RV converter w/ charge controllers

The RV solar FAQ tells how not to combine an RV convert and solar charge controller, but says nothing about how they should be combined, or even if they can be.

It would be nice to not have to remember to flip a nPDT switch, but I would think the respective controller circuits would drive each other nuts if the outputs were hooked up parallel.



  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: RV converter w/ charge controllers

    Actually, that FAQ says not to run the converter *output* IN TO the solar charger's *input*.

    To properly "combine" an RV converter and a solar charge controller is simple:

    1) Connect Converter output to battery (probably done at RV factory).
    2) Connect Solar Charge Controller output to battery.
    3) Miller time.

    Basically, you just have two separate battery chargers hooked up to the same battery - which is actually a fairly normal thing to do.
  • kswisonkswison Registered Users Posts: 6 ✭✭
    This is a rather old post, but on this topic, I have the following question.

    I have a 12 year old RV trailer completely off grid. I have a 530 W solar system on the roof and a 300W wind turbine all hooked into the RV's battery bank via a separate solar controller on each power/charging source. All seem to work well. Each on their own controller.

    According to my Bogart TM-2030 monitor, at high sun my MPPT system is operating at 14.3 volts and charging at about 32-34 amp. 

    The RV trailer had a IOTA DLS-45 Converter that crapped out shortly after I set up the solar system, maybe a month or so later. So I have been concerned that possibly the solar charging side took out (fried) my RV Converter. Or maybe its timing was just a coincidence. Not sure.

    Is it even possible that the solar side fried my RV converter ?

    Due to this, I was considering placing another solar controller on the RV converter charging line, but after reading this I won't.  Bad idea!

    However, the other option that I was considering was a rectifier blocking diode on the charging line from the RV Converter to the RV battery bank. So I just bought a 100V - 60Amp Rectifier Blocking Diode. It should work fine down to 13.6V at 55 amps. 
    I also just ordered a new RV Converter DLS-55, Volts: 13.6V, Output: 55 amps
    Now many of these converters have blocking diodes built in, so this may be redundant.

    Do I trust the blocking diode on the RV Converter ?

    However, if I install the blocking diode on the positive wire that runs from the DLS-55 Converter to the RV battery bank I do not have to worry about amperage from the solar charging side of the system ever effecting the RV Converter.

    Needed ?         Not needed ?          Good idea ?          Bad Idea ?

    I see in the comment above to just hook them up, but I am looking to see if this is an option, if it will help, or if it will create other problems for me.  I just don't want to fry another $425 controller (if that is truly what has happened.)

    Thoughts ?

    Thanks in advance.
  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    What's the voltage drop across the diode?  It may be enough to impair proper charging voltage, especially since 13.6v is on the low side for charging most batteries in a reasonable time in the first place.

    FWIW, I have a pair of (120vac) Iota45a, a mppt controller, and a pwm controller all connected to a single 12v bank with no issues.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators, Administrators Posts: 32,999 admin
    In general, you should not have had any problems with all of the different charging sources in parallel on your battery bank.

    The Iotas are, in general, a pretty good charger. One thing that has been known to fail, is the AC input diode(s) that charge the high voltage intermediate capacitor.

    They are not too expensive to replace, but you might check on costs to repair.

    Adding diode(s) between charger and the battery bus is usually more trouble (and another point of failure, and sometimes confusion for attached chargers) than it is worth.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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