Battery Charging Problem ***UPDATE***

LOG wrote:

pianotuna wrote:

LOG wrote:
It appears that your motorhome has the voltage drop problem that DrewE was explaining. And has nothing to do with a "smart" charging system.
Maybe you need a better battery isolation manager or combiner.

LOG,

I have dual charging paths with #8 wire (rating 50 amps) with dual solenoids, each rated at 200 amps continuous. I have manual control of the solenoids and charging from the alternator. Each charging path is protected by a 50 amp automatic circuit breaker.

If the house batteries are "hungry", then I see more than 75 amps of charging. (my meter only reads to 75 amps). On occasion I've observed at least one of the circuit breakers flipping off and then on.

On normal use, because my starting battery is given a maintenance charge when ever the sun is shining, I see little charging after the starter battery is full from the ecm's point of view.

I can "force" charging of the house bank by using the inverter and running the 1400 watt water heater. However this does, after about 20 minutes, cause the starter battery to go down to 12.3 volts. At that point, I use my manual control to stop the charging, and I disconnect the water heater. The reason for doing so, is the 1/3:2/3 duty cycle on the alternator which I do not wish to burn out.

After 40 minutes of highway driving, I can repeat the above process. The last hour of driving I use to return some charge to the house bank.

I can "see" one of the breakers flipping in and out if I run the engine and use the microwave (170 amps draw) and the induction cooker (70 to 130 amps) at the same time.

These observations are from 2013 when I had 8 identical marine jars, one of which was used as a starter battery, and the house banks were configured as 3 and 4. Both banks were wired in a balanced manner. The "house" bank was 875 amp-hours @ 12 volts.

It appears that your motorhome is not the typical motorhome that one would expect to see in a later model motorhome with a "smart" charging system as was explained in one of the first post in this thread by Theoldwizard1.
Would you provide an example of a newer motorhome that would not fully charge the house bank with the engine alternator.
My older 2005 motorhome does not have that problem.
I simply start the engine, drive to my destination, and when I arrive my engine battery and house bank are both fully charged, without my having done anything other than driving and listening to then radio.

What you say is exactly what I find with our 2005 Itasca Class C motorhome.

For traveling I have two (four place - xx.xx) voltmeters mounted on the cab dash right where I can watch them: One shows the chassis battery voltage, and the other other one shows the coach battery bank voltage (two 115AH 12V batteries in parallel). I also have an ammeter on the dash that gets it's input from a shunt in the main line of the coach battery bank right close to the coach battery bank.

Both voltmeters read nearly the same whenever traveling down the road because a heavy duty solenoid connects the coach battery bank and the chassis battery together in direct parallel whenever the ignition key is turned on.

After drycamping long enough to the draw the coach batteries down to around 50% discharged (a rest voltage of ~12.1 volts) and then hitting the road, the voltmeters at first read above 14 volts for awhile and then they slowly settle down to 13.X volts - depending upon the outside ambient temperature.

At first the ammeter can spike up to as high as around 80 amps for a bit before beginning to taper. After driving 3-4 hours, the ammeter will taper down to 2 amps or less - indicating nearly full coach batteries.

The original OEM Ford 130 amp alternator (a "G4" or "G5" or "GX" type?) has been charging all three batteries this way for about 14 years. The alternator is connected to the coach batteries (via the solenoid) by maybe 10 feet of 8 gauge cabling.

Somehow the Ford alternator and it's regulator and/or or engine ECM are doing something just right - with no sophisticated circuitry (i.e. isolaton diodes, etc.) added by Winnebago that I know of - per the Winnebago wiring diagrams.

The coach only has a good old Parallax 45 amp fixed voltage converter in it, and the coach batteries are deep cycle AGM with low internal resistance - which makes them charge much faster than liquid acid batteries - at all applied charging voltages. Lately when drycamped, I've been skipping long generator runs for charging via only this converter and instead merely idling the V10 engine for awhile to let the alternator do the heavy charging.

All this seems to play very well together ... if and only if the solenoid that connects the chassis and coach batteries together works and has "no" resistance in it's contacts when they're closed. If the two voltmeters that I mention above are reading very close to the same, then this solenoid is OK and hence passing charging current to the coach batteries without loss of voltage across the solenoid's contacts due to corrosion.