Typically the rear battery supplies house power, and the front runs the chassis.
There is a diode isolator on the firewall which allows the engine to charge
both batteries, but not to draw from the rear battery, or vice-versa, under
normal conditions. This is to ensure that if your house battery goes flat,
for whatever reason, that you can still start the coach. In the event that
the coach battery dies, the bypass switch on the instrument panel will actuate
a contactor on the firewall to allow you to start the coach from the rear
battery - this is why the cable is so heavy. Onan start comes from the rear
battery (normall), and the power converter charges just the rear battery.
In a pinch, you can use the bypass switch the other way to start the Onan,
but it would be better just to start the coach engine first, so you run no
chance of two dead batteries!
Also, the rear battery is typically a golf cart or other deep discharge battery
designed for lower amperages and much deeper cycles that the engine battery.
The engine battery will fail much more rapidly if put into this type of service
than it normally would - starting batteries are designed for very brief high
current output, and not to be discharged too deeply - the exact opposite
of the way the house battery is typically used.
Lastly, unless your coach has been severely modified, the back battery feeds
does much more than start the Onan (see above) and as such should remain in
place. If this coach has been greatly modified, then my comments indicate
what was present when it was built, and perhaps the state that you should
consider rewiring back to, if needed.
- - Tim
> >Dave and Dave: My 23' 1973 Glacier also has a battery in the back and it is
> >used to only start the Onan. The way mine is wired it does get charged by the
> >alternator, and the 110 to 12 volt charger/converter plugged in to outside
> >source or when the generator is running. It is normal with a run down rear
> >bat to be able to start it with the engine running. In lieu of running a main
> >battery cable to the back, replace the battery.
> >Am I glad I didn't open any of the voodoo posts or what. Dean Hanson's
> >73-23-gmc.
>
> Dean or ??, there's a heavy cable running from the firewall back to rear
> battery. Could that be just to carry the charge current, or could that also
> be used to start the Onan? Do we really need this battery, or is it either
> a new battery or run a new cable from the front batteries to the Onan?
>
> Dave (advisor/navigator) & Dege (everything else), '76 Royale, Santa
> Barbara, CA
>
>
>
- --
================================================================================
Tim Dawson (tadawson) Owner/Engineer
TPC Services Bellnet: (972)-221-7385
Lewisville, Texas 75067 FAXnet: (972)-221-0393
"The world is complex.
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