Originally Posted by Rickinbc
I bought a used 2021 Dutch Star 4369 about 3 months ago and after driving all day charging, being plugged in or with the generator once the charging stops and you have the inverter on, say an overnight parking lot stopover the house batteries are almost dead and the red low battery light is on. All that was knowingly on was the refrigerator. I suspect if I disconect all the house batteries and test them I may have a battery or two with a bad cell?? Any thoughts and suggestions? Thank you!
You have not provided enough information to conclude the batteries are defective.
Loose or corroded connections could also be a cause.
Lots of 12 volt devices each drawing a little can be a cause.
Less than complete charging can be a cause.
Battery Storage Capacity
How many of what type of batteries do you have? Are they 6 volt or 12 volt batteries. The spec you want is total amp hours of capacity.
6 volt batteries are combined in series pairs to produce one 12 volt battery. Two 6v 225 amp hour batteries makes a total of 225 amp hours at 12 volts. Two 12 volt 110 amp hour batteries add to make 220 amp hours. Batteries come in widely different amp hour capacities.
How many amps of charging from each source are you getting? Engine charging can vary from 10 to 100 amps. How many hours was the engine charging? This combines to make amp hours again. The only way to know is to measure current while charging. It will change under different conditions.
What is the charging capacity of the shore power charger. They come in widely different capacities typically from 10 amps to 100 amps. Provide make and model of charger or charger 12 volt amp capacity
Charging Lead Acid Batteries
It takes 14 to 18 hours to fully charge a lead acid battery. Four hours using a high capacity charger can provide 80% of capacity. The last 20% charging takes a long time.
There are many 12 volt devices in an RV that consume battery power. Some are more obvious than others.
Electric refrigerators can consume a lot.
Inverters even while idling can consume a lot.
Water heater, furnace, and A/C controls can consume some even when they appear to be "off".
Entertainment systems cans consume a little even when they appear to be "Off".
Block heaters are big silent consumers.
Water holding tank heaters are silent.
Many other possibilities.
The only way to know for sure is to measure power draw at the battery terminals. Get a shunt type battery monitor
and install in the negative lead to the battery bank. It will show current draw and keep track of state of charge better.
It will also show charging current. This is needed to determine charging rate while driving.