I Need Help On My Setup

Hello everybody, This is my first post so please forgive my ignorance. I just bought all this and haven't installed it yet, however I have a couple questions. Is an 80 watt panel going to come close to keeping my battery listed below charged? I'm running a Sunforce 30 Amp Digital Charge Controller from 80 WATT SOLAR 12V SOLAR PANEL to my battery (listed below) then I have AIMS 2000 watt pure sine wave 12 volt. I live in Florida so my mane concern is running the a/c on top of the roof. I have no idea what power it uses but I'm assuming it's the largest draw. I have a good generator but would rather not use it. Thank you:D

Voltage: 12V AGM

Lifeline Deep Cycle RV Battery - GPL-8DL
Rated Cap. Amp. Hrs. – 20 Hr Rate: 255
Length – in(mm): 20.76
Width – in (mm): 10.89
Height – in (mm): 9.73
Weight: 162.00lbs/73.60 Kgs

Cold Cranking Amps
68° - 1975
32° - 1675
0° - 1350

Minutes of Discharge
25 Amps 475
15 Amps 825
8 Amps 1670


  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: I Need Help On My Setup

    To start I going assume the you are in a RV trailer/motor home. We need to know if the AC 120 volts or 220 volts. You need to get the manual out. If you do not have one. Look for a tag on the AC unit. I think they place in under in intake filter/grid.

    Solar panel is way too small for that size battery. You should be using 150-300 watts of panel.
  • arkieoscararkieoscar Solar Expert Posts: 101 ✭✭✭✭
    Re: I Need Help On My Setup

    I've had several RVs and all had 110v AC units and all drew around 1700-1800 watts and took almost 30 amps to start. If the inverter will start it, it would be maxed out running and the battery you are using would be deep cycled in very short order even with full sun on the 80 watt panel.
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: I Need Help On My Setup

    At a quick glance, to answer your question,,,NO! your 80 watt panel won't even make a dent in the draw, especially if you include the ac.

    Do the math, figure out the loads, the expected amount of sun, the number of days of reserve you need etc. We run 210 watts of panel, live off grid full time with VERY little draw, a few lights, fans, water pump modem etc. No TV or power tools, no microwave. With that, we seldom have to run the generator.

    As we say all along, conservation first second and third, followed by PV solar, and then do (and understand) the math.

  • BB.BB. Super Moderators, Administrators Posts: 31,156 admin
    Re: I Need Help On My Setup

    Short answer is that to run an A/C system (even a "smaller" RV unit) is going to take more power than your solar panel or your battery bank will be able to supply (for any length of time)...

    For example, lets guess that your AC unit uses 12 amps at 120 VAC... That would be:

    12amps * 120 VAC = 1,440 watts...

    And lets guess you want to run that for 6 hours per day during the summer--so we need to add "Time" to the equation:

    1,440 Watts * 6 hours = 8,640 Watt*Hours per day

    And since this is summer when you need the AC unit, and that you have Datona Beach FL type weather. Using this link to find out how much solar power you can generate/will need (using all defaults, except using a derating factor of 0.52 for off-grid system), to supply 8.64 kWhrs per day during 6 months of "summer", you would need approximately 3,500 watts of solar panels (I have 20 full sized 175 solar panels on my roof--exactly the same rating).

    And an appropriately sized battery bank (using 3 days of no-sun, and a 50% maximum discharge = a factor of 6x your daily use):

    8,640 watts * 6 1/80% inverter efficiency= 64,800 Watt*Hours of storage.

    Using your RV battery, 12 volts at 255 Amp*Hours:

    (64,800 Watt*Hours / 12 volts) / 255 Amp*Hours = 21 batteries required

    So, if this A/C use is for a trailer/RV, you could not pack enough solar+batteries in it to supply your power. If this was an off-grid cabin, it will take a substantial investment in design, parts, and installation to give you a useful installation (there are issues, like don't use RV batteries, for as system this large you would be looking at 24 or 48 volt battery bank/inverter, etc.).

    Your 80 amp solar panel will run a smallish A/C unit for about:

    80 watt * 6 hours of sun * 52% efficiency / 1,440 watt*hours = 0.173 hours or 10 minutes per day

    Your choice is to run the generator or build out a very large solar system... Just to guess on generator usage (excluding oil, maintenance costs):

    (1,440 Watt*Hour / 5,000 watts per gallon of fuel) * $4 per gallon of fuel = $1.15 per hour cost in gasoline

    You may do better with diesel--but it will probably be roughly the same price (or a bit less) to run your A/C.

    And, to measure your power use, look at getting a Kill-A-Watt meter (120 VAC, 15 amps maximum--plugs into a typical North American home AC outlet)) to measure your loads over time (for example, a fridge takes 110 watts, but runs less than 1/2 the time, so the average power usage during the whole day is less than just taking the "peak power" * 24 hours per day).

    Does this help? (not really--I know). :cry:


    PS: You did not say if you where doing this for a Home with Utility power to save money or if this was an off-grid application (or even a hybrid type situation... Grid available, but want to survive 2-4 weeks without power after a big hurricane hits).

    Depending on your needs, the details (and costs) will be different.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,089 ✭✭✭✭✭
    Re: I Need Help On My Setup

    Here's some suggestions:

    To figure your loads, use this battery sizing calculator : (javascript required)

    Also, of note, beware the "diagrams" at the battery sizing tool site. They show a poor way to wire the batteries. Connecting on the "diagonal" will extend the life of the batteries by helping share the loads. Here's a great writeup on how to properly wire your battery bank (diagonally) http://www.smartgauge.co.uk/batt_con.html

    I've never heard of Sunforce 30 Amp Digital Charge Controller. Looking at their website, and all the manuals there: http://www.sunforceproducts.com/english/details.asp?id=74 I was not surprised to have the manual confirm it's chinese junk. While it does claim to have a 3 stage charge system, and PWM regulation, for spending $99, I'd return it if possible, and obtain a Xantrex C35 35 Amp Charge Controller http://store.solar-electric.com/tracc35solch.html Sale price: $98.00 This is a TRUSTED brand, works well, and likely better for your batteries. It also will accept a BTS (battery Temperature Sensor) which will help deliver a custom regulated charge to your batteries, regardless of the temperature of the the controller.

    However, there are newer style charge controllers, that use a MPPT regulation, and for your size panel you don't need a 30A unit.
    controllers http://store.solar-electric.com/chco.html
    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: I Need Help On My Setup

    Thank you everyone for your information. I'm still trying to digest all the information, by that I mean understand what your saying. I am determined and appreciative:D

    Oh the solor unit is for my rv, thanks for the info

    This is off the subject but!
    I was in (in home sales) home improvements for 15 years. In my personal opinion I think theres a mint to be made in the solar industry with energy charges as high as they are not to mention the environment. I know I could rationalize the cost of a good quality solar installation to a perspective buyer. If any of you are interested in being a partner in a joint venture (business) I would be interested in talking. I could handle sales and marketing and managing but would need the expertise and knowledge to help me put together a presentation understandable to the average buyer.
  • System2System2 Posts: 6,290 admin
    Re: I Need Help On My Setup
    FIREHAWK wrote: »
    [no need to quote the entire first post in this thread--Bill B.]

    Since Im putting this battery in an rv do I need to install it in some kind of box or can I secure it in a storage area under the coach??
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