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Thread: 5th Wheel RV Solar/Battery/Inverter Upgrade

  1. #1

    Default 5th Wheel RV Solar/Battery/Inverter Upgrade

    After reading and researching for quite awhile now, especially here on this forum, I've begun acquiring the components to add solar, inverter, and increased battery capacity to my 5th wheel RV.

    My goal is to extend dry camping time and limit generator usage. Also, I find solar power interesting, and am using this as an opportunity to learn more about solar, eventually hoping to get a larger setup for my home.

    Here's the parts list so far:

    Two Mage Powertec Plus 180 ME PV panels from NAWS (Thanks Eric!)
    http://www.magesolar.com/us/products...e-modules.html

    Rogue MPT-3024 MPPT charge controller (Thanks Marc!)
    http://www.roguepowertech.com/products/controllers.htm

    Xantrex Prosine 1800 inverter
    http://www.xantrex.com/power-product...s/prosine.aspx

    Four Trojan T-105 Plus 6V batteries wired for 12V bank
    http://www.trojanbattery.com/Products/T-105Plus6V.aspx

    I'm nearly ready to start the install, but a few nagging wiring/fusing details have me stalled.

    1.) The inverter instructions say to connect the inverter DC in leads directly to the battery with fuse on positive lead. Should the charge controller leads be attached directly to the battery too? Or should I use a bus bar?

    2.) The Rogue charge controller manual says I need a disconnect between it and the PV panels, and between the charge controller and the battery. What should these be?

    3.) For the inverter positive lead to battery, I believe I need a 250 amp rated fuse. What type of fuse should I use, a class T fuse or ANL fuse, or should I use a breaker?

    4.) I'm going to wire the AC side of the inverter with an additional breaker box separating the loads I want powered by the inverter from those I don't (like the AC, refrigerator, etc.). Something like this (from "Mark's RV Resource"): http://www.marxrv.com/12volt/inv3.gif

    5.) The inverter has a monitor that I plan on mounting remotely inside the RV. I think it's mainly an on/off control and voltage monitor. Do I need an actual battery monitor with shunt? Or will this suffice?

    Any help or constructive criticism would be appreciated!

  2. #2
    Join Date
    Mar 2006
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    SF Bay Area (California)
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    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    Quote Originally Posted by soleil View Post
    1.) The inverter instructions say to connect the inverter DC in leads directly to the battery with fuse on positive lead. Should the charge controller leads be attached directly to the battery too? Or should I use a bus bar?
    All the leads (charging, inverter, etc.) should be connected to the same "ideal" point (bus bar, common connection bolt, etc.) as per this:

    Smart Gauge Battery Wiring page


    2.) The Rogue charge controller manual says I need a disconnect between it and the PV panels, and between the charge controller and the battery. What should these be?
    For a small array with one or two parallel strings, you really do not need breakers/fuses for protection... So any DC rated switch should be fine in the solar array input.

    For the output, especially if you want to switch the batteries directly--one of this Boat A-B switches or equivalent would be nice (charge controller to A, inverter/other loads to B, batteries to common connection (oposite of how they are normally wired in a boat):

    Blue Sea Battery Switch 1-2-OFF 350 Amp

    3.) For the inverter positive lead to battery, I believe I need a 250 amp rated fuse. What type of fuse should I use, a class T fuse or ANL fuse, or should I use a breaker?
    Pretty much your choice... If everything is done correctly, the fuse/breaker should never pop unless the inverter input fails or you have a harness short. Using a DC Breaker is nice because it adds the "switch function".

    With any fuse/breaker/switch--It is always important to look at the voltage and current ratings. Many DC switches and breakers are limited to 12 or 24 volts--and are not designed for 48 volt battery banks (switch could arc instead of stopping current).
    4.) I'm going to wire the AC side of the inverter with an additional breaker box separating the loads I want powered by the inverter from those I don't (like the AC, refrigerator, etc.). Something like this (from "Mark's RV Resource"): http://www.marxrv.com/12volt/inv3.gif
    Should be fine...
    5.) The inverter has a monitor that I plan on mounting remotely inside the RV. I think it's mainly an on/off control and voltage monitor. Do I need an actual battery monitor with shunt? Or will this suffice?
    The monitor only gives you information on the inverter's power use and such...

    A battery monitor really does watch what is happening with the battery itself.... Basically, it is a bi-directional Amp*Hour meter / Totalizer. As you draw current*time out of the battery it counts down. As you return current*time to the battery, it counts up (in Amp*Hours).

    It also does some math--you tell it your battery's capacity--it will tell you it XX% state of charge. They also can account for Peurket Factor (higher current flow, the less efficient the battery).

    If you have others (spouse, kids, guests) that will not watch bank voltage/monitor specific gravity--the Battery Monitor is a very nice tool to help prevent damage to your battery bank (over discharge, deficit charging, etc.).

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  3. #3
    Join Date
    Oct 2003
    Location
    Paradise, CA
    Posts
    368

    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    I'll add that the control panel for that inverter comes off by removing 4 screws and can be remotely mounted inside your fiver. A regular telephone extension cord is all that's needed (although Xantrex would prefer you buy a high priced remote extension cord).

    I ran a ProSine 1000 for years in my fifthwheel that way (and only changed it because I had an extra 2000w inverter and wanted to occasionally run the microwave).

    Phil
    Happily off-grid since 1977

  4. #4

    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    Thanks for the helpful comments Bill and Phil!

    I drew a rough schematic of how I think I want to wire things (see below -- I haven't drawn in the negative side yet.). Does this look good? Anything I should do differently?

    Of note, the wire lengths are less than 5 feet from the batteries to the inverter, charge controller and generator. I believe the wire sizes are OK, right? (The drawing incorrectly shows 2/0 rather than actual 2 AWG from genny to battery.)

    Does the 250A fuse/breaker need to go between the positive bus bar and the inverter rather than between the batteries and the positive bus bar?

    Currently my 5th wheel has a Blue Sea switch, similar to the one you suggested, Bill, between the battery positive and a bar of over a half dozen loads. It is nice because when I store it, I just turn off the switch and it prevents the battery from being drained. I would like to have a similar arrangement when I rewire things. Will positioning the disconnect switch between the loads and the positive bus bar keep that same functionality? Would there be a better place to put that switch? I don't think I can put it between the battery and the positive bus bar, as then I couldn't have solar charging when stored. Will the inverter when off and the solar charge controller drain the battery when the RV is stored?

    Phil, I did buy the $49 remote panel interface that goes in place of the display panel on the inverter that I will mount somewhere convenient.


  5. #5
    Join Date
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    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    Quote Originally Posted by soleil View Post
    I drew a rough schematic of how I think I want to wire things (see below -- I haven't drawn in the negative side yet.). Does this look good? Anything I should do differently?
    Every positive wire that leaves the battery bank should have a properly rated fuse/breaker (close to battery) to protect the wiring against shorts/cuts/failures.

    No fuses/switches in negative leads.
    Of note, the wire lengths are less than 5 feet from the batteries to the inverter, charge controller and generator. I believe the wire sizes are OK, right? (The drawing incorrectly shows 2/0 rather than actual 2 AWG from genny to battery.)
    Should be fine.

    However, we don't know the DC charging current from the genset--So I cannot confirm the maximum fuse rating/current rating vs the AC charger output.

    For RV use, you can use the following table as a "maximum" rated current guide for generic open wiring. NEC will be quite a bit less allowed current (more conservative).

    American Wire Gauge Table

    Does the 250A fuse/breaker need to go between the positive bus bar and the inverter rather than between the batteries and the positive bus bar?
    Remember the fuse protects the wiring leaving your battery box... In theory, you can place the fuse in either location to protect the inverter + wiring.

    However, you would still need a fuse for every other wire (10 awg, 14 awg, etc.) that leaves the positive bus because the 250 Amp fuse would be way to big to protect the smaller gauge wires.

    Also, another issue... If you have the fuse between the battery and the battery bus--if you ever blew the 250 amp fuse--it would take out all of your electricity and leave you in the dark. If you fuse each load/wire branch--then a single fault would still leave you with some DC lighting, etc.

    Currently my 5th wheel has a Blue Sea switch, similar to the one you suggested, Bill, between the battery positive and a bar of over a half dozen loads. It is nice because when I store it, I just turn off the switch and it prevents the battery from being drained. I would like to have a similar arrangement when I rewire things. Will positioning the disconnect switch between the loads and the positive bus bar keep that same functionality?
    Sounds like a good idea... With the two position switch I gave you--it does give you the ability to have "two switched buses"... For example one to the heavy loads and a second to your solar charger (1, 2, 1+2, all off).

    Would there be a better place to put that switch? I don't think I can put it between the battery and the positive bus bar, as then I couldn't have solar charging when stored. Will the inverter when off and the solar charge controller drain the battery when the RV is stored?
    Read carefully through the inverter specifications--Each one seems to have its own way of working... Many inverters have no off switch--so you have to provide you one (or they will draw 6-30 watts of power even with no loads). Some have search mode (AC on for a few cycles, then off for a second, stay on if load > 8 watts is found, etc.). So they draw less power on "standby"--but still not zero.

    And some inverters have an "inhibit switch". And even when "off/inhibited", they still draw 1/2 a watt or so.

    Also, if you store your solar panels under cover/building/roofed area--Most charge controllers do draw a little bit of standby current too... If the solar panels are covered during storage, the charge controller should be disconnected from the battery bus too.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  6. #6

    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    Thanks for the good explanations, Bill! I think I'm starting to getting a handle on it.

    So I suppose I'll just switch and fuse everything.

    That switch you pointed out does sound good. Like two switches for the price of one.

    I've been looking for a nice surface mount 250A breaker for the inverter, but am having trouble finding one that I like and isn't too expensive. I'd like to use one of these (from NAWS):

    However, they're only available rated up to 150A. Would I be asking for problems if I used a 150A breaker like this instead of the recommended 250A? (I think I know the answer already, but I do like these breakers .) 150A X 12V = 1800W. How often would I be pulling max power from my inverter (unless start-up loads come in to play a lot)? I see a lot of people use the T-class fuses, too. Are they better than ANL fuses?

  7. #7
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    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    You have to hunt down the voltage ratings for each fuse type you want to use... I think the ANL where 32 volts max, and the T type were much higher.

    For example, a quick google search shows:

    ANL fuse rating:
    Bolt-On Fuse
    Ampere Rating : 60A To 300A
    Voltage Rating : 32Volts DC
    Material : Body-Bakelite
    Also there is an interesting chart near the top of the link that shows how fuses really behave to over current conditions:
    Typical AGU Glass fuse (round tube)
    time to blow ratings at XXX% of rated current:

    110% ; 100%

    • 35A ~ 80A
    • 4 Hours , Min

    110% ; 100%

    • 0.5A ~ 30A
    • 4 Hours, Min ; 1Hour , Max

    200%

    • 0.5A ~ 8A ; 10A ~ 30A
    • 5 Sec , Max ; 10 sec , Max

    300%

    • 35A ~ 80A
    • 4 Sec , Max
    The Class T JLLN fuse (Littlefuse PDF booklet) is rated for 125 VDC or higher (depends on physical size/current rating) and something like 20,000 AIR (amperes interrupt rating).

    Anyway--There are fast blow, standard blow, slow blow, etc. fuses... So, if you are intent on running large surge current and lower capacity fuses--You need to look at the tables (like in the PDF above) to see what will be acceptable to you or not for actual fuse rating.

    And remember, you should design for worst case current ratings (for safety and reliability)... If you really want to pull 1,800 watts continuous (more than 5 minuets at a time?)...

    • 1,800 watts * 1/10.5 volt inverter cutoff voltage * 1/0.85 inverter efficiency * 1.25 NEC safety factor = 161 amps minimum fuse/wiring rating.

    Could use use a 150 amp breaker there--probably just fine. I doubt that you will be running 1,801 watts, at 10.5 volts (near dead battery/lots of voltage drop). Running the breaker at 150 amps continuous--you may get false trips and/or the breaker may have less than a 20+ year operational life (if you have to replace the breaker in 5-10 years--I don't think you will be unhappy).

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  8. #8

    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    I'm getting ready to hook things up... I have another question regarding the 40A circuit breaker that I'm installing between the positive buss bar and the solar charge controller.

    Here's a picture of a 60A version of what I'm using:


    On the breaker, there are two connecting posts labeled "Line" and "Load". For the inverter, I connected the cable to the DC in on the inverter to the load bolt, and the line side to the battery. But for the solar charge controller, I'm not certain which way it should be connected, as power flows from the solar to the battery. (Is the battery the load then?)

  9. #9
    Join Date
    Jun 2003
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    pittsburgh, pa
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    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    "Is the battery the load then"

    yes, it goes by the direction power is usually flowing. the batteries are receiving the power from the cc so it is a load in this case.
    NIEL

  10. #10

    Default Re: 5th Wheel RV Solar/Battery/Inverter Upgrade

    Thank you! That makes sense.

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