Wiring for multiple batteries

[john massey]

Do I have a problem?

I've got three batteries in my 1977 Royale - Starting, House and
Generator.
The Maintenance manual diagrams, however, only show two. For example, the
diagram
entitled "1977 and 1978 GMC Motorhome Living Area 12-Voly DC Electrical
System...."
show how the "cranking" battery and "Aux" battery are connected.
Part of my problem is that the House battery wire, that I
would have expected to be routed back from the front, where the battery
is located, to the converter in the rear, is not. Tracing the wire under
the MH, the Red large gage wire is tied off in the vicinity of the
generator and is terminated in a heavy ring terminal which is not
connected to anything! Two inches away there is a Red wire from the
generator battery and that is connected a stud terminal on what I
believe to be a fuse (metal block about 2" by 3/4" with two studs). The
other stud terminal is connected to a Black very large gage wire which
goes to the converter. The "fuse" is just hanging in the air with the
wires attached. So it looks like the way it is connected NOW, the
generator battery is only charged by the converter and the house battery
is only charged by the alternator. Also the Generator battery is the only
source of 12 vdc for house needs.
If I were to connect the Red house battery wire to the same stud
terminal
that the Red generator wire is connected to, then, I think, I have the two
batteries in parallel. Then both batteries would be charged by either the
alternator when the engine is running or, when stationary, by the convertor
when it gets shore power or AC from the generator. I am concerned that
this would mean that, when the engine is running, the alternator would
be charging all three batteries - is this a problem?
This would also mean that when I select BATT BOOST, all three batteries
are available for starting.
All three batteries are identical, looks as if they were bought at the
same
time about a year ago.
I just don't see a reason for someone disconnecting the House battery
wire
in the first place and am a bit apprehensive about reconnecting it.
Hope this was clear enough.

John
FMCA 231235

 

[bill wallace]

John, I can help on this. My '78 Royale had same hookup. The "fuse" you describe
is a circuit breaker to protect in case of a short in the wire to the front
coach battery. The breaker on mine was wrapped in tape. Breaker was inoperative.
Wire from gen and battery goes to one end of breaker. Wire from converter and
wire from front coach battery goes on other end. Size of breaker, about 40 amp
should be stamped on it. I found one at Camping World. I also replaced gen.
battery with 2 golf cart batteries in series. Keep front coach battery to assist
with battery boost as circuit breaker at gen. will trip if starting with boost.
It is automatic reset. This way you have three batteries for coach operation. I
used replacement battery trays in gen. compartment to anchor batteries. Engine
gen. charges all batteries on road. Converter charges coach batteries when
plugged in and genset charges all coach batteries when running. Hope this helps.
If you need more let me know.
Bill Wallace

"This day will go down in history. For the first time
a nation has registered all firearms" Adolph Hitler, 1935

> Do I have a problem?
>
> I've got three batteries in my 1977 Royale - Starting, House and
> Generator.
> The Maintenance manual diagrams, however, only show two. For example, the
> diagram
> entitled "1977 and 1978 GMC Motorhome Living Area 12-Voly DC Electrical
> System...."
> show how the "cranking" battery and "Aux" battery are connected.
> Part of my problem is that the House battery wire, that I
> would have expected to be routed back from the front, where the battery
> is located, to the converter in the rear, is not. Tracing the wire under
> the MH, the Red large gage wire is tied off in the vicinity of the
> generator and is terminated in a heavy ring terminal which is not
> connected to anything! Two inches away there is a Red wire from the
> generator battery and that is connected a stud terminal on what I
> believe to be a fuse (metal block about 2" by 3/4" with two studs). The
> other stud terminal is connected to a Black very large gage wire which
> goes to the converter. The "fuse" is just hanging in the air with the
> wires attached. So it looks like the way it is connected NOW, the
> generator battery is only charged by the converter and the house battery
> is only charged by the alternator. Also the Generator battery is the only
> source of 12 vdc for house needs.
> If I were to connect the Red house battery wire to the same stud
> terminal
> that the Red generator wire is connected to, then, I think, I have the two
> batteries in parallel. Then both batteries would be charged by either the
> alternator when the engine is running or, when stationary, by the convertor
> when it gets shore power or AC from the generator. I am concerned that
> this would mean that, when the engine is running, the alternator would
> be charging all three batteries - is this a problem?
> This would also mean that when I select BATT BOOST, all three batteries
> are available for starting.
> All three batteries are identical, looks as if they were bought at the
> same
> time about a year ago.
> I just don't see a reason for someone disconnecting the House battery
> wire
> in the first place and am a bit apprehensive about reconnecting it.
> Hope this was clear enough.
>
> John
> FMCA 231235