still new to solar

rhine · August 2009

Hi everyone, I am interested in getting a solar setup for a little cabin. Where it is located line power is not an option and don't want to deal with a generator due to noise issues and it would be a hassel to start it up for just 10 to 15 min of power. What i'm wanting to power would be 9 20 watt lights but 4 of them would be rarly used. on average the more used 5 would be used at most 3 hrs a day for 3 days a week. also if i wouldn't be pushing it to far i would like to run a small tv and dvd player. I don't know the wattage of these two because i have not purchased them yet. the setup i am considering using is a http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200306869_200306869 along with a http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200332575_200332575?cm_sp=Customer%20driven-_-Recently%20Viewed-_-Product%20Page I would be hooking these to two 12 volt batteries in parellel. i already have a 400 watt inverter but might have to get a bigger one. thanks in advance for any input. Rhine

Cariboocoot · August 2009

Re: still new to solar

Please do two things:

First, take a look at our host's (NAWS) web site and do some price comparison. Like this: http://store.solar-electric.com/kysokc85wa12.html

Second, consider your long-term plan. How often are you there and how long do you stay? Is this likely to increase? Solar power is expensive, especially for short-term, occasional use. Small generators like the Honda Inverter series can be a viable alternative. Since you don't know your total over-all load, it's a bit hard to plan a system. Nothing worse than having something shut down at some critical stage because you spent too much time watching TV last night. You will likely find that your loads exceed the capability of an 80 Watt panel to replenish: 80 Watts is peak power, and under average conditions you might get 240 Watt/hours per day with good sun. That's not as much as it sounds.

You inevitably will need a back-up generator anyhow, as the sun doesn't shine all the time. And once you get used to having 120 VAC available, the 'need' for just starts increasing. As for the rest of the system, it isn't as simple as 'any battery will do' or even 'any inverter will do' as the batteries need to be able to handle the loads and take the repeated cycling (otherwise they go bad quickly) and the inverter must be able to handle power requirements, including the potential need for pure sine wave.

We'll be pleased to help you define your requirements and get a handle on a system design. It's much better to figure this stuff out before you spend the money!:D

BB. · August 2009

Re: still new to solar

Rhine,

Just so you know--this forum is hosted by a solar RE production retailer/wholesaler out of Flagstaff Arizona... Northern Arizona Wind & Sun.

So, we try, when possible, to link to products on their website when we discuss your options.

Northern Tool does (apparently) sell a lot of "beginning solar kits" and parts -- but does not do a lot of support/hand holding...

So, I am going to point to some example's on our host's website... Do not feel that I am pressuring you into buying there (and if you can get the same thing locally at a better price--especially after shipping charges--why not). Just respecting who is paying the bills here (free use to all of us). (note:NAWS gets a lot of phone call every day asking for support from other vendors like NT and others--does chew through his office reps' time).

Sharp is a fine panel--but you can get an 85 Watt panel for $150-$200 less here.

Regarding the Charge Controller--The Sunforce is not a very good controller... Our host sells some very good brand name (smaller charge controllers) from MorningStar or Xantrex--pick a model that supports the optional remote battery temperature sensor (RBTS)... Batteries are very sensitive to temperature and an RBTS controller does a much better job of giving your battery bank a full charge (and limit damage from overcharging).

Regarding desiging the Solar PV power system... Start with conservation... The less power you use, the smaller (and less expensive) your solar power system will be. A good start is every $1 you spend on converstion will save you ~$10 in solar RE electric system costs.

Next, measure your loads... AC loads are easy to measure (assuming you are in North America with 120 VAC 60 Hz) with a kill-a-watt meter.

You need to know the starting loads (such as a pump, fridge) in watts, the average power (in watts), and how long it will run (in watts)... The result is in Watt*Hours (kWatt*Hours is how your home's power is billed).

For your system:

5 lamps * 20 watts * 3 hours per night = 300 Watt*Hours per day

An 80 watt solar panel used in the summer (assuming "5 hours" of sun per day--but panel clear of shade at least 9am-3pm or longer). The overall efficency from solar panel rating, through charge controller, flooded cell batter, through a good inverter is around 52% efficiency:

80 watts * 5 hours * 0.52 = 208 Watt*Hours per average summery day

So--you can see, already you are using about 50% more power than your solar system is able to provide on an average day... So, either use less power, or install more panels (and batteries).

By the way, a Honda eu2000i or eu1000i is very much worth the weight and fuel costs to keep at the cabin to supply AC power (tools) and for charging you battery bank in cloudy weather.

-Bill

mike95490 · August 2009

Re: still new to solar

Northern Tool is nearly as bad around these parts, as Harbor Freight.

Sharp Solar Module — 80 Watt $550 ouch! The gracious host of this message board
has http://store.solar-electric.com/kysokc85wa12.html 85W $425.

As to the "Sunforce 30 Amp Digital Charge Controller" you are overspending,
it's 30A capacity is way higher than needed for a single 80W panel A c-12 controller
http://store.solar-electric.com/xachco.html would handle that fine. Be sure to get
the remote battery temperature sensor too. Saves your battery.

Then consider a battery. Something in the 60AH capacity would be the minimum I would look at. http://store.solar-electric.com/cosuagmba.html

But first, what can the panel support for power
85 x .8 (derate for heat) = 68W x 5 hours of good solar = 340W daily harvest
Assuming you get a low loss AGM battery, you will have 95% recharge efficiency
so you can consume 323 watts from each sunny day

That's 100W for 3 hours, or 50W for 6 hours or 25W for 12 hours. You can spend the power any way you want.

rhine · August 2009

Re: still new to solar

As for the long term plan, what i have is more or less a storage shed that i use for hunting. I do not stay the night there so that should help with some of the waste. when it is used though is before daylight for 30 min or so and sometimes after dark for no more than an hour. in my initail post i said 3 hours three days a week, in this estimate i tried to over estimate how much i will use to help with some of these undercalculations. As for the TV the only times it would be used would be in inclimate weather to pass a little time. Also it should be able to recieve good sunlight from sun rise until around 3 pm. I currently have 2 everstart maxx deep cycle batteries that i purchased about 3 months ago for a trolling moter but have since changed to optima batteries. so i still have these two batteries i would like to use. I really appreciate the quick and helpfull responses!!! if there is any more information i can help with just let me know. also thank you all for the links to this site and the products they offer, when i get it all figured out i will definatly search here first

Cariboocoot · August 2009

Re: still new to solar

Any idea of the Amp/hr capacity of those batteries? They're probably not 'true' deep cycle but the 'hybrid' RV/Marine type which means they won't last as long, but since you've got 'em, use 'em.

If we start with the battery rating we can calculate how much power they can provide and then set up the charging aspect and give you a limit on potential power available.

Roughly speaking, they're probably 100 Amp/hrs at most. That'd be 200 A/hr total, so that gives you a maximum of 100 Amp/hrs available. That's 1200 Watt/hrs at most. You'd also want about 120 Watts of solar panel to keep it charged with. Please note: this is ROUGH estimating; no finesse at all!

You could probably get away with less panel, but I doubt you'd be able to extract any more power from those batteries.

Lights will run fine off a modified sine wave inverter. The TV is 'iffy'; some audio/visual equipment 'doesn't like' the MSW and the imperfect wave form will cause interference in the signal quality.

Stay tuned for more replies!:D

icarus · August 2009

Re: still new to solar

Read through the "off grid" section of this forum.

There are literally dozens of folks that have posed nearly identical questions with nearly identical situations. You can spend an hour or so reading these threads and I suspect you will come away with some better answers.

Two things to note: Consider all your loads, and realize that over time these loads will grow,, take that into consideration as you read. Second, there are some really smart folks here on this forum who have in all probability forgotten more about this stuff than most of us will ever know. Using this site as a resource going forward will help you avoid the dreaded (and almost inevitable) "ready, fire, aim" mistake that too many make.

Welcome to the forum, and good luck,

Tony

rhine · August 2009

Re: still new to solar

Thanks again for all of the quick replies. I took your advice and read several of those other threads and just as you said there were a couple that were very similar!! From what I have read from all of you and on the other threads I have under estimated what I need. I also did some searching on this sites store as well and found a few possibilities. Also i looked at the tv and dvd at my home just to get a reference on consumption and what they list on their back is that the tv uses 120v 60Hz and 2.5 A max. The DVD was 120v 60Hz and it had 9a and 10w in boxes beside that. I think the max these would be used would be 2 hrs 2 days a week. Just a reminder these are the ones i have now and the ones i put in here would be smaller (and hopefully more efficient).

not to put the cart in front of the horse but I took some of your advise and looked at the host sites merchandise and I must say these prices are much better, i think i should be able to get a bigger pannel for the same dollar. I am trying to keep this simple and in doing so would like to keep everything either 12v dc or 120 ac. one panel that caught my eye was the kyocera 130 solar panel with junctiom box. this would run me about $517 after shipping which is still lower than the other panel!!!

following that I looked at the xantrex C35 solar charge controller for aobut $120
also you all said that i would need a remote battery temperature sensor which is another $30.

And last is a Trace digital meter for another $100

so looking at all of these prices it looks like it will run $800 after all shipping charges.

by upgrading to this system do you think it would be possible for this system to work. again i just want to thank everyone of you for helping me out, with out all you helpful people i would have bought a much smaller system months ago and wasted my money. so thank you again and i look forward from hearing from all of you.

icarus · August 2009

Re: still new to solar

Perhaps the best thing you can do, it accurately calculate your loads. Get a Kill-a-watt meter (around $20) and you can test everything you own, and see how much they REALLY draw. (The max amp listing on the labels are not a very good indication of real draw). From there you can work backwards to figure out what it is that you need. Like I suggest, consider as much as you can before you buy anything.

Tony

PS. Just a note,, the C35 controller is a bit on the large size, although not too expensive. I believe that Morningstar makes some nice 15-20 amp controllers for small installations

rhine · August 2009

Re: still new to solar

again i appreciate the quick reply and i will pick up one of meters over the weekend and post my results, and thank you for recomending a smaller controller, any money i can save on this systen would be nice. one question about the meter though, the readout it gives do i need to multiple that by how many hours or min. ow what to figure out how many watts it will use in a given day? thank you all again

BB. · August 2009

Re: still new to solar

Rhine,

Some other suggestions... Instead of the Trace/Xantrex remote digital meter, I would humbly suggest a Battery Monitor would be more useful... Darn near the equivalent to a gas gauge on the battery bank.

If you every go with AGM/Sealed batteries--almost a requirement to make sure you don't kill your battery bank with improper charging/discharging (too little of the former, too much of the later).

The batteries are virtually the "heart" of your system... And the most easy to kill quickly. Read a few Deep Cycle Battery FAQ's and understand how your battery bank will fit into your plans.

I would suggest getting a very good (but smallish) True Sine Wave Inverter like this one:

Morningstar SureSine, 300 Watt Sine Wave Inverter 115VAC

Not cheap--but efficient enough that for things that have a choice between 12 VDC (like a laptop computer, cell phone chargers, and such) and 120 VAC--I would run your devices on the 120 VAC inverter...

12 VDC is very difficult to send long distances (10 amps at 12 volts vs 1 amp at 120 VAC = 120 watts for both) and that deep cycle batteries run from ~10.5 to 15.5 volts--which the typical cigarette lighter converter may self destruct on (the +15 volts seems to take quite a few of them out).

To read about the differences betwen TSW and MSW (Modified Square Wave) inverters, read these FAQs:

All About Inverters
Choosing an inverter for water pumping

For remote cabin/home use--I would humbly suggest that a few hundred watts of TSW is the way to go. (by the way, NAWS/WindSun has spread lots of little FAQ's all over their store--typically in each major section (batteries, charge controllers, inverters, etc.).

Size your system, wiring, charge controllers and such that you can easily double your solar panels and battery bank... If you decide that you need more power--at least you can add it without too much issue (and tossing undersized, but perfectly OK equipment away).

And--you have found the seceret to good prices on solar panels--look at the >100 watt sizes. They are physically large--but are very nice prices and easier to wire up vs 10x 15 watt panels. But make sure you look at the Vmp and Imp--many larger panels can be an issue when running on 12 volt PWM controllers (their "native" Vmp >18 volts typically used for 12 volt systems).

Also--depending on your needs--you may need to get a small 15-30 watt panel that you can put on the side of the cabin for winter/off season charging. Small panel, not a big loss if it is damaged or stolen--and does not attract near the attention that one or two 130 watt panels may.

For measuring AC power--the Kill-A-Watt at $30 or less is the only way to go. Also very handy for use at home to see if that old fridge is still working OK or how much power that entertainment center take when "powered off"--etc.

Have fun.

-Bill

icarus · August 2009

Re: still new to solar

Rhine,

A Kill-a-watt will give an instantanious reading of current/watts etc, as well as a cumulative watthours. It has a clock in it so if it records say 1kw of load, you can see that the load has been plugged in for 48 hours, meaning .5kwh/day. An essential tool for proper planning.

Tony

rhine · August 2009

Re: still new to solar

Thanks for the kill a watt info, i'll get one this weekend and start figuring out how much electricty i'm using in each light and the tv/dvd player.

I know it is still along way off but i was going to see about basic instalation and wiring. i'm sure i well get several thing wrong here but from my understanding this is how it should work.
1. on the back of the solar pannel the will be a box where i should attach my two 8 gauge wires and run them inside to the charge controler (the shorter the better i assume).

2. run two more short 8 gauge wires to my batteries. my two batteries should be hooked + to + and - to- . the wires from my charge controler should go to the + of one and to the - of the other.

3. next i need to run 2 more 8 gauge wires again from the same two opposite post from the two different batteries into my inverter. and then from there wire it up as a normal ac house.

the questions i have on this are: 1. where do i need fuses, with this much power i assume i need more than one installed.
2. what is the best way to ground this system?
3. I am planning on mounting the pv pannel to a 4x4 post that is already there what is the best way to go about that?

I know this is a lot for one post but thank you all again for all of the help you have given and all of the help to come. Rhine

BB. · August 2009

Re: still new to solar

I am not quite sure how much current you are planning on drawing, or how long your wire runs are...

But, in general, it is better to keep the runs short between the charge controller and the battery bank (you want the charge controller to measure the battery voltage very accurately--so long wire runs + voltage drops is not desirable).

Placing the "longer" run of wires between the solar panels and the charge controller is normal. And you need to size the wire for max current / fusing (normal stuff); and you want to calculate how much voltage drop you will have and size the copper wire (make it bigger) to reduce voltage drop and power loss (long distances for panel to charge controller can get expensive because of the voltage drop issue--there are other ways to minimize the problem with MPPT charge controllers--but MPPT controllers are not cheap either).

If you want, there is an Excel Spreadsheet where you can plug in the numbers (remember, wire runs are 2x way--a 6' run will be 12' of wire).

voltage drop calculator

Regarding grounding... The standard is to drive a copper coated/steel rod (get one from the home center) into the earth and ground the negative battery terminal. If you are in a lightning prone area--we will have to have more discussions (there are several schools of thought--and they don't agree).

If you are going with an inverter--some can be grounded on the line side (neutral bonding) and others cannot be (more expensive/TSW usually can/cheaper MSW's usually cannot be). If you are worried about 120 VAC shock--you can add a Ground Fault Interrupter to the system.

When you are talking about 130+ watt solar panels you are getting near 3'x4' in dimensions... Solar panels are thin, tempered glass, devices with a thin aluminum frame around the edge. The aluminum frame is intended to be mounted to a ridged sub-frame (which will resist twisting and movement in all axises). If you try and mount just the aluminum frame with a couple hinges and struts--any wind could cause the frame to twist and the glass to shatter (this is a non-repairable event).

You can build a rigid 2x4 (or whatever is handy) frame out of pressure treated lumber and mount the panel to that--if you want. Be aware, pressure treated lumber requires special screws/hardware because of the metals used for pressure treatment will cause corrosion in the fasteners. Just make sure that the frame is secure and rigid before you mount your solar panel (it is just about the thickness of a single pane window glass).

-Bill

rhine · August 2009

Re: still new to solar

Thank you for the information on the grounding i'll make sure i do that properly. also i think i will build my frame from 2x4's im sure i can make it strong enough that shouldn't be a problem. one question i have though is you said all wire runs are 2x. are you refering to the + and - wires both comming from one thing to the next i assume? thank you again for all the help. one last comment i looked at my batteries today and they are both 125 amp hours

niel · August 2009

Re: still new to solar

"one question i have though is you said all wire runs are 2x. are you refering to the + and - wires both comming from one thing to the next i assume?"

that is quite correct. that is why a wire run is specified because that only lists the distance the wire travels, but because there are 2 wires, a + and a -, that it needs to be 2x the wire run. that assumes that both the + and the - wires are equal in length for if one should be longer than the other then you can't just go 2x the run length and must add the + wire length and the - wire length together.

rhine · August 2009

Re: still new to solar

Hi everyone, thank you all for all of the help so far. I was just given a 1000 watt black and decker inverter from a friend who had it extra. I was wondering should i use this one or will it hurt it to leave it turned on full time.

for the rest of my system i think i will be going with kyocera 135 watt panel with the junction box.
Also i think i'm going to go with the xantrex c35 controler, I think this controller will also allow for expansion if i chose to do so in the future.

and for batteries i already have 2 everstart maxx marine 125 amp batteries so i'll use these until they go bad.

I think this system should be able to run the 9 20 watt lights (only 5 will be used most of the time) for the 3 hours 3 days a week i need. The TV and DVD are not a definate and i think i will cross that bridge when i get there. The main thing I needed was the lights and the TV was going to be a bonus. I would like to see how this works and observe my usage before installing the tv.

I appreciate all of the help I have recieved. Please let me know if any of you find any thing wrong with the setup i have listed. Also any imput on the inverter??? Thanks in advance, Rhine

niel · August 2009

Re: still new to solar

don't leave the inverter on during no load times as it will still draw power from your batteries.

sub3marathonman · August 2009

Re: still new to solar

niel wrote: »

"one question i have though is you said all wire runs are 2x. are you refering to the + and - wires both comming from one thing to the next i assume?"

that is quite correct. that is why a wire run is specified because that only lists the distance the wire travels, but because there are 2 wires, a + and a -, that it needs to be 2x the wire run. that assumes that both the + and the - wires are equal in length for if one should be longer than the other then you can't just go 2x the run length and must add the + wire length and the - wire length together.

I think I'm still confused about this. I don't know why you need to add the - wire length into the voltage drop.

Could you show an example calculation of a voltage drop?

niel · August 2009

Re: still new to solar

there was another explanation of the voltage drop and how to calculate it here on the forum, but i forgot just where it is and who put it here. in any case i can simply say the calculation is based on the current flowing through the wire's, resistance and calculated as a percentage of the battery system voltage. increases in the length of the wire increases the resistance it would present. it revolves around ohm's law. failure to account for the total length of wiring involved in the circuit path would make the results off by 2x.

still new to solar

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