am I even close

evaeva Registered Users Posts: 13 ✭✭
Hello,

I've read,calculated and scratched my head and I am planning my very small system to bring to my off grid place in baja. It is only 2 rms and a bathroom. I have a propane fridge and cooking equipement. All I will be powering is a small stereo (not bought yet) a shurflow 115vac water pump w/pressure tank, a few lights, probably an occasional blender. There are 4 lights in the garage ( not wired yet) I have a honda eu2000 for tools and backup. My plan is 2 kyocera 135, morningstar 300 sinewave inverter, 4 trojan t105s. Don't have a clue about what charge controller to get. My needs will not grow into the internet for at least 3 yrs since the satellite service is too$$ for the time I am there. Maybe occasionally watch movies on a computer. The house is on the sea of cortez about 2 hrs north of cabo san lucas (+++sun) Any opinions will be greatly appreciated. I will not be building the rest of my house for 5 yrs at best.
Thanks in advance, eva

Comments

  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: am I even close

    I would double the amount of pv. Your loads are probably doable with the Pv you list if you are very careful, but the charging current is too low. Batteries should be charged between ~5-13% of Ah rating. Your 4 T-105s have a rating of ~450 ah if memory serves, so would like ~20 amps minimum.

    Your 270 watts of panels (depending on the controller), will be lucky to put out ~ 15 amps. With the heat of Baja, I would be surprised to see that much. (A Rogue 2430 would be a nice controller with some room to grow).

    Just Fyi. We have the same battery set, we use ~600 wh/day,(~45 ah) and in the cooler north, we are able to charge ~20-25 amps using 400 watts of panels.

    Good luck,

    Tony

    PS, A couple of rules apply. Despite your thinking that your loads won't grow,,, they will! I have yet to see a system not grow. Second, most people over estimate their solar input capability, and underestimate their loads.

    T
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: am I even close

    Weelll ....

    The best way to do it is to start by getting a firm grip on your loads. Both in terms of maximum draw at any one time and total used Watt average for a day.

    That said, let's take a 'sideways' look at the equipment you're thinking about.
    The first problem would be that 2 135 Watt panels won't do for 4 T105's. The battery bank would be 450 Amp/hrs and needs a minimum 22.5 Amps for proper charging. Roughly speaking, that's about 400 Watts of panel. In Baja you're going to have some significant derating for heat (and if anyone is wondering why I'm not putting the PV Watts promo in here it's because Bill likes to run the numbers on that and I won't deny him his little pleasures. :p )

    But do you need 450 Amp/hrs? Probably not. I've got less than that and can run everything, including electric 'frige and computer/satellite system! So perhaps cut your bank to half - it's cheaper than adding more panels and you still have the Honda gen just in case. For occasional use, this makes better economic sense than buying $1000 more panel that you don't use most of the time.

    Your 270 Watts of panel will probably net you nearly 1 kW/hr of power per day. I didn't use PV Watts (which also doesn't run on this Linux wonder) - just an approximation. That doesn't sound like much, but you'd be surprised what you can do with it. It should also be just enough panel to handle 225 Amp/hrs of battery - maybe not; I'd worry about the heat effects here. I come up with about 15 Amps of current potential. Could be wrong.

    Which charge controller? Any good PWM type like those from Morningstar could handle it. There's no real advantage here (that I can see) in spending the extra $ for an MPPT type. But go with one that has more than 15 Amps capacity, so you have room to expand without having to go buy another one. The Prostar 30 might be a good choice: http://store.solar-electric.com/ps-30.html

    You might want to go up in size on the inverter if you can afford to, for the same reason; future expansion.

    But that's just my opinion; others will no doubt have different insights!

    EDIT: Tony's post had not appeared when I posted mine; this is two different people independently coming to the same conclusion here! :D
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: am I even close

    Marc,

    Seems like we are both bored this evening!

    T
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: am I even close
    icarus wrote: »
    Marc,

    Seems like we are both bored this evening!

    T

    It's 3 hours earlier here, Tony. :p
    I 'stop in' here when I'm resting between bouts of working.

    And neither of us remembered to mention the need for a decent battery charger!:blush: The Morningstar doesn't have one built-in. For $260, that would be a miracle. BTW, you can get 600 Watt Samlex for slightly less money. Just an option.

    So, is it "great minds run in the same channel" or is it "fools think alike"? :p
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: am I even close

    I'm not sure the Samlex will support a grounded neutral.

    The Morninstar will.

    Tony
  • PhotowhitPhotowhit Solar Expert Posts: 5,022 ✭✭✭✭
    Re: am I even close

    I think your close, as the others have mentioned, your balance is a little off, I'd think you could do fine with a 3rd panel, but I always recomend sticking with pairs of panels starting out so you can continue to use them if you expand into a 24 volt system.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • evaeva Registered Users Posts: 13 ✭✭
    Re: am I even close

    Thanks for the input so far. I forgot to add, I will also use a small ceiling fan (no light) on hot nights. 27 watts on medium speed. Sooo... I cant' afford 2 more panels this yr. My options: I can add 1 panel and use 4 batteries, or possibly 2 batteries and 2 panels if very careful. When I figured my usage it came to about 550 w/hrs. per day. With 15% loss factored in. I didn't think about the hot climate 75-90 in the day. While we are there. I will have to read up on the rogue controller and I just checked out the prostar 30. I forgot to ask about the battery charger. I really don't see much expansion in the next 3-5 yrs. I spend about 2 mos/yr there. Just using a generator is not an option. Its been luxury camping so far. Pretty comfortable. My husband really likes the idea of 2 panels and 2 batteries. At least the t105s aren't too expensive. Our friends in Baja say to get the golfcart batteries at costco there since we could cut the life of the batteries during this learning process.( improper charging :( )
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: am I even close

    If you go with more battery and less panel you can use the generator and a good charger to make sure they're up on any days when usage gets a bit high. Iota chargers are good, just make sure it's sized for the battery bank: http://store.solar-electric.com/bach1.html

    I'd agree with the Costco batteries; others here have had good experience with them and they are cheaper - just in case! :D
  • evaeva Registered Users Posts: 13 ✭✭
    Re: am I even close

    Hello again, I read about the prostar30, and about 1/2 the long thread about the rogue 3024. about 100$ diff. if I get the prostar30 w/meter. Is the 3024 wasted if I just use 2 batteries as mentioned?? or can I use 3 panels for more charging and 4 batteries. In the past I always figured doing things in pairs, but I guess I don't need do. I know the fans use +power if used much and baja can get HOT. This probably seems simple and mixed up but I have a medical/technical background not electronics so I really have to put effort in attempt to keep it all straight. Thanks
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: am I even close

    If it were me,

    I would build the system this way, to allow it to grow with the least problem:

    I would use the 4 T-105's, I would use the Rogue (mostly because I know it vs the Prostar which I know not at all!) and the Rogue is IMHO a great controller with great user interface for the non-technical types. I would buy a good battery monitor, as well as a good IOTA or Xantrex TC 20 or 40 charger to use with the genny.

    That way, I have a lot of room to add panels up to the limit of the controller. Remember, to some limited extent you can have "more" panel capacity than the panel's theoretical maximum. For example, the Rogue controller will limit output to 30 amps, even if the input exceeds 30 amps now and again. So designing the total PV for the controller might not be based on Imp of the array, but more the consistent average output of the array. In my case for example, the total Imp of my system might, under very cold conditions come in at ~40 amps say, but under "normal" conditions, it might put out ~25 amps (99% of the time).

    I would then use the battery monitor tell me when I need to charge the battery from the genny.

    Good luck,

    tony
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: am I even close

    I agree with Tony, because he's right.

    I have no experience either with the Rogue or the Prostar, so I'll trust his judgment there. But it sounds like a good plan. :D
  • evaeva Registered Users Posts: 13 ✭✭
    Re: am I even close

    Thankyou both for all the help. I am going to Mexico in a week. I really wanted to have somewhat of an idea to present to a friend that will be helping us w/our system. He is going to consult with us and (give us much instruction and guidance) and we will do the physical labor. Now I have a good solid idea of where to start, and of course continue my learning.
    Thanks again , we will keep you posted on our progress.
    eva
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: am I even close

    I should add, the Prostar is a PWM controller, so that you will not gain as much harvest as you would with the Rogue mppt controller. Probably not a huge deal, but the MPPT should give you ~10-15% net more harvest.

    Tony
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