question

I have been tackling the same thing. Found a common solution used by a lot of cruisers that is basically what I am adopting for my boat.

You can put all of the 50hz appliances on the opposite side of an inverter, so that the inverter always powers the appliances. You will not use the EasySolar to do this. You will have a good charger and then an large inverter. The Quattro's seem like a good choice. Size the inverter to handle all the 50hz items you want to run at once. Might be 8k, or even bigger. I am using a 15k on a big power hungry boat. You would also have an isolation transformer to handle the voltage difference. IT is a good device anyway, regardless of where you are plugged in.

Then just use a separate Smart Solar controller. (which will talk to the Victron chargers and inverters) This goes from your 1 device plan, to a 3 device plan, but you can then be delivering 50hz power all the time as everything will be running through the batteries first.

Your lithium batteries will handle the charge/discharge easily, but it does take some configuration to keep them at that 90% SOC sweet spot they like.

A 10kw frequency converter is about $14,000 - so this is a more practical solution.

One other option is to get serious about converting 50hz appliances to 50/60hz versions that take both. Some things are easy to find that way, but some items (microwaves) tend to only be built in one version or the other. If you can get to that point, you can then just use the Isolation Transformer to get the voltage right.

Hope this helps