How can I make this work on solar?

[maple flats]

I have a camper set up on a site in the woods. It has 2x12volt deep cycle batteries hooked in parallel. I want to go solar on it. I have purchased a 24V 150 watt solar panel. I bought the 24V because the panel will be set up about 200' away and voltage drop was a concern. The camper has a converter going from 120v to 12v, with a .5amp charge feature. What must I do to use the panel? Can I convert the panel directly to 120 and use the charger built in? I am trying to find how much battery bank I would need to run the camper on battery for about 4 hrs including the AC which might run about 50% on hot days. I realize the panel is not enough but I could run a generator for an hour or 2 to charge the battery too as needed. Eventually I want to add more panels but I am looking into making my own this winter on days when it is not fit for man nor beast to work outside (this is really few days for me because i like the cold down to about 0 F if no wind and my woods do very well at blocking the wind.) Until then I will have just 1 panel at 24v 150 watt. It is rated at 30V max output

[Gary_C]

I just read this web site today for a similiar situation for myself. Here is a very good site for your questions:  http://www.windsun.com/Photovolaic_Systems/RV_Systems.htm

I recall that it is not a good idea to use the very poor converter in the camper with a solar system. Also you are going to need an inverter for the 120 volts and it is doubtful that you will be able to run an air conditioner off the batteries thru the converter without spending a ton of money. Maybe small appliances and a microwave but not an AC. Even the 2000 watt low noise generators will not handle an AC, it takes two of them.

It looks like very good info on that site above.

[Radar67]

With the 24v panel, you will have to connect your batteries in series to get a 24v rating. The panel will charge the batteries. You will then need an inverter to change 24v to 120v (the existing converter will not work). You will not be able to run an AC off this, as Gary said. The wattage rating for your inverter will determine the largest load you can run. Backwoods Solar is also a good source of information. The 150 watt panel will theoretically deliver 150 watts per hour of sun, to the batteries. You have to figure out how many hours of sun you get each day to find out just how much power the panel will supply. ie 6 hours of sun is worth 900 watts of juice to charge the batteries. Figure out your daily usage and you can figure out how long the batteries will run the load. Also, to make the batteries last longer, you should only discharge down to 50-75% capacity. If the battery holds 1000amps of power, only use between 250 to 500 amps of juice before you recharge.

[pineywoods]

To do what you are talking about, you'll spend enough money to keep you in generators and diesel fuel for at least 50 years.  So much for going GREEN..

[DanG]

I think a lot of it depends on your lifestyle while camping.  When Linda and I used to camp in the Minnie Winnie, we could run for about 3 days on a single deep cycle battery if we had no hook-up.  If we were hooked up in a campground where we had electricity, it altered our camping style radically.

Your cheapest, but more labor intensive solution may be to just buy 2 more batteries and swap them out every day.  You could hook them up in series for charging from the 24 volt panel.

[ErikC]

  You said the panel would be a ways away from the batteries, right? Dad uses a 24v hydro wheel to charge his 12v system because of the voltage drop over the distance between the wheel and his house. gets to the house at 17 or 18 volts and works like a charm. He has 300 or so feet between. Sounds like what you originally were thinking.

[zopi]

K...set up the panel wherever you want it...string your cable to about where the batteries are ans measure the voltage at the output end..I'm betting you'll get in the neighborhood of 16-19 volts if you have the right sized cable...google up how to do the math to figure out how to scale a voltage divider..(just a pair of resistors) that will give you the 13.5-14.5 or so volts DC to charge the batteries directly...might want to use a battery isolator as well..but I don't really remember how they work....of course, you could just add somemore wire in there until you get down to the voltage you want..it's be easier..but not necessarily cheaper...

[maple flats]

Maybe I should further explain. Concerning my question on how I can make the solar panel work. Within 2-3 yrs we plan to be grid tied solar with a battery bank backup, but not the deep cycle marine batteries in the camper. I want to get a jump start now just for charging the camper batteries but I will need a grid intertie inverter. Our plans are to go with about 2000-3000 watts solar, plus up to 1000 watts wind with a generator backup too. I am looking for the way to connect this now but to be ready for my growth plans as they happen. My additional solar and wind will also be 24V and they will not all happen in one step but rather in multiple steps as I can add I will. I want the system expandable and do not want to need to change out components later. This means I want the proper inverter now even if I only have 1 panel to start.
Hopefully this helps to get someone to chime in on how to make it work. My panel location now will not even be the final location. Now I will set the first one up in the clearing near my eventual home site just to help run the camper and sugarhouse lighting. As I add more panels they will all be set up in a field about 150' from the new house and 200' from the sugarhouse. The inverter, med sized battery bank, etc will then be moved to the new house basement or main floor as appropriate.
Dave

[jpgreen]

Dave-

For that run you're gonna need a 48v system.  It's to far away for 24, plus you have to size all of your cable wire accordingly if I understand you correctly.

When you run that kind of amperage in DC, for any distance you need BIG copper cable which is expensive.

Better bet is to plan to have your inverter and battery bank close as possible to your power source, then run AC the long distances, and even then always follow the proper wire sizes to occomodate distance and draw.

A 150 watt panel is going to charge your batteries, and let you run a small inverter that will power the TV, video, computer, vacumme, and lites but not all at the same time.

2-3k watt system in panels is a bunch of power if you use it correctly. We have lived off grid for 10 years and I now have a machine shop all powered off grid, maybe the only one in the country, and I do it based on 1000 watts of solar in 24v, plus DC direct to battery charging.

There are ways to make it happen.

[Fla._Deadheader]

 

We have lived off grid for 10 years and I now have a machine shop all powered off grid,

  JP, could you elaborate a little more on your system

[maple flats]

JP, you are not the only one. My wife and I went on a solar/wind energy tour 2 or 3 years ago. At one of the locations open to tour they had over 2000 watts solar and a 3KW wind generator at the end on a road called Fire Tower road. The home was about 3 miles from the nearest grid power. They had a huge log home powered off this, a smaller guest cottage a few hundred feet away also powered off this too. Then in an old barn they had a full size woodworking shop, table saws, planers, jointers, and many other tools. They said they could run the shop for just over 2 hours using the 240V saw and planer before their batteries dropped too low. Then they had to do other things the rest of the day to let it re charge, or they had to use a generator. I don't remember how many batteries they had but the battery room was about 10' long with 3 shelves (or was it 4) of batteries. If I had to guess I might say about 40-50 batteries. Of the 5 or 6 systems we visited that day, this was by far the most awsome to look at.

[maple flats]

Back to my question, and more info.
I have now bought a second 150 watt panel, now 2 total, 24V. I will now connect them in series to get 48 volt for less voltage drop. I have an inverter, 2500 watt. 24VDC in and 120/240VAC out. I still do not have the wire but am getting ready soon. At 24V it looks like I can go my 240' on 4ga CU or 2ga AL. Aluminum is not reccommended (but it does meet code) because a solar panel will last up to 50 years and the aluminum wire would likely fail and need replacing before that. However, I may use aluminum this time because (price) the house to be built will only be about 100-110' from the panels and everything will be re-wired at that time. Then I will likely use copper. I now need a 48 volt charge controller to charge a 24V bank. Outback has one that looks good, any voltage in, 12-24-36-48-60 and select the battery bank voltage from any of the same voltages. It will hold the desired voltage and vary amperage as the input varies. I hope to have this up and running by late Oct. (if I am not too busy sawing lumber for the house)

[jpgreen]

 

We have lived off grid for 10 years and I now have a machine shop all powered off grid,

  JP, could you elaborate a little more on your system

Here's an old link bout' 8 years ago, but it's basically the same setup today.

http://www.westcoastminisplitter.com/Solar.html

[jpgreen]

JP, you are not the only one. My wife and I went on a solar/wind energy tour 2 or 3 years ago. At one of the locations open to tour they had over 2000 watts solar and a 3KW wind generator at the end on a road called Fire Tower road. The home was about 3 miles from the nearest grid power. They had a huge log home powered off this, a smaller guest cottage a few hundred feet away also powered off this too. Then in an old barn they had a full size woodworking shop, table saws, planers, jointers, and many other tools. They said they could run the shop for just over 2 hours using the 240V saw and planer before their batteries dropped too low. Then they had to do other things the rest of the day to let it re charge, or they had to use a generator. I don't remember how many batteries they had but the battery room was about 10' long with 3 shelves (or was it 4) of batteries. If I had to guess I might say about 40-50 batteries. Of the 5 or 6 systems we visited that day, this was by far the most awsome to look at.

Dave-

I meant a metal machine shop in production, producing a product. Have not heard of anyone doing that with solar as yet.

The system you describe above is an example of a poorly designed wastefull setup if that's the power input they have with that many batteries, and that much usage.

One of the keys to an efficient system is to go big on the inverter.  As big as you can afford. The next key is not try to size a system to run wasteful machines and appliances.

For instance- that small system I show in my link (with all 10 panels) produces 25 amps solar DC on average in 24v when the suns out.

In addition to the house, which is just me and my wife- and this is improtant as the more house hold members, the more power is consumed-

I run my shop with a Hardinge precision tool room lathe, an old Logan 11" lathe, and an 80's vintage Bridgeport knee mill. Plus all the various supporting shop equipment, compressors, band saws, grinders, etc.

When I'm busy, I usually have the Hardinge running all day without shutting it down, as I can set the power feed on it and walk away. It has a clutch stop.

While that's happening, I'm either running the Logan or Bridgeport, and cutting rough stock at the same time on the horizontal band saw.

I pretty much use 20-25 percent of my solar system for the day. That's 12 Trojen L-16 batteries as shown.  Pretty much even steven when the suns out.  During a busy week, I gradually start using more than the suns putting out, and that's when I kick on the DC generator for a few hours in the morning or evening. I always try to never draw the battery bank below 50%, as this ads greatly to your battery life, and the top half charges much faster, then trying to bring your batteries up from the lower half of 50%.

Your probably asking "how can he be doing this?". One answer is to dump the heavy draws. You do not want to run inefficient equipment and appliances. With a little study it's not hard to find items that will do the same job with much less power draw.

The next is equipment retrofitting. On my Bridgeport for example (actually it's a WEBB clone- Identical.) I dumped the draw hogging 3 hp, 3phase drive motor with a 3 hp Permanent Magnet DC drive motor from an industrial exercise treadmill. The DC has tons of torque with variable speed, and only uses 10-12 amps with 110v under load....! The machine's a step pulley and I have yet had to swap pulleys.  Haven't even had to put it in backgear.

Next, I swapped out the 1.5 3phase Hardinge motor with an 1.5 hp Industrial Baldor motor, again wired in 110, that has performed flawlessly. Amps are amps, and I certainly do not agree with the thought that 220v is inherently more efficient just because it's 220v.  It's not.

Now- my needs are rather small. I'm making smaller parts and dies and I do not need to run a giant machine that will turn a huge piece of steel. All things are relative to your needs.  This is just an example of what can be done.

Next- I have a Hardinge "Super Precision" CHNC lathe with Fagor 8025 computer control I acquired that I need to get online. Time will tell what will be the best way to get this machine going effciently and I will be looking at transformers and VFD drives as well. It will be my next challenge.

The 4000 watt inverter sends about 65 amps AC continuos out to my shop in 110 single phase- pure clean power. 80-100 amps peak. Had I not gone with this size of a inverter minimum I would not have been able to do this, and would have been severely handicapped in the house as well for running the freezer, toaster over, microwave, etc.  My wife has every appliance darn near.

The last key is DC charging.  Running AC generator to your inverter, which then uses it's internal battery charger to finally send DC to the battery bank is a big waste of dollars.  The inverter produces a lot of heat, and the internal fan has to come on. Just seems to task the inverter needlessly.

The little Delco DC alt will put 50 amps clean power direct to the bank continuos, and depending on the engine you use to turn it with, fuel consumption is minimal. The best setup I have used to date is a lower RPM large flywheel water cooled diesel that burns less than a gallon of fuel in 6 hours.

Added to that benefit is the peak power draw. If I run a big generator (and I've got big here that I only use for heavy 220v welding tasks), to the inverter as most folks do to charge batteries, if I run my equipment in the shop at the same time I notice a considerable drop in power on the start up surge.

With DC charging running at the same time, there is absolutely no power drop on surge motor startups. The motors have full power and are happy.



Shop timbers courtesy of the "Kawa-mizer"  ...

[Fla._Deadheader]

    JP, GREAT write up on both pages. 

  We went off grid in Arkansas, for 4 years. Maybe we didn't have things as efficient as we could have, but, while running the table Saw on a Wisconsin engine, we were always topping off the Caboose batteries we had. While running the Planer, we were always topping off the Caboose batteries. Solar was too expensive, at the time, and, money was short.

  IF needed, we ran the Edison 1 lunger set up, and charged the batteries. Also, stuck a small tube into the carb throat, and ran the engine on Propane, with NO mods.

  Built the 4KW wind generator, but, it wasn't great, because we needed another 50' or more added to the top of the 100' tower we built.

  I'm lookin into water and wind right here, right now. At this moment, we have about a 20 MPH wind blowing, and, the rain is just running down hill to the small creek.

  VERY nice setup you have. I'm envious.

  I'm looking into running a car battery to the UPS on the computer, so I can disconnect from the grid. Had ONE blow out already. Don't need another

[jpgreen]

Thanks FLDH,

I was kind of thrown into the machine shop. Always wanted one, but didn't think I would be into it this soon.

If you have wind and water, there will be no need to invest in panels.  Water is the neat expensive per watt to install, and wind is next.

Do you mean you're trying to use your car battery to power your computer?  ..

[Fla._Deadheader]

 Well, actually a spare battery.   The UPS is 12V battery back up, no   Why won't a larger battery run the UPS on battery mode, and not use the house current

  Standard UPS battery should give 5 minutes of back up power, so, if the UPS does not get hot, why not use a larger battery

[Radar67]

FDH, I'm not sure if the UPS will work with a larger battery, but I know for sure a 600 watt inverter will run the computer from a battery. I have run a desktop machine with a flat panel monitor from a 400 watt inverter. I had to shut the screen down until the computer was completely loaded though. After the load I would turn the monitor back on and everything was good.

[Fla._Deadheader]

 There are people using large UPS's to do what I want.  I only have a 350KVA, right now, and, a 1400 kva is too heavy to carry on a plane, unless you pay the thieves $100.00 extra. 

  You are probably correct about starting the 2 pieces seperately.

[jpgreen]

THe term UPS is throwing me.  What is UPS, aside from a brown truck? ...

[fishpharmer]

http://en.wikipedia.org/wiki/Uninterruptible_power_supply

[Radar67]

The inverter could be carried on a plane. My 400 watt only weighs a couple of pounds.

[Fla._Deadheader]

 A small inverter is good for a small usage. I am looking into running more of our electrical devices from alternative energy.

  Used UPS's are inexpensive, compared to normal inverters, and are actually inverters in a way.

  Our rates down here, DOUBLED, in August.    There are many who talk of doing something, but, don't understand how. Maybe I can assist them. Water is everywhere, and wind is good in hilltop areas, like where I live.

[jpgreen]

For wind or hydro to pay off it needs to be constant.

Here is a ton of info on hydro:
http://www.backwoodssolar.com/catalog/hydropower.htm


Boy the price of that stuff sure has gone up since I last looked at it. Personally, I think everyone should have a system at some level for emergency backup if nothing else. It doesn't have to be an all or nothing deal. You can run a small system to power certain things.

In this day and age I would not be totally relying on the government for power and security.

[Fla._Deadheader]

 Link is right back to this page 

[jpgreen]

oops. Obama did it.

[James P.]

JP very nice setup. I don't have any alternative electric but I use on average about 250 kw a month. I have a small 4 cylinder kohler electric plant that puts out 1500 watts but doesn't get run unless power is out. It would be relatively easy for me to get off grid with my consumption . I hope you are right about prices on the solar equipment going down. the only catch with the electric company partial funding. they want you to get everything done by an approved contractor. So for me that is a deal killer. I agree people use way to much electric and alot don't seem to mind going to work to pay for the Tv left on while they are outside. I shut it all off even hot water. When I know I need it I turn it on 20 minutes before and Its hot. Shut it off and go use whats heated. I know its not alot but if you add it up over years like a cable bill. It amounts to a small fortune. Good luck and thanks for sharing the info. Nice machine shop too. I have a sheldon lathe, burke #4 mill and hanchette grinder Grob 18 bandsaw with welder and 24 in Cinncanatti drill press with air over hydraulics. Not as nice as yours shop  but it helps me fix those little parts i can't afford to have someone else make. James P.

[rbarshaw]

 A small inverter is good for a small usage. I am looking into running more of our electrical devices from alternative energy.

  Used UPS's are inexpensive, compared to normal inverters, and are actually inverters in a way.

  Our rates down here, DOUBLED, in August.    There are many who talk of doing something, but, don't understand how. Maybe I can assist them. Water is everywhere, and wind is good in hilltop areas, like where I live.

You can hook a larger battery to a UPS, as long as the battery voltage is the same, then the UPS will have the larger capacity to draw from. As long as you don't exceed the output rating of the UPS you will be fine.

[Fla._Deadheader]

 OK. Then, how do I draw from the UPS if the AC power is working   Would I need to find the proper leads and install a switch

  I'm thinking, if the AC is turned off, the whole UPS is shut down

[rbarshaw]

Just hook the larger battery inplace of, or in parallel with, the existing batt. the UPS will operate normally on AC power and charge the batt. while suppling ac to your load. If starting with no AC power, just turn the UPS on and it will supply AC to your load till the battery is drained. Some UPS's will not work as they can't turn on unless AC power is first supplied to them.

[Fla._Deadheader]

 OK. I may have it figured out. Thanks Robert

[tughill]

Wow what a great thread.

JP- nice shop.  Your setup is very well thought out, and I think you  spent your money in the right places.

A UPS is an inverter, the difference is that it has a rectifier on the input side to convert AC to DC to both charge the battery, and supply the DC to the inverter.

A word of caution though, regarding batteries.  DO NOT hook different size or types of batteries in series OR in parallel.  It's ok to jumpstart a vehicle for instance temporarily, but for a RE (renewable energy) system like this, the different internal impedances of different batteries will probably not match correctly, and generally the smaller battery will die a horrible death, from charging and discharging more than it's fair share.  If you've ever had a truck or tractor that was 24VDC, you may have noticed that even using 2 different brands of batteries killed one or the other too quickly. (because of the impedance mismatch)

Maple Flats- We are practically neighbors, if you need any help with your solar setup, send me a message.  I think you should really consider setting up your solar panels much closer to your inverter, and your inverter close to your loads.  The voltage drops you refer to are known as I^2*R (I squared R) losses, and basically means you are using your expensive solar panel generated electricity (ok I know the sun is 'free' but I'm talking about the cost of the panels) to heat up wire, so that your 150 watt solar panel is at best outputting 100 watts of usable power and 50 watts of heat to the atmosphere around your cables.  (sounds bad, right?).  You already mentioned that you would need a bunch of VERY expensive cable.  It maybe worth putting in a small outbuilding/shed near your solar panels to house your inverter/charge controller/batteries, if you really can't locate your solar array near the load.

[maple flats]

setting the panel closer to the batteries and inverter is not an option. According to the immage I get using a solar pathfinder far too many trees would need to be removed, my maple trees that I use for making maple syrup. I have set the poles and strung 240' of 2 ga Aluminum, the same as would be used for many service supplies from the utility companies. The wire runs from pole 1 120' to pole 2 and then 120' to the sugarhouse. I then have another 25' of 2 ga entrance cable between the two ends, pole 1 top to 5" above the ground the connect to the panels and at the sugarhouse from the top  of the conduit down and into the sugarhouse.  From here it will go to the charge controller and to the batteries at the battery box.For now I am using a small charge controller at 24v but when I can add 2 or more additional panels I will go with the Outback unit I spoke of earlier that will do 12-24-36-48-60 volts in and any of the same out. Then I can up the input voltage and still control the 24v battery bank and inverter.

[woodbowl]

A big part of the expense are the solar panels themselves. I've searched for information on how to build homemade solar panels with little success. Most sites are kits you can buy, experiments and science projects, but not much there for the serious builder. Does anyone know of some good sites that "build from scratch"?

[Fla._Deadheader]

 Contact Solar Panel Factories. You can sometimes buy rejects, that have blemishes or are "slightly" under spec output.

  I have read where guys get them for free or for a token price, but, they live close to the factories.