solar newbee needs help

wvwoodsman

My wife and i are relocating and want to stay off the grid. We purchased DIY instructions on building solar panels, to save on cost. We built 16 / 18volt/ 3.5amp/ 75watt panels and i bought a charge controller( www.colemanair.us / modelc160 ). The reason i bought it was because we could introduce wind to it also. They claim to be one of the only companys that builds these. So i thought before we go further we need to know what else we need. Do i need a combinder box to go between them ? i was told if i built a 24volt system , it would store the power longer and use 6 volt batteries. Is my thinking right? I have other question on inverters and wire size , but i figured , take one step at a time.Thanks

Cariboocoot

Re: solar newbee needs help

Welcome to the forum

Yes indeed; one step at a time.
It helps if you begin with the first step, which is determining your loads. If you don't know how much power you need you'll have a hard time figuring out how to get it. So:

1). The maximum amount of Watts you need to supply at any one time determines the size of the inverter.
2). The total Watt hours used per day is the basis for sizing the battery bank.
3). The size of the battery bank will dictate how much PV you need and what charge controller to handle it.

Trying to go about designing the system any other way leads to headaches - and heartaches.

A couple other things that you should be warned about right from the start:
1). Homemade solar panels don't stand up to long-term use. They are often not worth the effort/expense considering the quality and price of commercial units.
2). Small-scale wind rarely is worth the investment either. It suffers from poor site problems (not as much wind as you think, not a good install) and poor quality turbines with exaggerated claims. When you get into good wind equipment you're spending lots of money. Read through the wind power section of this forum.

Sorry to be the bearer of bad news, but we try to stay practical and realistic around here. we don't like to see people waste money and be disappointed with the results of their efforts.

BB.

Re: solar newbee needs help

You are sort of approaching the problem from the middle... Buy/building you hardware without a detailed plan of what your electrical needs are and what equipment you will need to satisfy those needs.

We can try and size a system to what you have right now--but we would probably need a bit more detail--For example your solar panels, do you know if it is 18 volts with no load (Voc--voltage open circuit) or is that Vmp (voltage at maximum power)...

Typically for 12 volt systems, Vmp~17.5 volts and Voc~21 volts... Solar panels, at they get hot will really drop their output voltage (by 20% or more from Vmp at standard test conditions)... So to charge your battery bank to ~14.5 volts + 1-2 volts drop for wiring and charge controller, you need Vmp > 16.5 volts or so...

I personally do not know anything about the charge controller--but if your panels and battery bank are compatible with each other (operating voltage and current), you can connect them up and see how well it works.

I would humbly suggest not buying any more hardware until you have a plan worked out on paper first. It will probably save you a lot of money in the end (and off-grid solar PV power is not ever cheap--designing your loads for maximum efficiency/conservation will save you a lot of money in the long run too).

-Bill

By the way, it is helpful too in predicting solar output to know where the system will be located. Somewhere around Philadelphia PA?

wvwoodsman

Re: solar newbee needs help

Thank you for the info you gave to us it never hurts to learn more ,but for right now we have built 16 panels and have a charge conrtoller that we dont want to go to waste. So we were hoping you could help us build a system with what we already have for now. This system will be temporary , because when elec co does bring power down the road we will upgrade whole solar system to a grid-tie. we will then use the homemade panels to power the coops and barns on small inverters. But for now we need to get a small amount of power for home use. So we just need your advise to complete this system so we can run tv, small refg, comp., a few lights. We also have a gas generator and a deep cell 12 volt battery charge to use when sun is low. Right now we use the generator to start the well pump , run saws , drills, ect., we are trying to use the generator as little as possible. Again thank you for your help.

mike95490

Re: solar newbee needs help

I don't see any indication of a "microprocessor" on the simple PCB they show. Looks more like a couple of timers, comparators and relay drivers. At least it was not too expensive of a lesson. You will need instead, a solid 3 stage controller for deep cycle batteries. Trace, Morningstar.... our host - WindSun, has a good selection of reliable units http://www.solar-electric.com/chco.html
forget wind, unless you like renting a crane or cherry picker to fix the thing.

1200w of DIY panels - impressive. Will be even more impressive when they are up and working.

But, you really need to define your loads, and how much battery you will actually need, before you do anything else.

BB.

Re: solar newbee needs help

Assuming these are properly designed and working Vmp=18 volts and Imp=3.7 amp solar panels (~67 watts) and you have 16 of them... Our typical rule of thumb for battery bank sizing and you are setup for a 24 volt battery bank--Using a 13%/10%/5% rule of thumb battery bank sizing (minimum battery bank to maximum battery bank for a fixed sized charging source):

• 16x 67 watts * 0.77 derating * 1/29 volts charging * 1/0.13 rate of charge = 219 AH @ 24 volt minimum
• 16x 67 watts * 0.77 derating * 1/29 volts charging * 1/0.10 rate of charge = 285 AH @ 24 volt nominal
• 16x 67 watts * 0.77 derating * 1/29 volts charging * 1/0.05 rate of charge = 569 AH @ 24 volt maximum

The above is the, rough, rule of thumb for sizing a battery bank to a solar array for proper battery charging with a flooded cell deep cycle storage battery bank. If you are in that range--you will usually be OK.

Assuming you are building in West Virginia mountains, I will give Elkins WV a shot with the PV Watts Website. Assuming a fixed array with nominal system efficiency, flooded cell battery banks, AC inverter, I will use a system derating of 0.52 and assume a fixed solar 1,072 watt (1.072 kW) solar PV array:

"Station Identification"
"City:","Elkins"
"State:","West_Virginia"
"Lat (deg N):", 38.88
"Long (deg W):", 79.85
"Elev (m): ", 594
"PV System Specifications"
"DC Rating:"," 1.1 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.6 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 38.9"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:"," 6.2 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 2.91, 49, 3.04
2, 3.41, 52, 3.22
3, 4.06, 68, 4.22
4, 4.76, 75, 4.65
5, 5.06, 79, 4.90
6, 5.16, 76, 4.71
7, 5.12, 77, 4.77
8, 5.09, 76, 4.71
9, 4.64, 68, 4.22
10, 4.30, 70, 4.34
11, 2.85, 44, 2.73
12, 2.38, 39, 2.42
"Year", 4.15, 772, 47.86

Assuming that ~3 months of the year you will use a genset to recharge your battery bank, that gives us March as the "break even" month for power at 68 kWH per month:

• 68,000 WH per month * 1/31 days per month = 2,200 Watt*Hours of AC power per day (long term average)

Sizing the battery bank for ~2 days of no sun (between 1-3 days is the normal rule of thumb) and 50% maximum cycle depth for long life, we can estimate:

• 2,200 WH * 1/0.85 typ. inverter efficiency * 1/24 volts * 2 days * 1/0.50 max discharge = 431 Amp*Hour @ 24 volt battery bank

Yes, there are several ways of calculating battery bank capacity--Note that this calculation falls in the range of the above bank sizing based on solar panel output capabilities.

To charge 431 AH battery bank with a smaller genset (say a Honda eu2000i) a 20 amp charger minimum (~5% rate of charge).

If you want a better fit for charging--you can hunt around for a power factor corrected 1,000 watt charger that will output around 27 amps at 29 volts... If you interested in the bloody details behind selecting the "optimum" charger for a small genset, this thread is a great read--If you are not--just skip it. :roll:

Question about battery charger selection with EU2000 generator.

If you have a different size genset, we can discuss your optimum charging setup...

Typically, you want at least 50% load on a genset for good fuel economy and shorter run-time... Having a very large genset with a smaller battery charger can cause you to burn way more fuel that you have too... Also, if you are running a diesel genset, most folks will recommend a minimum of 40-50% minimum loading to prevent "wet stack", "coking", carbon buildup, cylinder wall glazing, etc... Some engine manufacturers recommend 60% minimum loading.

Lots of guess and assumptions on my part--but the above is a good starting guess.

-Bill

mike95490

Re: solar newbee needs help

panel building:
http://fieldlines.com/board/index.php?PHPSESSID=2217ba36ada3e9efa590eb08bf4dac94&topic=145005.0

wvwoodsman

Re: solar newbee needs help

Hi Bill, we have a briggs & stratton 6200 running watts/ 8750 starting watts , gas generator. It has 4/120 outlets & 1/240 outlet , we used it to charge our batteries with a small deep cell charger, but it takes 5 hours to charge it. So i see some inverters have chargers also , am i better off getting that to charge them or what are my options? Also how many 6 volt batteries do you think i need, i was looking at Deka l-16 wet cells 6v/ 370 ah. thanks !

BB.

Re: solar newbee needs help

If you look at my post above, a 370 AH 24 volt battery bank would certainly be "balanced" with your current solar array...

Without knowing your daily expected loads, it is difficult to size the battery bank and solar array any closer. What you have should power your loads (run tv, small refg, comp., a few lights) OK...

If you are at 370 AH and 24 volts, you could either use a smaller genset or look at using a larger AC battery charger to better load the 6kW genset. A large genset with a small battery charger and battery bank is usually a waste of fuel (figure out your kWH per gallon of fuel and see if you are efficiently running the genset or not).

Roughly, you should be seeing ~5-6kWH per gallon of gasoline when running > 50% load and perhaps down to 3kWH per gallon at lower loadings... If you get much below that, you should revisit your generator strategy.

There are some very nice AC Inverter / Chargers out there... Good power factor (>0.95) which is great for using with a genset and some have programmable maximum input AC power (you can use a smaller genset to power a large inverter/charger--the I/C limits the input AC current to the maximum programmed).

Down side is that if either the inverter or the charger section fails, you are out both the inverter and charger function and need to get repair/have spares to keep you going.

If you are going to have grid power to your place eventually--You probably do not want to spend too much money on your off grid / battery system... There are hybrid inverters (operate both in Grid Tie and Off Grid modes) which can be very nice if your area has long periods of power failures (ice storm damage, etc.) and it takes weeks or longer to get your AC power back.

-Bill

wvwoodsman

Re: solar newbee needs help

Thanks Bill i have learned alot so far. Can you tell me how i would wire up those panels for a 24 volt system? Also do you know what the dump load would be on them ? Thanks

Cariboocoot

Re: solar newbee needs help

wvwoodsman wrote: »

Thanks Bill i have learned alot so far. Can you tell me how i would wire up those panels for a 24 volt system? Also do you know what the dump load would be on them ? Thanks

Unlike wind turbines, solar panels don't need any dump load. They don't care if there's a load on them or not.
As for wiring 18 Volt panels for a 24 Volt system, assuming the 18 is Vmp, two panels in series to get a Vmp of 36 and eight parallel sets - each with its own 5 Amp fuse (again, going by your specs). You're going to end up with an output around 30 Amps to the controller, so size the wire accordingly. 8 AWG is probably a good idea here, especially is there is any significant distance.

Other wiring arrangements would require an MPPT controller, which is an expense you probably don't want at this point.

wvwoodsman

Re: solar newbee needs help

Carriboo thanks ! What size wire should i run from the panels to the combinder box ? The box will be in the middle of the array , approx. 6ft - 10ft away from panels. Also could i use a combinder box with "abc" type fuses , i found one on ebay that holds 10 conn. and you buy fuses what ever size you need.

icarus

Re: solar newbee needs help

The question that isn't asked, but might warrant an answer anyway. Why the desire to "go off grid"? Is the grid not available? Is extending it "too expensive? Are you trying to be "green"?

The only realistic reason to go "off grid" is the first, the grid simply isn't available. Battery based PV comes at about twice the price with half the efficiency of grid tie solar, yielding a net of power that is ~ 4 times as expensive as grid tie (and grid tie is net/net About twice as expensive as simple grid power.

So calculating the cost to bring the grid to the homestead needs to look realistically at what the long term cost/benefits of having the grid available. At first glance, $10 or $20 K may seem "too expensive" but factoring in the life cycle cost of PV hardware relative to it's output might make that number seem cheap in the net/net.

Battery bases PV are decidedly not green by most calculations. The environmental cost of batteries and their replacements come at some considerable environmental cost.

If you are wishing to "go off grid" because you are considering Armageddon type scenarios and what effect it may have on your local grid, consider what effect it is likely to have on long term sources for batteries and other PV hardware as well.

Just for example, we live off grid because the nearest grid power is ~ 100 kms away. We live very frugally with 400 watts of PV. On a daily basis we can produce all the power we use with a good three day reserve. We use a generator for all power tools, we have a gasoline powered washing machine. WE have to run the generator to top up the batteries only very rarely.

If you take our system, as an average, the installed cost of the 400 watts of PV, the charge controller, wiring, batteries,inverter, battery chargers etc might be ~ $3000. Add to that the need for at least one generator, and ideally at least two, (a small Eu 1000 for battery charging, and a larger 3 kw for tool use) and the total system price of
~ $5000.

This for a system that puts out ~ 1 kwh of power per day on average over the course of the year,,, that 1 Kwh would cost on the market ~ $.10,, ten cents! Add in the fuel needed to run the shop etc and you can see that this is not a "cheap" life choice.

Our annual out of pocket cost might look like this, not including replacement of any hardware except for batteries.

50 Gallons of fuel @ $4= $200
8 year replacement of 4 T-105 batteries, $600/8= $75

So call it $365 per year if you include a rough number for other hardware replacement,, or $1 per day. So my power probably cost ~ $1 per Kwh, or roughly ten times what a grid connection would cost. Doubling the PV output might reduce that some what, but that would then entail a bigger battery, and a bigger cost.

So if you wish to play with solar power, build homemade panels as a hobby to learn what you can (and cannot do) I say, great. But if you think that you are going to live cheaply I suggest that you do some more reasearch.

Once again, a question not asked, so ignore it if you wish.

Tony

wvwoodsman

Re: solar newbee needs help

The power is a couple miles down the road and they want to charge us $12,000 just to get the wire to the house. That doesnt include the meter or panel , so we are trying to make some segnifagent power. Our neighbors between us and the power are suppose to break ground this fall, thus they will want power,then we get it cheaper. But i have tons of work to do finishing our house, so if i use tools off the generator, our solar system will run the rest of our needs. Thats my predicament !

BB.

Re: solar newbee needs help

Wow... $12,000 for several miles is cheap from what others here have said.

In the long term, paying for the power from the utility will probably a much better investment than going Off-Grid and all of the expenses that involves for ongoing maintenance and such.

In many areas, rural electrification is no longer subsidized. Was somebody here quoted $1,000 per pole or something similar? $50,000 per mile?

Anyway, given that costs for the initial service have been going up--It may be to your advantage now to lock in and pay the $12,000 than to wait a few years.

Of course, check out the details... You may have a remote service charge or a high minimum bill/base charge per month.

And you may have to keep paying for the service--It is not unknown that the utility will remove the wire (or some scavenger) if there is nobody currently paying for service--then charge again to re-establish service a few years down the road.

-Bill

wvwoodsman

Re: solar newbee needs help

We are commited to building a small system. I do appreciate your concern , but we are looking for your advise to help us build one. Can you answer me this, if my panels are wired for 24 volts, contoller is set for 24 volts, 4 batteries wired at 24 volts. What should my inverter be (12 volts or 24 volts) ? Also does it matter what size it is? Is 1100 watts ok? It has 2 outlets to get us by,cheap. Thanks

niel

Re: solar newbee needs help

wvw,
you have an opportunity to hook up cheaper when your neighbors do and i'd take advantage of it if i were you. it is an expense no matter what you do, but it would take some pressure off of you.

the down side to end of the line wire runs is that during outages you would be among the last to be reconnected. that means you may want to back it all up. you have a genny, but a completed home may draw more that an occasional tool. don't get a different genny unless you feel you have to down the line, but for quick responses to outages a backups with an inverter and batteries could be done. if you wish to maintain those batteries via solar you could, but feeding power from solar to the grid may be better as this could reduce your bottom line costs with the utility. the problem arises when you need to use the solar gt to power the batteries during an outage and charge controllers are now going high voltage so some of them may be able to be transferred from the grid to the cc to charge the batteries in the grid's absence. that inverter/battery backup can be made as large or small as you would like, but remember any item that uses coils such as motors, compressors, fans, pumps, etc will need a sine wave inverter to preserve the life of the appliance and to prevent extra power usages from the msw harmonic content.
this is what i'd do, but you can do as you see fit. do not count on having corner cutting like making your own pvs work out very well. of course if the cost of a good solar install bothers you then your answer is quite clear to run the utility to your place.

mike95490

Re: solar newbee needs help

wvwoodsman wrote: »

We are commited to building a small system. I do appreciate your concern , but we are looking for your advise to help us build one. Can you answer me this, if my panels are wired for 24 volts, contoller is set for 24 volts, 4 batteries wired at 24 volts. What should my inverter be (12 volts or 24 volts) ? Also does it matter what size it is? Is 1100 watts ok? It has 2 outlets to get us by,cheap. Thanks

in a 24V system, the inverter would also be 24volts.

As to what size for the inverter, that depends on what you are running. A power saw will need at least 3,000W to spin it up.
Some motors are fine with the mod-sine waveform from cheap inverters, some motors and power tool chargers need pure sine power.
for power tools, a large enough inverter wont be cheap

wvwoodsman

Re: solar newbee needs help

We only need the system to run a small frig , tv, computer and my c-pap machine at night ( i have sleep apnea ) . As far as lights we have oil lamps, tools will be ran off the generator and i have a small deep cell battery charger i can use to top off batteries if the suns not out.Thanks guys !

Cariboocoot

Re: solar newbee needs help

I don't know how prices go where you are, but it sort of looks like $12k to hook to the grid or $12k to put in off-grid. Rock-and-a-hard place deal.

So if you're determined to go off-grid, step #1 is get a Kill-A-Watt (or similar) meter. About $30 and it will save you a fortune in headaches alone. Measure the actual power usage equipment you want to use and get some real world numbers on maximum Watts consumed and the all-important Watt hours per day. This will tell you two hings: where you can reduce your power consumption and how much you're going to need to supply for the rest.

That is where you start to design a system. Trying to do it other ways ends up being more expensive, wasteful, and extremely frustrating when the 'frige goes off at 2:00 AM because the batteries are dead.

mike95490

Re: solar newbee needs help

wvwoodsman wrote: »

We only need the system to run a small frig , tv, computer and my c-pap machine at night ( i have sleep apnea ) . As far as lights we have oil lamps, tools will be ran off the generator and i have a small deep cell battery charger i can use to top off batteries if the suns not out.Thanks guys !

ditch the small fridge. They use as much power >1KW as a full size Energy Star fridge. Make it a Large!

Now to harvest enough power to run this gear, you have 4 hours in the day to accumulate it.

I actually got a new CPAP last month, and had it on my kill-a-watt last night, but didn't get to read t today. Lets call that 50 watts, for 7 hours, is 350wh. Out of a 12V battery, that's 29 amp hours. To recharge just that nighttime use, you need 700wh of harvest (a battery system is only about 50% efficient).

Add the measurements for your fridge , laptop and TV, and you are getting somewhere pretty fast.

You can cut back a little bit, by using your genset to power an AC battery charger, and pump some charge amps into the battery that way too.

icarus

Re: solar newbee needs help

Consider a Propane fridge for the short term.

Going forward, full time off grid, a good .5 kwh/day energy star fridge is the preferred choice, but if you might get grid power in a few years, you could consider using Propane until then.

I also suggest, that the $12k to get the grid to your house is a bargain by any measure!
For $12,000 up front to get 24/7/365 200 amp service which would allow you to use anything any time, as opposed to a $12,000 battery bases Pv System, maybe ~ 1500 watts of PV.

1500/2X4=3000 wh/day on average useable power over the course of the average year. That into a battery bank that might cost ~ $2-4000 and last 5-10 years. In short, it really is a no brainer.

Tony

wvwoodsman

Re: solar newbee needs help

This forum should be called " Go Big or Go Home ". All i have asked is for your help to guide me to build a small solar system and incorporate the parts i already have. So if your all going to use your time and energy into telling me how not to do it , why not build me a system and show me how to wire it and make it so i can expand if i want. I know your just trying to help, but your not helping me.Let's start over ,ok. These are the parts i already have - ( 12 > 75 watt / 3.5 amp solar panels , wired in series , 1> 160 amp charge controller by coleman air model c160 ( www.colemanair.us ) , 1> Briggs & Stratton generator model# 030240 / 8750 starting watts - 6200 running watts and 1> deep cell battery charger. Could you please tell me what else i need to generate some ac power for under $2000 . Maybe a diagram of the wiring layout . I would really appreciate it ! Thanks

mike95490

Re: solar newbee needs help

wvwoodsman wrote: »

This forum should be called " Go Big or Go Home ". All i have asked is for your help to guide me to build a small solar system and incorporate the parts i already have. So if your all going to use your time and energy into telling me how not to do it , why not build me a system and show me how to wire it and make it so i can expand if i want. I know your just trying to help, but your not helping me.Let's start over ,ok.

These are the parts i already have -
( 12 > 75 watt / 3.5 amp solar panels , wired in series ,
1> 160 amp charge controller by coleman air model c160 ( www.colemanair.us ) ,
1> Briggs & Stratton generator model# 030240 / 8750 starting watts - 6200 running watts and
1> deep cell battery charger. Could you please tell me what else i need to generate some ac power for under $2000 . Maybe a diagram of the wiring layout . I would really appreciate it ! Thanks

1st , the coleman Air controller, is not a 3 stage controller, it's a wind generator diversion controller, but can be used for solar, in a crude fashion. (regardless of their web claims). they had wire diagrams on their site, just hook a fuse and inverter to the batteries.
Do you have the "Dump Load" to go with the controller ? (big 12V light bulbs, or a cheap inverter with a 120V heater on it)

2nd what are your loads ?
> tv, small refg, comp., a few lights
so, for starting the motor in the fridge, let's "hope" that a 1000w sine inverter can manage it, if not too much else is turned on.

You will have to resolve the mod-sine vs pure sine, and if you think your gear will be happy or live long, on mod-sine. Personally, I'd suggest pure sine.
inverters: http://www.solar-electric.com/inverters.html

and we do small too:
60 w system:
http://tinyurl.com/SolarMonolithConst

BB.

Re: solar newbee needs help

Probably the reason for the frustration is that we are still missing some fundamental information...

Your panels, I really need to know the Vmp and Imp rating... These are "home built" panels--so do I assume they are 36 cell in series type panels for Vmp~17.5 volts or so? If it is Voc=18 volts, the answer can be entirely different.

The solar charge controller you have selected, as near as I can tell is PWM. PWM controllers need Vmp~17.5 volts @ 12 volt bank and ~35 volts @ 24 bank, etc..

If you used a different solar charge controller of the MPPT type... Then we have more options. We can place three or four panels in series (say 4 panels in series, in 4 parallel strings, with a Iseries fuse of ~7.5 amps per string for safety using a "Combiner Box" with 4x breakers or fuses) and you can charge either a 12 or 24 volt battery bank.

By the way, running the panels 4x up in series will reduce the Imp-array to 1/4 the current--this allows you to use, up to, 6 gauge sizes smaller (or you can put the panels much further away from the charge controller).

Running Vmp>>Vbatt-charging is one reason why MPPT (which are 2-4x the price) are so nice.

MorningStar has a very nice 15 amp 12/24 volt MPPT controller and very nice 45-60 map 12/24/48 volt MPPT controllers. And Rogue has a nice 12/24 volt 30 amp MPPT controller (lower cost, lower Vpanel voltage). MorningStar becomes pretty pricey if you purchase their "optional" displays and such. If you have the option, get the Remote Battery Temperature Sensor.

Inverter wise, there are lots of questions here...

1. What is your average and peak 120 VAC load (watts) and do you need 240 VAC for any reason?
2. The whole TSW/MSW type inverter question. TSW (true sine wave) are much more expensive but provide utility quality power. MSW (Modified Square Wave) are much cheaper, but can damage some electronics and motors (over heating from non-sine wave shape). Some people use a smaller TSW for electronics, cell chargers, etc... And use a big and cheap MSW for running power tools.
3. 12/24/48 volts... My recommendation (rough rule of thumb). For 1,200 watt loads you can use 12 volt battery bank. For 1,200-2,400 watts, look at a 24 volt battery bank. For >2,400 watts, look at a 48 volt bank.
4. And then there is the AC to DC battery bank / Generator sizing questions (bank voltage, bank AH, Generator kW rating, etc.).
5. Add that there are some nice integrated DC Inverter/Charger units too (basically the hardware section of a UPS including AC transfer switch).

Some information:

All About Inverters
Choosing an inverter for water pumping
All About Charge Controllers
Read this page about power tracking controllers
Deep Cycle Battery FAQ
www.batteryfaq.org

Typically, we tell people to go smaller, rather than bigger... Large Off-Grid systems are expensive to build and maintain. Have the savings to replace the chargers/inverters every ~10 years and replace battery banks every 3-15 years.

Keeping systems (and loads) small, really reduce the overall lifetime costs.

-Bill

dwh

Re: solar newbee needs help

wvwoodsman wrote: »

Maybe a diagram of the wiring layout . I would really appreciate it ! Thanks

There's not much to it really...looks like this:

pv modules (solar panels) -> charge controller -> batteries -> inverter -> loads
also
generator -> battery charger -> batteries


If you want a "24v nominal" system, then you rig your batteries for 24v and hookup a charge controller that can put out the right voltage to charge a 24v system. Same with battery charger from the generator. You also need an inverter that can -draw- from a 24v battery bank.

12 > 75 watt / 3.5 amp solar panels , wired in series

That statement makes no sense. Are you saying that the cells in each panel are wired in series, or are you saying that there are a dozen panels all wired in series? If the latter; then what is the voltage of each -panel- both under load (Vmp) and under no load (Voc) so we can figure out the voltage of the whole series string?

If you don't know the voltage of your solar array, then how do you expect to hook it up and have it work?

There's no magic wand here - you either do the math or you don't.

If you want us to do the math - no problem, we enjoy doing it. But YOU have to give us the numbers to work with.

icarus

Re: solar newbee needs help

Just to be clear, every piece of wire needs to be protected by a fuse or circuit breaker as well. Series fuse between PV and controller, fuse at the battery, fuse between the battery and the Inverter, fuse on the charger, fuse(s) on the loads, be they 12 vdc or 120 vac.

All fuses need to be sized for the wire size that they are protecting! Remember, a 1500 watt inverter might draw over 125 amps at 12 vdc (more as a surge load) and as such the wire must be sized both to carry the current without significant voltage drop, as well as fused accordingly.

Don't take the advice of anyone here lightly. There are some very smart folks who have spend their lifetimes learning more about PV than most of us will ever know. They come to it everywhere from serious hobbyists, off gridders, Electrical engineers and solar designers. So ask your questions, folks are more than happy to answer even what seems to be the simplest question. That said, don't bristle when people request more information from you. Often the wrong answers are given in the absence of good information. Also when people give advice that is contrary to your own opinion, at least you should consider it in the spirit in which is given. Like I said, many of us ahve " been there, done that" and as a result we have made the whole range of mistakes. Having done so, allows folks like you not to have to repeat those mistakes.

Good luck and keep in touch,

Tony

Cariboocoot

Re: solar newbee needs help

Clarification:

Every circuit needs to be protected by a fuse or breaker.

The panels to the charge controller is one circuit*.
The charge controller to the batteries is another.
The batteries to the inverter, yet another.
The inverter to load(s) still another circuit.

*This one does not always require fusing, just to make things more complicated. More than two panels or strings of panels in parallel and all must be protected by fuse/breaker.

wvwoodsman

Re: solar newbee needs help

Mike, if you read back some , Carriboocoot told me that solar panels don't have a "Dump load" . Is this right or not ?

wvwoodsman

Re: solar newbee needs help

I have 12 solar panels. Each has 36 cells each at .5 volts x 36 = 18 volts. When i check voltage with my meter in the sun , i produce from 18 to 20 volts and 3.5 amps. The 36 cells are soldered in series , for higher voltage not amperage.

icarus

Re: solar newbee needs help

Unlike wind, solar panels do not NEED a dump load, they can simply be turned off (by the controller) or dialed down.

Wind needs a dump load as most turbines will over speed if you pull the load off them and then they will self destruct.

Tony