[Feature Request] Prevent simultaneous EV charging and battery grid charging (Capacity Tariff optimization)

[xxxxminingxxxx]

Hi there,

First of all, thank you for the amazing work on Predbat. It’s a game-changer for Home Assistant energy management!

I would like to propose a new feature specifically aimed at users in regions with a Capacity Tariff (like Flanders, Belgium). In Belgium, we are billed based on our highest monthly peak (kW). Simultaneous high-draw activities can be very expensive.

The Problem: Currently, Predbat might decide to charge the home battery from the grid while the EV is also charging. If the battery charges at 5kW and the EV at 11kW, we hit a peak of 16kW instantly. This significantly increases the monthly bill due to the capacity tariff.

Proposed Feature: Add an option (e.g., in apps.yaml) to block or pause car charging whenever the home battery is actively charging from the grid.

Suggested configuration option:

YAML
car_charging_block_during_battery_grid_charge: True/False

Proposed Logic: If car_charging_block_during_battery_grid_charge is set to True:

• When Predbat initiates a battery charge from the grid (charge_enable is active), it should treat the EV charging slots as "unavailable" or force the EV charge to pause.

• Once the battery grid charge is complete, the EV charging can resume in the next available/cheapest slot.

This would allow users to spread their energy consumption over time, keeping the peak load as low as possible without sacrificing the benefits of cheap energy windows.

I am not a programmer myself, but I believe this would be a massive benefit for all Belgian users and anyone else dealing with peak-based billing.

Would this be something you'd consider adding to the roadmap?

Best regards, Mark

[gcoan]

Thanks for your suggestion. I think you could achieve this without needing predbat enhancement by varying your car charge rate and/or battery charge rate via an automation.

An automation could detect that your car is charging and reduce your battery charge rate in predbat, and conversely, if the battery is charging, throttle the car charge rate.

The car charge rate will depend on your EV charger integration, but to throttle the battery charge rate in predbat an automation action would look like this:

action: select.select_option
alias: Trickle charge battery, set charge rate to 1500W
target:
  entity_id:
    - select.predbat_manual_api
data:
  option: inverter_limit_charge(0)=1500

If you want to stop the charging totally, use ,inverter_limit_charge(0)=0

And set inverter_limit_charge(0) to its max value when you want to resume full rate battery charging.

[xxxxminingxxxx]

Thanks for your help finding a solution. It works, but... ;)

The problem with the current solutions:

Scheduling deviation: To avoid peaks, I use an automation to force the battery to charge at 4 kW (or 1 kW now when the EV is charging). However, Predbat still calculates its plan based on the 10 kW capacity of the hardware (we have a 10 kW inverter and a 10 kW and 20 kWh battery).

"Although Predbat recalculates regularly, it currently 'optimistically' schedules charging only during the cheapest times, using the full capacity of the inverter. By the time it realizes that the state of charge isn't rising fast enough due to my external limitation, the cheapest times are often already over. This causes Predbat to miss the intended state of charge or to have to charge during more expensive hours to catch up."

Limiting solar energy production: I can't simply set a general inverter limit in Predbat/Home Assistant, because that would also limit my solar energy production. If the sun produces 8 kW, I want to store all of that in the battery, but I want to limit grid charging to 4 kW or less to avoid capacity peaks.

Proposed solution: Introduce a specific parameter for the grid charging limit, independent of the inverter's physical limit, and a limit for battery charging when the car is charging.

grid_charge_limit: 4000 (Watts) -> Predbat uses this for its grid charging plan.
grid_charge_limit_ev_active: 1000 (Watts) -> A lower limit that is automatically activated when Predbat is charging the electric car.

Why this is a game changer:

Accuracy: Predbat can accurately predict how long it takes to charge the battery at these lower grid rates and adjust charging times accordingly.

Safety: It prevents the electric car and battery from piling up their load and causing high capacity costs.

Unfortunately, I can't implement these adjustments myself. ;)

[gcoan]

Thanks for the extra info.

You could change the batter charging rate depending on solar power prediction (max power forecast) and time of day (eg reduced charging overnight when import rates are generally lower).
These might help you achieve much of what you want in the short term.