Complete DIY install of Battery & AC Inverter

I have my own professionally installed and officially registered GivEnergy battery system which I monitor via the GivEnergy portal (& Home Assistant).
I'm doing a small DIY solar install for my daughter and I'm thinking of buying a 2nd hand GivEnergy AC Inverter from ebay along with a battery to add along side it, my question is has anyone done a similar thing with the intention of NOT registering it with GivEnergy and ONLY using a system like Home Assistant to monitor it and will an AC Inverter & battery actually work correctly without being associated with the GivEnergy Portal.

Graham_Harrison it will be in no shape or from condoned, but in theory it should be possible. Reality may mean some hiccups with it registering battery capacity and so on depending on how it was left before disconnection.
HA or rubikube app (paid) will do everything you need day to day however once you start needing to delve deeper, then you are going to come unstuck (such as export level setting or anything else like that - so you will be luck of the draw - you might buy one that was set to 0 export or something else limiting its function...)

Visibility of errors may be a bit hit and miss, I'm unsure how well errors like "BMS comms fail" translate through GivTCP, it may be ignored and hence leave you wondering why things have stopped working.

For clarity- I have a guinea pig gen 1 inverter to meddle with, it is not commissioned to the portal and controllable fine just with a dongle stuffed in it. Didn't add a battery to it though as wasn't needed for what I wanted it for.

I will also have to point out that although I applaud things like this, depending on just how DIY you are going, you may not find much sympathy from your DNO or building controls, insurance etc should things go wrong. That's your risk/reward call to make, I'm not your mum!
(Alternative brands might be more favourable to your plans)

Cheers hoggy, when you say "gen1" are you referring to a hybrid inverter not an ac only inverter.
I'm suspecting the guinea pig inverter that you are referring to is a hyrbrid and you are using it only with solar panels as you said you had not bought a battery.
If I'm correct with the above assumption then I might buy a hybrid instead as I can get 1 for about £300.
Any suggestions on "Alternative brands", I already have 2 small solis inverters (split system East / West) so I require an AC only inverter + battery.

Graham_Harrison it's a hybrid yes but actually just sat on a 13A plug with nothing attached to it. (I use it to try things out on the modbus library without risk of screwing a "real install")
The AC3 is essentially the same inverter with the PV parts removed so I'd imagine both would work the same while not connected to the cloud portal.

As far alternatives solis seem fairly solid. Allows you to use Pylontech (or any other knock off pack really as most of those imported batteries mimic a Pylontech one way or another)
Don't really have much experience in any other than Goodwe which was an obscure one I had fitted personally.

Given the number that have been sold on ebay and elsewhere, I suspect there are quite a few people running unregistered equipment.

If you want to use my android app, the free monitoring part can be run entirely off-line. Just download the app, the connect the phone/tablet directly to the dongle, and see what is happening. However to control the inverter (set timed charge, etc.) you would need the premium upgrade which is an in-app purchase through google play store. The in-app purchase tries to check in with google once a day, and if it makes no connection for 7 days, you will get an error screen. Easily fixed by connecting to google, but could be a pain if you want to run entirely off-line.