Upgrading Test System #1 to Test System #2...could use some input.

Vikelf

Greetings,

It's been sometime since I've had time to address my project, but here I am again.

Originally, I setup a HF 45w system and connected to a pair of Thunderbolt Magnum Solar 68680 12 Volt, 35 Amp Hour Universal Battery (labelled AGM on the battery itself) connected in parallel. I also have 6-8 7.2Ah 12v UPS batteries that I toy around with.

Now, I was very ignorant when I first approached solar and for that matter all the electrical knowledge needed. I am now less ignorant about Solar requirements but in saying that I am really only qualified to install a HF 45w Solar system

On to project #2.

Goal: 24/7 lighting around the exterior of the house using 12VDC LED Flood lights (LENBO 10W 12V DC Warm White LED Flood light High Power Waterproof Outdoor Lights)


I decided to up the size of the backyard solar installation to 400w using four 100w Mono panels from a competitor. (Renogy) Basically, free shipping wins.
Technical Specifications:
Solar Cell Monocrystalline 125x125 (5 inches)
No. of Cells36 (4x9)
Dimensions 1195x541x35 mm (47x21.3x1.4 inches)
Weight7.5 kgs (16.5 lbs)
Front Glass 3.2 mm (0.13 inches) tempered glass
Frame Anodized aluminum alloy
Junction Box IP67 rated
Output Cables 4.0 mm2 (0.006 inches2), 600mm (23.6 inches)
Connectors MC4 Connectors
Fire Rating Class C

Electrical Characteristics:
Optimum Operating Voltage (Vmp) 18.9V
Optimum Operating Current (Imp) 5.29A
Open - Circuit Voltage (Voc) 22.5V
Short- Circuit Current (Isc) 5.75A
Operating Module Temperature -40°C to + 90°C
Maximum System Voltage 600 V DC (UL) / 1000 V DC (IEC)
Maximum Series Fuse Rating 15A

I haven't decided on PWD or MPPT, but it seems MPPT would be a better option here since these are 12v panels.

So now I have an issue. I have ~70AH of battery but really only ~25AH of useful power so I don't kill my cheap HF batteries. Here come the questions.

1) How many of these 12VDC (10W) lights can I power reliably support for ~24hrs
2) What is the required wire gauge
a) 1 Light up to 30'
b) 2 Lights up to 20'
3) Is 400w overkill?
4) is 70AH is enough?
5) Should I use the larger 24v panels (250w)?


Feel free to suggest other solutions as well.

Several links I used in the past for information are shutdown at the moment...

bmet

Re: Upgrading Test System #1 to Test System #2...could use some input.

Vikelf wrote: »

Greetings,

It's been sometime since I've had time to address my project, but here I am again.

Originally, I setup a HF 45w system and connected to a pair of Thunderbolt Magnum Solar 68680 12 Volt, 35 Amp Hour Universal Battery (labelled AGM on the battery itself) connected in parallel. I also have 6-8 7.2Ah 12v UPS batteries that I toy around with.

Now, I was very ignorant when I first approached solar and for that matter all the electrical knowledge needed. I am now less ignorant about Solar requirements but in saying that I am really only qualified to install a HF 45w Solar system

On to project #2.

Goal: 24/7 lighting around the exterior of the house using 12VDC LED Flood lights (LENBO 10W 12V DC Warm White LED Flood light High Power Waterproof Outdoor Lights)


I decided to up the size of the backyard solar installation to 400w using four 100w Mono panels from a competitor. (Renogy) Basically, free shipping wins.
Technical Specifications:
Solar Cell Monocrystalline 125x125 (5 inches)
No. of Cells36 (4x9)
Dimensions 1195x541x35 mm (47x21.3x1.4 inches)
Weight7.5 kgs (16.5 lbs)
Front Glass 3.2 mm (0.13 inches) tempered glass
Frame Anodized aluminum alloy
Junction Box IP67 rated
Output Cables 4.0 mm2 (0.006 inches2), 600mm (23.6 inches)
Connectors MC4 Connectors
Fire Rating Class C

Electrical Characteristics:
Optimum Operating Voltage (Vmp) 18.9V
Optimum Operating Current (Imp) 5.29A
Open - Circuit Voltage (Voc) 22.5V
Short- Circuit Current (Isc) 5.75A
Operating Module Temperature -40°C to + 90°C
Maximum System Voltage 600 V DC (UL) / 1000 V DC (IEC)
Maximum Series Fuse Rating 15A

I haven't decided on PWD or MPPT, but it seems MPPT would be a better option here since these are 12v panels.

So now I have an issue. I have ~70AH of battery but really only ~25AH of useful power so I don't kill my cheap HF batteries. Here come the questions.

1) How many of these 12VDC (10W) lights can I power reliably support for ~24hrs
2) What is the required wire gauge
a) 1 Light up to 30'
b) 2 Lights up to 20'
3) Is 400w overkill?
4) is 70AH is enough?
5) Should I use the larger 24v panels (250w)?


Feel free to suggest other solutions as well.

Several links I used in the past for information are shutdown at the moment...

Welcome back to the forum. Am at work, so only have time to steal some of B.B.'s math to get you started.

400 watts of panel * 0.77 panel+controller deratings * 1/14.5 volts charging * 1/0.05 rate of charge = 424.8 AH @ 12 volt battery. Ideally you would not want to exceed 50% state of discharge, so that gives you 212 AH.

You want to support a 12V, 10W light for a period of 24 hours. Using a Watt to Amp calculater, we see that a single 10W light consumes 0.83 Amps of current at 12 Volts.

0.83Amps*12V*24Hours = 239 Watt Hours.

Folks here usually like to start with the Load requirements to determine how to best size the system to meet it.
Could you be a little more specific on your use? Do you really want to run a 10W light continously for 24Hours, or is that a 'reserve' capability?

Anyway, gotta get backto work. Have a great day.

Vikelf

Re: Upgrading Test System #1 to Test System #2...could use some input.

Bmet,

Thanks for the response. I actually wouldn't mind them turning off during daylight, but I would like the system to be completely automatic. I am not intending to use the system for emergency back up at this time since I have 3 generators. I just need this as a test platform to determine in what direction I want to go. Ideally, I want a system that is Grid-Tie but also provides power lights/frig to house as soon as the grid goes down. I think SMA has something like this. Eventually, I will have a whole house emergency backup generator, but for now it's just portable units.

For now, I will use to charge all my cordless lawn equipment, run shop led lights, run exterior lights, etc. Basically, it's a toy to experiment with...

I'm giving myself a 2k budget to purchase everything I need with the understanding that none of it can be permanent (no roof mount, etc).

So if I am understanding this right, you are saying that each light will consume ~240w per 24hr period or ~20AHs. So to run 4, I would need ~80AH of storage for 24hrs.

Now, if I am running the lights during daylight (Baton Rouge, LA), how many Amps or AHs would I be storing in a 70AH battery bank per day while I am draining the system of a 3.5amp draw from the lights without going below the 50% discharge point. This is where the math gets confusing to me with all the X-hours vs X. panels rated in X, usage is rated in X-hours, storage is in X-hours, etc.

Thanks again!

PS Mono or Poly panels for Louisiana?

BB.

Re: Upgrading Test System #1 to Test System #2...could use some input.

Vikelf wrote: »

Bmet,

Thanks for the response. I actually wouldn't mind them turning off during daylight, but I would like the system to be completely automatic. I am not intending to use the system for emergency back up at this time since I have 3 generators. I just need this as a test platform to determine in what direction I want to go. Ideally, I want a system that is Grid-Tie but also provides power lights/frig to house as soon as the grid goes down. I think SMA has something like this. Eventually, I will have a whole house emergency backup generator, but for now it's just portable units.

Solar is pretty easy to configure to meet your needs--The question is what are those needs. If they are mostly 120 VAC--I would start with a Kill-a-Watt type meter and measure your loads.

Pretty much, you need to estimate the starting current (VA), average Watts, and number of Watts*Hours per day you want to power.

You can purchase smaller lighting/charge controllers--They will, for example, turn the lights on when it is dark (using the solar panels for sensors) or for 5 hours per night, etc.

More or less, if you have "small loads", a 1 kWH per day system is "smallish". As soon as you add a refrigerator, your system needs go up towards 3.3 kWH per day... A full "energy efficient home" using natural gas for cooking/washing/heating--And you are looking at a 10kWH per day system (very rough numbers).

So--What are the ratings/hours per day of tools/appliances you would like to try and run?

For now, I will use to charge all my cordless lawn equipment, run shop led lights, run exterior lights, etc. Basically, it's a toy to experiment with...

One lawn mower has a 24 volt 20 AH battery (24v*20A=480 Watt*Hours + charging losses)... That would, buy itself, pretty much use 1/2 to all of the power from a 1kWH per day system (for a fully discharged lawn mower battery)... Sort of gives you an idea of how little power 1 kWH per day is.

I'm giving myself a 2k budget to purchase everything I need with the understanding that none of it can be permanent (no roof mount, etc).

We can take a shot at designing a $2,000 off grid system--And then see how much power it will generate for you.

So if I am understanding this right, you are saying that each light will consume ~240w per 24hr period or ~20AHs. So to run 4, I would need ~80AH of storage for 24hrs.

The calculation is correct Volts*Amps*Hours of use = Watt*Hours

Watt*Hours / Voltage = AH @ xx volts

And there are "losses". For solar panel to charge controller to battery bank to AC inverter to AC loads--The rough end to end efficiency is roughly 52% or so... Yes, 1/2 of the solar panel's rating is lost in real life.

And, you would not want to drain the battery dead--More or less, the "optimum" battery (for daily cycling) should be ~4x your daily loads (rules of thumbs we use around here).

Now, if I am running the lights during daylight (Baton Rouge, LA), how many Amps or AHs would I be storing in a 70AH battery bank per day while I am draining the system of a 3.5amp draw from the lights without going below the 50% discharge point. This is where the math gets confusing to me with all the X-hours vs X. panels rated in X, usage is rated in X-hours, storage is in X-hours, etc.

I am a little lost, on your desired power usage... How many watts for how many hours per day? 120 VAC or 12 VDC?

PS Mono or Poly panels for Louisiana?

Does not really matter--If you want (slightly) smaller panels (limited space for panels), then Mono-Crystalline panels would be a bit better... Otherwise, just buy on $$$/Watt basis.

But don't get too far ahead of yourself--Lets understand your loads first (best we can), then size the system. You can then pick components to optimize costs.

-Bill

Vikelf

Re: Upgrading Test System #1 to Test System #2...could use some input.

BB,

Thanks for the responses. I think I confused us both here.

1) Goal #1 - Run Exterior LED 10w 12VDC flood lights (quantity 4) for 24/7
2) Design an inexpensive "Learning" system with meters/monitoring in order to better understand the technology
3) System should be able to run simple AC loads from inverter ie Drills, LED lights, jigsaw, and possibly a circular saw for very short periods of time(no major household items)
4) Nothing has been purchased yet except existing 2x 35AH 12v AGM batteries, HF 4w solar kit, Stanely 800w MSW inverter (Initial learning setup)
5) Not permanent

Goal #2 - Run a GE 6,400 BTU, 10.7 EER, 5.6 amps window A/C for 4 hours /day (~ 650W AC and 6500W DC?) That looks like a no go unless I have a huge setup, lol

My initial plan was using 4 100w 12v mono PVs (~$170ea delivered) and tossing in some cheap 6v golf cart batteries ~ $100ea 232ah @ 20hr followed by a cheap $200 MPPT charge controller.
If purchased in a Kit, ~$850 delivered (PV, controller, wire, connectors, mounts) Free shipping is nice.

That being said, I am completely open-minded on any suggestions of design, manufacturer, and distributor. This being a simple & small off-grid system that will not be permanent.

BB.

Re: Upgrading Test System #1 to Test System #2...could use some input.

Vikelf wrote: »

BB,

Thanks for the responses. I think I confused us both here.

1) Goal #1 - Run Exterior LED 10w 12VDC flood lights (quantity 4) for 24/7

With solar power, we always prefer to conserve power. In this case, 8 hour of light at night vs 3x as much power to run them 24 hours per day (unless you are using the lights in a garage/shed and need 24 hour lighting).

40 watts * 8 hours = 320 WH per day
40 watts * 24 hour = 960 WH per day

That is a 3x larger system. A 1,000 WH per day system will usually run all the loads for a small, energy efficient cabin (lights, laptop, small RV water pump, cell phone charger, etc.).

2) Design an inexpensive "Learning" system with meters/monitoring in order to better understand the technology

I understand the desire to build a system and start measuring stuff/experimenting. With solar, the operating parameters are pretty well known and, if possible, we would like to design a system that meets your rough requirements. If we design a system that is 1/3rd your needs--It will not have a chance of operating your loads. If we design one 3x larger than you need, we just wasted your money.

3) System should be able to run simple AC loads from inverter ie Drills, LED lights, jigsaw, and possibly a circular saw for very short periods of time(no major household items)

Drills and lights--You may draw 300-600 watts... The circular saw, upwards of 1,800+ Watts...

4) Nothing has been purchased yet except existing 2x 35AH 12v AGM batteries, HF 4w solar kit, Stanely 800w MSW inverter (Initial learning setup)

This is a "small" system... It cannot really run any of these loads very long (maybe 200-400 Watt*Hours per sunny day). The batteries themselves, cannot support very large loads or for very long.

5) Not permanent

Solar panels are made from single weight window glass (it is tempered)... Very easy to break. So even a portable system needs to have the panel solidly mounted to something so they don't blown over by a gust of wind (or get kicked by somebody walking by).

Goal #2 - Run a GE 6,400 BTU, 10.7 EER, 5.6 amps window A/C for 4 hours /day (~ 650W AC and 6500W DC?) That looks like a no go unless I have a huge setup, lol

Yep--Size the system to your loads. There are a number of people using A/C on off grid solar power systems--But they have to be sized for the loads.

My initial plan was using 4 100w 12v mono PVs (~$170ea delivered) and tossing in some cheap 6v golf cart batteries ~ $100ea 232ah @ 20hr followed by a cheap $200 MPPT charge controller.
If purchased in a Kit, ~$850 delivered (PV, controller, wire, connectors, mounts) Free shipping is nice.

That being said, I am completely open-minded on any suggestions of design, manufacturer, and distributor. This being a simple & small off-grid system that will not be permanent.

Don't buy a kit yet--Let's figure out what size components you need. You really have not given me much information--But lets take a stab at it. A circular saw needs around 2kWatts/kVA just to start/cut wood. A flooded cell lead acid battery can supply ~C/2.5 surge current reliably (over age, temperature, states of charge):

• 2,000 Watts * 1/24 volt battery bank * 2.5 Surge * 1/0.85 inverter efficiency = 245 AH @ 24 volt battery bank

That is close enough to 4x 6 volt @ 220 AH golf cart batteries in series (close enough for your needs).

The daily Watt*Hours for such a battery bank, assuming 2 days of storage and 50% maximum discharge (recommended for daily cycling):

• 24 volts * 220 AH * 0.85 inverter efficiency * 1/2 days of storage * 0.50 rate of charge = 1,122 Watt*Hours at 120 VAC per day

So, assuming 5% to 13% rate of charge for such a bank:

• 220 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 414 Watt array minimum
• 220 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 829 Watt array nominal
• 220 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,077 Watt array "maximum cost effective"

If you want a minimum of 1,122 Watt*Hours per day for ~9 months of the year, assuming you have ~4 hours of sun outside of winter:

• 1,122 Watt*Hours * 1/0.52 system efficiency * 1/4 hours sun per day = 539 Watt array minimum.

If you want your ~960-1,122 Watt*Hours per day in the dead of winter, you may only get ~3 or 2 hours of sun per day (depending on where the system is installed).

OK--I have sized out a system based on "your needs"... ~400 Watts of solar panel is close enough to your minimum needs (at least to experiment). And 6 volt golf cart batteries--You did not say how many.

Also, the AC inverter--No wattage or battery bus voltage listed. Also, it does not list MSW or TSW (modified square wave or true sine wave). To run your saws, drills, jigsaws, etc.--A MSW inverter will be fine. To run your electronics and LED lighting, a TSW inverter is frequently better.

All About Inverters
Choosing an Inverter - Home Power Magazine

A 2kW AC inverter is pretty good sized--I would suggest a 24 VDC inverter--Although, there is a ~1.8-2.0 kWatt Xantrex sine wave 12 volt AC inverter that several people here have used and are very happy with it.

-Bill

Vikelf

Re: Upgrading Test System #1 to Test System #2...could use some input.

Bill,
You are already depressing me, lol.

My original plan of 400w just became 1kw.
My original plan of 2 6v ~220AH batteries just became Six 6v 220AH
My original plan of a 12v Battery Bank just became 24v
My original plan of a 1000w 12v TSW inverter just became 2000w 24v TSW
My original plan of 12v panels just became 24v panels

I think my goal is still the same...

So many questions and I need to learn to communicate better since I seem to be forgetting to inform you all with the basics.

Well, lets go with it! So what would you recommend?

BB.

Re: Upgrading Test System #1 to Test System #2...could use some input.

I am not really trying to "up sell you"... I am an engineer by trade--So we tend to be a conservative bunch. For most people with off grid homes--A reliable system that meets their needs is very important.

And the system I penciled out for you should do what you asked (so far) reliably.

But, if you drop your daily WH load and surge/maximum power by 1/2 to 2/3 (8 hours of light, no skill saw) -- Then you could get away with a 12 volt system (2 golf cart batteries) and a really neat MorningStar 12 volt 300 watt (600 watt surge) TSW inverter with remote on/off and low power "search mode".

If you cut the circular saw but still want the 1,000 WH per day for lighting (and other loads), the 12 volt 300 watt AC inverter plus 4x golf cart batteries (two in series, two parallel strings) would be a very functional system too.

You could also get a large/cheaper 12 volt MSW inverter and try powering your circular saw with that, Note that at 12 volts, the battery bus current is now 2x higher or:

• 2,000 watt * 1/0.85 AC inverter * 1/10.5 volt cutoff = 224 amp 12 volt current to AC inverter

Lots of options. And the choice of hardware really depends on the sizing of the battery bank.

I would suggest at 24 volt system normally--But if your needs are usually much less, then the smaller 300 watt/600 watt surge AC inverter is actually going to be more efficient for you.

One of the nice things with going to a higher battery bus voltage--The charge controllers can handle a larger array. For example, a Rogue 12/24/48 volt 30 amp mid-range charge controller can support:

• 30 amps * 14.5 volts charging * 1/0.77 panel+controller deratings = ~565 watts (cost effective maximum)
• 30 amps * 29.0 volts charging * 1/0.77 panel+controller deratings = ~1,130 watts (cost effective maximum)

If you go with a ~1,000 watt array at 12 volts--You are going to need a ~60+ amp charge controller.

There are a lot of decisions to make--And each one will affect available options down the road.

-Bill

Vikelf

Re: Upgrading Test System #1 to Test System #2...could use some input.

Bill,

You have me sold on the 24v system. (added bonus is the wire size requirements)

I do have question about the MorningStar inverter, everyone I speak to about inverters says it's a great and I should get one. My only fear is that it is really on 300w with a 200% surge capability but still 300w. It's priced like a high quality 600-800w TSW inverter as well. (just my opinion) Keep in mind, this is a "Backyard" installation that will move with us. I will not rely on it for any power beyond lighting and occasional tool use. Eventually, I will install a grid-tie system and this will be used to power my shop (think weekend warrior style- small 8x8 shop)

Ok, Back to the project:

If we expand the system to 1kw of PV and go with a 24v system, what Inverter should I use now? I was thinking ~1000w TSW. I can add a cheapo MSW 2kw inverter for trash use later (circular saw)

Now, I will need 4 batteries min if 6v 220AH correct?

Oh, and I will need to switch to 250w 24v panels as well?

How comfortable are you with the Rogue MPT-3048?

Trying to get my shopping list down, thanks again for your input!

BB.

Re: Upgrading Test System #1 to Test System #2...could use some input.

My system is Grid Tied--So my experience is what I have read here...

The MorningStar 12 volt AC inverter is a very rugged/reliable unit. It has features that no other low power AC inverter has.... But if you need 24 volts and/or more power--It simply will not work for you (rumors the MorningStar is working on a 24 volt AC inverter--But have not seen anything).

I am not sure what inverter to recommend for 1kW 24 volt sine wave--I will let others here take a stab at that one.

If you get true "24 volt panels" (Vmp~35-38 volts)--You can run them in parallel with a PWM controller (less expensive controller).

If you use a MPPT charge controller (the one you PMed me works to 100 Voc max)--You can put a pair of panels in series and the voltage will be more than high enough to charge the 24 volt battery bank. MPPT controllers can take the high voltage/low current from the solar array and efficiently down convert to the low voltage/high current needed by the battery bank. The panels you are looking at can run a PWM controller (or even MPPT) at a single panel as their Vmp~37.5 is fine for charging 24 volt battery bank. Placing to panels in series for higher Vmp-array is how your vendor connects them (allows you to use less wire on the Array to Charge Controller run (higher voltage/lower current, smaller wire gauge).

4x 6 volt ~220 AH golf cart batteries in series will give you a 24 volt @ 220 AH battery bank.

There were two earlier versions of the Rogue controllers were very nice controllers. And if there were any problems, Marc took care of them quickly (according to posters here). This is his 3rd generation controller and should be working well (I have not read any reviews from any posters here--It has been out only for a few months). Contact Rogue if you have any questions.

-Bill

Vikelf

Re: Upgrading Test System #1 to Test System #2...could use some input.

Bill,

Thanks for all the experienced advice you have provided. I will put it to good use! I'm sure I ask more questions when I get closer to the purchase point. For now, I still have a lot of diagrams to create to figure out what and how I am going to do it.