1) The seller told me 'these two batteries' are for the chassis and 'these two' are for the coach. In looking at the set up I'm pretty sure he had it backward. Specifically, the 'set' he said were for the chassis is the set that has all the extra connections feeding back into the coach. Seems apparent to me that means those are the coach batteries...right? I imagine I can just disconnect those batteries and confirm my suspicion. Any advice regarding this observation/process would be appreciated.
I agree, a test is in order. I suspect the seller was correct. A wider view of battery compartment may also help.
2) The batteries are fairly new (labeled 2020). But I can not find info for them online in order to determine their capacity. I intend to install an upgraded battery monitor but, as I understand it, I need to program the capacity of the batteries in order for that to serve any purpose. The batteries are labeled:
HDA Truck Pride Heavy Duty Premium. They are EITHER 31XHE-HD (925 CCA) or 31HE-HD (750 CCA). But the batteries don't specify which. When I search for info on these batteries online I get nothing. HDA Truck Pride appears to be some sort of distributor/rebrander and I can't find specs for my batteries. I'm MOSTLY interested in the amp hours available to me.
Deep draw coach batteries are usually rated in amp hours. Engine start batteries are usually rated in cold cranking amps. You are probably looking at engine start batteries even if they are connected to the coach system.
4) The cheap/original battery monitor has four states indicated with a light for each:
L - Low 5-11.9 V
F - Fair 12-12.5 V
G - Good 12.6 - 14.49 V
C - "Convertor, more than 14.5 volts (unfiltered circuit or dead cells in battery)"
At the moment the coach has been sitting unplugged for a few days and it reads Fair. On a few occasions when I check it reads Good. Each time I've had it plugged into the house for a day or two the reading seems to be C.
I'm trying not to get too worked up about this because that monitor is so rudimentary. Should I worry about this? Is my convertor bad/going bad? Suggestions?
Significantly higher than 14.4 volts while charging is a red flag for the converter charging, or engine charging. However, for flooded cell batteries occasional exposure is minor. You may need to add distilled water to the batteries more often.
Some RV battery chargers require a battery be present when shore power or generator power is present. Disconnecting the battery may allow voltage to climb beyond best practice.
F - Fair 12-12.5 V means above 50% state of charge when there is no charging or discharging.
Lead Acid Battery Voltages
There are three basic lead acid battery voltage profiles. They are "charging", "discharging", and "static".
Static means batteries are neither charging nor discharging. Voltage will slowly stabilize. Usually 3 hours rest provides accurate voltage. The static voltage can be used to estimate state of charge.
12.7 = 100%
12.1 = 50%
11.3 = 10%
Voltage starts a "static" level and slowly rises to what ever the charger is programed for. Typical voltages may be 13.2, 13.6, or 14.4. Many chargers will raise to 14.4 volts when charging deeply discharged batteries and later drop to 13.6 volts. 13.2 is ideal for long term storage.
Discharging voltage is always lower then static. The higher the current being drawn, the lower the voltage will go. When discharge stops, voltage will slowly raise to static level.
Battery University https://batteryuniversity.com/articles
How does the Lead Acid Battery Work?
How do battery chargers work
How to Charge and When to Charge?