Was going 420w @ 12v but opted for 280w @ 12v...

ywhic
ywhic Solar Expert Posts: 621 ✭✭
Well I changed a few things up after all the information I learned on here yesterday..

With 2 panels at 140 watts I still end up losing something.. (12v X 15amps) works to 180watts/chrg hour=900 watts.. I'm loosing 100 watts worth of panel.. (280 rated - 180 actual)

if I went with 3 panels of 140watts I end up at 277watts/chrg hour=1386 watts (12 x 23.1amps).. but I'd lose 143 watts worth of panel.. (420 rated - 277 actual)

So heres what I came up with.. and the costs seem OK for a start..

2-140 watt Solar Cynergy Panel (7.82A and 17.9V each) (12v panels)
1-Morning Star Sunsaver 20Amp Controller
1-Morning Star 300W Sine Wave Inverter
2-30 Amp breakers (1 for panels and 1 for battery)
1-Midnite Solar Baby Box (for breakers)
50-feet of 10AWG wire.. (actually using <=18' length from roof to Baby Box/Controller).
2-MF & FM MC4 Latchs for the parallel.
1-180AH US Battery (12V)

Works to $1133 for the entire system with the battery.. Should be at a 4% loss based on calculators..

I may step to 8 AWG for the run from the roof to the Baby Box/Controller..

Whats says the crowd.. does the 1st part of this post make any sense as far as LOSS??

Comments

  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...

    I don't get your first part on 280 rated 180 actual.

    On a first system, I'd skip the breakers and breaker box, I'd go with 2 - 6 Volt golf cart batteries in series, Sams or Costco @$75 each.

    As to 'LOSS' there are other losses/ineffiecencies in a battery based system, usable enduse is 50% or less, Charge controller and inverter don't work at 100% batteries as storage have considerable loss. Not trying to discourage you, just hope you have realistic expectations.
    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.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...

    Let's just go over the math again.

    280 Watts of panel operating at 77% typical efficiency is 215 Watts effectively.
    Over 4 hours of equivalent good sun that would be 860 Watt hours DC per day. About 560 Watt hours AC.

    It will supply a potential peak charge current of around 16 Amps with a PWM type controller. (An MPPT controller might squeeze 2 more Amps out on average.) Output of the charge controller should be based on that.

    As we discussed before, the biggest problem is with the V-drop from the array to the controller. Your plan to use separate 10 AWG wires per panel over 15 feet should solve that. There would only be a 2% drop this way. Changing to two runs of 8 AWG would reduce this to 1.2% (Anyone who wants to check those calculations feel free to do so.)

    Keep in mind this is power loss under maximum load conditions. As the battery charges the current will go down as the Voltage goes up and the power loss will decrease. If the battery is not too large you likely will not see maximum current most of the time. You could use up to 320 Amp hours (5% of which is 16) but would be better off with 160 (10%) to 220 (8%).

    The 180 Amp hour battery at 25% DOD will provide about 540 Watt hours DC, slightly less for AC (around 486 depending on the conversion efficiency of the inverter).

    I know this is all confusing, but it's because one thing effects another. For instance temperature changes will alter the numbers everywhere: cold panels put out more, hot panels less. Atmospheric conditions change panel efficiency. But more so, how you use the system will alter its performance. Battery capacity is dependent on the rate of draw at the time, so it effectively goes up and down as you use it irrespective of charge. Once the batteries are charged you have "surplus" power available from the panels which can add to your daily supply providing you can make use of it at the time. How much will depend on (same old song) a number of factors. You can only approximate performance; you can't carve it in stone.

    Over-all the only thing I'd alter to your plan is to go for the 220 Amp hour 6 Volt batteries.

    But let's see what other people's opinions are. :D
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...
    Photowhit wrote: »
    I don't get your first part on 280 rated 180 actual.

    On a first system, I'd skip the breakers and breaker box, I'd go with 2 - 6 Volt golf cart batteries in series, Sams or Costco @$75 each.

    As to 'LOSS' there are other losses/ineffiecencies in a battery based system, usable enduse is 50% or less, Charge controller and inverter don't work at 100% batteries as storage have considerable loss. Not trying to discourage you, just hope you have realistic expectations.

    Yesterday in discussions.. Two 12v panels with a 7.7 amps each (when in parallel) equals out to 180 watts going into the battery.. per Cariboocoot. Its volts * amps = wattage.. then multiply x 5 hours of daylight (avg) = 900 watts..


    Its $220 for the 1 12V 200AH battery.. I don't have any warehouse stores within 250 miles of the location..

    A small box fan (or 2) and some CEL bulbs at 9w each and a laptop..

    Thats all I need to run.. for about 7 hours a day.. and not even the lights during the day as I have 2 skylights in my 'cabin'..

    I'll be in way South West TX.. (79855 zipcode) thinking alot of SUN..


    Al
  • Sparkletron
    Sparkletron Solar Expert Posts: 71 ✭✭✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...

    If this thread is a continuation of an existing thread, then why not simply continue the discussion there?
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...
    If this thread is a continuation of an existing thread, then why not simply continue the discussion there?

    I thought I was GTG in that thread.. obviously not..

    Yesterday.. Cariboocoot said how Trojan recommends as a general rule of thumb, the total amps from your PV panels should be sized between 10% and 20% of the total amp-hours (Ah) of the battery pack.

    Now with this revised setup will I be OK with 2 of the 6v T105's?? and get to the recommended 10% number???


    Albert
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...

    Ah, kind of mixing the formulas.

    Panel efficiency rating is based on "nameplate rating" * "typical efficiency of panels & controller"
    That's how we get 280 Watts * 77% = 215 Watts.

    This doesn't apply to PWM charging or daily Watt hour "harvest" but is key to understanding panels' "real" output and determining conditions for MPPT controllers. I probably confused you by flinging tons of numbers and formuli at you. Sorry. :blush: We were discussing many possibilities including MPPT and even I get confused.

    A PWM controller is basically a switch and will only pass the peak current available from the panels irrespective of Voltage. So 7.82 * 2 = 15.64 or 16 Amps. The panels on their own can not produce more current than this except going into a short circuit. The panel Voltage will be "pulled down" to battery Voltage + losses from wiring/controller/heat. This is why "12 Volt" panels have a Vmp around 17-18 Volts: after going through wiring there is hopefully enough Voltage left over to be above the battery Voltage and thus provide charge current. The MPPT controllers can sneak a bit more out if the wiring is efficient enough and can take advantage of cooler panel temps (which increase Voltage).

    One of these days we've got to post the whole lengthy formula with all the variables. Maybe in time for Halloween. :p
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...
    ywhic wrote: »
    Trojan recommends as a general rule of thumb, the total amps from your PV panels should be sized between 10% and 20% of the total amp-hours (Ah) of the battery pack.

    Now with this revised setup will I be OK with 2 of the 6v T105's?? and get to the recommended 10% number???

    Thanks for clarifying.. I was talking to MorningStar this morning and they said the same on the PWM controllers.. (pretty much straight in and stright out..)

    So based on all that can I get the 10% number Trojan recommends if I utilize 2 of their 6V T105's in series with this setup??


    Al
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...

    Ouch, south west Texas on fans...

    I've lived in Missouri on a setup very similar to what your suggesting, in my case 220 watts of panels, 2 golf cart batteries, old SCSII(?) charge controller, 200 watt MSW inverter. I ran laptop, a 13 watt CF lamp (had 2 but rarely ran more than one) MP3 player, Fan O2cool, VCR and TV once in a while(not much)

    I don't think it's a bad idea to plan ahead and grow the system somewhat, add a combiner box(breakers or fuses) when/if you add panels, you could start with a MSW inverter, I had no problems, but I think you mentioned a pump which I would want a pure sine wave. all those car inverters people sell for using your laptop in cars are MSW. I think some people have had a buzz from CF lights, but I never did.

    Might pick up those golf cart batteries when your taking a trip, or if you have a friend making a trip, or in rural areas you might find that stores make a trip to pick up supplies at Sams/Costco. If your near Big Bend, you may need to travel for other needs at times.

    O2cool fans are very effiecient and pump out a lot of air. I didn't have a problem with MSW inverter with these as they are 12volt and run off a wall wart. Their new wall warts don't get nearly as hot(read more effiecent) than their old ones.

    Be sure to place your cabin in the shade(if you can find any) might even build an seperate roof over to help prevent the cabin for gaining heat. Might build your own 50% or more of the cost of those cabins is labor and transportation. I build my insulated wired/finished(mostly) 6" wall 8" floor 14' height 10x16 cabin for @$2600 5 years ago.

    If this is a weekend retreat, or you take regular trips it might make it easier on your batteries, I had reasonable luck but I typically spent 1 day a week away from the trailer(220 watt system, before I bailed and built the cabin so I could have AC.)
    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.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...
    ywhic wrote: »
    Yesterday.. Cariboocoot said how Trojan recommends as a general rule of thumb, the total amps from your PV panels should be sized between 10% and 20% of the total amp-hours (Ah) of the battery pack.

    Now with this revised setup will I be OK with 2 of the 6v T105's?? and get to the recommended 10% number???

    You will get 8% peak charge current with a couple of golf cart/T105 batteries. These will be 220 to 225 Amp hours. 8% is close enough to 10% that with monitoring (watch the SOC, SG, and water level) and occasional equalization charge (which your panels would be capable of) you will still get years of good service from them, especially as you would only be discharging them about 25%.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...

    Well NA Sun has the T105's for $155 each.. x 2 would be $310 (then the horrible shipping.. lol)

    Still it would give me a deeper reach I think then a single 200ah 12v..

    Things to ponder.. and I found a Costco in El Paso.. only 120 miles away (1 direction).. this may solve all the battery issues. ;)
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...
    ywhic wrote: »
    Well NA Sun has the T105's for $155 each.. x 2 would be $310 (then the horrible shipping.. lol)

    Still it would give me a deeper reach I think then a single 200ah 12v..

    Things to ponder.. and I found a Costco in El Paso.. only 120 miles away (1 direction).. this may solve all the battery issues. ;)


    Found a NAPA in town.. they have a 186AH 6V Battery #8144 (replacement for T-105).. for $118 and $20 for core..
    Another website said its the same as the Exide E3600 and Sams Club Stowaway STGC2 battery you folks I think were talking about..
    Sams has it for $80 and core.. but not available in TX (per there website)..

    That just made my YEAR pretty much..

    Anyway thanks for ALL the help and getting me somewhat straight as to what I may need later in the fall for this adventure...

    Keep you folks posted..


    Al
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Was going 420w @ 12v but opted for 280w @ 12v...

    Sams (and I think Cosco) will often take car batteries as core's for deep cycle, I think you can get a one day costco or sams club card for @$20, I'd check before you travel. Might even get an introduction card for free...

    Another option, might be to see what other auto parts store could get them for.
    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.