Matt,
I'm not sure what coaches had only a #10 wire running to the batteries in the rear. Was 23ft coaches with the batteries up front that had only #10
wire to the back?
My 77 Palm Beach, 26ft with the house batteries at the rear has a #0 gauge wire running from the front boost solenoid to the rear batteries. The
wiring diagrams for the 75 and 77/78 show the #0 wire running back to the junction terminal behind the electric cabinet, then onward to the rear
solenoid with #1 cable. Voltage drop during charging should approach 0V through those cables from either the engine or power converter/charger. I
would expect his '76 to be similar.
My experience with deep cycle batteries is in public safety radio communications systems for emergency power backup. The chargers had a separate
output to the battery so they could monitor the battery voltage and current. The charger could then tell the current state of charge for quickest
recharge without overcharging. Our GMC's use a "loaded battery" system... the loads and the battery are connected together so the power converter has
no idea how much current is being consumed by loads (lights etc) and how much is being used by the battery in recharging. So the converter either
just goes through a set time in each stage or steps through the stages based on current flow, some of which was consumed by other loads. Not the
ideal for quickest charge and longest battery life.
Our alternators are fairly dumb in comparison to the converters. The Delco service manual shows the schematic. Its basically a constant voltage
regulator with a thermistor to sense operating temperature. As the alternator heats up, the thermistor would reduce the output voltage slightly. This
would give a faster charge (higher voltage) after starting that would taper down a bit when the engine warms up. This works fine for a passenger car
or light truck typically used for short commutes. I can't find any information on the output vs temperature of the regulator. Newer replacement
regulators may have more smarts, but if they do they don't publish any info on it, so I doubt it. I just rebuilt my alternator using a Transpro
regulator. I logged a 1 hour trip on my EBL and the voltage stayed withing +/- 0.1 volt the whole time, so I'm guessing it does not have a
temperature sensor, or being cooler the alternator did not get that hot.
As far as how long your battery will last, with lead acid batteries that is a crap shoot. My experience with deep cycle batteries is since about
2010, most don't meet capacity specs right off the delivery truck (most now made off-shore). You mentioned using the furnace, so that means its cold
out and your batteries will be cold, so their capacity drops significantly. Add to that the duty cycle of your furnace is going to vary widely
depending on outside temperature. A few years ago I measured the current draw of my furnace and I believe it was about 8 Amps when on shore power.
So depending on your battery's age, quality of construction, state of charge, battery temperature and furnace draw and duty cycle, no one can give you
a hard answer.. it is what it is.
One thing I noted was my furnace would run and there didn't seem to be much air flow out of it. I checked all the ducts and vents for obstructions
and they are clear. I could hear the high limit switch click and the flame would shut down while the fan continued to run, they it would restart the
flame. So obviously the chamber was hitting the high temperature limit. One cold rainy camping day, I took off the front cover of the furnace and WOW
the blast of hot air was unbelievable. The coach was warmed in minutes and the duty cycle of the furnace dropped considerably. Finally a tasty warm
coach in minutes. To this day the cover is off and we just open the door when we use the furnace.
Just my experience.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
