Forum Discussion

ramsaymike's avatar
ramsaymike
Explorer
Feb 20, 2022

House battery charging by alternator

I am trying to understand how the charging system works on our 2007 Coachmen Concord. It seems that the truck alternator charges the house batteries at different times. For instance on a recent day trip, the alternator was not charging on the first 1 hour driving segments. On the third start, it started charging the house batteries. I have no idea how it determines when to charge. I do have a solar system as well so not sure if this is causing some confusion but it seems clear that alternator charging is not consistent. Any ideas?
  • ramsaymike's avatar
    ramsaymike
    Explorer
    Feb 20, 2022
    Right - Class C. Just thinking.... maybe there is some sort of 'alternator protection' strategy in play. The load on the alternator might be an issue if it is asked to charge 4 batteries of unknown status???
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Feb 20, 2022
    Lwiddis wrote:
    Here’s a pretty good explanation of why a TV alternator doesn’t do more than an 80% charge under the best circumstances. Repeatedly charging to only 80% isn’t wise. See…

    https://askthervengineer.com/youre-not-actually-charging-your-rv-battery-with-your-tow-vehicle/
    I believe the OP has a Class C MH.
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Feb 20, 2022
    wolfe10 wrote:
    Lwiddis wrote:
    Without extra equipment the alternator won’t do a good job of charging your house batteries. Upgrade your solar system to charge them.


    Sorry, I have to disagree.

    While solar is a worthwhile upgrade for those who spend time "off the grid", the alternator SHOULD charge both battery banks.

    To the OP: You need to troubleshoot your charging system. Do you have a diode-based battery isolator or a solenoid-based battery isolator?
    X2 I'm not aware of any MH that doesn't charge both banks from the alternator. Most likely problem is the solenoid as significant amps are involved and DC is prone to pitting the contacts. It could be the connections which should all be clean and making good contact. It could also be the setup that activates the solenoid coil.

    I'd be surprised if you have a diode based system.
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Feb 20, 2022
    Here’s a pretty good explanation of why a TV alternator doesn’t do more than an 80% charge under the best circumstances. Repeatedly charging to only 80% isn’t wise. See…

    https://askthervengineer.com/youre-not-actually-charging-your-rv-battery-with-your-tow-vehicle/
  • ramsaymike's avatar
    ramsaymike
    Explorer
    Feb 20, 2022
    As far as I understand, it uses a solenoid to join the batteries. I have 2 chassis and 2 house batteries. I do not know anything about the logic it uses to control the solenoid - it has 4 control inputs as far as I can see. I assume one is the dash switch.
  • wolfe10's avatar
    wolfe10
    Explorer
    Feb 20, 2022
    Lwiddis wrote:
    Without extra equipment the alternator won’t do a good job of charging your house batteries. Upgrade your solar system to charge them.


    Sorry, I have to disagree.

    While solar is a worthwhile upgrade for those who spend time "off the grid", the alternator SHOULD charge both battery banks.

    To the OP: You need to troubleshoot your charging system. Do you have a diode-based battery isolator or a solenoid-based battery isolator?
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Feb 20, 2022
    Without extra equipment the alternator won’t do a good job of charging your house batteries. Upgrade your solar system to charge them. Otherwise, charging systems usually work together with no issues.
  • larry_cad's avatar
    larry_cad
    Explorer II
    Feb 20, 2022
    ramsaymike wrote:
    I am trying to understand how the charging system works on our 2007 Coachmen Concord. It seems that the truck alternator charges the house batteries at different times. For instance on a recent day trip, the alternator was not charging on the first 1 hour driving segments. On the third start, it started charging the house batteries. I have no idea how it determines when to charge. I do have a solar system as well so not sure if this is causing some confusion but it seems clear that alternator charging is not consistent. Any ideas?


    The charging system is decided by the manufacturer and there are several kinds out there. Typically the system determines when to charge the house batteries vs. when to charge the truck battery.
  • steveh27's avatar
    steveh27
    Explorer
    Feb 20, 2022
    Wow, never heard of that. My alternator always charges until the batteries are fully charged.

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