DouglasBray

Any News on this configuration? Are you still just using Manual?

Your Typical 100A Deep Cycle Battery has a Maximum Charge Rate of 25A. For each Battery you place in Parallel you add the Charge rate (This is Roughly accurate and there are a number of factors that could influence this). So Effectively you are charging 300Ah Battery with 5A Charger (about 30 Hours to Charge from 50% or 15Hours to charge from 25% - again roughly and depending on so many factors). You really want to charge at around 50-80% of the Maximum of the Battery, so in your case 30-40A Charger.
These are just basic figures to help you understand, there are a number of Engineering Factors that still need to come into play, but if you look at it from this perspective: the amount of power you take out during load shedding is the same amount of power you must put back in while the power is on as long as it does not exceed the Battery or Charger Specifications (I like to use 50% of the Specified Maximum Values to be safe - Yes I know, I Over Engineer Everything, But is lasts...)