I was originally told that there was an option to have a smart plug turn on when the battery was full. I have a few plugs but can't find any way to do this.
What I would like to do is...
When battery is full and its before X time, turn on the plug which controls the immersion heater.
This is because the export tarrif is pointless if I then import later on to heat water. Also its cheaper to heat it from solar (cost of the export loss) vs gas
StevenFitch if it's the GE smart plug, it's coming soon apparently.
If they're not GE your best be is using some automation tool like Home Assistant to control this
It'll need to be a good plug to run an immersion heater at 3.6kW...
I’d use the smart plug to activate a relay that switches a load from a separate feed.
Smart plug isn’t going to survive very long switching a large resistive load at or beyond its maximum rating.
Eddi would let you divert only if battery is full and vary the rate based on your export which might be better.
If you use an ordinary switch of any sort it will switch on the whole 3kW Immersion heater load. If the sun then goes in or it gets to dusk, the heater will start drawing your battery down. I've used an iBoost relay, which (by sensing the power being exported) uses only the available 'extra' power for the immersion heater. iBoost is fairly expensive and does have some restrictions, but it has given me 'free' hot water since installation in mid-May (In fact today, when there has been solid cloud and heavy rain all day, is the first day our boiler has fired-up since the iBoost was fitted, because the battery did not get fully charged)
Thanks for the replies. Yes its currently a GE smart plug. The iBoost sounds like the way forward then so will look into that. I had wondered about the power level through the smart sockets as seen some burn out in the past which were rated 13amp but clearly couldn't handle switching it. The relay idea would solve that though.
StevenFitch you can get a DIN Rail-mounted 20A DP contractor from Screwfix for less than a tenner. You then just need something to switch the 240v to energise it. The 20A contractor will last a long time compared to even a 16A relay.