Solar Craft Shed setup

[Skegeej]

Hello
I wanted to double check my setup for my Design Shed. I'm new to solar and I wanted to take a stab at DIY myself.

Current Setup
2- 100W Panels
2- 12V Batteries(parallel) Sealed Lead
Epever 40A Controller
TopBull 3000W 12V Modified Sine Inverter

I want to be able to run lights, portable air condition (24hours if possible to keep candle wax cool), computer, Laser cutter, 3D Printer, TV and Cricut machine. Currently live in Southern Cali and its been 100+ temps lately. So I'm not sure if the air condition is even possible.

Do I need more panels and batteries? Or more of one or the other? How many amps should I be seeing from my panels(6.6A) and battery(8.5A)? Are there default settings I should be using for the EPEVER?

 

[DThames]

Need the specifications of the AC unit but both panels and batteries would appear too small for AC use.

 

[Skegeej]

Need the specifications of the AC unit but both panels and batteries would appear too small for AC use.

AC is 9,3000 BTU 10Amps 1135 WATTS

 

[DThames]

AC is 9,3000 BTU 10Amps 1135 WATTS

200w of panel, you might get 150w times 5 hours per day, so about 750 watt hours, so could run your AC for 40 minutes or so. That is excluding the battery from the calculations. Depending on room heat gain, insulation, etc, if the unit ran less than 50%, say 500 watt hours per hour, you would need 12kwh worth of usable battery just for the AC load. $1000-$2000 for batteries, rough guess. Maybe 3000 watts of panels.

 

[Skegeej]

200w of panel, you might get 150w times 5 hours per day, so about 750 watt hours, so could run your AC for 40 minutes or so. That is excluding the battery from the calculations. Depending on room heat gain, insulation, etc, if the unit ran less than 50%, say 500 watt hours per hour, you would need 12kwh worth of usable battery just for the AC load. $1000-$2000 for batteries, rough guess. Maybe 3000 watts of panels.

Oh my so this wasn't a good idea after all.

So do I have enough to run the air condition during the day and the off at night?

 

[DThames]

Oh my so this wasn't a good idea after all.

So do I have enough to run the air condition during the day and the off at night?

If you had about 2000w of panels and the sun was shining, you could run during the day, for a good part of the day. 2000w is max but in real life less than perfect sun angle and hot weather make the output go down. You would need a constant output of 1200w or more to stay ahead of drawing down your battery. A battery that small, you would only want to draw in like when a bird flew over or small cloud. Note, you can get 300-400w panels that are bigger than a door that are less cost than many 100w panels.

 

[DThames]

Oh my so this wasn't a good idea after all.

So do I have enough to run the air condition during the day and the off at night?

That inverter may or may not start that AC unit. You should test that early if you plan to spend money on other components and can't afford to get a larger inverter.

 

[Skegeej]

That inverter may or may not start that AC unit. You should test that early if you plan to spend money on other components and can't afford to get a larger inverter.

The AC starts with the inverter.

 

[DThames]

The AC starts with the inverter.

Do you have space and money for some larger panels?

 

[Skegeej]

Yes I have the roof available.

 

[x98myers7]

air conditioning is hard to run on solar. it works, but is very high consumption. Will has a few good videos on youtube about running a small sized AC unit on solar.

don't forget that for lead acid/AGM cells you can only run them down to 50% before damaging them, so you'll need to account for that

what's your location? have you done a PVWatts calculation to see how much solar power you can generate?

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

 

[DThames]

Yes I have the roof available.

4 or 5 of these panels should provide power for the AC and a bit more under good solar conditions. Should provide enough under slightly less than good conditions providing your battery can provide the rest of the power needed. Good sun followed by a little cloud shading would cause some battery draw followed by charging before the next cloud. Or with light/bright overcast 5 of them might keep you above the 1200watt mark for your AC.

 

[Skegeej]

4 or 5 of these panels should provide power for the AC and a bit more under good solar conditions. Should provide enough under slightly less than good conditions providing your battery can provide the rest of the power needed. Good sun followed by a little cloud shading would cause some battery draw followed by charging before the next cloud. Or with light/bright overcast 5 of them might keep you above the 1200watt mark for your AC.

So if I understand correctly I need to have enough panels that will total over the watts for the air condition?

Example: 100W x 5=500 x 5hours of sunlight=2500W

 

[JoeHam]

So if I understand correctly I need to have enough panels that will total over the watts for the air condition?

Example: 100W x 5=500 x 5hours of sunlight=2500W

Not even close.

That is still just 500W PER HOUR while your AC is burning over 1100W PER HOUR.

That is also ignoring cloudy/rainy days.

 

[DThames]

So if I understand correctly I need to have enough panels that will total over the watts for the air condition?

Example: 100W x 5=500 x 5hours of sunlight=2500W

The panels that I linked to are 445w each. 5panels x 400w each would be about 2000w of panels, times 5 hours would be 10,000 watt hours or 10kwh per day, if the sun was shining on the panels, no shade. That is a good solar condition. 2000w when your load is 1200w would allow some room to run with less than good conditions. That difference 2000-1200 would also give you some extra to charge with while the AC is running, again under good solar conditions.

 

[dcGuide]

Not even close.

That is still just 500W PER HOUR while your AC is burning over 1100W PER HOUR.

That is also ignoring cloudy/rainy days.

Welcome aboard @Skegeej -- Now that you've gotten some replies you might do some re-considering! To begin, how much power is your shed really drawing? Does your AC really pull 1135 watts? Do you have a wattmeter?

What if you run everything in your shed on solar except the AC? What if you bought a new, smaller, more efficient AC? What if you hang a ceiling, say T-bar, reducing the amount of space you need to cool? How big is your shed?

Does your shed run on the grid now? You need to know how much your AC will really run; if it starts early in the morning before it gets hot, does it keep up? Will it cycle off in the cooler early morning hours? You need to complete an entire energy consumption worksheet; something like this:

https://diysolarforum.com/resources/system-energy-audit-and-sizing-spread-sheet.12/download

Good luck!

 

[Skegeej]

Welcome aboard @Skegeej -- Now that you've gotten some replies you might do some re-considering! To begin, how much power is your shed really drawing? Does your AC really pull 1135 watts? Do you have a wattmeter?

What if you run everything in your shed on solar except the AC? What if you bought a new, smaller, more efficient AC? What if you hang a ceiling, say T-bar, reducing the amount of space you need to cool? How big is your shed?

Does your shed run on the grid now? You need to know how much your AC will really run; if it starts early in the morning before it gets hot, does it keep up? Will it cycle off in the cooler early morning hours? You need to complete an entire energy consumption worksheet; something like this:

https://diysolarforum.com/resources/system-energy-audit-and-sizing-spread-sheet.12/download

Good luck!

Hi dcguide
I would have to agree. I have gone to several several sites and I added up all of the watts that I thought I would need and from what I calculated I could run it with the 2 panels and 2 batteries. However, something is not correct.

It is a brand new shed so I’m doing every new. I got the wattage from the documentation for the ac. And I don’t have a wattmeter. I’ve been looking for a smaller ac but I wasn’t able to find one that didn’t go in window. Maybe I’m not looking in the correct place.

My shed is 10x14 so it isn’t very big. I will fill out the worksheet and see what I come up with.

 

[Skegeej]

The panels that I linked to are 445w each. 5panels x 400w each would be about 2000w of panels, times 5 hours would be 10,000 watt hours or 10kwh per day, if the sun was shining on the panels, no shade. That is a good solar condition. 2000w when your load is 1200w would allow some room to run with less than good conditions. That difference 2000-1200 would also give you some extra to charge with while the AC is running, again under good solar conditions.

Thanks for clarification. That is what I thought you meant. I thought I was on track with the calculation. So in my mind upping my panel watts and number of panels would help and the more the better?

And I assume more batteries wouldn’t matter unless I have enough panels to charge them with the extra energy?

Ultimately air conditioner may not be a option in the beginning until I add way more panels.

 

[DThames]

Thanks for clarification. That is what I thought you meant. I thought I was on track with the calculation. So in my mind upping my panel watts and number of panels would help and the more the better?

And I assume more batteries wouldn’t matter unless I have enough panels to charge them with the extra energy?

Ultimately air conditioner may not be a option in the beginning until I add way more panels.

About more batteries....in your situation, yes there is some number of panel watts needed for some number of amp hours in the battery storage. Not always the case.....we have a hunt shack where we spend 4 or 5 day weekends. If the battery can carry us through those weekends with a little solar charging along the way, that is fine. If (because we have only one 250w panel) it takes 10 days to recharge and no one will be there for 2 or 3 weeks, then we can live with that. But for daily use, the first sentence (above) is true.

More panel watts are better up to some point maybe 2 to 4 times your load. Of course that is my opinion. I want enough panels on a battery system that I can,
1. run my load during a sunny day
2. and charge the battery
3. and charge the battery in no more than half a day because I might only get 2 or 3 hours of sun on some days.

I think of days being like 10-15 percent not enough sun to matter, maybe 30-60% days with some sun, and maybe 20-30% with good sun. If I can fully charge in 3 hours of sun, I can fully charge on most days. Of course you can get by with less and many do. Some locations have sunny days most of the time, so they could get by with less. Somewhere that a sunny day is rare, they will need more than typical.

Truck shipping on large panels is such that it is wise to get the panels you think you need for now and near future so cut down on shipping cost. Some places want you to order at least 10 to make handling them worth their effort.

 

[dcGuide]

I got the wattage from the documentation for the ac. And I don’t have a wattmeter.

Often appliances draw less than what the doc says. You can find watt meters on Amazon for $15 and just plug the AC into it. Let it run for 24 hours and record some data.

My shed is 10x14 so it isn’t very big. I will fill out the worksheet and see what I come up with.

You'll want the AC running for 24-hours and see what happens. We set our window AC in the ECO mode and it shuts down completely when the set point is hit. Our small (6,000 btu) AC didn't keep up on hot days until we put in a ceiling. Our shop is 12x16. This made a HUGE difference for the AC and how much power we needed. Did I say HUGE?!

Ideally, you are running your AC in the daytime using solar AND charging your batteries at the same time. In the overnight hours, the AC does not run continuously like it does on hot days. Power consumption off the battery bank is much less than in the daytime. Maybe with your larger AC and smaller shed your unit won't be on 24/7 but will cycle off when it is caught up.

We unrolled insulation for in between our studs, added drywall and put in a drop ceiling. Did I mention the huge difference all this makes?!

You want to know how much power you need from sundown to sun rise. This is the power you need stored in batteries. You want to know how much power the shop and AC draw when you are in there doing stuff. Eventually you'll know how much power you need to generate to both run things and store power for evenings.

Issues to contend with, like these are our issues:

• Our panels don't start generating anything meaningful until late morning.
• In the hot summer sun, our panels are less efficient
• We get lots of clouds and cloudy days in the summer (in Kentucky)
• We need more than one day of power in the batteries, even in the summertime, especially in the summertime.

You have one more issue to contend with, the MAX PV INPUT of your charge controller. You mentioned a 40amp Epever. What is the voltage limit? Is it 92-volts? You want to know how much voltage your panels are producing. In series, current stays the same while voltage is additive. For example, the Canadian Solar 445W Panel @DThames suggested has a "Max power voltage (VMP): 38.3 V." If you bought two panels, you are at 38+38 or 76-volts. Adding on the two 100-watt panels you already have might push your controller past its limit and it will shut down.