OFF GRID POWER; various thoughts on...

[MountainDon]

>>Am I looking at this right?  
Looks okay from here.  

Power use seems to grow with time. We already have a couple of small appliances that were not in the original plans. You might want to consider that possibility and leave room for another string of batteries. The battery gurus warn against adding batteries to an existing system. Maximum time interval seems to a year, though others have ignored that. Remember if you only draw the batteries down to 80% they will last longer than if drawn down to 60%.


>>With a 24V system and 6V batteries the number of batteries in the bank have to be a multiple of 4?
Absolutely correct.



>>With charge controllers is it best to go with the most amps you can afford?
Well, looking ahead to growth it may be advisable to have the ability to add more panels without needing a larger controller.   The flip side of that is if you add on panels at some time, you can always add a second same size controller and have the protection of some paralleled redundancy.  

I bought the 60 amp Outback, not because I needed the capacity right now, but because it will allow me to install another paralleled set of panels and use the same 300 feet of cable if in the future we want more power. There were other considerations as well.


>>As far as converters for a small system, will a $300 Samlex, or Exeltech type converter be just fine?  A $3000 Outback converter can't really be necessary for a small system, can it?  

It's not necessary, unless you want to be able to run a microwave (1200 watts draw) and not have to worry about someone (I won't name who) also popping some bread into the toaster (800 watts). Or similar things. The microwave was the complicating appliance in our case.  PS. I got ours for $1650. I had some luck and hit on a clearance loally. They'd had it in stock for over a year. It was a special RV/Marine model, but ideal for our small cabin.

I'd use a pure sine wave type in any event. Square wave can bring along problems.

I like the Exeltech inverters. I had one of their 1100 watt units in the RV for several years until I cooked it.  

Keep in mind that the better quality inverters ($$) are also chargers. The ones I've looked at have the capability of performing an equalization charge with the generator running. Most standalone chargers can not do an equalization charge.

Speaking of equalizing... The principle is basically to apply a higher voltage charge (15 volts on a 12 volt battery) for a period of time. If you have loads attached to the batteries while equalizing it is possible to run into the situation where you may "over volt" something in the system. This is why good inverter/chargers switch the inverter o when the generator is activated. They will usually use a "pass through" mode where the genny now supplies the power to the cabin while also using some genny power to charge the batteries.

Anyhow, I'm rambling on as one thing reminds me of another.  

[Squirl]

Bevers,
Don't forget about water pumping.  I don't know how you get your water, but it is a factor I frequently forget to add into my calculations.  Most DC deep well pumps seem to use around 150 watts an hour for 60 gph rate.  So if you use 120 GPD per person per household that averages to 300 watts a day per person for electricity.  This is off the top of my head and I welcome any corrections.

[MountainDon]

Good point. I tend to forget that too as our water comes in a trailer tank.

[Bob S.]

would it be feasible to design and build a off grid soler system that had several stand alone smaller systems. Like one for lighting, one to run the refigerator one to run a fan ect.

[EcoHeliGuy]

Not really because its not the batteries that makes the difference its the other hardware

lets say you have a 500Ah 28v system with each battery being 100Ah at 6v, and then you want to add another load needing 100 Ah more.

A) one large system
so first you have 5 batteries in a sting to get 500Ah combined,  and you need 4 strings to make 28v. then in order to add another 100Ah all you do is get another 4 batteries and connect one each to a string. and you need to buy a bit of cable and connectors.

B) multiple systems
Lets say you have the same system as above, 5 batteries a string and 4 strings. now you want to add another 100Ah. we know you need 4 more batteries, cable and connectors. But you also need a charge controller, inverter, and power source (solar, wind, hydro ect). buying a smaller system at first might have saved you money, but buy two small systems instead of a medium one cost way more because your doubling up the equipment.

(the numbers used aren't real, you need many more betteries to take into account trying to keep a couple day reserve and not depleting all the power from your cells each day)

Think of it this way, you can either buy two 1/2 ton trucks to pull two horse trailers, and burn tones of gas in both, plus wear and tear on both trucks and trailers, or buy a larger trailer and a 3/4 ton truck and save tones of money on not doubling things up. and pull the saem nubbier of horses. 

[MountainDon]

would it be feasible to design and build a off grid soler system that had several stand alone smaller systems. Like one for lighting, one to run the refigerator one to run a fan ect.

The problem that first arises in my mind is that it is more difficult to properly size three or more small systems than one larger system. A larger system with everything drawing off one large battery bank would be more forgiving if you found it necessary to run extra lighting for some occasion for example.  That's my opinion.

[Beavers]

Bevers,
Don't forget about water pumping.  I don't know how you get your water, but it is a factor I frequently forget to add into my calculations.  Most DC deep well pumps seem to use around 150 watts an hour for 60 gph rate.  So if you use 120 GPD per person per household that averages to 300 watts a day per person for electricity.  This is off the top of my head and I welcome any corrections.

No water to pump, we are on city water.  Forgetting to add in water pumping could be a bummer on a real small system like what I'm planning on. 

[glenn kangiser]

My pump pulls about 10 amps at 240v or 2400 watts for 1.5 hours per day in the summer, when pumping for the garden.  That is why I need the bigger system.  The smaller pump would still have the same horsepower requirement, but just run for more time.  

I already had the pump 320 feet down the well when I decided to go solar. I like having plenty of power so I can weld and run my shop - band saw, air compressor, etc.

Horsepower requirements change a lot and go a lot higher on a deep well.  The Grundfos SQ Flex is likely one of the most efficient but the numbers should work out similar to mine I think.  We use around 600 gallons per day or more for the garden in the summer.

[Dave Sparks]

My pump pulls about 10 amps at 240v or 2400 watts for 1.5 hours per day in the summer, when pumping for the garden.  That is why I need the bigger system.  The smaller pump would still have the same horsepower requirement, but just run for more time.  

I already had the pump 320 feet down the well when I decided to go solar. I like having plenty of power so I can weld and run my shop - band saw, air compressor, etc.

Horsepower requirements change a lot and go a lot higher on a deep well.  The Grundfos SQ Flex is likely one of the most efficient but the numbers should work out similar to mine I think.  We use around 600 gallons per day or more for the garden in the summer.

I am trying to remember your garden but....  Glen, that is alot of water! Our drip system in (3) 4x8 sq.ft. garden boxes used 1500 gallons all season! What do you get an hour from the pump? I actually like your set-up over the grundfos for solar as you can get it done fast during the afternoon. You do need the panels though! I am doing one like yours now with an xw6048 in NM.

Had Heirloom tomatoes off the vine yesterday....ah California 

[Beavers]

I found a PDF Inspector guide to PV systems. 

It gives suggested checklists for inpectors, and what to look for.
Would be real handy for anyone dealing with inspections, along with the PV code guide that Don posted a link to.

http://www.builditsolar.com/Projects/PV/InspectorsGuide0306.pdf

[MountainDon]

That made my head hurt Beavers. Thanks.       It does give one an idea of what to expect. That seems to be focused a lot on grid intertie, but it is indicative of the hoops a legal installation must have.


Just a note on one thing I saw.Figure 4 illustrates a ground wire connected to what appears to be an aluminum PV panel frame. In some of the information I've read that may not be allowed anymore or maybe at some time in the future... depends what the local code enforcement gurus are doing/using.

Here's the theory... All other electrical connections must be able to be un-fastened and re-fastened ten times with no deterioration in the fasteners effectiveness. Self tapping or self threading screws do not meet that criteria. It does make some sense. So there was talk about changing this type o connection to requiring a tapped connection with a certain minimum number of threads engaged, or requiring the use of stainless screw machine screws and nuts with stainless steel washers, or those special ground lugs I used. So while I don't know for certain what is what, I went with the special clips.


http://countryplans.com/smf/index.php?topic=6059.msg92455#msg92455







http://countryplans.com/smf/index.php?topic=6059.msg92455#msg92455

[Beavers]

That made my head hurt Beavers. Thanks.       

Really, I didn't think it was any worse than any of the other fun to read code stuff. 

I noticed it was written in 2006, so some stuff might of changed.  I've got a copy of the 2008 NEC on the way from Amazon, so hopefully I can figure out what the latest and greatest methods are.

Those clamps look pretty heavy duty!

[MountainDon]

They are nice. The thin plate is stainless steel, with punched thru holes that have a rough edge that digs thru the anodized aluminum to make secure contact. The clip itself is tin plated for conductivity and comes with stainless steel hardware. I got them from TheSolar.Biz

[MountainDon]

I was looking at the Trojan Battery site and noticed something either new or something I missed.

They have an RE series of some batteries. RE = Renewable Energy. I don't recall seeing the RE's before. The capactites are the same as their industrial relatives, but the warranty is better. 24 months free replacement plus 60 months pro rated on the L-16RE series (7 year total). The 6 volt T-105 batteries have the 24 month free replacement plus a 36 month pro rated warranty (5 year total).

The real interesting this is they have an L-16RE 2 volt cell. I recall Dave Sparks mentioning in some other thread that Surrette now had an L-15 2 volt cell available so I looked it up too. It looks like the case size is in the L-16 series too.

The Surrette S-1380 is rated at 1050 amp-hours and the Trojan L-16RE-2volt at 1110 amp-hours, both at the 20 hour rate. Either one would be just about perfect for many of grid users. The one visible thing different on the T-105RE 6 volt, compared to the other iterations of that 6 volt battery are the terminals. The T-105RE has lug terminals only.

Here's a shot of the T-105RE-6 volt, the L-16RE-2 volt and the Surrette S-1380 2 volt









             Did anyone notice the oddity?  

[Beavers]

             Did anyone notice the oddity?  

With the new T105 you can use 50% less cable?  I'll have to get some of them, should save me a lot of money. 

[MountainDon]

Mmmm, no, unless I don't follow what you mean.      



It's to do with the L-16RE-2 volt battery  ..........

[Beavers]

Looks like only one battery terminal in the T105 pic.   

[OlJarhead]

I have an Evolution 1 tent trailer with a built in charger that works when AC power is connected to the trailer.  I'm thinking of hooking up the connections to two batteries in parallel in a box with a solar panel to provide a charge when the AC is off.  I'd like to connect both the trailer and a camper to this and be able to leave it for extended periods of time without damaging the batteries.

The plan is to be able to drive back to the site where I am building my cabin and not have to worry about  the battery being low when I need to power a propane heater (built into both) and lights (we arrive most times at night) becuase I hate to have to pull out the generator right away -- much rather settle in and relax after the long drive.

Of course this will help me learn about solar power so I can build an off grid system.

I've found this panel which seems at a decent price:  http://www.siliconsolar.com/85-watt-solar-panel-p-501611.html

and this controller:  http://www.siliconsolar.com/solar-charge-controller-p-16156.html

Have this battery:  http://www.lesschwab.com/batteries/rvdeepcycle.asp

And will use it on this trailer:  http://www.colemantrailers.com/e1 as well as an old 1978 camper with 12v lights, fan and propane heater (which may not work).

I've also got an old car battery that I'm using to power my well (12v pump) but plan to get a 2nd deep cycle battery to put into the box with the first one.

So, there are 3 wires coming to the battery in the trailer and then a standard trailer hookup on the camper (which I figure I can get a female hich connector and wire to the batteries directly).

What are your thoughts on doing this and could I install an inverter that would give me the power to run a laptop if I wanted to?  Or a toaster?

Thanks!

[MountainDon]

Looks like only one battery terminal in the T105 pic.   

It's just the angle of the shot. It has two terminals.

What I noticed was that the 2 volt L-16RE has three watering caps just like the 6 volt L-16 version and the 6 volt T-105 batteries. That struck me as unusual. Have a look at the 2 volt Surrette S-1380. It has one cap, because it is a single cell. It might be that the L-16RE-2 volt battery is simply a standard 6 volt L-16 that has the three cells internally connected in parallel instead of in series. If that is true the L-16RE-2 volt is not really any better than a collection of the normal L-16 6 volt batteries. It would cut down on the cabling though compared to a series/parallel system of L-16-6 volt batteries.

The Suerrette is a true 2 volt cell and the L-16RE is a 2 volt battery. That would make the Surrette a better choice from the view of the number of cells to water. The Surrette likely costs a lot more than the Trojan, but may really be a better unit.     So ya' gotta look it over and make your choice.

[MountainDon]

....and this controller: ........

That controller is not suited to that panel. The panel has a maximum power current rating of 4.71 amps. The charge controller is rated at "4A maximum input charging current".

The place to start designing any system is to start with what the daily load total will be. Do that before jumping at parts.

Make a list of all the DC items you want to use. Get the power ratings on the lamps or whatever. Multiply the DC wattage of each unit by the number of hours of expected use. Be honest. Total that up to get the DC watt hours for the DC total.

Make another list of any AC loads you wish to run. A Kill-A-Watt meter is handy for determining how much power is being used by the various AC powered items. Multiply the AC wattage of each unit by the number of hours of expected use. Be honest. Total that up to get the AC watt hours for the AC total.

Then come back with the list.  With those numbers the battery capacity required to run one, two or three days can be calculated. With that known the PV power required can be calculated. You also need to know expected number of hours of usable sunshine. That changes summer to winter so you need to decide where are going to aim for.


Or go here and use one of the calculators.

I don't like to just say, here, do this or use this and everything will be fine as your deiniation of "average" or "normal" can vary from mine. But I'll be happy to help sort it out.

[MountainDon]

I mention the Kill-A-Watt because I noticed that in some cases the actual power consumed is less than the rating on the name plate. My laptop is a case in point it uses about half the label rating in normal use. That was based on measuring consumption over an actual period of several hours of typical use. The LCD TV in the cabin also uses less, averaged over several hours of use. On the other hand the microwave uses every watt it says it will.

On determining power used by a microwave... note that the rating that is advertised, 650 watts, 800 watts or whatever is the cooking power not what is needed to power the unit. To illustrate what I mean our home microwave has a cooking power of 1100 watts but consumes 1630 watts out of the wall socket. The cabin unit, rated at 650 watts cooking power, consumes 1100 watts.

On picking an inverter, square wave inverters are common and lower priced than pure sine wave. As I've noted before, not everything runs well on square wave. Our small microwave does not heat on square wave; it runs the fan, the light, but no heat becasue it doesn't like the square wave power. Our vacuum runs hotter on square wave. The blower on the wood stove air inlet makes more noise on square wave, and likely runs hotter as well. Hotter operation can mean shorter life. Running hotter is also a waste of battery power as heat = power.

Yes, I am biased towards pure sine wave. It depends on how what the inverter supplied AC power is going to be used for.

[glenn kangiser]

I also like only pure sine wave after low efficiency pumping and burning up power tools on modified sine wave.  My 220v water pump put out appx twice the water in the same amount of time with the pure sine wave.  Most will not pump using as much power as I need though.  I already had the big pump in the well so built the system up to handle it.  There are various adapters to smooth out the pump for modified sine but I felt that I should just do it right.

I only use modified on my small stuff or things that don't mind the choppy electricity.

[OlJarhead]

....and this controller: ........

That controller is not suited to that panel. The panel has a maximum power current rating of 4.71 amps. The charge controller is rated at "4A maximum input charging current".

The place to start designing any system is to start with what the daily load total will be. Do that before jumping at parts.

Make a list of all the DC items you want to use. Get the power ratings on the lamps or whatever. Multiply the DC wattage of each unit by the number of hours of expected use. Be honest. Total that up to get the DC watt hours for the DC total.

Make another list of any AC loads you wish to run. A Kill-A-Watt meter is handy for determining how much power is being used by the various AC powered items. Multiply the AC wattage of each unit by the number of hours of expected use. Be honest. Total that up to get the AC watt hours for the AC total.

Then come back with the list.  With those numbers the battery capacity required to run one, two or three days can be calculated. With that known the PV power required can be calculated. You also need to know expected number of hours of usable sunshine. That changes summer to winter so you need to decide where are going to aim for.


Or go here and use one of the calculators.

I don't like to just say, here, do this or use this and everything will be fine as your deiniation of "average" or "normal" can vary from mine. But I'll be happy to help sort it out.

Understood, and was doing -- but my question is specific to what I'm doing now.  You see I'm planning on doing far more, but I want to charge a battery now -- maybe two.

Perhaps I'm not explaining myself well, but I tend to take small steps.  I run off one battery now -- I know that does what I need for the most part but also realize that will grow.

So, for now, today, I just want to run off that battery but add a 2nd for the camper and be able to charge them both.

Power tools are run off the generator.

[EcoHeliGuy]

What he is saying is with that panel and controller set up, your going to release the smoke 

In direct sun light on a cold day, your going to cook that controller before you ever get the peak output on the panel.

[MountainDon]

Oh, I understand now OJH.

In that case we need another look. But that charge controller has to go or that panel would cook it.

But before that, what is the amp-hour rating of those batteries? You want two in parallel as I understand it.


OR pick a panel that's smaller.... have to run some numbers.....