House battery charging by alternator

ramsaymike wrote:
As it happens, I monitor and record battery voltages continuously. This is what I got on the last drive. On start, the chassis batteries go to (about) 14.2 and slowly drift down to 13.6 over the 90 minutes of driving. The house batteries are at 12.0 and slowing increase as solar builds in the morning. After 20 minute break, the chassis batteries go to 13.7 but soon settle at 13.2 where they stay. The house batteries continue to build and are at 13.2 at engine off. It appears that at this point the solenoid is activated. From this point on the voltages of both sets of batteries are the same and it is obvious that they are connected. It now appears that the solar charge controller is controlling the voltage as both sets now start increasing. It is difficult to see what is going on as solar is variable but both are held at around 13.6. At the end of the drive the solenoid is deactivated - can't be sure exactly when but before final switch off. Trying to understand what is going on.....maybe just faulty solenoid?

Need to disconnect solar and just watch what alternator charging alone does to see if there is a problem.

Two chargers at different charging voltages will have the higher voltage charger raising the battery voltage up past the voltage of the other charger so it does not provide any more amps, leaving the higher voltage charger doing it all.

Your results are confusing for their timing when the solar would take a long time to get the battery voltage higher so the alternator should be still providing amps early on. Best thing to do is take the solar right out of the picture temporarily to remove all confusion