[Dsull]

Quick question as I'm not 100% knowledgable on 12 volt systems beyond what I read to install my solar, and Automotive systems.

First, the system.
I have the 400 Watt Kit from Renogy. Running 8 AWG between panels to Junction box, and then 4 AWG to controller. 40 AMP breakers on either side of the controller to my buss Bar
2/0 cables to my 4 6-volt batteries
80 amp breaker to Inverter, 300 Amp Catastrophic fuse between battery bank and Bus bar. Inverter running 2/0 Gauge wires to 1000 watt Aims inverter.

Meter is a Victron BMV-712 with 500 Amp shunt. Wired through 2/0 Gauge between bus bar and battery ground.

During the summer I rarely saw it drop below 12.2 volts even with the kids watching movies at night, Mini fridge and my CPAP. Now that it's cold, I'm seeing voltages under load around 11.6-11.7 but the meter only showing about 120 amp hours used. This is with the Furnace running pretty heavy (5-7 amp Draw), a minifridge for the coldies (2-3 amp draw intermittent) and my CPAP going all night (it's a hog, 7-10 amps before I turned down the humidity and heated hose settings to lowest). I got paranoid and ran my little honda 650 generator direct 12 volt to batteries the second night as it charges fastest that way (15 amps output).

I guess my question is should I be scared of the voltage or is it normal with the amount of load hitting the batteries. The meter showed full voltage by around 5 PM after charging around 27 amp hours during the day during full sun, and the tail in and tail out periods as the sun went up and down. Never lost inverter power to A/C system, and furnace was good all night. Just not used to seeing the meter drop that far and throw on low voltage alarm.

Do I need to run 2 more batteries or is this normal?