New to Solar and Beginner Off-Grid Setup

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Comments

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Don't have buyers remorse, learn from what you have, take some time then move up to more comprehensive systems,  but don't advance faster than your knowledge, read, read and read some more, information is not knowledge, but it sure will help you understand what it is you are dealing with, you know the old adage, baby steps, start slow in the beginning, things will fall into place later on.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Something to think about is that you are measuring the wattage on a Kill-A-Watt meter plugged into your inverter. So the 'fan' is using 26.6 watts, but that is NOT your load as it doesn't measure the inverter as a load. The inverter is likely about 85% efficient, so figure another 15% above the 26.6 or around a 30 watt load.

    More on the 'math' is that the battery's amperage is based on a discharge rate of 1/20th of the capacity. as you are drawing 2.5 amp out of a 18 amp battery (18/2.5=) or 1/7.2th of the battery capacity your usable amperage will be decreased.

    I personally wouldn't worry about the amount of usage from the battery, other than to keep it from being completely discharged, The inverter should have some protection from this. The fan may seem like a small load, but it's a pretty big load for your system. There is likely a good bit of voltage sag from that load. To see where you stand voltage wise, you might disconnect the fan and measure the voltage 5 minutes later then and hour later and see how much it bounces back with out being charged. 

    A car radio is normally between 5-10 watts. Motors and heating/cooling things are the most challenging to run off solar.

    I don't think you've done too badly for an experimental system. If you wanted something that is expandable I would have suggested the 165 watt panel from amazon about $180 shipped, and direct you to a 20 or 30 amp charge controller around $30 and a pair of golf cart batteries about $80 each + core charge (Sam's club or Costco). Quite a bit more expensive and you could only add a panel or 2 before needing a larger charge controller (or another one). I'm pleased you have a 'balanced' system.

    Yes, DC loads will bypass the inverter losses, You might go ahead and create a bus bar for dc loads. I really like the O2Cool 10" fans, they draw about .5 amps a 12 volts (6-7 watts) and put out a good bit of air. You could also pickup a car USB outlet and hard wire it in to charge cell phones and other items that can be charge from USB, like tablets. USB output has grown with each new version, USB 1 was .5 amps, 1.1 was 1 amp and 2 is 2.1amps. That said most USB chargeable items will charge off .5 amps. I would recommend just buying a usb corded outlet that plugs into a cigarette lighter attachment and hard wiring it in (the center is positive)

    I see that your inverter has a car cigarette lighter plug, it might be hard wired directly, you might just plug in a dollar store USB adapter to that. You could check to see if it's 'live' with your inverter turned off, with your voltage meter.
    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.
  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
     Dennis461,      And I quote,     "Now, I have an inverter that did not behave properly and the inverter vendor told me to connect the inverter directly to the battery, which in my professional opinion was not correct." What is your profession? I certainly hope it doesn't have anything to do with electronics, Solar or renewable energy if you are giving out this kind of advice.
    To the OP, hook up the inverter anyway you like, you now have been given more than one option.
    My small setup has been running for over two years now.
    I want to be sure the battery is protected from deep discharge as I leave everything connected 24/7.
    So on my setup, my inverter is connected to the load terminals.

    In the medical profession, many people get second opinions.
    Same applies in engineering.

    As for my profession, littleharbor2, shoot me a PM.


    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Most AC inverters have some sort of low battery cutoff.

    The LCB for AC inverters (and what is configured for charge controllers with LCB) are set to protect the inverters themselves from overheating as the battery voltage drops (power=voltage*current; for AC inverter as the battery voltage drops, it must draw more current to keep the constant AC power output).

    Simple (cheap) inverters usually have the LCB set to ~10.5 VDC. That is taking a lead acid battery pretty much dead.

    Higher cost inverters may have LCB set to 11.5 volts, or have it programmable--Such as below 12.0 volts for 30 minutes, 11.5 volts for 5 minutes, or below 10.5 volts for 10 seconds (or use this settings to auto-start a genset).

    Part of the problem is that Lead Acid battery voltage is not a great way to estimate the battery state of charge. Temperature, load current, and even age will also affect the measured battery voltage.

    There are Battery Monitors that use a shunt (precision resistor) to estimate battery state of charge and use dry contacts to signal an alarm or shutdown:

    https://www.victronenergy.com/battery-monitors/bmv-700

    However--Even battery monitors can drift given the right circumstances.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset