question

You aren't mixing chemistry. You are mixing construction methods. They are both lead-acid, and it is a minor concern at best. Charging schema for FLA and AGM easily overlap. If you are charging to a compatible absorption and float voltage, I see no concerns. I would not replace them unless the FLA batteries are worn out.

Properly maintained FLA batteries will almost always outlast AGM batteries.

Would recommend the addition of a BMV 702 for current and voltage sensing and accurate State of Charge (SoC) reporting.

Something that will impact battery substantially is proper temperature compensation when charging. When batteries are cold, they should be charged to a higher voltage, and when warm, they should be charged to a lower voltage. At 77°F a battery that should be charged to 14.4V should be charged to 15.15% @ 32°F.

Secondly, preventing the house batteries from discharging below 50% will also improve their lives. The BMV 702 actually counts current in and out of the battery and computes it's actual state of charge as voltage is very unreliable for that purpose. Hopefully, the BMS can be adjusted to optimize battery life.

I always loose one or two lead acid batteries from the truck bank each year. I'm assuming from overcharging. The house AGM's are fine and have been in for the past 4 years. They are being charged from the truck alternator so I'm not able to control the charge voltage. Am I able to use (2) BMV 702's, one on each bank, and connect both of them to the Cerbo? I don't know how the solenoid connecting and disconnecting the banks will effect the SOC data?

IMHO, no BMV on the starter batts. You can if you want.

Disconnecting them at 12.6V should ensure they're still at a very high SoC when it transitions exclusively to house batteries.

The chassis bank won't affect SoC because the BMV on the primary (-) at the house battery is measuring net current to/from the house bank only. It will always report house bank SoC accurately. The chassis bank is just "bonus" capacity that probably won't contribute much overall.

Thank you for your input.

If you're losing batteries out of the starter bank, consider overcharging as a cause. Alternators charge at fixed voltage, unless you have a modern smart alternator. This means the batteries are at max charging voltage while the engine is running.

Probably worth looking at what the alternator is doing, consider either modifying it for variable output or replacing it with a smart version. I can't remember the name of the kit that often gets recommended here, though. Sorry.

The alternator is a 300 amp brushless, internally regulated, non adjustable unit. I am looking into either modifying it or replacing it with an adjustable externally regulated unit. I would then wire it to the house battery bank and use a DC to DC charger to charge the truck bank. Anyone with any input on this?

What size Multi II are you looking at installing, what are your power requirements?

Have you got anything else like heaters, fridges etc. running straight off the 12V house bank, or does all your stuff run off AC?

Have you considered replacing the house bank with lithium?

I'd look at completely separating the truck bank and house bank, in other words only use the truck bank for starting and running things while driving, while the motor is running, don't use the truck bank for heavy currents at all while parked.

Let the alternator charge the truck bank, then install multiple Orion DC-DC's to charge the house bank while driving.

If you totally separate the truck and house banks I'll also look at maybe going with a 24V, even 48V house bank rather than 12V.

I see you plan to install a 3000VA Multi, the rule of thumb is to try keep your amp draw on the DC side under 100A, with a 12/3000 Multi, you'll be drawing 250A, with a 24V Multi half of that.

Thank you for your input. I appreciate it.