New setup with 2 panel: 175W & 130W

key5000

Hello All,

I'm planing to build a new solar that can power my LED lights:
1- 60W LED: need to be ON for 8 hrs/day
2- 60W LED: need to be ON for 3 hrs/day
3- LEDs are running at 12V

The following is my equipment:
1- 175W 24V solar panel with 35.8V @ 4.9A
2- 130W 12V solar panel with 16.4V @ 8A
3- 2 Optima DeepCycle 12V battery rate @ 38AH
4- 30A charge controller

What is the best way to setup those solar that can handle all the needs for my LEDs.


Thanks
KEY

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

Welcome to the forum.

Let's do some math!

One 60 Watt (? rather high for an LED isn't it?) running for 8 hours = 480 Watt hours.
Two 60 Watts (120 combined) running for 3 hours = 360 Watt hours.
Total: 840 Watt hours.

Since this is direct DC (? it is, isn't it?) there's no inverter to power or conversion loss. So we divide 840 by the nominal system Voltage of 12 and get 70 Amp hours used.

You have two Optima 38 Amp hour batteries for a total of 72 Amp hours. Problem; that would mean running the lights would drain the batteries completely and they would not recharge.

Since it is unlikely you want to run the lights during the day when the panels are producing you will need to at least double the size of he battery bank in order to keep the depth of discharge below 50% so that they may be recharged. New problem: using those batteries you'd end up getting four in parallel which becomes difficult to manage (current sharing problems). I'd recommend you get different batteries of higher capacity so that you don't have that trouble.

Recharging: You've got more problems. One of your panels is a 24 Volt which will not work efficiently on a 12 Volt system without an MPPT charge controller. They are expensive (over $200 for one that actually works). The other two have a Vmp lower than what is recommended for a 12 Volt system, meaning they may not be able to bring the batteries up to full Voltage under certain conditions.

Otherwise, you would be looking for enough panel to provide about 14 Amps peak current to recharge a 140 Amp hour battery bank. This would be something like two 140 Watt commercial panels on a 20 Amp PWM charge controller.

The two 130 Watt panels would do it, providing the Voltage losses from heat and wiring resistance don't prevent them from being able to raise the battery Voltage to the proper charge level. It's a close thing.

The one 175 Watt panel would just do it (low charge rate, but you might have enough sun time to manage it) providing it was used with something like the Morningstar MPPT 15 controller.

Or you could put the two 130 Watt panels in series on the MS MPPT 15 to be sure the Voltage was high enough.

You could even parallel such a string with the 175 Watt panel and get a total of 435 Watts feeding an MPPT controller and realize about 28 Amps of charge current, but you would need a larger (more expensive) controller to make use of it. Such would be able to recharge a couple of 220 Amp hour 6 Volt golf cart batteries which could definitely supply the power needed to run those lights.

Does this help?

BB.

Re: New setup with 2 panel: 175W & 130W

Need a bit more information on where it will be located and the actual power needs (say advertising sign on freeway to Las Vegas vs a sign in the North West with lots of marine layer in the winter, etc.). PV Watts can help you understand the amount of "average hours of sun" per day for your location(s).

For now, assume you want to run this during the winter in Long Beach California (fixed array tilted to latitude):

Month    Solar Radiation
(kWh/m 2/day)
1      4.43     
2      5.00     
3      5.52     
4      6.21     
5      6.12     
6      6.09     
7      6.63     
8      6.79     
9      6.18     
10      5.46     
11      4.81     
12      4.34     
Year      5.63      

So, a minimum of 4 hours of sun, on average is a good number (sunny winter climate).

60 watts of LED lighting is a lot... And I would suggest looking for different lighting systems and see if you can reduce the power usage. I would guess that you could reduce this to as much as 1/10th the wattage, and reduce system costs a lot--but that is your applicaton.

First, total amount of power:

• 8 hours * 60 watts + 3 hours * 60 watts = 840 WattHours

Battery size... Assuming two days of storage and 50% maximum discharge:

• 840 WH per day * 1/12 volt battery * 2 days of storage * 1/0.50 max discharge = 280 AH @ 12 volts minimum (i.e., two 6volt golf cart batteries)

The solar array needed to run:

• 840 WH * 1/0.65 DC system eff * 1/4 hours of sun = 323 watt minimum solar array

A start...

-Bill

key5000

Re: New setup with 2 panel: 175W & 130W

Thank you all for your reply.

Yes, those 60W LEDs are custom to use on my Aquarium fish tank.

Below is my current setup, I can power up my 60W 8HR/D on 1 battery and the other 20W 8HR/D + 60W 3HR/D are on second battery. By the end of the day, 8PM, the voltmeter show power I had left over is 22.3V.

Attachment not found.

Any other setup that I can use my second 130W 12V panel to extend the power of my LED?

inetdog

Re: New setup with 2 panel: 175W & 130W

key5000 wrote: »

Thank you all for your reply.

Yes, those 60W LEDs are custom to use on my Aquarium fish tank.

Below is my current setup, I can power up my 60W 8HR/D on 1 battery and the other 20W 8HR/D + 60W 3HR/D are on second battery. By the end of the day, 8PM, the voltmeter show power I had left over is 22.3V.

Any other setup that I can use my second 130W 12V panel to extend the power of my LED?

Well, any system that tries to run independent unequal 12 volts loads on halves of a 24 volt battery bank is going to cause a large imbalance between the two batteries which may require frequent equalization.
You can get a device that allows you to take 12 volts off a single tap of a 24 volt battery by regulating a balancing current, drawing power equally from both batteries with minimal power loss. But they are pretty expensive.

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

There are two things wrong with that: Voltage is not a good indication of actual state of charge, and you shouldn't be drawing two 12 Volt loads of halves of a 24 Volt battery bank.

It works now, but the batteries are unbalanced because the loads on them are not equal while at the same time they are being charged as one battery. This will translate to shortened battery life.

22.3 Volts on a 24 Volt system is about dead. Definitely below 50% SOC.

key5000

Re: New setup with 2 panel: 175W & 130W

Cariboocoot wrote: »

22.3 Volts on a 24 Volt system is about dead. Definitely below 50% SOC.

What do you mean battery about dead?

By 8PM, the battery is measured at 22.3V because both LEDs, 120W total, has been running on it right after the sun is down.
The next day, when the sun coming up, the charge is again for few hours before the 40W LED turn ON at noon.
At peak time, charge controller show about 26.5V @ 4.9A

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

About dead as in you've got 1.3 Volt "margin" left before you're into the Voltage area where the likelihood of recharging it becomes lower and lower. Normally a "24 Volt" system will run between 24 Volts (slightly lower under load) to 25.5 Volts (at rest; no loads or charging). Charging Voltage should be more like 28.8 Volts.

Yes it is working now, but batteries being used like that are not going to last as long as they should. With the unequal load of the two halves you are getting some Voltage rebound as the less discharged battery pushes a bit of Voltage back to the more discharged one.

key5000

Re: New setup with 2 panel: 175W & 130W

Cariboocoot wrote: »

About dead as in you've got 1.3 Volt "margin" left before you're into the Voltage area where the likelihood of recharging it becomes lower and lower. Normally a "24 Volt" system will run between 24 Volts (slightly lower under load) to 25.5 Volts (at rest; no loads or charging). Charging Voltage should be more like 28.8 Volts.
.

Understood.

What is the ideal voltage on the battery that I need to shut down when it's under load?

key5000

Re: New setup with 2 panel: 175W & 130W

Would you please let me know which of the following design is better and why?

175W @ 36V
Attachment not found.

130W @ 16V
Attachment not found.

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

key5000 wrote: »

Understood.

What is the ideal voltage on the battery that I need to shut down when it's under load?

Technically that depends on the load. However you can test it to find out. The "no load" Voltage would be 24; this indicates approximately 50% SOC which is about the 'tipping point' for recharging.
If you discharge the battery to this Voltage at rest and then apply the loads you will see the Voltage drop further. That point would be a fairly accurate absolute under load minimum. You can even get a Voltage controlled relay to trigger at this point and disconnect the load or sound an alarm or such.

With inverter systems I usually recommend programming the low Voltage disconnect to shut down at system nominal, which ensures that when the load is removed the battery Voltage will rebound to above the 50% SOC level.

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

key5000 wrote: »

Would you please let me know which of the following design is better and why?

Attachment not found.
Attachment not found.

The second image is better for the batteries as it will keep the load even on both. It would be made even better by a simple change of either the positive or negative to the other battery.

The only part wrong is the insufficient charging provided by a single 130 Watt panel for the two batteries.

key5000

Re: New setup with 2 panel: 175W & 130W

Sorry, I don't understand your image, would you please explain to me on that?

Any idea on combine 175w with 130w to charge this 2 battery while power the LED?

Should I replace charge controller with MPPT or save $$$ and invest on more/another battery?

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

The image is a standard depiction of two parallel battery strings. Usually we see this with four 6 Volt golf cart batteries, hence the four in the picture. You can think of each string of two 6 Volts as a single 12 Volt. The key thing to note is how all the positive connections are made to one string while all the negative connections are made to the other. This is the best you can do for keeping the wiring resistance even between the two strings and thus minimizing current differences.

Your 175 Watt panel really can not be used efficiently on a 12 Volt system without an MPPT controller. Otherwise it will produce the current but not the Voltage, resulting in a loss of around 100 Watts - more than half its capacity.

You actually have too little battery for what you want to do and less than ideal charging. Under the circumstances I think changing the batteries for higher capacity like 220 Amp hour golf cart batteries and charging them with the two 130 Watt panels in parallel would be the best course of action here. The charge rate would be on the low side but since the lights don't get used during charging (do they?) it should still work.

niel

Re: New setup with 2 panel: 175W & 130W

key5000,
2 points.
1> you are charging a 24v battery bank and then splitting the loads between the 2 batteries with different wattages. this imbalance will kill one of the batteries. if you have 12v loads from a 24v pv then you need to get an mppt controller to down convert and run the batteries in parallel for 12v to accommodate the 12v loads more equally.

2> you cannot draw off more than 50% of the battery capacity without starting to compromise battery life. a 12v battery is considered dead at 10.5v which amounts to 0% capacity left or 0% state of charge (soc) as we often refer to it. this could actually damage the battery.

key5000

Re: New setup with 2 panel: 175W & 130W

OK, I will rewire my 2 battery with parallel connection so I can get 12v out of it with 72W total, right.

Will 175W with MPPT provide more power than 130W with Charge controller? (with the setup on 2 of 12v bat in Par)


If I get a goftcart battery 220AH, can I charge it with 175W+130W in parrallel with MPPT to get 300W output?

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

The 175 Watt panel has an Imp rating around 5 Amps, right? So if connected directly to a 12 Volt battery that's all the current you get: 5 Amps.

The 130 Watt panels, being "12 Volt", have an Imp rating around 7.8 Amps. So even one of those will actually provide more charging current than the 175 Watt without an MPPT controller.

With an MPPT controller you could expect about 11 Amps from the 175 Watt panel. The current increase comes from the controller's ability to change the higher Voltage into greater current.

But the two 130 Watt panels together would provide 15.6 Amps, using a less expensive PWM type controller.

These are theoretical numbers for comparison purposes, not an absolute guarantee of what you'll get. One of those "all other factors being equal" situations. There is still the concern that the 130 Watt panels may not develop enough Voltage to bring the batteries all the way up to Absorb level, especially on a hot day.

key5000

Re: New setup with 2 panel: 175W & 130W

Since I only have one 130W panel therefore the option with two 130W panel is not going to be.

I have to find out the best way to get how Amp or Wattage out of my current 175W & 130W, please understand this.

Can I use the setup below:
Attachment not found.
Please let me know what is the Amp and Wat I get for this setup?

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

Somehow I got the impression you had two of those 130 Watt panels. Must be one of the other fifty people I was talking to.

One 175 Watt and one 130 Watt. Problematic any way you look at it as they both have different Voltages and current.

The cost of an MPPT controller being $200+ even for a small one, you'd be better off buying another "12 Volt" panel to use with the 130 Watt and sell the 175 Watt.

Otherwise putting them in parallel on any type of controller will give you roughly the two Imp's added together: 12.8 Amps. That equates to about 189 Watts maximum, as opposed to the theoretical 305 Watts. Pretty bad, huh?

There may be some small gain over that with an MPPT, but not enough to justify the money. Small MS 15 Amp controller http://www.solar-electric.com/mosumpsochco.html $225, small 130 Watt panel http://www.solar-electric.com/sosp130wamum.html $244 (either would bring current up to 15 Amps).

See what I mean? All you need is a bargain deal on another 12 Volt panel (as long as the Vmp is close to what the 130 Watt panel's is it will work).

key5000

Re: New setup with 2 panel: 175W & 130W

OK, if I go with 2x130W panel for my 12V batterries, do I need another MPPT or can I just use my existing 30A charge controller? And will I get maximum current out of that (260W)?

What is the best cable AWG for connecting 2 battery together? or can I just use 8AWG solid electrical wire on this connection?

Do I need install the fuse? where to install?

For cable running from Solar to charge controller, I'm using 12AWG, is that good enough?

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

You will not need an MPPT type controller to use "12 Volt" panels on a 12 Volt system; the advantage to MPPT here is being able to convert higher Voltage (as in the 175 Watt panel's 35 Vmp) to greater charge current.

The max current you get from two 130 Watt panels through your PWM type 30 Amp controller will be the Imp ratings of the two panels added together. If they both have an Imp of 7.8 the total would be 15.6 Amps. This will never be the exact Watt rating of the panels because that rating is based on the maximum current * the maximum Voltage (Imp * Vmp). The Vmp is inevitably higher than the actual system Voltage (usually 17.5). This is necessary to make sure the charge source (panel) Voltage is above the battery Voltage at all stages of charging even after losses from heat (panel Voltage goes down the hotter it gets) and wiring losses (all wire has some resistance; you can minimize it but never eliminate it).

Two panels in parallel will not require fuses.
The charge controller output should have a fuse on it, rated to protect the wire used. The same goes for the connection between batteries and any loads.

Wire sizing depends on three things: current, Voltage, and length.
It has to be large enough to handle the current. In the case of the two 130 Watt panels this means a minimum of 12 AWG, which is rated for 20 Amps continuous.
The battery output to loads is nearly always the highest current load. 8 AWG will handle about 50 Amps. If that is more than the load draws it will work.
Voltage and length come in to play for Voltage drop: higher Voltage means less V-drop, lower current means less V-drop, larger wire means less V-drop. As a rule we try to keep Voltage drop under 3%.

Example:
Panels to charge controller is usually the longest run. In this case the Voltage is nominally 12 and the current no more than 16. If you use those numbers you get these kind of results:
20 foot run on 12 AWG: 8.7% Voltage drop, which is unacceptably high.
20 foot run on 10 AWG: 5.5% Voltage drop, which is still too high for most cases.
20 foot run on 8 AWG: 3.4% Voltage drop, which may be acceptable.

See what I mean about needing the higher Vmp on panels?
BTW if you use 8 AWG you can still use a 20 Amp fuse as the current will not be any greater than the 16 Amps expected; the larger wire size is only to reduce the Voltage drop.

The run from batteries to loads is usually fairly short and so often does not have the same V-drop loss problem. But it can so it should be considered.

And yes we do all use Voltage drop calculators like this one: http://www.powerstream.com/Wire_Size.htm

niel

Re: New setup with 2 panel: 175W & 130W

usually we consider combining 12v and 24v pvs to a 12v or 24v battery bank to be incompatible in most cases excepting where the current outputs are similar enough to allow the 2 pvs to be placed into series and only used for mppt ccs. this begets 2 different systems to charge a single battery bank. a pwm cc will work fine on 12v pvs for a 12v battery bank, but the larger pv with its higher voltage would need an mppt cc to utilize the power best on a 12v battery bank. as coot said it would allow the 5a of current to pass from the 175w pv if fed into a pwm cc.

key5000

Re: New setup with 2 panel: 175W & 130W

Cariboocoot,

Thank you very much for all your input during the last couple days on my new Solar setup, your information is very helpfull to me.

Vote A+++++++++ for Cariboocoot

Thanks
KEY

key5000

Re: New setup with 2 panel: 175W & 130W

Last night, I had my setup reconfigure using 1x130W panel with 2x12v batterries in parrallel.

As I checked the status on my charge controller, the display show 3.6A under loaded when 8 hrs/d LED set is turn ON. The display show 7.8A when both LEDs set (8hrs/d and 4hrs/d) are ON.

As specification from my panel, the panel produce 8A @ 16.3v.
The first LED light (3.6A) is turn ON as schedule from Noon to 8PM
Second LED ligh (4.2A0 is turn ON as schedule from Noon-2PM then 6PM-8PM.

With above condition, how much time can the battery handle the LEDs when the sun is out?

Another question, what is the cut off voltage from controller I can set? Can I set to 16V for my 12V battery?

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

Tricky.
The reason being the panel will be able to supply some of the load directly while also charging the battery a little bit. How much so will not be constant because over the time period the panel's output will vary according to how much sun it's getting.

So the panel output will be a bell curve over the course of the day, with current peaking around (solar) noon providing it is oriented that way.

The load on the other hand has three variations: no lights on (pre-noon), one light on (2 PM to 6 PM) and two lights on (Noon to 2 PM and 6 PM to 8 PM).

If we assume 2.5 hours equivalent good sun before noon you will get full charging benefit during those hours. This will be offset by the after 6 PM consumption of two hours at full current.

So we are left with the afternoon edition of charge vs. discharge. In simple numbers it would be 2.5 * 8 Amps from the panel, or roughly that equivalent: 20 Amp hours. Meanwhile the consumption between noon and 6 PM is more predictable at 3.6 Amps * 6 hours for 21.6 Amp hours on one lamp alone, and then 4.2 Amps for 2 hours on the other for 8.4 Amp hours.

Production: 20 Amp hours. Consumption: 30 Amp hours.

Morning production of 2.5 hours * 8 Amps = 20 Amp hours, and evening consumption of 7.8 Amps * 2 hours for 15.6 Amp hours.

So whereas your panel may (and we are assuming a lot here) produce 40 Amp hours per day the consumption will be 45.6 Amp hours in a day.

Even without fine tuning this amounts to inevitable deficit charging.

You can't run your charge controller Voltage up any higher than what the battery requires, which is usually under 15 Volts. if you were to do so you would be subjecting it to conditions which will shorten its life. It would not gain you any capacity; the battery can only store so much power.

key5000

Re: New setup with 2 panel: 175W & 130W

Thank you so much for your valuable explanation.

key5000

Re: New setup with 2 panel: 175W & 130W

Last night, around 9PM, I went up to my roof and add an addional 175W to my existing 130W panel, wiring in Parralell.
The total wattage I will get around 190W at peak or about 13AH

So, I think with this power, I should be able to power up my LED while charing the battery.

Below is my current setup (without the FUSE)
I'm planning to the fuse this weekend, please review and let me know if the FUSE LOCATION is OK for this setup.
If not, please let me know where is the best FUSE location.
Attachment not found.

What kind of Fuse can I use and where to get it?

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

If the panels were matched you would not need fuses on them.
As it is, they will function as a matter of current rather than Watts. The 175 Watt panel has an Imp of 5, yes? And the 130 Watt panel has an Imp of 7.4? I'm tempted to say this is so close as to not be a worry. Otherwise it would be a 7.5 on the big panel and a 10 on the little one (which seems counter-intuitive).

The charge controller output is not going to exceed the combined Imp's: 12.4 Amps. Let's see, NEC regs would put a 20 Amp fuse in there and the wiring should be able to handle at least that. Some of this depends on future expansion and your use of the controller to feed loads (if the loads can draw more in total than the panels will put back to the battery - you always have to go for the highest potential constant current in the circuit).

BTW, fuses need only go on the positive line.

I did not get a nap today so this could be wrong.

key5000

Re: New setup with 2 panel: 175W & 130W

175W panel has 4.9A
130W panel has 8.0A

So, what you are saying is I don't need any fuse on my setup ???

Yes, it's my bad on drawing, the fuse should be on Positive line only.

Cariboocoot

Re: New setup with 2 panel: 175W & 130W

key5000 wrote: »

175W panel has 4.9A
130W panel has 8.0A

So, what you are saying is I don't need any fuse on my setup ???

Yes, it's my bad on drawing, the fuse should be on Positive line only.

Well should the 175 Watt panel short the 130 Watt can put 3 more Amps than it was designed for through it. But you have to wonder how likely that is to happen.

Another weird thing that can happen is that the 175 Watt can hit the 130 Watt with too much Voltage, causing reverse current flow. But the 130 would have to be heavily shaded and the 175 not. Also highly unlikely.

You can't plan against every contingency, 'cause meteors can fall from the sky too (as the dinosaurs found out).

key5000

Re: New setup with 2 panel: 175W & 130W

What you are saying is I can not use 175w parrallel with 130W?

Please explain in more detail, i'm confused on this.