Noob PVA Selection/Wiring Questions

Hi! I just registered for this forum. Seems like there are some people here who know what they're talking about in regards to installing solar systems.

My partner and I are doing a bus conversion. We're in the planning stages :confused: and we're thinking of using the following components, but are unsure of (several things including) which solar panels would work best with the controller, and how best to wire them for optimal use with the other pieces. (was eyeing these pups, but don't know...)

Any advice would be very much appreciated. Thanks!

1. Magnum Energy MS2812
2800 Watt Sine Wave, 12 Volt DC Input With 125 Amp Charger
http://www.solar-electric.com/maenms2020wa1.html

2. Morningstar TriStar 60 Amp MPPT Solar Charge Controller
http://www.solar-electric.com/motr60ampmps.html

3. (4) of these guys, wired in series/parallel for 12volts/~800 rated AH
Concorde AGM PVX-4050HT Sealed Deep Cycle Battery, 405 Amp Hour, 6 Volt
http://www.solar-electric.com/pvx-4050.html

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Noob PVA Selection/Wiring Questions

    Welcome to the forum!

    Now stop. Before you spend any money on anything figure out what you intend to run with the system. Nothing is more important to getting the design of an off-grid system right than accurately determining the loads.

    You need to know the maximum Watts to be supplied at any one time (everything that will be running all at once) and the total Watt hours you'll be using in a day. If you have the things you want to run already you can plug them in through a Kill-A-Watt meter and get some real-world readings on power consumption. This will save you a lot of hassle, headache, and disappointment.

    There's nothing wrong with any of the equipment you mentioned (except that 2800 Watts is a tad high to expect from a "12 Volt" system), but let's make sure it will suit your needs first, eh?
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Noob PVA Selection/Wiring Questions
    faraday wrote: »
    Hi! I just registered for this forum. Seems like there are some people here who know what they're talking about in regards to installing solar systems.

    My partner and I are doing a bus conversion. We're in the planning stages :confused: and we're thinking of using the following components, but are unsure of (several things including) which solar panels would work best with the controller, and how best to wire them for optimal use with the other pieces. (was eyeing these pups, but don't know...)

    Any advice would be very much appreciated. Thanks!

    1. Magnum Energy MS2812
    2800 Watt Sine Wave, 12 Volt DC Input With 125 Amp Charger
    http://www.solar-electric.com/maenms2020wa1.html

    2. Morningstar TriStar 60 Amp MPPT Solar Charge Controller
    http://www.solar-electric.com/motr60ampmps.html

    3. (4) of these guys, wired in series/parallel for 12volts/~800 rated AH
    Concorde AGM PVX-4050HT Sealed Deep Cycle Battery, 405 Amp Hour, 6 Volt
    http://www.solar-electric.com/pvx-4050.html

    Don't spend your $$ yet.

    With what you are talking about, why not go to a 24V system. Batteries in series always works better than trying to get parallel ballanced. And the inverter will be happier with 2x the voltage droop capacity, and half the amps. (that a 12V inverter would need)

    If getting the Tristar MPPT , also get the remote battery temp sensor, and the digital meter panel (replaces the blank front panel) Yes, extra $$, but you wont have to log into a web page to see what the batteries are doing. And at 24V, you get twice the watts (1440w) , as at 12V (720w) charging capacity

    What is your charge source ?? With the batteries you listed, you should have about 700 - 900W of PV to keep them happy, and maybe a small genset (auto-throttle inverter type) to manage on cloudy days.

    But even first, you need to know what your loads are, to size the batteries properly.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2System2 Posts: 6,290 admin
    Re: Noob PVA Selection/Wiring Questions

    Thanks Mike & 'Coot.

    Hadn't considered 24 volts. Mind blown. Basically we chose those 6volt AGM batteries in that configuration because they fit our requirements and the space/weight restraints of an RV.

    We have a Kill-A-Watt and we are assuming that we can get by using 100 amp hours per day (though hopefully less). We're planning on using propane for cooking and water heater, mostly DC and LEDs for lighting. We don't plan on having any AC phantom load.

    We'll have a Honda eu1000iA (or maybe 2) as backup and for air conditioning.

    I went to the Morningstar website and tried to use their calculator. I think I read somewhere that the amps coming from the solar panels are more crucial than the volts. :confused: erg.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Noob PVA Selection/Wiring Questions

    A 2800 watt inverter is really a no go on a 12 vdc system, requiring wire sizes for ~ 250 amps with the requisite line loss. Doubling the voltage to 24 would reduce that to ~125 amps.

    Besides, what are you planning on running on the inverter on a Bus any way. We live just fine with a 300 watt inverter. A 1000 watt inverter would be more in line with what one might expect. Also, please understand that running a A/C system, or coffee pots or electric stoves and even micro waves on a smallish battery based system are also no no's especially if you are primarily charging with PV.

    Please also note the 50%X4 rule. Take the name plate rating of the PV, divide that number by 2 to account for all system and wiring loses then multiply that by 4 to account for the average number of hours of good sun one might reasonably expect per day on average over the course of the year.

    So a 300 Watt RV installation might look like this,, 300/2=150*4= 600 watt/hours/day. (or 2.4 kwh/day) In a typical RV installation the numbers get even worse, primarily because the panel orientation is almost never ideal. Additionally, the biggest loads on most RVs is A/C loads so parking in the shade is often more palatable than parking in the sun.

    The mistake most people make when delving into PV is over estimating the amount of solar energy they can actually harvest, whilst at the same time underestimating their load.

    Good luck and keep in touch,

    Tony

    Ps edit after your previous post. 100 ah/day at 12 volts is ~ 1.2 kws,, about double what said same 300 watt system might produce. Also, I don't think that 2 Honda Eu 1000s will run a roof top A/C unit. If memory serves they require well over 2 kw to run. 2 Eu1000s will only put out a combined ~1800 watts with a few extra for surge, but not enough to start a roof A/C system. You might think about an unconventional installation of a Mini-split A/C system.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Noob PVA Selection/Wiring Questions
    faraday wrote: »
    Thanks Mike & 'Coot.

    Hadn't considered 24 volts. Mind blown. Basically we chose those 6volt AGM batteries in that configuration because they fit our requirements and the space/weight restraints of an RV.

    We have a Kill-A-Watt and we are assuming that we can get by using 100 amp hours per day (though hopefully less). We're planning on using propane for cooking and water heater, mostly DC and LEDs for lighting. We don't plan on having any AC phantom load.

    We'll have a Honda eu1000iA (or maybe 2) as backup and for air conditioning.

    I went to the Morningstar website and tried to use their calculator. I think I read somewhere that the amps coming from the solar panels are more crucial than the volts. :confused: erg.

    Well ... both Amps and Volts are important. Maybe what you read was trying to explain that PV's are a current source (Amps) rather than a Voltage source. The Volts will shoot up instantly the minute they get any light, but they don't really produce any power (Watts = Volts * Amps) until they get some strong, direct sunlight. Panels have lots of ratings, including 3 Voltage ratings and 2 current ratings. Even then some of those figures vary depending on conditions!

    100 Amp hours isn't much. You'd be surprised at how easily that number is surpassed just because someone left a light on or something. I can understand your wanting to use 12 VDC if you were planning on having some charge feed from the bus' system, but you really want to keep the Watts down with 12 Volts so as to avoid the problems with high current.

    Those Hondas are nice units, but like Tony said won't run an AC. Maybe a bigger, RV type gen? You know you can usually get stuff from old campers/RV's pretty cheap. :D
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