Diverting PV and battery to immersion heater

Hi, in lieu of getting GivTCP working with my old Synology DS214play I am in the process of building a cheaper version of an iBoost using v1 of the cloud API.

The idea is to use a smart 16 amp switch (I'm going to give a frient smart cable a go), when certain conditions apply. My hope is to use home assistant to integrate the frient with this node-RED flow. I'm still learning node-RED (not sure my use of parallel API calls is right or efficient) but it works in principle. I haven't hooked up the frient yet, so using a mobile phone notification to indicate when to turn the immersion on or off.

The logic is to turn on the immersion heater when battery is at 100% and there is a good amount of sun around (using forecast.solar to measure next hour's incident Wh) so it'll both supplement the battery and fully recharge the battery again afterwards. The immersion heater has a dual switch, so either heats a bit of water at around 2.5kW or the whole tank at around 3.2kW. Then turn it off when water temperature reached (i.e. the thermostat kicks in and power demand falls).

I have a 3kWp array and a GivEnergy AC 3.0 inverter.

Any thoughts?

The only issue I see is that you will be discharging and charging the battery quite a bit because the immersion heater is on off and even the lowest power will be close to the max the inverter will do if you include power for the house and anything less than full solar output.

I have a 3.6kW hybrid inverter with two strings - south and west (well 20’ off) with a total power of 4.6kw - though that won’t ever be seen - best I’ve seen is 3.5kw or thereabouts- given it was only installed in December so not had a full annual cycle yet.

anglefire

anglefire you're unlikely to see any more than 3.5kW with your two arrays at different angles - the geometry spreads out the peak generation over time (which is a good thing).

jkazer No need to forecast the solar, use the 5-minute actuals as your import will be tiny if the sun goes in anyway. You may want to set the charge threshold to a little less than 100% as the charging process may taper off, depending on the battery.

I put in a delay as yes anglefire it was "bouncing". In terms of solar prediction, I like this because it tells me the battery should be able to fully recharge again. But maybe I'm missing something and it can be simpler (I do just like the integration and logic of the different data sources though!). I'll certainly consider a trigger below 100%