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GSORK1961's avatar
GSORK1961
Explorer
Mar 11, 2015

Info on a chasis battery chager from coach batterys

Looking for the name of this unit. It is mounted in battery bay and transfers 12 volt from house to chasis.
Thanks Gary

5 Replies

  • I would think that any of the black boxes above would be easy to identify from its label. So are you asking about the continuous duty solenoid?
  • We use this one.

    Charges the chassis battery from the house batteries IF the house batteries are a 13.0 volts or higher. Also works on 24 volt systems.

    Max charge current is a respectible 15 Amps.
  • The bi-directional relay is the way to go because it also enhances alternator to house battery charging ability.
  • That device is called a BIRD a Bi Directional Isolator Relay Delay.


    It operates by sensing the voltages on both batteries.
    When either of these voltages exceeds 13.3 volts for
    approximately 1 minute, which happens when either battery
    is being charged, the control will close the isolator solenoid,
    connecting the two batteries together, charging them both.
    (Normal charging voltages are from approximately 13.8 to
    14.4 volts.)
    After the solenoid has been closed, the system continues to
    sense the voltage. If the ignition switch is off and the battery
    voltage drops below 12.8 volts for approximately 1 minute,
    which might occur when the converter is heavily loaded,
    the solenoid is opened to prevent the chassis battery from
    being discharged by the coach loads. When the voltage goes
    above 13.3 volts again for approximately 1 minute, the solenoid
    closes again. Thus always keeping the Coach as well as Chassis battery charged. Regardless of the parasitic draws on the chassis battery that run it down while sitting unused.

    These are more useful than the battery minder type of charger because of the way it works, sensing where the charge needs to go and maintaining both chassis and Coach batteries.

    Mine has worked flawlessly, keeping all batteries properly charged.