 amp Charge Controller

[SolarJoe]

Pettral- The best advice i can give you is call a professional here is the number to the company that set up my Solar system also i paid zero down.

Mod note - I removed ad and suggest you don't repeat this.