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ApexAZ's avatar
ApexAZ
Explorer
Sep 13, 2021

Solar system with both 12v and AC inverter

So we should be picking up our new Fuel Toyhauler on Saturday and we need to install a solar panel kit with inverter.

I have about a zillion questions regarding solar, but my most pressing question is in regards to AC inverter and DC converter.

I have to use a CPAP machine at night and my particular model doesn't seem to support AC Inverter supplied power. I plan to call them tomorrow to confirm and find out why, but based on their battery use instructions, they say a DC-to-DC converter is needed and AC Inverter is not recommended.

We also want to install an AC inverter to be able to use tv, small appliances, chargers, etc.

So my question is this: could I connect a single battery to both an AC Inverter and a 12v outlet in the bedroom to be used specifically for my CPAP, or will this cause issues having two different types of circuits drawing from the same battery?

Hopefully that makes sense.
  • DrewE's avatar
    DrewE
    Explorer II
    Sep 13, 2021
    There's no problem at all with having the same battery bank supplying both 12V loads and an inverter. That's the most common setup for RVs with an inverter, and in my opinion the most sensible, as it allows you to use all the available battery power in whatever way is necessary without artificial divisions.

    Your CPAP machine would probably be just fine with a pure sine wave inverter; indeed, it would have no way of "telling" that the power is from an inverter and not a generator or the utility. A modified sine wave inverter is a different story altogether. That said, the DC to DC converter will probably be more efficient overall (you'll waste less power than using an inverter and the usual AC power supply).
  • ApexAZ's avatar
    ApexAZ
    Explorer
    Sep 13, 2021
    DrewE wrote:
    There's no problem at all with having the same battery bank supplying both 12V loads and an inverter. That's the most common setup for RVs with an inverter, and in my opinion the most sensible, as it allows you to use all the available battery power in whatever way is necessary without artificial divisions.

    Your CPAP machine would probably be just fine with a pure sine wave inverter; indeed, it would have no way of "telling" that the power is from an inverter and not a generator or the utility. A modified sine wave inverter is a different story altogether. That said, the DC to DC converter will probably be more efficient overall (you'll waste less power than using an inverter and the usual AC power supply).


    Excellent. Thank you!

    In a video I watched, the guy moved his lithium battery to inside the storage compartment and closer to the inverter.

    Is this a fire hazard?
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    Sep 13, 2021
    ApexAZ wrote:

    In a video I watched, the guy moved his lithium battery to inside the storage compartment and closer to the inverter.

    Is this a fire hazard?

    There are 2 types of lithium batteries. The large ones that you would purchase are very safe/can not explode/burn.

    IMHO, all-in-one devices (solar charge controller, battery, inverter) are NOT the best "bang to the buck". Look up Will Process on YouTube. Lot's of good videos on solar, batteries and inverters.
  • wanderingaimles's avatar
    wanderingaimles
    Explorer
    Sep 13, 2021
    Your TH likely already has a Pure sine wave inverter, for powering TV's or the fridge. In my Winnie I simply tapped the TV outlet in the bedroom with an extension cord for the CPAP on nights we are not connected to shore power.
  • ApexAZ's avatar
    ApexAZ
    Explorer
    Sep 13, 2021
    wanderingaimlessly wrote:
    Your TH likely already has a Pure sine wave inverter, for powering TV's or the fridge. In my Winnie I simply tapped the TV outlet in the bedroom with an extension cord for the CPAP on nights we are not connected to shore power.


    I should learn more from the tech guys when they do the walkthrough on Saturday, but the salesman didn't think so. I am not sure if the TV is 12v, or if maybe the generator has an inverter connected to it somehow? I really have no idea. My understanding is the generator needs to be running to power things like the AC, tv, outlets, etc. So maybe it does have an inverter and the salesman just doesn't know?

    The spec sheet only lists a 55A converter and 30A shore power. I'm not even sure why those figures are different, which tells you how ignorant I am on the subject lol. I'm currently drowning in solar info and looking at brands like Victronic, Renogy, GoPower, etc. It's overwhelming.
  • dodge_guy's avatar
    dodge_guy
    Explorer II
    Sep 13, 2021
    Check out DIY Solar with Will Prouse on You Tube. He will have all the answers you need. Very good for beginners.
  • DrewE's avatar
    DrewE
    Explorer II
    Sep 13, 2021
    The 55A for the converter is the maximum 12V DC output current (for charging the battery and powering 12V devices when there's 120V AC power available). The 30A shore power is a 30A 120V AC connection. 55A at 12V DC is 660W of power that the converter can, well, convert. The shore power connection is capable of supplying up to 3600W. More generally, for the same power, you need a proportionally greater current at lower voltages.

    If you need to run the generator or be connected to shore power to have 120V AC electricity available, then you don't have an inverter working.
  • wanderingaimles's avatar
    wanderingaimles
    Explorer
    Sep 13, 2021
    I would not worry too much, you do have simple options.
    IF the trailer does not have an inverter already, you can also power most cpap units off of 12 volts. 12 volt cords
    If your machine has a "brick" in the regular power cord, chances are that it actually runs on 12 volts, making these cords a simple solution.
  • ApexAZ's avatar
    ApexAZ
    Explorer
    Sep 16, 2021
    DrewE wrote:
    The 55A for the converter is the maximum 12V DC output current (for charging the battery and powering 12V devices when there's 120V AC power available). The 30A shore power is a 30A 120V AC connection. 55A at 12V DC is 660W of power that the converter can, well, convert. The shore power connection is capable of supplying up to 3600W. More generally, for the same power, you need a proportionally greater current at lower voltages.

    If you need to run the generator or be connected to shore power to have 120V AC electricity available, then you don't have an inverter working.


    Thanks!

    Yeah, I confirmed there is no inverter. We need to run the generator to power the outlets, microwave, ac, etc.

    We'll check out solar options in the coming months.

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