Questions about putting batteries, solar panels, and Inverter in an older Motorhome

I have an older Allegro Motor Home that I am restoring and installing solar.
I have a few questions about setting up the batteries, solar panels, and Inverter.
Right now Shore line is 30 amps and connects to a breaker panel. In the rear where the generator sits there is a 30 amp female outlet that runs to another 30 amp female outlet in the compartment where the shore line is stored. When using the generator you plug it into the 30 amp outlet next to the generator and you plug the shore line into 30 amp outlet that is in the compartment that the shoreline is stored.
The starting battery is connected to an isolator that will charge the house battery when the motor is running. There is a converter that will charge the house battery when connected to shore power or generator power.
So here are the questions/wants.
I want to disconnect the 12 volt house battery and replace with 4ea 6 volt batteries setup 24 volt.
I want to only connect the 24volt bank to the solar charger and inverter.
When I am using shore power I would plug the 30 amp plug into a shore power pedestal/outlet and let the converter run the 12 volt lights and etc. but disconnected from the battery so it is not trying to charge the new 24 volt bank
When I am using the generator I would plug the 30 amp female and plug the shoreline into the other 30 amp outlet from the generator compartment. Also run the 12volt stuff from the converter.
When using battery only I would have a 30 amp plug on the inverter and plug it into the 30 amp outlet that runs from the generator compartment to the shoreline compartment. Plug the shoreline into the 30 amp female outlet. Again letting the converter run the 12 volt.
The converter currently connects to a 110 outlet and converts the 110 volt AC to 12 volt DC

Comments

  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    I'm curious about why you want a 24 vdc house bank. How do you plan on using the 24 vdc when everything in the RV is either 12 vdc or 120 vac? Maybe I'm missing something.
    hharvey wrote: »
    When using battery only I would have a 30 amp plug on the inverter and plug it into the 30 amp outlet that runs from the generator compartment to the shoreline compartment. Plug the shoreline into the 30 amp female outlet. Again letting the converter run the 12 volt.

    Let's see if I understand that..... use the 24 volt battery bank to run a 24 vdc to 120 vac inverter AND use the converter to change 120 vac to 12 vdc.... That has a whole lot of conversion losses.... dc to ac and back to dc again. Personally I would rethink that proposed system. We used to have a similar coach and I used 4 6 volt golf cart batteries for the house system. But I used them in a series / parallel system for 12 vdc. Worked well for about 15 years.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • hharveyhharvey Registered Users Posts: 6 ✭✭
    I'm curious about why you want a 24 vdc house bank. How do you plan on using the 24 vdc when everything in the RV is either 12 vdc or 120 vac? Maybe I'm missing something.



    Let's see if I understand that..... use the 24 volt battery bank to run a 24 vdc to 120 vac inverter AND use the converter to change 120 vac to 12 vdc.... That has a whole lot of conversion losses.... dc to ac and back to dc again. Personally I would rethink that proposed system. We used to have a similar coach and I used 4 6 volt golf cart batteries for the house system. But I used them in a series / parallel system for 12 vdc. Worked well for about 15 years.

    I want 24 volt because later I want to remove the system from the RV to use for a cabin/small home after it is completed. I know would most likely have to replace batteries but I would be able to reuse the panels and inverter later
    I had intended to go with 12 volt and I still can because I have not purchased anything yet.
    If I do go with 12 volt I would unplug the converter when using the inverter power, should I use the 30 amp outlet in the generator compartment or would I need to wire the inverter to a sub panel?
  • retepretep Registered Users Posts: 9
    First- I'm still working on my systems, so I am no expert, but I have been studying this for a while and have one system up and running nicely.

    With the inverter plugged in place of the generator, it will use the same electrical panels you have been using, which I assume has been working fine.
    How long and what gauge will the run be from the batteries to the inverter? It is much more efficient to run the long cord from the inverter to the generator plug.
    You want the charge controller and the inverter both as close as possible to the battery bank, but with the batteries vented separately away from them.

    The common converter installed in most RVs will not maintain your 12 volt batteries well. Both of mine just put out 13.6 volts. Since this is a motorhome, I assume you have a 12 volt starting system. Make sure your battery isolator actually isolates. Twice now, with motorhomes, I have found failed isolators with both battery banks permanently mated. I would disconnect my house bank and see how the system functions without them. Leave the cable that went to the battery bank unconnected and insulated. If this is successful, you now understand you are working with 2 separate systems, the new 24 volt panels, charge controller, batteries, and inverter, with the old already functioning system plugging into the inverter's output.

    The only part of the new system that will not readily convert between 12 and 24 volts is the inverter. Do you not already have a 12 volt inverter in the motorhome that has already been functioning? The less you change at one time, the easier troubleshooting will be, and the less likely it will be needed. used mediocre (and bad) 12 volt inverters are all over Craigslist. Ask here (in a new thread) before you buy if unsure of the make or how to test. Also, by the time the cabin is built, will there be newer, better, more fun charge controllers and 3D panels, and will you be loathe to rip a functioning system from your restored Allegro motorhome? Will you want to keep the Allegro as a guest cottage with it's own functioning solar system?

    - Peter.
  • hharveyhharvey Registered Users Posts: 6 ✭✭
    retep thank you for the information

    Right now the only thing I have is a 30 amp 12volt/24volt PWM controller.
    The Mother-ship (Motorhome) currently has a 12 volt battery that needs to be replaced. I have still not decided if I will go with 12 volt or 24 volt yet.
    I am replacing all of the 12 volt light fixtures so I can get 12 volt or 24 LED, the Gas/110 volt Refer and heater still need 12 volt to run the controls
    The Controller, and Inverter will be mounted in the generator compartment that is next to the Battery compartment, so everything will be about 18 inches from the battery bank
    I would prefer to purchase 24 volt panels for a few reasons - I only have room on the roof for 3 panels and I think 3 145 watt 24 volt panels would be better than 3 100 watt 12 volt panels - I read that a 1500 watt inverter would be better on 24 volt system - I would like to use the 24 volt stuff later for pumping water.
    My wife and I only plan to be in the Mother-ship for a year or less. We have our house plans and we know the area were we want to purchase land will be off grid.
    When we complete the home the Mother-ship will be retired we would most likely try to sell it.
  • retepretep Registered Users Posts: 9
    Hharvey- I always think better when I have a foil, I hope some of this might help you.

    If you change the lighting to 24 volts, it seems you will have to leave a 24 volt system in the motorhome when you sell it.

    Your charge controller will handle twice the wattage at 24 volts than at 12, but assuming that you will be purchasing more panels to support an off grid house, do you want to lock yourself into buying more 24 volt panels then? The voltage of your panels, at least to the same charge controller, do need to match. Currently the best price I'm seeing in panels- under .50 a watt- is in 1x2 meter 300ish watt, 40ish volt panels. The savings from 6 panels we put on the bus more than paid for the fancy MPPT controller.
    It might be useful to think of your solar electric system as having the same evolution potential as a personal computer. You might possibly think of the system you are putting on the Allegro today as an nice little 8086 PC. By the time you have found the land, bought the land, graded the drive and house pad, built the house, dug the well, and whatever else, the 286's might be gone and the 386's or Pentiums might be out. If these terms are foreign to you, substitute wired into the car "mobile phones" evolving to the latest, greatest, Buy-Phone. Will it really be worth transferring the system from the Allegro? What new technology will be available for the house?
    I would be considering the present functionality for the Allegro as the priority determiner for the system. If you can fit an extra 50% wattage using 24 volts, that is a fine argument for 24 volts. I considered switching the bus over to 24 volts, but the pre-existence of a 12 volt LED lighting system, ventilators, heater blowers, starter, and inverters made it so much more practical to stay with 12 volts.
    If you haven't already, you might try a bit of CAD (cardboard aided design) to check the placement of the different panel sizes you are looking at to see how many and where you can fit them.
    If you don't already have a 12 volt inverter on the motorhome, then going 24 volt will cut the amperage in half. Your existing 30 amp controller will be thrilled with that, as will the wires. If you do switch to 24 volt, there are 24 to 12 volt converters that will power your 12 volt refer and heater boards, or you can wire them to the starting battery without much draw. The heater's blower, on the other hand, does draw a lot if it is running all night. Don't forget the 12v water pump. If you use it a lot and don't drive a lot, you might not want it on the starting battery either.

    If you haven't read it already, I recommend a read or two through HandyBob's rant- https://handybobsolar.wordpress.com/
    I do like my Trimetric. The Pentametric is sometimes neat the same price, but I am told it is not as user friendly.

    Hoping some of this is useful to you- Peter.
  • hharveyhharvey Registered Users Posts: 6 ✭✭
    retep, Thanks again for the very detailed options for me to think about. I am a IT Administrator so I got the computer references. I have read Handy Bobs Blog.
    -HH
  • lipetslipets Solar Expert Posts: 61 ✭✭
    I just did my RV last year, I used a KID controller, 4 6 volt T-105's batteries a 2000W inverter, I traveled 3 months last summer, never plugged in (can't run the AC),
    I think to change to a 24volt system is totally unnecessary, try selling it when your done it will attract less buyers.

    Kept it simple

  • hharveyhharvey Registered Users Posts: 6 ✭✭
    I am going to stick with a 12 volt system.
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