Yes exactly. Even the 2x AGM you installed was a bit light. Should have been 4. I recommend 280+ Ah with LFP to drive the microwave through the inverter. Yes you can often squeak by with less but it leaves a system that could be unreliable or wears out prematurely.Not sure what you meant by 'inverter connected to the microwave'. I installed the inverter in 2018 along with 2 group 31 AGM batteries. And yes, the original battery was likely installed by the dealer. The inverter, battery and charge controller are all mounted together in a side compartment. No direct connection between the inverter and microwave. The shore cord plugs into the inverter to power the trailer/microwave. I still need to verify whether the trailer converter is trying to charge the battery in this configuration.