finalizing our setup

idiggplantsidiggplants Registered Users Posts: 27 ✭✭
ok, so we finally THINK we have our remote cabin system sized, and our components selected. i was hoping for you guys/gals to give it a once over, as well as help us with wiring stuff...

we are planning on going with one of these panels
http://www.solar-electric.com/kyocera-kd140sx-ufbs-140-watt-polycrystalline-solar-panel.html
and this charge controller(not sure if we will get the meter or not)
http://www.solar-electric.com/modubachco251.html

they will charge 2 12v 100ah deep cycle batteries. the charge controller has the ability to charge 2 batteries separately and concurrently.

we figure that controller will let us upgrade to a second or even a third panel when money becomes available, and our need increases.

the panel(s) will be about 20' from the controller. everywhere we see says to use #10 wire. isnt that unnecessarily big? we have a ton of #12 wire around that should handle 20 amps?

fuses/breakers... where do we need them and how big? i was told that we need 3 15amp circuit breakers. one on each battery and one on the panel line. id like to understand the reason for these. i would think that we would need a 25a one since it is a 25a charge controller?

thanks a whole lot. sorry for the newbie questions.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: finalizing our setup

    One of those 140 Watt panels is barely enough to charge a single 100 Amp hour 12 Volt battery. With loads drawing at the same time even that becomes "iffy".

    The charge controller can handle about three of those panels. But I don't think you'll be happy with one panel on that much battery. The 'charging separately' is only of use in this case if one battery is already charged; you probably do not have enough daylight to do one first, then the other. So unless you are keeping one 'in reserve' it won't help much.

    Another thing is that two 12 Volts in parallel may not be the way to go if they're being used as one; a couple of 220 Amp hour 6 Volts in series may be cheaper.

    Panel wiring: 20 feet is not very far. But even using 10 AWG on one panel (8 Amps @ 12 Volts) you have a V-drop just under 3%. Push that up to three panels (22 Amps) and the V-drop soars to over 7%. You see it is not so much a matter of handling the current as keeping the Voltage from falling below the point where the battery can actually be charged.

    You might consider going with a bigger panel (less $ per Watt) and more expensive MS 15 Amp MPPT controller to reduce this wiring problem and give yourself more charging current. But that limits future expansion.
    fuses/breakers... where do we need them and how big? i was told that we need 3 15amp circuit breakers. one on each battery and one on the panel line. id like to understand the reason for these. i would think that we would need a 25a one since it is a 25a charge controller?

    :confused: I don't know who gave you that fusing info, but it's wrong.
    A single PV does not need any fuse on it, nor do two. But if you go with three each will need a fuse or breaker. The series fuse rating for the panel determines this. It is usually a maximum of 15 Amps, and often 10 Amps.
    The wire and fuse between charge controller and battery should be size for the maximum expected current. With one panel this is <10 Amps, but if you go with your expansion plan to three panels you would size it for the controller's max 25 Amps. No sense in wiring it twice. With separate lines to two different batteries each has to be sized for the max.

    Overall I think the biggest problem you have with your design is starting out with too little panel. If you can leave one battery out of the mix until you get the second panel it will work better, save being short on battery capacity.

    On that note let me point out that to treat the two batteries separately they have to be separate at all times: you can not hook them to the controller as individuals and then tie their terminals together so that both power the same loads at the same time.
  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    Re: finalizing our setup

    Why do you want to charge two batteries separately? Generally, it is better to have one battery bank for your loads. The dual battery system is suggested for a vehicle where you don't want to kill the vehicle's battery if somebody uses to much power from the house battery. Otherwise you are left with trying to balance loads for your cabin from two different batteries (may make sense if you have an electric trolling motor battery you want to keep charged separate from the house battery).

    For 12 volt battery systems, you do not have a lot of head room for voltage drop... In general, you don't want more than 1/2 volt drop for any of your wiring runs. 12 AWG is certainly fine for short power runs... But longer runs / higher currents need to be looked at.
    .
    For example, if you have 25 amp from your solar array @ 20 feet (one way run for this voltage drop calculator) and 12 awg wire will give you 1.9 volt drop... That is too much. A 3% drop * 17.5 volts Vmp would be 0.525v maximum voltage drop recommended. The recommend wire size for three parallel solar panels would be 6 AWG cable. (note, you want short/heavy cable between charge controller and battery bank for, ideally a 0.050 to 0.10 volt maximum drop).

    Which gets us back to your panel needs... Even a relatively small solar array of 420 Watts would probably benefit from using a MPPT charge controller (put two or three panels in series behind a MorningStar 45 amp MPPT charge controller).

    Then you are looking at 3% of 3*17.5 volt Vmp panels = 1.6 volt drop. At 8 amps and 20', that could use as small as 16 AWG wire from the array to the charge controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup

    first, thank both of you very much for your time and response....

    but, how did we go from talking about wiring sizes, to suggesting that i get a mppt controller that is more expensive alone, than our entire setup? it seems like every time i post something on our setup, people just automatically triple our cost. right now we are looking at $450. you guys are saying go mppt, and go with 3 panels.. your talking about $1500-2000. i went through the sizing calcs with the www.solar-electric.com rep and everything seems about on track with the 140w panel, but he said a second wouldnt hurt. another local company agreed. and yet another said that we would actually be fine with 85w.

    im sorry for the rant, but its frustrating when the people who are selling us stuff, and know our daily usage, are saying we will be fine with a small setup, but then people jump to a conclusion that we need to spend thousands, when they dont even know what our usage is going to be. all i wanted is help with wiring sizes and breakers.

    ok.. so on with that...

    we already have the batteries, which is why im saying we would use two. if we should only use one, thats fine. i figured rather than deplete one 10% in a day, it would be better to deplete two 5% in a day. perhaps i am wrong. also, i was under the impression that 2 batteries in a bank would cause them to drain each other. that basically both batteries would have the capacity of the weaker battery? if one dies, it would kill the other? finally, 6v batteries would not be an option for us. its important that we have the ability to use the batteries separately. should we decide solar is not the way to go, we would be stuck with these 6v batteries. our current setup is to run the cabin with one, and have the other as a backup. then we take both back and charge them after a weekend. should the solar not work out for our needs, or fail, we wouldnt be able to go back to that setup. additionally, we are figuring worst case with the setup. if it is undersized, we can use one battery as our "optional" usage items... radio, superfluous lights, etc, while the one on the solar panel ran our every trip items. this would let us carry one battery in rather than 2. it would also give us the option of not using the radio should we not want to haul either battery back. the panel would charge one battery, and the other would simply be tended till the next time we come up.

    ahh, line loss. i had a suspicion that was the issue for the heavier wire...
    sorry, i dont quite understand that calculator. i see no 12v option...
    assuming that we will have 3 panels.. go with 6awg... 2panels? 1 panel?

    we actually have some short lengths of 0,2 and 4awg that we can use from the controller to the batteries. we were basically planning on using the biggest that will fit in the controller's terminals. this will be about a 2' run.

    ok, so we will use a 25a breaker on each of the battery positive runs. simple enough.. i think this kit: is what lead me to believe that we would need one to the pv...
    http://www.solar-electric.com/rvkitwi140wa.html
    http://lib.store.yahoo.net/lib/wind-sun/RVKit01-diagram.pdf

    im sorry if my rant made me sound unappreciative. i understand that your giving your best advice.
  • PhotowhitPhotowhit Solar Expert Posts: 5,656 ✭✭✭✭✭
    Re: finalizing our setup
    ...but, how did we go from talking about wiring sizes, to suggesting that i get a mppt controller that is more expensive alone, than our entire setup?
    Nobody here knows your needs other than you, we can only go by what your posting. I've lived with a 150 watt array and about 210 Ah battery, it's not a lot of energy.
    ... ....www.solar-electric.com rep and everything seems about on track with the 140w panel, but he said a second wouldnt hurt...
    Likely they know more about your needs than we do.
    ...
    another local company agreed. and yet another said that we would actually be fine with 85w.
    They are nuts, not enough to properly charge a 200 amp hour system.
    ...
    im sorry for the rant, but its frustrating when the people who are selling us stuff, and know our daily usage, are saying we will be fine with a small setup, but then people jump to a conclusion that we need to spend thousands, when they dont even know what our usage is going to be. all i wanted is help with wiring sizes and breakers.
    None of the moderators work for or sell equipment, just offering their opinion and guidance from years of experience.
    ...we already have the batteries, which is why im saying we would use two. if we should only use one, thats fine. i figured rather than deplete one 10% in a day, it would be better to deplete two 5% in a day. perhaps i am wrong. also, i was under the impression that 2 batteries in a bank would cause them to drain each other.
    Not really if they are well maintained and well wired, equal resistance through each...
    ... that basically both batteries would have the capacity of the weaker battery? if one dies, it would kill the other? finally, 6v batteries would not be an option for us. its important that we have the ability to use the batteries separately. should we decide solar is not the way to go, we would be stuck with these 6v batteries.
    Basically true, you don't add new to old batteries, but if they are born and live together they should be fine, multiple strings, more than 2, (some say 3) are not advised.

    All batteries are made up of cells, your 12 volt batteries are 6 cells, 2 6 volt batteries are just 6 cells and in series are a 12 volt battery, We like to call this a battery bank, but both 12 volt systems are the same, you have the batteries, lets go from there.... (some say 3) are not advised.
    ... our current setup is to run the cabin with one, and have the other as a backup. then we take both back and charge them after a weekend. should the solar not work out for our needs, or fail, we wouldnt be able to go back to that setup. additionally, we are figuring worst case with the setup.
    Solar, if setup properly will be more reliable than grid, from my 10 years of experience
    ... if it is undersized, we can use one battery as our "optional" usage items... radio, superfluous lights, etc, while the one on the solar panel ran our every trip items.
    Likely what we are trying to help you with is not being undersized.
    im sorry if my rant made me sound unappreciative. i understand that your giving your best advice.
    We are doing the best we can with what we got...lol

    I'm sending you a PM with what I would use in already having 2 12 volt - 100 Ah batteries, and assuming they are the same age...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    Re: finalizing our setup

    It is frustrating... Low voltage solar systems are a pain because of voltage drop if there are any >10' distances involved.

    And, in my defense, I did give two options. heavy wire or MPPT charge controller based on your eventual 3 panel design.

    Unfortunately, that is my training/experience as a systems engineer. It is relatively easy to cobble something together that can work sort of OK... But if you want something that is reliable, efficient, safe, and does not require hand holding--It does cost money.

    With the voltage drop calculator link I gave--You don't need to worry about the "voltage". Just calculate whatever voltage drop you want (3% * 17.5 volts = 0.525 volt maximum drop).

    And, we are not there at your place. We try to make our suggestions clear with reasons why each choice was made. If your system was only going to be a 1x 140 watt panel with 20' of wiring (and not the eventual three), then a 20', 8 amp, 0.5 volt wire run would be around 10 awg and ~0.4 volt drop.

    But you would have to add more wire if you expanded the array (3x 10 awg is close to 6 awg worth of wiring).

    Regarding the battery question... If you go with less than 5% rate of charge, it can take days to recharge the battery bank... Plus as batteries age (particularly heavy duty traction cells), near the end of their life, they can take nearly a 5% solar array just to keep charged due to self discharge.

    A common way that many batteries are "killed" is "deficit charging". Basically, the batteries are discharged some amount and are not returned to full charge (generally several times a week recommended)--But instead keep getting to lesser and lesser states of charge (i.e., 100% to 95%, back to 99% then to 94%, then back to 98% and to 93% and on and on) until 6-12 months down the road folks complain that their battery bank has "lost its zip".

    If we made some mistake about your energy usage, please let us know. In the original post, it did not state if you will be using LED lighting and a small DC radio for 10+ hours per day or needing to power a water pump (presurize plumbing) or run a small microwave for 15 minutes per day... The amount of current (surge and average) is critical to sizing the wiring/breakers.

    12 AWG is healthy sized wire--And can supply (20 amps * 120 VAC * 0.80 NEC derating = ) 1,920 watts (16 amps) over a 100' extension cord with 1.3 volt drop.

    A 12 AWG cord can send 16 amps with 0.5 volts of drop about 7.5 feet -- Or about 192 watts (7.5/100 =) 0.075 times as far at 12 volts (vs 120 VAC).

    "The Math" is devastating for all but the smallest loads on a 12 volt power system.

    For example, a 12 volt 200 AH battery bank should be very able to supply C/8 (8 hour discharge) very comfortably... The branch circuit design would be:

    200 Amps * 1/8 discharge rate * 1/0.80 NEC derating = 31.25 amps wiring/fusing minimum
    31.25 amps * 12 volts = 375 Watt of power

    And if you want to run that power 20 feet with a maximum of 0.5 volt drop (12 volt battery running down to 11.5 volts, and 0.5 volt drop taking battery to 11. volts and another 1/2 volt drop for surge current to start a pump for example)), you would need 4 AWG wire (0.37 volt drop).

    It is numbers like above why I like to suggest a 300 watt TSW AC inverter instead... 120 VAC is easy to send long distances, and you can plug in the normal AC battery chargers that everyone has (not everyone has their DC car adapters for games, computers, etc.).

    So--If you can tell us a bit more about your power requirements (AC/DC, average current, peak current, what the loads may be), then we can be a bit more helpful.

    Sorry for being so frustrating--It is not our intent to "up-sell" anyone. There are lost of trade-offs to be made in any system design. None of us moderators are in the solar business at all--And we get no commissions/salary from NAWS for being here.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ThomThom Solar Expert Posts: 196 ✭✭✭
    Re: finalizing our setup

    I wonder if your salesman lives off grid !

    Thom
    Off grid since 1984. 430w of panel, 300w suresine , 4 gc batteries 12v system, Rogue mpt3024 charge controller , air breeze windmill, Mikita 2400w generator . Added [email protected] 100w panel with a midnight brat 
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup

    thanks guys. i know you dont know our setup and are working with what i gave ya. was just more shocked cause i asked about wiring, and got told that my array was too small. probably some of the misunderstanding was that we have the batteries that are x size, although we only need batteries that are half that, or whatever.

    give me a bit to absorb all of this new info, and ill give a better response.

    thanks again.
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup

    hey guys. to give a little more info.. we have a meter on our cabin.. a watts up meter if anyone has heard of that... from what we have figured since we have gotten it, is in 3 days we generally use about 30ah. so 10ah in 24hours is the average. im not sure what our peak draws are. id have to go up and check how much all the items pull. we arent very judicious in our usage, and are completely prepared to be more judicious if we need to. we are happy with using this solar to make the cabin more "rustic." the most we are up there for is 3 days. if we go up longer than that, we are prepared to run a generator and concurrently charge the battery(s) and run the 12v off of a converter.

    i want to run the wire to the panels big enough so we can handle 3 panels anyways, so 6awg looks like our ticket. 20' is actually real conservative now that i think of it. its probably closer to 15'.
  • PhotowhitPhotowhit Solar Expert Posts: 5,656 ✭✭✭✭✭
    Re: finalizing our setup
    ...we have a meter on our cabin.. a watts up meter if anyone has heard of that... from what we have figured since we have gotten it, is in 3 days we generally use about 30ah. so 10ah in 24hours is the average. ....

    A Watts Up Meter measures amps on a 115 volt circuit, so what your using is 10 amps x 115 volts or 1150 watts, a 12 volt x 200amp battery holds about 2400 watts or reserve. For this large of a load you'll want a larger system, unless there is a 12 volt "Watts Up" meter?

    When looking for an image to post I did find a 12 volt version so perhaps, we are comparing apples. Amps is a measure of current, watts a measure of power.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup

    haha. yes. its this guy:
    http://www.amazon.com/Watts-Meter-Analyzer-WU100-Version/dp/B001B6N2WK

    pretty sweet thing to have for our cabin. we can get a good idea of what everything is actually pulling.
  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    Re: finalizing our setup

    A Watt's Up meter is probably the higher resolution (lower current limit) member of the Doc Wattson DC Amp*Hour/Watt*hour meter family--I believe:

    http://www.rc-electronics-usa.com/electrical-test-equipment.html

    10 amps * 24 hours per day is a pretty small system (that is good--keeps your costs low). Just need to undertand the loads (a few amps average probably).

    If the loads (average and peak currents) are correct--You could get away very nicely with even a ~40 AH battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup
    BB. wrote: »
    A Watt's Up meter is probably the higher resolution (lower current limit) member of the Doc Wattson DC Amp*Hour/Watt*hour meter family--I believe:

    http://www.rc-electronics-usa.com/electrical-test-equipment.html

    10 amps * 24 hours per day is a pretty small system (that is good--keeps your costs low). Just need to undertand the loads (a few amps average probably).

    If the loads (average and peak currents) are correct--You could get away very nicely with even a ~40 AH battery bank.

    -Bill

    thats the one we have... thats great news...

    our water pump is pretty average for an rv type pump. i forget what the numbers were, but i remember being surprised that it was only the equivalent of a couple/few 1157 incandescent lights. even when our water level was low, measurement taken just before the pressure kicked the pump off, so basically worse case scenario.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: finalizing our setup

    Just a comment that a town friend/neighbour at the lake, said to me after we got his single 100w panel up and charging his 2-6volt 150Ah battery bank... This is great! Now, how many lights can I run in the cabin?

    One of the mods here, off line a lot these days, likes to say: RULE #1 - loads grow over time...

    I would seriously look towards at least 2 panels to start, they are quite cheap these days /Watt. If you go for a 200+watt one , essentially made for grid tie setup, but usable with an Mppt CC, they can be the best $/watt around... one would suffice.

    hth
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup
    westbranch wrote: »
    Just a comment that a town friend/neighbour at the lake, said to me after we got his single 100w panel up and charging his 2-6volt 150Ah battery bank... This is great! Now, how many lights can I run in the cabin?

    One of the mods here, off line a lot these days, likes to say: RULE #1 - loads grow over time...

    I would seriously look towards at least 2 panels to start, they are quite cheap these days /Watt. If you go for a 200+watt one , essentially made for grid tie setup, but usable with an Mppt CC, they can be the best $/watt around... one would suffice.

    hth

    a lot of people say that, but honestly, we dont want our cabin to turn into a beachhouse. we like it rustic and minimal. the only things we see doing in the future is getting more lumens. but we plan on doing that by upgrading the incandescents to led. its not like we are going to add a tv, or microwave, or coffee maker. that would make the place loose its spirit. most of the time we only use the place as a bunkroom, and hang out under our pavilion.

    for work weekends we bring up a generator to handle any powertools.

    so assuming the 10ah a day, with no future increase, do you guys agree that the initial 140w panel will be ok?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: finalizing our setup

    All the specifications, including wire size, are related to how well the system will perform. Choking power through too-small wires may cost you more than biting the bullet and going up in panel & controller. You have to look at more than one option before you spend the money.

    'Tis better to do it right the first time than to have to redo it all later.
    How do I know? I spend a great deal of my time reworking systems that were inadequate to begin with.

    But no one has to take my advice.
    I think I'll start charging double when I have to rework a system when my suggestions were ignored to begin with. :p
  • PhotowhitPhotowhit Solar Expert Posts: 5,656 ✭✭✭✭✭
    Re: finalizing our setup
    ... when my suggestions were ignored to begin with. :p

    I don't think he's ignoring your, my or others suggestions, I admit to having pointed him at the DMSolar 2 panel deal, and I think he's looking at 290watts charging the 12 volt - 200Ah battery bank, should put him at about a 7+% charge rate and a minimal discharge. He's just being considerate, and not mentioning an outside source.

    Having a meter is a nice perk, and as a weekend use cabin, I suspect, he'll be fine until someone decides they have more power available, Momma Bear or little ones as they grow up?...

    ... hope he watches the meter as time moves on....
    ...maybe he can even come back and tell us how the dang kid has to have a tablet running to watch movies.

    I think he should be able, if theft isn't a problem to leave the system standing and expect fully charged batteries on returning. I don't know if we've asked where this system is and suggested winter panel angles to prevent snow accumulation.

    Kinda been puny today, after some stormy weather in the Midwest. Hope to post some good news after all the hassles I've had this Spring tomorrow. After 5 months the big battery is here and most of the wiring in place, off grid by Tuesday?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: finalizing our setup

    Uh, that was a joke. Hence the smiley face.
    Besides, double nothing is still nothing. ;)
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: finalizing our setup

    Photo...
    "The big battery gets here?" Moved from you cabin or going 48 volts?
    Just curious
    gww
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup
    Uh, that was a joke. Hence the smiley face.
    Besides, double nothing is still nothing. ;)

    didnt seem like it to me on first read, but its ok. im not trying to ignore any comments. not sure what comment of yours i even ignored. there are a lot of numbers and calculations being thrown around, i may not have understood something.

    im still kind of waiting on people to give me their opinions on the setup with the new data. 10ah/day. 1(or 2) 140w panels(depends on what the other "funding party" has to say about it), 25a charge controller, 6awg wire from panel, no breaker, even larger to the battery, 25a breaker in line. battery - 27 series 100ah deep cycle. what are we missing? should we leave the second battery out of the mix(we can find a use for it), or should we use it?

    system is in northern central pa. planning on pretty steep angles for the panels. theft is a concern of mine, i wanted the array to be mounted on a telephone pole.. but the "funding party" seems to be ignoring it. as a compromise, i think we are going to use a type of "security bolt"
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: finalizing our setup
    didnt seem like it to me on first read, but its ok. im not trying to ignore any comments. not sure what comment of yours i even ignored. there are a lot of numbers and calculations being thrown around, i may not have understood something.

    You really have to know me for a while to get the jokes. Then you're sorry you do. :p (That was another joke.)
    im still kind of waiting on people to give me their opinions on the setup with the new data. 10ah/day. 1(or 2) 140w panels(depends on what the other "funding party" has to say about it), 25a charge controller, 6awg wire from panel, no breaker, even larger to the battery, 25a breaker in line. battery - 27 series 100ah deep cycle. what are we missing? should we leave the second battery out of the mix(we can find a use for it), or should we use it?

    Well 10 Amp hours a day on 12 Volts is only 120 Watt hours. Does that meet the power requirements?

    A 100 Amp hour battery (sounds like one of those dreadful RV/Marine units) is capable of double that easily, and could be recharged from one 140 Watt panel (7 Amps = 7% peak current rate) providing simultaneous loads don't draw too much. Two panels would be maximizing the charge rate and may even work in PA. :p

    The size of the wires and fuses will depend on the final installation design, as they need to be determined not just for current but also Voltage drop over distance.

    Add that second battery and you will definitely need that second panel. On the plus size you get twice the power capacity.
    system is in northern central pa. planning on pretty steep angles for the panels. theft is a concern of mine, i wanted the array to be mounted on a telephone pole.. but the "funding party" seems to be ignoring it. as a compromise, i think we are going to use a type of "security bolt"

    One good thing about paying for stuff yourself: you always know the available budget. The downside is that it tends to be "$0". :p (Yes; that was another joke.)
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup

    yep, its one of those rv/marine units. we get good deals on 2nds locally, so they are hard to pass up...
    ok, so i think i convinced my father to go with the double 145w panels. he has a much harder time accepting that we will need as much of an array, than i do.

    and the 25a charge controller sounds like our best bet. could handle a 3rd panel if we deem necessary...

    my questions are now focused on the wiring... so the morningstar pwm controller seems to have a terminal that accepts 10awg wire. if we have a 6awg wire coming from the panel... then what do you do? just mash as many strands in there as possible? and then what about the mc4 connectors? it seems to me that they make these super slick watertignt connectors that i will only be able to run 10awg out of the back of, and then have to solder/crimp/shrink wrap it to a 6awg... wouldnt it be easier to just solder/shrink wrap the panel direct to the 6awg and eliminate the stupid connectors?

    or do they have mc4 connectors that can handle 6awg?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: finalizing our setup

    The thing to do when you need to transition from one wire size to another to fit terminals is to make a short pigtail of the smaller wires size. Fasten it securely to the larger wire, solder it for sound electrical connection, then seal it with heat-shrink tubing.

    This works here because the 10 AWG can carry 30 Amps; the larger wire size is being used to minimize resistance over the long run. Yes, the smaller size wire is higher resistance; but the length is so short it has no significant affect on the Voltage.

    Panel leads tend to be 10 AWG with MC4 connectors. You can buy "extensions" with male/female MC4's on either end and cut them in half to make pigtails to splice to heavier wire. http://www.solar-electric.com/incaforsoelp.html

    Cutting the connectors off the panels may void the warranty as it counts as an "alteration" to the panel.
  • idiggplantsidiggplants Registered Users Posts: 27 ✭✭
    Re: finalizing our setup

    gotcha. well, it seems like this pair of panels comes with a "y" to combine the panels into paralell. so ill just plug them together, chop the Y, and solder on some 6awg. ill probably shrink wrap it, as well as put it in a watertight box.

    for now i think we will stick with one battery. i doubt we will have a problem having enough capacity. if we do, ill add in the second and see how that goes.
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