Diversion controller on dc coupled system

Background; outback mx60 mppt feeding into a LiFePO4 pack, 2.4kW peak. 3kW outback inverter, no grid at this property.

I’m regularly in float my midday in the summer and I want to divert into my newly installed immersion heater (my tank never had one before yesterday).

I need a diversion controller that will accept an ‘enable’ input (my mx60 aux relay can be set to activate when in float’) that will then monitor the shunt I have in the -ve bus and then convert this into a phase angle to fire the immersion off the 230v side.

I don’t want to just connect the 3kW directly across the 230v side when in float as this will pull the battery voltage down and I’ll come home from work with probably 1/3rd of my capacity gone into the hot water. I want to track the excess solar production so I stay at my target %SOC.

I don’t want to run the immersion on battery power directly, as the batteries are 100m away from the house in an outbuilding.

Does anyone make what I’m looking for? If not then I’ll ditch the immersion idea and just use the float relay to turn on a modified swimming pool heat pump that I’ve bodged onto my vented cylinder. That will probably sit around 400w which the panels will just track and cover the demand for.

Edited August 23, 20233 yr by HughF