Announcement

Collapse
No announcement yet.

RV system sizing & practicality?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • RV system sizing & practicality?

    Hello Everyone,

    I am preparing my travel trailer for a 2-3 month road trip. A month or more will be in Mexico. This will be my first RV trip to Mexico and have been told by frequent Mexico travelers that many of the places I plan to visit will have power quality issues. Over/under voltage, frequent power failures and limited current hookups (10-15amps).

    My last RV had an 8kw diesel generator, 2-8D batteries and a 2kw MSW inverter. I found that, in the absence of power hookup, running the generator for 45-60 minutes in the morning to accommodate heavy loads (hair dryer, coffee maker etc) and battery charging would keep me well supplied with power. I comfortably spent up to 3 weeks at a time without shore power. At that time diesel prices were under $1 a gallon.

    My current rig is MUCH more basic. 3kw generator and a single group 27 deep cycle battery.

    I was looking at adding a single 8D and a 1kw inverter. While looking around at inverters I stumbled across some very reasonably priced solar gear and thought "why not add 300-400 watts of solar capability to reduce generator runtime?".

    Then my 6cubic foot propane fridge died. Replacement cost $1200..... I can fit a 10.7ft apartment fridge in the same space with minor cabinet mods. Cost $404.

    I asked the fridge manufacturer for locked rotor and run current. Their response was "120volts@15 or 20amps". Not quite what I was looking for.... The Energy Guide for the fridge indicates 386kWh annually. A bit over 1kWh per day.

    Now I am considering 500-600 watts of solar capacity and a400+ a/h battery bank and a 1500-2000watt PSW inverter.

    My expectation is to greatly reduce generator runtime and support the refrigerator completely on days that I am away from the trailer.

    What do you all think?

    Thanks

    Steve

  • #2
    Before I would do anything is get your RV equipped with a battery Isolator so you can charge the house batteries with the vehicle alternator while running. That will produce a lot more power than panels will for any length of time. $60 will do more work in a few hours than $2000 worth of panels and equipment can do in a week.

    The fridge you are looking at is extremely inefficient. It uses more power than my 30 cubic feet LG French Door model uses. A fridge that size should only use 1/4 of that power.
    MSEE, PE

    Comment


    • #3
      Originally posted by Sunking View Post
      Before I would do anything is get your RV equipped with a battery Isolator so you can charge the house batteries with the vehicle alternator while running. That will produce a lot more power than panels will for any length of time. $60 will do more work in a few hours than $2000 worth of panels and equipment can do in a week.

      The fridge you are looking at is extremely inefficient. It uses more power than my 30 cubic feet LG French Door model uses. A fridge that size should only use 1/4 of that power.
      Thank you for your response.

      I do intend to charge my house batteries from my tow vehicles alternator. Unfortunately the current carrying capacity of the 12v connection between the tow vehicle and the trailer is limited. Around 10-20amps. Also, I will be traveling 6-8 hours every 2-7 days. That will severely limit the charging capability from my tow vehicle.

      I would greatly appreciate it if you would point me to an affordable and more efficient refrigerator. My primary limitation on the fridge is that it be 24" wide or less.

      Thanks again.

      Steve

      Comment


      • #4
        http://www.vfamerica.com/eng/index.html link for refrigerator

        It will be worth the effort to run a new wire for more charging current.

        Are you ready to spend thousands of dollars for what a generator can do on several gallons of gas?

        3x 250w grid tie panels
        Morningstar MPPT 60a
        Sun xtender pvx-4050ht x2
        Iota dls-55 ac charger or inverter charger

        If you want a really nice inverter with a transfer switch the Magnum Energy ms-4024RE is awesome. It is way overkill on sizing but you can program limits on all currents.


        I have found more panel to be better on an rv to extend your charging time later in the day. I will have 1500w on my trailer by spring.

        Comment


        • #5
          Originally posted by FlyLow View Post
          http://www.vfamerica.com/eng/index.html link for refrigerator

          It will be worth the effort to run a new wire for more charging current.

          Are you ready to spend thousands of dollars for what a generator can do on several gallons of gas?
          Very nice fridge!!!

          Unfortunately it costs 4 Times what the other one I was looking at and, as far as I can tell, it would consume .96kWh/day compared to 1.08kWh/day on the Whirlpool unit.

          If I run an additional charging circuit from the tow vehicle and want to accommodate 50 amps I will need 6awg minimum. I am concerned that between the 50-60 feet of wire and the resistance of the receptacle/plug that the voltage drop may be an issue. Perhaps going with 4awg would be best? Can you recommend an appropriate plug & receptacle for 12v @ 50amps and accommodate 4awg conductors? Keep in mind that my run time on my tow vehicle will be 6-8 hours / 1-2 days a week.

          My generator is the Honda EU3000i. One of the quietest generators I have ever seen. I still don't like to listen to it run all day. To avoid excessive run time I will need to stick with a propane fridge or add solar to support an electric fridge.

          My original plan was to add batteries, charger and inverter. When I saw 400 watt solar packages (pwm) in the $600-800 range and 500watt solar packages (mppt) in the $1000-$1500 range I thought that may be a worthwhile investment. Then my propane fridge died and I started looking at alternatives.

          I see 3 options but am open to suggestions.

          1- Replace the failed fridge with a like 6cu ft unit, add an 8D battery,1000watt inverter and battery charger. Cost $1900-2000.

          2- Same as above and add 400 watts of solar. Cost $2700-$2800.

          3-Replace the failed fridge with the 10.7cu ft Whirlpool. Add 2-3 8D batteries (or equiv), 1500-2000watt inverter, battery charger and 500watt solar package. Cost $3000-3500.

          I think 500 watts of solar capability (assuming solar insulation of 5 or more) should support the fridge. Additional loads will require some generator run time.

          Comment


          • #6
            I just found a 600 watt package (mppt controller) for $1129 from a well reviewed vendor: https://www.renogy-store.com/600W-Pr...remium600d.htm

            Thoughts?

            Comment


            • #7
              What fridge model are you looking at? My VF fridge uses 65w running and it only runs 10hr every 24hr. The non stainless versions are less expensive.

              Looks like another junk kit. You get what you pay for.

              Comment


              • #8
                Originally posted by Sunking View Post
                Before I would do anything is get your RV equipped with a battery Isolator so you can charge the house batteries with the vehicle alternator while running. That will produce a lot more power than panels will for any length of time.
                Sunking

                That joke gets funnier every time you tell it.

                Comment


                • #9
                  Originally posted by FlyLow View Post
                  What fridge model are you looking at? My VF fridge uses 65w running and it only runs 10hr every 24hr. The non stainless versions are less expensive.

                  Looks like another junk kit. You get what you pay for.
                  http://www.12volttechnology.com.au/v...e-freezer.html

                  http://www.homedepot.com/p/Whirlpool...SFAW/203554368

                  "Another junk kit" Do you have any info on this (well reviewed) vendor? Or is this just a general statement?

                  Thanks.

                  Comment


                  • #10
                    The Vtirifrigo website gives current draw (compressor running) but no duty cycle or average daily power consumption. Searching for details I found 2 numbers. One indicated an average consumption of 40watts. The other indicate less than 1 kWh per 24 hours.

                    The first was a bit vague but if you take it to mean 40 watts average over 24 hours then you would consume 960 watt hours over a 24 hour period. A bit less than 1kWh per 24 hours.

                    Edit: The Vitrifrigo site says 65watts for the DP2600. Same as what yours uses. The question remains:duty cycle? If only running 10 hours a day then at 650watt/hours daily. Compared to 1080 with the Whirlpool that starts to look more attractive.

                    Comment


                    • #11
                      Originally posted by PNW_Steve View Post
                      I just found a 600 watt package (mppt controller) for $1129 from a well reviewed vendor: https://www.renogy-store.com/600W-Pr...remium600d.htm

                      Thoughts?
                      Be careful. That charge controller has a 500watt limit for 12volt system and 1000watt for 24volt. So with those 600watts of panels you would need to use a 24volt battery system.

                      Also the max solar input voltage is 100VDC so if you could use 5 of those panels wired in series as long as they don't exceed 20volts each.

                      Comment


                      • #12
                        Sharp 250w panels $279 each x3 = $837
                        Morningstar mppt 60a $500
                        Pvx-4050ht x2 = $1200 if you need more battery than this the best way would bd to use 2v batteries.
                        Iota charger $145
                        Combiner, breakers, etc $350ish

                        Use the geny if you need ac

                        Comment


                        • #13
                          Originally posted by SunEagle View Post
                          Be careful. That charge controller has a 500watt limit for 12volt system and 1000watt for 24volt. So with those 600watts of panels you would need to use a 24volt battery system.

                          Also the max solar input voltage is 100VDC so if you could use 5 of those panels wired in series as long as they don't exceed 20volts each.
                          I didn't catch that.

                          Could you arrange 6 panels in a 2x3 series/parallel configuration. That should yield a ballpark maximum of 36volts and 24 amps.

                          Comment


                          • #14
                            Originally posted by PNW_Steve View Post
                            I didn't catch that.

                            Could you arrange 6 panels in a 2x3 series/parallel configuration. That should yield a ballpark maximum of 36volts and 24 amps.
                            You can use all 6 panels in a 2x3 config but will have to set it up to charge a 24volt battery. That charger has a limit of 500 watts for a 12volt battery.

                            An MPPT type charger doesn't really care what the input current is, just the total watts. Watts in = Watt out. So 600 watt / 12 volts = 50amps which exceeds that 40 amp charger. Now 600 watt / 24volts = 25amps

                            The system looks to be at a good price but it has limitations. Just thought I would give you a heads up.

                            Comment


                            • #15
                              Originally posted by SunEagle View Post
                              You can use all 6 panels in a 2x3 config but will have to set it up to charge a 24volt battery. That charger has a limit of 500 watts for a 12volt battery.

                              An MPPT type charger doesn't really care what the input current is, just the total watts. Watts in = Watt out. So 600 watt / 12 volts = 50amps which exceeds that 40 amp charger. Now 600 watt / 24volts = 25amps

                              The system looks to be at a good price but it has limitations. Just thought I would give you a heads up.
                              Thank you for clearing that up for me.

                              I see some merit in running a 24 volt system. Unfortunately supporting our 12 volt loads becomes problematic.

                              Comment

                              Working...
                              X