Battery - to take advantage of 2am to 5am cheap rate electricity - v2

I'm thinking of buying a battery set up of Life po4 15-20kwh to use cheap ev rate. I have two evs but one charge each a weak usually covers them. I'm not adverse to a diy battery but having done some research and watched alot of Will Prowse reviews, I've been turned off the Aliexpress route (unless someone can recommend a good seller) My roof is not great for solar but may add at a later date, at back of house on a separate structure yet to be built. Can anyone recommend a good value system that's safe/reliable and an installer who knows what they're doing (greater Dublin area).One final thing, has anyone imported any EG4 hybrid/batteries from USA or is it cost prohibitive. I was on their site and shipping looks to be about $350 to Ireland, which I wouldn't mind paying as it seems great kit. Don't know how import duties would affect the price either. Any response/guidance much appreciated.

Really appreciate your advice and it's just what I needed to hear. I will have a look at your suggestions and whatever I end up doing, I'll post here. Thanks.

Thanks, appreciate the help and support. One thing that concerns me is do RECI electricians have any reluctance when connecting diy battery build to the grid to complete the set up.

Should have gone JKBMS version since it has built in balancer and potentially better compatibility with inverters (and support from boardsies) but either way I'm sure it will work out better than non DIY packs

Well done, I'm starting down a similar path soon hopefully.

China. EU stock was considerably more expensive. 7-10 days to ship, 60-70 days to deliver, should be here early to mid December.

90 days is more realistic so be prepared for that.

Just tell them to wire the battery fuse/disconnect to the inverter and then you just wire up the batteries yourself, very easy to do.

You also do NOT need RECI approval to connect DC batteries to your system so for insurance purposes you're all good.

You can do the batteries afterwards yourself. Just have the battery case and fuse holder dimensions before the RECI starts and ensure space is left for them.

Yes, will do that down the line when I get solar. Problem is, nobody just adds an inverter to the house without solar or battery.

Similar setup and I'm using 35mm2 from the batteries to the switch and then 140mm2 from both + and - to inverter 2x70mm2 for + and - which is overkill but the inverter requires two connections for each to reach 300a and the cables aren't getting hot.

Was thinking about that calculator as well and how it underestimates the value, as I might split the batteries to bus bars so I can add a rectifier for extra pumping in winter.

Also that 400a bus bar has 11 holes in it, surely if you remove all that copper then it should no longer carry the same?

I've seen domestic bus bars been given different ratings depending on how you connect them.

So if you connected your inverter at one end and the batteries at the other then the bar will see the whole current as apposed to connecting the inverter in the center and the batteries at the ends its only seeing half the current .