question

Just having a thought...

In that default, lets call it, "RV Mode". It would give me what I want out of the box with the only stipulation being, it would be up to me to manually (or via smart switch) give the Multiplus "shore power".

It doesn't need to know where the shore power comes from or why its there now and not before. It can shut up and charge the damn batteries and produce AC power.

Blunt, but does that work? I can then, maybe, later upgrade to allow the Victron ESS/Eco-system control more of the process?

Yes all the settings you mention work, however the words you've used aren't the words victron uses as you'd expect.

Personally when I was shopping around victron seemed one of the few providers that seemed (with some configuration) to support most if not all scenarios. Whereas other systems (which sounds like you've noticed) require some external internet connection gadget or some cloud app to function.

I think for your setup you either need a GX inverter or cerbo gx or a raspberry pi (with venus OS). If you go raspi route you'll need some adapters to turn victron devices into USB (MK3 to usb for multiplus and another for MPPT i cant remember the name of that one though sorry)

I'm making assumptions here but given you know what a raspi is I think victron is a good choice for you. A lot of potential for adding your own drivers (for DIY tank sensors and many more) and all data is accessible via MQTT and modbusTCP so you'll have fun adding custom devices/systems. It's far more open than other solar systems I've seen. The fact their monitoring system can run on a raspi (it's not debian based but still really useful).

When you say when battery gets to specific voltage what it swaps to grid if available is just Min SOC setting in ESS if you go ESS route. However in your setup you want shore to be used when connected in which case you'd set this to 100 as you want shore to charge batteries to 100 (ie shore preference).

This done on battery state of charge rather than voltage you mentioned. Which I imagine you'll do if you're using LiFePO4 as voltage is often difficult metric for SoC on LiFePO4.

You'll wire AC/Shore into ACIN then your loads on ACOUT1 or ACOUT2 (ACOUT1 stays on when grid goes down whereas ACOUT2 does not).

Depending on your setup if you're using a supported BMS with you LFP battery the SoC and other battery data can be connected to the victron system. If you're using a BMS that isn't supported (yet) or you dont want to stress about configuring the communication between victron and BMS then you'll need a smart shunt which essentially counts amps in vs amps out to track SoC of LFP batteries given voltage isn't a great indicator. (I personally prefer smart shunt setup, however if your BMS isn't supported there are tonnes of community made drivers to integrate them or you can make your own, most are written in python and Victron provides template drivers to add to venus os to help get you started on writing python scripts to integrate your own devices).

Thank you for taking the time. I have purchased a Multiplus 24/800.

My next question is a little more tricky, apparently. I think it's simple, but others disagree.

Given the "Multiplus range", at least some models "can" be configured as "grid tie" inverters they will require G98/G99 and DNO sign off to be connected.

I'm not convinced the 24/800 MP actually 'can' feed the grid. Even if I configured it so.

I'm also not convinced I need to do anything other than get an electrician to install the unit and it's correct earthing.

I used to be sure about where the regulations ended, but the recent updates to those particular british regulations are ... untenably and obviously an industry support effort "impetus" from teh government. The contenous issue is the net now extends to include, any and all storage and generation equipemtn regardless of AC/DC off grid of on grid. All come under the regulations.

The reality is probably that very, very few line items actually apply, but reading some of the documentation on gov.uk and those documents are not for consumer use and include everything from 5MW CCGT plants to 3MW wind turbines and makes scant reference to anything under 0.8kW... however it "implies" that all ESS systems are covered now.

Like most British standards if taken verbatim and word for word, you wouldn't be able to do ANYTHING. Working out which clauses apply and which parts apply in which circumstances requires an engineering degree!

That's absolutely fine if you ARE installing a 5MW renewables generation plant in your farm field, but not if you are trying to run a fridge and server off a solar panel in the garden. It forces you into paying for engineering talent, certification and skill sets which are hard to find and very expensive.

While ESS may be a solution, it does require Venus OS.

Instead, you could use the "Ignore AC input" virtual switch or assistants all within the Multi.