question

I've not looked at this from the Dbus side, but I detect throttling on my system by looking at the max current setpoint of the MPPT unit. Once this is reduced from the unit maximum, throttling is taking place. You can try looking at the following dbus services:

Once the MPPT operation mode goes from MPPT to CC/CV mode, then you know that limiting is taking place.

you also need to check when the MPPT first goes into CC mode, that the Battery current from the MPPT register is LESS than the maximum current for the unit.

How are you going to vary consumption? Normally in a system this is determined by the load, which is an uncontrolled variable?

Let me explain the original main goal behind the question.

The EV charger can either use 1phase, or 3phases.

The minimum charging current per phase is 6A.

When the EV charger starts with 1phase, the load on one phase bumps immediately by ~ 1380W,

When the EV charger starts with 3phases, the load bumps immediately by ~ 4000W,

The goal is to determine whether there is enough *Excess PV Power* available to start the EV charger, either on 1phase, or 3phases without drawing the power from Grid.

In our case, I will do this mostly when the house battery is already full.

A side note: house battery is much smaller than EV battery, so when the EV charger is active, the house battery needs to be put into idle mode so that it is not accidentally discharged into the car.

So you are left with Grid and PV only to charge the EV.

Computing excess PV is easy when Grid Feed In is enabled, because DC/AC coupled PV works on its maximum and you can easily compute the excess PV, for example by looking at the grid feed in.

But when the Grid Feed In is disabled, for example because the spot rices are negative, the AC/DC PV will get throttled to only accommodate the load.

The workaround I am using right now is to start the EV charger on low speed (6A) from grid anyway and observe for some time whether the PV has enough juice and whether it will ramp up, and if not, it will stop the EV charger automatically after some time, and then try manually again.

But out of academic interest, I'd love to find a nice solution that allows me to leave the car plugged in all the time, and push remaining PV juice in when available...

So to answer one of your questions.... Mppt is throttling when it is in abs or float mode.

mppt mode is available as a dbus value. Off the top of my head I think it is called "state".

As for knowing how much potential pv is available without trying to power a load, you would need an irradiance meter.

But you could do something like-

if mppt.state == 2 or mppt.state==3 (abs or float) then switch a relay to divert the panels to a fixed resistance dump load, measure the power produced and if it is enough then switch panels back to the mppt and enable the charger. repeat every 30 mins to check the sun is still out and power is enough.

I made an irradience meter from a small solar panel ( about 5W or so) , loaded with a low value power resistor (P > panel rating). This was connected to a spare analogue input, the resistor value was low enough that under full sun the voltage was less than the MPPT voltage, this ensures that you are operating in the linear range. You can then use the voltage across the resistor as an indication of the pv power available. The panel should be mounted in the same plane as the main solar array.