RV electrical question

Marcel
Marcel Solar Expert Posts: 39 ✭
in General Solar Power Topics #1
Our battery bank is 24 volt but the RV we're in is 12 volt. Is this what I need?

http://store.solar-electric.com/sa24voto12vo1.html

Thanks.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: RV electrical question

    Do you want to charge a 12 volt battery bank, or do you want to run 12 volt devices from the 24 volt battery bank.

    What you linked to, from what I can tell, is for running 12 volt devices and not designed to charge a 12 volt battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Marcel
    Marcel Solar Expert Posts: 39 ✭
    #3
    Re: RV electrical question

    Yep, need to run the stuff in the RV on our 24 volt battery bank. The RV stuff, like water pump, lights, heater blower are all 12 volt. Not sure what to get for that. Thanks.
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  • PhilS
    PhilS Solar Expert Posts: 370 ✭✭✭
    #4
    Re: RV electrical question
    Marcel wrote: »
    Our battery bank is 24 volt but the RV we're in is 12 volt. Is this what I need?

    http://store.solar-electric.com/sa24voto12vo1.html

    Thanks.

    Marcel,

    I'm misunderstanding your question. I've had an RV for over 30 years (well... not "an" RV, but different ones).

    WHAT/WHERE is 24V? I assume NOT the RV, as to have batteries wired for 24V in an RV is trouble looking for a way to manifest itself.

    Is the 24V on a battery bank external to the RV? If that's the case, that converter won't do much, if anything, to help the RV since it's limited to 12 amps.

    Phil
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #5
    Re: RV electrical question

    I assume that there is a solar charged 24V battery bank. The OP wants to connect this bank to the existing 12V circuits. The device suggested will do this, within the amperage constraints.

    I considered rewiring my battery bank from 12V to 24V to take full advantage of the Morningstar 15A MPPT controller's 400W output (limited to 200W at 12V) but concluded that any gain would be lost in the inefficiency of the DC-DC converter.

    K
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #6
    Re: RV electrical question

    Yes, you can use that Samlex, but it only puts out a pre-set voltage - it's not an actual battery charger so you might want to "top off" the RV battery once in a while.

    Also make sure that 12a is enough - if not then you might need more than one.

    Personally, I would rather do it with a proper battery charger - something like this:

    http://sterling-power-usa.com/24volt-12volt30ampbatterytobatterycharger.aspx
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #7
    Re: RV electrical question

    Too many assumptions and guesses here. We need more information from Marcel.

    1. Is there more than one battery bank? Perhaps a stock 12V and a retrofitted 24V.
    2. Is there a PV system charging the 24V bank? If so, what PV capacity and which charge controller?
    3. What is the AH capacity of the 24V bank.
    4. What are the load requirements of the existing 12V circuits?

    dwh, until these questions are answered, I can only guess that there is not a 12V battery in the system.

    Please! Marcel, help us help you!

    K
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #8
    Re: RV electrical question
    Kamala wrote: »
    Too many assumptions and guesses here. We need more information from Marcel.

    1. Is there more than one battery bank? Perhaps a stock 12V and a retrofitted 24V.
    2. Is there a PV system charging the 24V bank? If so, what PV capacity and which charge controller?
    3. What is the AH capacity of the 24V bank.
    4. What are the load requirements of the existing 12V circuits?

    dwh, until these questions are answered, I can only guess that there is not a 12V battery in the system.

    Please! Marcel, help us help you!

    K

    Brutha Kamala, you know I love you man, but you could do what I did and "view all posts by Marcel" and get some of those questions answered. :D
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #9
    Re: RV electrical question

    Shud've. My lack.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #10
    Re: RV electrical question

    Ya. Basically, he's got a 24v off-grid system and wants to feed the 12v RV from it. Simplest way would just be to connect the output of one or more of those Samlex DC-DC converters straight to the RV battery.

    That should supply the loads and keep the RV battery topped up to 13.8v, but for long term use he might be better off with a proper multi-stage charger.

    But there is the "50 bucks vs. 400 bucks" issue as well so the "real" charger probably wouldn't be worth it.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #11
    Re: RV electrical question

    Ah. Good money after bad...
    Or is it bad after ???

    :confused:
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  • Marcel
    Marcel Solar Expert Posts: 39 ✭
    #12
    Re: RV electrical question

    Sorry, folks. I should have provided more info. Yes, we have a solar charged 24 volt system of 12 Trojan 2 volt batteries. Currently the RV has 2 golf cart batteries running it'sDC electrical system. I want to change the RV over to the Trojans because the golf cart batteries are about to give up the ghost. I'm sorry but I don't know the load requirements of the RV. Its got the usual stuff in an RV. Water pump, lights, heater blower, whatnot.

    We've got 3 different sets of panels and 3 different charge controllers. 948 watt array with an MX60 and 2 C-40's. The inverter is a Xantrex 3624.

    Thanks folks for the help.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #13
    Re: RV electrical question
    Marcel wrote: »
    I'm sorry but I don't know the load requirements of the RV. Its got the usual stuff in an RV. Water pump, lights, heater blower, whatnot

    The Samlex can only supply 12a. That might be enough - IF the RV batteries are good - since it will eventually push the battery charge up to 13.8v. As long as your loads are intermittent then you would probably be fine.

    But if the batteries are bad, and/or you are also running an inverter supplying 120v loads, then you could end up drawing more than the 12a that the Samlex can supply - in which case you might need to parallel a couple of them.
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  • Marcel
    Marcel Solar Expert Posts: 39 ✭
    #14
    Re: RV electrical question

    I still am not sure what I need to run the RV off the solar powered 24 volt battery bank. Currently, I have 2 close to dead golf cart batteries running the RV. I have this big fat 24 volt battery bank and I want to use it! Sorry, but I am not understanding what needs to happen. Thanks a lot.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #15
    Re: RV electrical question

    There are several ways of getting the 24 VDC down to your 12 volt system...

    I guess, my question, is this for maintenance charging of the RV (when parked for storage), or is the RV going to be lived in next to the 24 volt system?

    Also, how far are you planning on parking the RV from the 24 volt battery bank. If a long distance, using a 120 VAC inverter to send the power from the 24 volt bank to the RV might be a better deal. Sending 24v (or worse 12v) a long distance is pretty difficult.

    If you need to use AC power anyway--Placing a nice Inverter on the 24 volt battery bank might work out well... Use it to power your 120 VAC loads, and have a small battery charger to keep the RV batteries charged and available for (the now reduced) DC power needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #16
    Re: RV electrical question
    Marcel wrote: »
    I still am not sure what I need to run the RV off the solar powered 24 volt battery bank. Currently, I have 2 close to dead golf cart batteries running the RV. I have this big fat 24 volt battery bank and I want to use it! Sorry, but I am not understanding what needs to happen. Thanks a lot.

    You take that Samlex converter you linked to. Connect the 24v side to your big battery bank, and the 12v side to your RV battery bank.

    Done.


    But, your RV might be drawing more than the 12 amps that the Samlex can supply - in which case you might need two of them.


    Another problem is that the Samlex converter is not an actual battery charger. It will eventually push your RV battery up to be fully charged, but it will take a long time - and it might never get the RV battery properly charged if the RV's loads are drawing 10a because there will only be 2a left over the charge the RV battery and that's just not enough.

    In which case - again - you might need two of them.

    OR

    A proper 24v-12v battery *charger* of a decent size like say 30a.

    OR

    As Bill said, for a long distance use an inverter and run 120v out to the RV and plug it in and let the built-in converter charge the RV battery.
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  • Marcel
    Marcel Solar Expert Posts: 39 ✭
    #17
    Re: RV electrical question

    That's the problem, the RV battery is close to dead and I don't want to use it anymore. I want to use the 24volt bank to run the RV. No more RV battery bank. But since the RV is 12 volt and the big fat expensive solar battery bank is 24 volt, I need to get the 24 volt down to the RV's 12 volt. I thought I could run the DC to DC inverter from the battery bank to the RV battery cables. Will that work?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #18
    Re: RV electrical question

    I could work--Do you know what the maximum 12 VDC current is you will need? I guess a forced air heater and, fan over stove, a few DC lights? Run 120 VAC inverter for the other power needs to keep the 12 VDC power usage low enough for that converter to manage the loads?

    A 12 amp converter may be enough to run the loads if you don't run the heater with the vent fan and lights, etc...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Marcel
    Marcel Solar Expert Posts: 39 ✭
    #19
    Re: RV electrical question

    Sounds good, I think I have it now. Thanks a lot everyone!
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