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jpratt2's avatar
jpratt2
Explorer
Apr 05, 2018

General charging question

I'm curious about the possibility of "back flow" in a charging system, given the multiple charging sources on most RV's (shore power, generator, alternator). What keeps one charging source from potentially harming another? I know that solar panels should have a blocking diode for this purpose. Is there a similar blocking device on each charging source before connecting to to the batteries?
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Apr 05, 2018
    • Panel diodes are to minimize partial shading losses
    • For the rest of your listed items they have inherent protection meaning it would take many hundreds of volts to harm them
    • There is no competition between charging sources
    • You could do well obtaining a primer on RV electrical systems :)
  • valhalla360's avatar
    valhalla360
    Navigator
    Apr 05, 2018
    Why would you try to connect, generator, shorepower and alternator simultaneously?

    Generator and shorepower should have a transfer switch anyway as it can hurt your appliances if you mix power sources without special equipment to sync the cycles.

    I suppose you might wind up hooking up the truck cable before unplugging from shore power for a few minutes but shouldn't hurt anything.
  • ricklord2001's avatar
    ricklord2001
    Explorer
    Apr 05, 2018
    I had a transfer switch go bad during warranty and Entegra sent a mobile tech out. This guy was excellent and really knew about RV power systems. Some how we got talking about this. A lot of times in warm climates I would start the gem before disconnecting the power. His response was why take that chance, yes you can do it but he advised not to, as any issue could result in a major problem. Now I shut everything down and unplug before starting the generator. As he said why take the chance.
  • brulaz's avatar
    brulaz
    Explorer
    Apr 05, 2018
    I've had multiple charging sources (shore charger, solar charger and alternator) connected to the 12V batts with no big problems.

    However I once had an adjustable power supply that caused a small drain on the batteries when it was not connected to shore power. Blocking diodes fixed that or, better, running it's output as input to a solar charger.
  • jpratt2's avatar
    jpratt2
    Explorer
    Apr 05, 2018
    Thank you for your responses. I have no intention of running more than one charging device at a time...I was just curious that since solar panels require a blocking diode, whether backflow was an issue with the other charging sources when they are not in use. Sounds like it's not an issue. Still learning.
  • RJsfishin's avatar
    RJsfishin
    Explorer
    Apr 05, 2018
    Perdy simple if you ask me,.....
    Their all charging a 12v system, its all about voltage.
    A charging system can't tell the difference between a battery, or another charger, except the difference in voltage. If you have 1 charger connected putting out 13.8 volts, connecting another charger will see it as a full charged battery, and just go to float,......or if capable of a higher voltage, may raise the system voltage for a regulated time, shutting down the other charger completely. Equal voltage chargers may even share the charging equally.
    12-15 volts is a 12v system voltage, whether its in a battery or another charger, it really doesn't care.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Apr 05, 2018
    jpratt2 wrote:
    I'm curious about the possibility of "back flow" in a charging system, given the multiple charging sources on most RV's (shore power, generator, alternator). What keeps one charging source from potentially harming another? I know that solar panels should have a blocking diode for this purpose. Is there a similar blocking device on each charging source before connecting to to the batteries?


    You are correct when it comes to Solar Panels. the charge controller will have a blocking diode on it's output

    Alternators have at least SIX diodes

    The Converter also has blocking diodes

    So do all other charging sources.

    A blocking diode is a "One way valve" for electricity. So though it is, in theory, possible for one device to harm another. ALL devices designed for RV use have blocking diodes. and most external automoative chargers as well

    For one thing. the Diodes. are what makes DC out of AC
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    Apr 05, 2018
    One of the nice things about Samlex's line of EVO Inverter/Chargers is that ALL connection from power sources enter into it and are "properly" handled ! This includes switching from shore power to inverter to generator for 120VAC and it switches from solar input to the built in charger for DC input. The AC power is certainly done by automatic transfer switches/relay.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Apr 06, 2018
    Hi,

    My solar plays nicely with the OEM converter, and the Magnum hybrid inverter charger, and the alternator.

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