Very new to all of this, any help would be appreciated

Kwell
Kwell Registered Users Posts: 7
Just a week ago I didnt know what a terminal or connector was or that wire came in different gauges so please be gentle. I want to install solar panels on my van but cannot afford to have it proffesionally done. Im starting with a 100 watt panel but do plan on getting two more and expanding. I have bought a 30 amp charge controller so I wont have to change it when I install more panels. I have an exide agm battery because I will be keeping it in the van. A 2000 watt inverter.

So here are a few of the questions I have...
Im going to run 10 gauge wire wth a 25 amp inline fuse to the charge controller, after that im a bit confused. Can I run 10 gauge from the charge controller to the battery? Some sights are saying yes, others say 4 gauge and others 2 gauge. It make sense to me to run 10 gauge also from the charge controller to the battery. Since the battery is storing the energy and can send large amounts of amps to the inverter would I use a 2 gauge wire with a 200 amp inline fuse going from battery to inverter? Any help would be appreciated, thanks.

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Very new to all of this, any help would be appreciated

    Sounds like you have a workable plan going for a 200 sf house.

    The first thing to do, is measure how much power you use, or look at your electric bill, and figure how many Killowatt Hours of power, you used the last month.
    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 ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Very new to all of this, any help would be appreciated
    Kwell wrote: »
    Just a week ago I didnt know what a terminal or connector was or that wire came in different gauges so please be gentle.

    We all started there at one time or another.
    Im starting with a 100 watt panel but do plan on getting two more and expanding.

    As you have probably picked up, the larger the current, the thicker the copper wire you need (and lower AWG number)... A 14 awg wire (typical house wiring) is good for 15 amps (per National Electric Code). 12 AWG good for 20 amps, and so forth.

    Another issue with solar and battery systems is voltage drop. So, the longer the wire, the more resistance. The more resistance, the more voltage drop. So, many times, you need heavier wire for longer runs of wiring.

    Normally, you run the long wire from solar panel to charge controller (voltage drop is not critical). And run short/heavier wire from the controller to the battery bank (where you can really only have 0.050 to 0.100 volts of drop (for a 12 volt bank). And very heavy/short wires from battery to inverter (heavy current and less than 1.0 volt drop).

    All this depends on system voltage and the current to be carried in each set of wires (and their length). So, you will need to supply us with a bit more information for us to give you better help.
    I have bought a 30 amp charge controller so I wont have to change it when I install more panels. I have an exide agm battery because I will be keeping it in the van. A 2000 watt inverter.

    A 30 amp 12 volt PWM controller should be good for about 400 Watts of "12 volt" (really Vmp~17.5-18.5 volt) solar panels.

    Note that the size of your battery bank is important... Both for sizing your solar panels/backup charging system, and for how much Surge and hours of continuous power you can get out of your battery bank.

    For most RV installations, a 2,000 watt inverter is way too big. First, because a 100 watt solar panel will supply about 15 minutes worth of power at 2,000 watts. And, most smaller 12 volt battery banks + wiring cannot support 2,000 watts continuous or 4,000 watts worth of current. Lastly, large inverters can waste a lot of power (from 10-20 watts or even more).

    I would suggest that a 300 watt (600 watts for 10 minutes) is a much better size for your needs. The MorningStar 300 watt TSW (true sine wave) 12 volt inverter is usually a great fit for your type of application.
    So here are a few of the questions I have...
    Im going to run 10 gauge wire wth a 25 amp inline fuse to the charge controller, after that im a bit confused. Can I run 10 gauge from the charge controller to the battery? Some sights are saying yes, others say 4 gauge and others 2 gauge. It make sense to me to run 10 gauge also from the charge controller to the battery. Since the battery is storing the energy and can send large amounts of amps to the inverter would I use a 2 gauge wire with a 200 amp inline fuse going from battery to inverter? Any help would be appreciated, thanks.

    If you can give us the panel model name / number and/or Vmp/Imp plus the length of wire run from panel to charge controller (3x total panels?).

    Length of wire from charge controller to battery bank.

    The size/configuration of your battery bank (i.e., 2x 6 volt @ 220 AH batteries in series or 2x 12 volt @ 100 AH batteries in parallel, etc.).

    The maximum load(s) and average loads you wish to use (watts or amps@xxx volts; and hours per day of usage).

    Size of inverter and length of wire between battery and inverter.

    Fuses and breakers are important, but we need to size your system first before defining wire awg and fusing.

    Welcome to the forum.
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Kwell
    Kwell Registered Users Posts: 7
    Re: Very new to all of this, any help would be appreciated

    Thanks for your help. The 100 watt solar panel will be on the roof near the passenger seat. I havent bought the panel yet but have been looking at different models. Then I plan on using a marine water tight deck fitting and running the 10 gauge wire to the back of the van, thats about 10 feet. Then should I use a 4 gauge wire from the charge controller to the battery? They will be very close together. I also thought the larger size inverter would be better when I expand my system. Doesnt it only use power when you have things plugged into it? Dumb question probably. But couldnt I just monitor my battery and not let it discharge below 50%? As for the battery I have the biggest exide that they sell, 750 cold cranking amps and 200 minutes of reserve.

    The reason I went so large is because I also plan on adding a roof ac. The turbokool that can running continuously with just a 60 watt panel is what is advertised. Running on high using less than 5 amps.
  • Kwell
    Kwell Registered Users Posts: 7
    Re: Very new to all of this, any help would be appreciated

    Besides the air conditioner I would be running a tv and dvd player a couple hours per day, low energy refrigerator(power chill), laptop a couple hours per day, recharging cell phone. I have read that you should get a larger inverter than you think you will need do to powe surges, is this true? I wont be running all these items until I get all 3 panels in place. Im hoping 300 watts of solar panels is enough because that is all that will fit on the roof with the air conditioner.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Very new to all of this, any help would be appreciated
    Kwell wrote: »
    Im hoping 300 watts of solar panels is enough because that is all that will fit on the roof with the air conditioner.
    You shouldn't hope, you should know. You will know (and we can help you know) when you provide us more detailed info on your intended power consumption. How much power does your TV, fridge, laptop, etc consume?
    Kwell wrote: »
    I have read that you should get a larger inverter than you think you will need do to power surges, is this true?
    As BB. mentioned, a large inverter uses quite a bit of current just by being turned on. You need to scale down your expectations with 300 watts of panels, especially since the panels, if mounted on a van, will not be optimally oriented for maximum production.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Kwell
    Kwell Registered Users Posts: 7
    Re: Very new to all of this, any help would be appreciated

    Im not really concerned about the power consuption. The only thing that is an absolute must is the air conditioning unit and I know that it will run off this system. If the fridge drains my battery it will become a cooler with ice. I will have the maximum watts that my roof will hold. I just need to know how to get it hooked up without burning down my van.

    I am just confused why I would need a larger wire from the charge controller to the battery. Its a 30 amp charge controller with a 25 amp fuse from the panels to the charge controller. The most that should be coming out of the charge controller to the battery should be 25 amps, so why would I need a heavy wire? Is there back flow current from the battery, doesnt the charge controller protect for this? I see why I would need a large wire from the battery to the inverter because the battery is the power house and can send large amout of amps to the charge controller. I was think a 200 watt fuse but maybe a 150 watt and a 2 gauge wire going to the inverter. 150 amps x 12 volts = 1800 watts, just under the 2000 watts of my inverter. Please correct me if im wrong which I probably am. As for the inverter, I was not aware that it used that much energy just being hooked up, I will have to research that further. Any help to make the fog im in a little clearer would be appreciated.
  • Kwell
    Kwell Registered Users Posts: 7
    Re: Very new to all of this, any help would be appreciated

    Correction, I meant the battery can send large amount of amps to the inverter.
  • Kwell
    Kwell Registered Users Posts: 7
    Re: Very new to all of this, any help would be appreciated

    Sorry about all the typos. I meant amps not watts when referring to the fuses.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Very new to all of this, any help would be appreciated

    Basically, there are transistors, transformer, wiring, electronics in the inverter that all waste some power just making AC power (with nothing plugged in). And larger inverters waste more power (and true sine wave, while better inverters, waste even more power). Sort of like a gasoline powered generator, just to get AC voltage, the motor has to run and consume fuel. And a larger genset with a larger motor consumes even more fuel with zero or light load.

    Also, we have to be careful here--As you say, you don't want to start a fire. For example, you are correct with your math that "nominally", it would appear that 1,800 watts would take 150 amps of 12 volt current (more than the starter on your vehicle). But, "engineers" design for worst case, which would be:
    • 2,000 watts * 1/0.85 inverter eff * 1/10.5 volts minimum operating voltage * 1.25 NEC safety factor for wiring+fuses = 280 amp branch circuit wiring+breaker/fuse
    As you can see, that 150 amps of nominal power use all of a sudden becomes 280 amps. And, many (good) inverters will support upwards of 2x rated output for surge (starting motors), and you are looking at needing to support ~560 amps for a fraction of a second (will not blow a normal 300 amp fuse for short term current surge).

    Because of the very high current and difficulty in wiring up cabling to support 300 amps of current, normally we tell people about the maximum sized inverter we would recommend for a 12 volt battery bank would be ~1,200 watts maximum. Even that size inverter would need around a 175 amp branch circuit (using the above math).

    Given that RV's typical have a smaller battery bank, you would not expect a battery bank to output that much current for very long before the batteries overheat and/or get sucked dead (which is very hard on battery life).

    You can see why the inverter wiring is so critical. The reason that charge controller to battery bank wiring is so important is that the charge controller needs to measure the battery voltage pretty accurately to properly supply charging current an "know" when the battery is full... For a 12 volt battery bank, ideally, you would want no more than around 0.05 to 0.10 maximum voltage drop. At 25 amps and 4 feet of wiring (one way run) using a generic voltage drop calculator:
    • 25 amps of current, 4 feet of wire, 0.05 volts drop => 4 awg wire gives 0.06 volt drop
    Cutting the wire length to 2 feet would drop the wire gauge to 8 awg--A much smaller wire (about 1/2 the amount of copper).

    In the end, it is difficult to design your system in a cost effective and safe matter if we have to support "huge" loads when, in reality, the application probably limits you to 200 watts of continuous load as a practical matter.

    For example. Let's look at your 5 amps @ 12 volt load for cooling. Assume it runs for 10 hours a day/night. Assuming 1 day of battery storage and 50% maximum battery discharge (for longer battery life):
    • 5 amps * 10 hours * 1 day of storage * 1/0.50 max battery discharge = 100 AH battery bank @ 12 volts
    That is a very reasonable sized battery for a small RV. (just a big bigger than a typical starting battery).

    If you need to support other loads, lets assume you use two "golf cart" sized batteries. 2x 6 volt 220 AH. Or 12 volt 220 AH battery bank.

    The maximum continuous recommended power drawn from such a battery bank with an AC inverter would be:
    • 12 volts * 220 AH * 0.85 efficient inverter * 1/8 rate of discharge = 281 watts continuous load for ~4 hours to 50% discharge
    The maximum surge power would be:
    • 12 volts * 220 AH * 0.85 eff inverter * 1/2.5 max surge current for flooded cell battery = 898 watts max surge (around a 450 watt rated inverter)
    Or, about 1/10th the size of your current plans of a 2,000 watt inverter.

    A 300 watt solar array with a 281 watt continuous load, assuming you get ~4 of sun per day (typical summer day in North America) and 0.52 overall system derating:
    • 300 watts * 0.52 eff * 4 hours of "noontime equivalent sun" = 624 Watt*Hours
    • 624 WH per day / (281 watt load * 1/0.85 inverter eff) = 1.89 hours per day = 113 minutes per day
    All of the above is just basic "Rule of Thumb" for solar math. And based on guesses of the size of system that is practical for your RV.

    Of course, I could very well be wrong, but we do need more information to help you out (and not waste your money--we are all pretty cheap folks here).

    Most people underestimate their loads and over estimate how much power they can get from solar. Extreme conservation and understanding of your load/power requirements will help you build a system that will best meet your needs.

    A couple small system thread. One a portable power unit, another a small RV trailer. Similar to what you will be designing/installing:

    Emergency Power

    Basically a very long thread that starts from the beginning with a few vague requirements through design and assembly for a "portable" solar RE off-grid power box.

    And here is another example by Mike90045 called the Solar Monolith:

    attachment.php?attachmentid=384&stc=1&thumb=1&d=1234752636

    attachment.php?attachmentid=385&stc=1&thumb=1&d=1234752653

    Update pictures/information here.

    Here is a nice thread with video from Kevin in Calgary Canada that shows designing and installing solar PV in a small RV trailer.

    -Bill

    PS: Don't worry about the typos... We all do it (at least I do :blush:). Just go back in and edit your post. If it makes a difference, you can bold your corrections.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Kwell
    Kwell Registered Users Posts: 7
    Re: Very new to all of this, any help would be appreciated

    Thanks so much for your help. I will be down grading to a 1200 watt inverter. So if I use a 10 gauge wire with a 25 amp fuse going to the charge controller with about a 10 foot run. Then a 4 gauge going to the battery with about a 2 foot run, then a 2 gauge going from the battery to the 1200 watt inverter with a 175 amp fuse, I should be ok, right? The run on that would be about 2 feet also. Im also confuse on what size fuse to use from the charge controller to the battery, any suggestions?