My solar off grid shed/workshop

[jasonl549]

In November, I finished a few months worth of learning and research into solar panels and proposed a setup for critique as a newbie to the forum (here is the original post).

This system was designed to provide power to a storage shed/workshop that I built this spring so I could run some lights, pumps, a small inverter for charging batteries, and maybe more in the future. I just wanted to report on my results and review the DM Solar 145 watt panels that I have installed. One thing to note is that I have yet to purchase and install the final battery set up with (2) Trojan T-105RE batteries. Currently I am using (2) 4.5ah 6v UPG style batteries so that I can "practice" on these and learn from any mistakes I make on cheap throwaway batteries instead of the Trojans.

I chose to buy the DM Solar panels against the recommendations and words of caution of a few of you on here and I don't regret it. They were about $1.10/watt including shipping as they were just small enough to ship UPS instead of freight. That helped to keep the cost way down over alternative options. The build quality of the panels is good and there were no defects that I could see. Open voltage with no load is consistently 19.0-20.5 or so depending on the direction of the sun and the cloud cover. And I get 15 amps as tested with my multimeter for short periods of time. I have an ammeter that I am in the process of installing that will tell me safely how much I am consistently getting soon. Time will tell, obviously, how these panels hold up over the years but for the price I don't think you can beat them.

Here is a video of my final impressions of the panels (I reviewed the panels after unboxing them in January, too):

I did end up using the MorningStar SS-20L-12V LVD charge controller and it has been great. I couldn't stomach paying double for a MPPT controller at this time. When I get 2 more of these panels in the future and have to upgrade the charge controller I may upgrade to MPPT but for now this works great.

If any of you are curious about the shed and some of the other electrical bits that I installed in the system, such as a combiner box and dc load center, I put up another video here but I can't embed it in the post.

I would really like to thank everyone on this forum that has helped. I know I haven't posted much but I have read a lot and I appreciate all the info!

[FloridaSun]

This system was designed to provide power to a storage shed/workshop that I built this spring so I could run some lights, pumps, a small inverter for charging batteries, and maybe more in the future. I just wanted to report on my results and review the DM Solar 145 watt panels that I have installed. One thing to note is that I have yet to purchase and install the final battery set up with (2) Trojan T-105RE batteries. Currently I am using (2) 4.5ah 6v UPG style batteries so that I can "practice" on these and learn from any mistakes I make on cheap throwaway batteries instead of the Trojans.

I chose to buy the DM Solar panels against the recommendations and words of caution of a few of you on here and I don't regret it. They were about $1.10/watt including shipping as they were just small enough to ship UPS instead of freight. That helped to keep the cost way down over alternative options. The build quality of the panels is good and there were no defects that I could see. Open voltage with no load is consistently 19.0-20.5 or so depending on the direction of the sun and the cloud cover. And I get 15 amps as tested with my multimeter for short periods of time. I have an ammeter that I am in the process of installing that will tell me safely how much I am consistently getting soon. Time will tell, obviously, how these panels hold up over the years but for the price I don't think you can beat them.

I would really like to thank everyone on this forum that has helped. I know I haven't posted much but I have read a lot and I appreciate all the info!

hey jason!
My system includes the dmsolar panels as well and they seem to be fine after 8-9 months of use, consistent output and no defects to date but.... like you say.. only time will tell. The panel price was good, .79 a watt (plus fast FedEx delivery) and I've noticed at this time the price has gone up, .85@W for 158W panels of the same dimensions. I presently use 580W of dmsolar panels with a Morningstar TS-45 PWM to keep my 200Ah @ 24v bank of hybrid (cheapo walfart marine batteries) charged and all's fine for now but next fall plan on going with a Morningstar MPPT, save the TS-45 for back up or possibly diversion load in future.
My recorded max results from the 145W panels were/are 16+Ap w/PWM, 21+Ap w/MPPT.
Your 4.5Ah batt/bank at 12v seems a bit light and no reason you could not have a much more (100Ah) Ah bank with the panels you have. My upgrade to TSW inverter was a great help, being able to run my forge blower (I'm a blacksmith) where the old 12v MSW inverter made my 120v forge blower make some very odd (read that dangerous) growling noises. Playing with solar has been a blast... think about going 24v in the near future if you can. Really does make sense if you're serious on continuing with the solar hobby, buying good 24v inverters now instead of 12v cheapos can save some future bucks.
Nice clean set-up but your panel mounting seem WAY too close, not enough air space for proper panel cooling. Get those panels off the shingles! I built a simple south facing add-on to my shed, pressure treated lumber framing with no roofing where much air can circulate under panels.

ack!!! gotta run... lights are flickering and just heard a nearby transformer pop.... ahhh... the joys of way out in th stix grid service.... (My UPS saves me)

[jasonl549]

hey jason!
My system includes the dmsolar panels as well and they seem to be fine after 8-9 months of use, consistent output and no defects to date but.... like you say.. only time will tell. The panel price was good, .79 a watt (plus fast FedEx delivery) and I've noticed at this time the price has gone up, .85@W for 158W panels of the same dimensions. I presently use 580W of dmsolar panels with a Morningstar TS-45 PWM to keep my 200Ah @ 24v bank of hybrid (cheapo walfart marine batteries) charged and all's fine for now but next fall plan on going with a Morningstar MPPT, save the TS-45 for back up or possibly diversion load in future.
My recorded max results from the 145W panels were/are 16+Ap w/PWM, 21+Ap w/MPPT.
Your 4.5Ah batt/bank at 12v seems a bit light and no reason you could not have a much more (100Ah) Ah bank with the panels you have. My upgrade to TSW inverter was a great help, being able to run my forge blower (I'm a blacksmith) where the old 12v MSW inverter made my 120v forge blower make some very odd (read that dangerous) growling noises. Playing with solar has been a blast... think about going 24v in the near future if you can. Really does make sense if you're serious on continuing with the solar hobby, buying good 24v inverters now instead of 12v cheapos can save some future bucks.
Nice clean set-up but your panel mounting seem WAY too close, not enough air space for proper panel cooling. Get those panels off the shingles! I built a simple south facing add-on to my shed, pressure treated lumber framing with no roofing where much air can circulate under panels.

ack!!! gotta run... lights are flickering and just heard a nearby transformer pop.... ahhh... the joys of way out in th stix grid service.... (My UPS saves me)

Thanks for the response. Yeah, the batteries I have now are just for playing with. I don't want to spend hundreds of dollars on a big battery bank before I know how to properly take care of them. I have no reason to go 24v in the future as my wiring runs are not very far and I will need to step it back to 12v to power my lighting and pumps anyways. Someday if I put panels on the roof of my house I would definitely do 24v or higher. Also, I haven't heard of needing to put the panels higher up. Right now they are about 2 inches off the surface of the roof but I don't think there is a lot of head radiation underneath because the panels under them are shaded. I haven't noticed a decrease in performance anyways.

[inetdog]

Thanks for the response. Yeah, the batteries I have now are just for playing with. I don't want to spend hundreds of dollars on a big battery bank before I know how to properly take care of them. I have no reason to go 24v in the future as my wiring runs are not very far and I will need to step it back to 12v to power my lighting and pumps anyways. Someday if I put panels on the roof of my house I would definitely do 24v or higher. Also, I haven't heard of needing to put the panels higher up. Right now they are about 2 inches off the surface of the roof but I don't think there is a lot of head radiation underneath because the panels under them are shaded. I haven't noticed a decrease in performance anyways.

The problem is not the panels receiving heat from the roof. That will not happen. The problem is that without circulating air underneath for cooling the panels will get a lot hotter (approaching twice the temperature rise of mounting in open air) and at the temperature increases the voltage output and therefore the power output of the panels declines badly. Most of the difference between the STC and the PTC power rating of a panel is the temperature effect.
On the other hand, studies also show that once you get beyond about 6" from the roof, with unobstructed air flow at the bottom and top edges of the space, your gain from more height decreases rapidly.
In either case, you will get less heat into your attic, but again with 6" of space your attic under the panels will be cooler than with 2".

[jasonl549]

The problem is not the panels receiving heat from the roof. That will not happen. The problem is that without circulating air underneath for cooling the panels will get a lot hotter (approaching twice the temperature rise of mounting in open air) and at the temperature increases the voltage output and therefore the power output of the panels declines badly. Most of the difference between the STC and the PTC power rating of a panel is the temperature effect.
On the other hand, studies also show that once you get beyond about 6" from the roof, with unobstructed air flow at the bottom and top edges of the space, your gain from more height decreases rapidly.
In either case, you will get less heat into your attic, but again with 6" of space your attic under the panels will be cooler than with 2".

Understood. In the perfect world I would do that. Unfortunately, I live in the suburbs and my HOA articles ban "solar collectors" altogether. Luckily I can lean on Texas state law, which says that HOAs cannot ban solar devices as long as certain conditions are met. The HOA may still be able to prohibit "solar devices that are on the roof if they extend above the roofline, are not parallel to the roofline, or do not conform to the slope of the roof." Elevating the panels any farther would definitely look funny and cause them to poke out well above the roof line of my shed.

[inetdog]

Elevating the panels any farther would definitely look funny and cause them to poke out well above the roof line of my shed.

Yeah, the scale of a 2" versus 6" separation on a large house roof versus a small shed roof can have a disproportionate visual impact. Just be careful to minimize anything else that might interfere with the airflow. Like horizontal mounting rails, for example.

[Sunking]

I just wanted to report on my results and review the DM Solar 145 watt panels that I have installed. One thing to note is that I have yet to purchase and install the final battery set up with (2) Trojan T-105RE batteries. Currently I am using (2) 4.5ah 6v UPG style batteries so that I can "practice" on these and learn from any mistakes I make on cheap throwaway batteries instead of the Trojans.

Well first thing you are going to learn is what C Rate means, and C Rate limit on batteries being charged and discharged.

C = the Battery AH capacity and in your case is 4.5 AH @ the 20 Hour rate. . Those are AGM batteries so they can withstand very high charge and discharge rates. The manufacture maximum charge rate is C/2. The #2 in the formula means 2 hour charge rate. So the maximum charge rate they can withstand is 4.5 AH / 2 H = 2.25 amps maximum. You are charging at 15 amps or a 3.3 C rate which means you will burn them up very shortly. So get on a fast learning curve.

The Trojans you are looking at are 225 AH and have a max charge rate of C/8 or 225 AH / 8 H = 28 amps so 15 is not a problem. On th eother hand they also have a minimum charge rate of C/12 or 225 / 12 = 18.75 amps, so you are a little short at 15 amps. But can squeak by barely.

I chose to buy the DM Solar panels against the recommendations and words of caution of a few of you on here and I don't regret it. They were about $1.10/watt including shipping as they were just small enough to ship UPS instead of freight. That helped to keep the cost way down over alternative options. The build quality of the panels is good and there were no defects that I could see. Open voltage with no load is consistently 19.0-20.5 or so depending on the direction of the sun and the cloud cover. And I get 15 amps as tested with my multimeter for short periods of time. I have an ammeter that I am in the process of installing that will tell me safely how much I am consistently getting soon. Time will tell, obviously, how these panels hold up over the years but for the price I don't think you can beat them.

I did end up using the MorningStar SS-20L-12V LVD charge controller and it has been great. I couldn't stomach paying double for a MPPT controller at this time. When I get 2 more of these panels in the future and have to upgrade the charge controller I may upgrade to MPPT but for now this works great.

This is where you will learn that being being cheap is expensive. I assume you have 2-145 watt panels correct? That is a total of 290 watts, and you get 15 amps out of your inexpensive PWM controller right? You number sound correct for my assumption.

Here is where it sucks. 15 amps x 12 volts = 180 watts out of your 290 watt panel/ Yes you heard right only 180 watts. But no worries because nothing is wrong as that is the way PWM works. Now if you had bought a MPPT controller those 290 watt panels would produce a charge current of 25 amps.

No problem all you need is two more panels to get up to MPPT performance on an inexpensive PWM controller. Moral here is if you had went with MPPT to get 15 amps all you would have needed is a 180 watt panel and 15 amp controller which I bet you money is less expensive than your two panels and PWM controller you bought.

[jasonl549]

Well first thing you are going to learn is what C Rate means, and C Rate limit on batteries being charged and discharged.

C = the Battery AH capacity and in your case is 4.5 AH @ the 20 Hour rate. . Those are AGM batteries so they can withstand very high charge and discharge rates. The manufacture maximum charge rate is C/2. The #2 in the formula means 2 hour charge rate. So the maximum charge rate they can withstand is 4.5 AH / 2 H = 2.25 amps maximum. You are charging at 15 amps or a 3.3 C rate which means you will burn them up very shortly. So get on a fast learning curve.

The Trojans you are looking at are 225 AH and have a max charge rate of C/8 or 225 AH / 8 H = 28 amps so 15 is not a problem. On th eother hand they also have a minimum charge rate of C/12 or 225 / 12 = 18.75 amps, so you are a little short at 15 amps. But can squeak by barely.

I appreciate this information. I think I had read this before but didn't really understand it. This is why I wanted to test things out on 2 cheap $8 batteries for a couple months to give me more time to learn and make sure of things before I invest $300+ in batteries. $16 mistake vs. $300 mistake is a no brainer. Now I can make a better decision on a long term solution than I would have several months ago.

This is where you will learn that being being cheap is expensive. I assume you have 2-145 watt panels correct? That is a total of 290 watts, and you get 15 amps out of your inexpensive PWM controller right? You number sound correct for my assumption.

Here is where it sucks. 15 amps x 12 volts = 180 watts out of your 290 watt panel/ Yes you heard right only 180 watts. But no worries because nothing is wrong as that is the way PWM works. Now if you had bought a MPPT controller those 290 watt panels would produce a charge current of 25 amps.

No problem all you need is two more panels to get up to MPPT performance on an inexpensive PWM controller. Moral here is if you had went with MPPT to get 15 amps all you would have needed is a 180 watt panel and 15 amp controller which I bet you money is less expensive than your two panels and PWM controller you bought.

You obviously know a lot but you have a tendency to come across as snarky and smug. Being cheap here was the right choice. I knew I was going to go to at least 4 panels in the future with 600-900 watts of total power. That would roughly translate to 40-60 amps. So I had 3 choices. I could buy the full blown MPPT charge controller up front to the tune of $600+ for a 60amp unit of a reputable brand. Tempting but I didn't have the cash. I could buy a smaller, cheaper MPPT controller right away only to have to upgrade it and shelf it in less than a year. Stupid choice. Or I could spend $70 and get a good PWM controller to hold me over for a year until I got more panels and then upgrade to MPPT later. Winner!

I know the difference between PWM and MPPT. I also know that I could have bought another set of 2 of these solar panels for the difference in price between a Morningstar/Xantrex type 20a MPPT controller and the PWM controller I got. So thank you for your input but I made the right decision for me.

[john8750]

Thanks for the show and tell Jason. I have 600 watts for my hobby shop out back. Will go up to 1KW as money allows. Using 3 large batts, were free from a friend, and a 60 amp pwm CC. Three inverters, 400,1000,1500 watt. Plan to power outside and all shop lights, tools radio, and some circuits in the house for lighting, fans, and TV's. Having a lot of fun. Must keep expenses down for now. Might build my own CC if I go higher than a 24 volt battery. Would like to hear more about your system. We will keep the fun in it.

[jasonl549]

Thanks for the show and tell Jason. I have 600 watts for my hobby shop out back. Will go up to 1KW as money allows. Using 3 large batts, were free from a friend, and a 60 amp pwm CC. Three inverters, 400,1000,1500 watt. Plan to power outside and all shop lights, tools radio, and some circuits in the house for lighting, fans, and TV's. Having a lot of fun. Must keep expenses down for now. Might build my own CC if I go higher than a 24 volt battery. Would like to hear more about your system. We will keep the fun in it.

That sounds like a nice set up! Mine is all for fun, too. I love tinkering on projects and learning new things. I also plan on running all my outdoor lighting, water feature (coming soon), shop tools, and a battery recharge station outside as well as a few things in the house. Thanks for keeping the fun in it

[Sgtdic]

Nice work Jason. I wish I had someone even remotely related or interested in, to help me here in Georgia. I know of no one and actually talked to a guy at the power company. He said like 5 in my area have grid tied systems. I'm more interested in off grid but either or I like it. Hobbies and toys cost money. So?

[jasonl549]

Nice work Jason. I wish I had someone even remotely related or interested in, to help me here in Georgia. I know of no one and actually talked to a guy at the power company. He said like 5 in my area have grid tied systems. I'm more interested in off grid but either or I like it. Hobbies and toys cost money. So?

I can help you with any questions you have. I might even consider a road trip with the right motivation lol.

[Sunking]

Nice work Jason. I wish I had someone even remotely related or interested in, to help me here in Georgia. I know of no one and actually talked to a guy at the power company. He said like 5 in my area have grid tied systems. I'm more interested in off grid but either or I like it. Hobbies and toys cost money. So?

Well there is a good reason for that. Electric power is cheap in your neck of the woods, thus no incentive for anyone to go solar. Who wants to pay more if they do not have to? As for Off-Grid Battery is incredible expensive, some 10 to 15 times more per Kwh the rest of your life vs buying it from the POCO.

[Sgtdic]

Thanks for any future help Jason.

Sunking, unfortunately I guess it is the nature of the beast. I really hate the facts, but I like to compare it to something like, say, a boat for example. You go and probably pay a premium price for something that isn't going to help you but will give you enjoyment. Knowing from the beginning that it will not return the investment you put in it when you first bought it. So why did you do it? Because you wanted to and thought it would add enjoyment to your life. Anyway, this may not make sense. It just boils down to several things. I like the thought of free renewable power. I'm not a 'prepper' but like to be prepared. We've had power outtages for days in the past. I'm a what-if person I guess. And I want to do the projects without breaking the bank. I've added a lot of LED bulbs around the house.

[Sunking]

Sunking, unfortunately I guess it is the nature of the beast. I really hate the facts, but I like to compare it to something like, say, a boat for example. You go and probably pay a premium price for something that isn't going to help you but will give you enjoyment. Knowing from the beginning that it will not return the investment you put in it when you first bought it. So why did you do it? Because you wanted to and thought it would add enjoyment to your life.

Well you are talking about off-grid and there is no enjoyment with an off grid battery system, it is very painful in the wallet and means you get a new part time job with no days off.

Anything you take off-grid, the power will cost you at least 10 times more than you pay now for the rest of your life. There is no such thing as Free Remewable Energy, and there is nothing Green or Earth Friendly with an off-grid battery system as they can never generate more energy than it takes to make the system. You go off grid and you increase your carbon foot print, not reduce it.