Predbat + Tesla Powerwall 3 + Octopus Intelligent Go + IONIQ 5 — Is my config correct for my circumstances?

[thorrrr]

My Setup

• Battery: Tesla Powerwall 3 (13.5 kWh), 20% backup reserve set in Tesla app
• Solar: Recently installed, Solcast integration working
• Tariff: Octopus Intelligent Go — 7p off-peak (23:30–05:30), 30.51p peak
• EV: Hyundai IONIQ 5 (77.4 kWh), Hypervolt 7kW charger, charge limit set to 80%
• EV pattern: Car is plugged in almost every night. Weekdays it goes to work so needs a proper overnight charge. Weekends it barely moves — 2–3% used at most — so only needs a tiny top-up (~2
  kWh)
• Predbat status: Monitor mode. Export MPAN being added by Octopus on 9 March, then switching to control mode

---

Relevant apps.yaml config

inverter_type: TESLA
soc_max: "13.5"
battery_minimum_soc: 20
inverter_reserve_max: 80

car_charging_battery_size: 77.4
car_charging_soc:
- sensor.ioniq_5_ev_battery_level
car_charging_limit:
- number.ioniq_5_ac_charging_limit

octopus_intelligent_slot: 're:(binary_sensor.octopus_energy([0-9a-z_]+|)intelligent_dispatching)'
octopus_ready_time: 're:((select|time).octopus_energy([0-9a-z_]+|)intelligent_target_time)'
octopus_charge_limit: 're:(number.octopus_energy([0-9a-z]+|)_intelligent_charge_target)'

days_previous:
- 7
days_previous_weight:
- 1

charge_stop_service:
- service: number.set_value
entity_id: number.starlight_cottage_backup_reserve
value: "20" # preserves Tesla 20% backup reserve

---

Issue 1: Car charging massively overestimated on weekends

The plan consistently shows 3.7 kWh per 30-min slot across the entire cheap rate window = 44.4 kWh total car charging. But on a weekend the car is at 77% SOC with an 80% limit — it only needs
~2.3 kWh.

I've added car_charging_battery_size, car_charging_soc and car_charging_limit but the plan hasn't changed. I suspect Predbat is reading Octopus Intelligent's planned dispatch slots instead of
calculating from live SOC/limit.

Worth noting: vehicle_battery_size_in_kwh: null in the Octopus dispatching sensor — Octopus doesn't know the car battery size.

Is there something I'm missing in the config to make Predbat use the live car SOC rather than historical/dispatch data?

---

Issue 2: Powerwall not being charged during cheap rate on poor solar nights

On nights where Solcast is forecasting poor generation the next day, the plan shows the Powerwall sitting at its 20% floor for the entire cheap rate window — all cheap slots are attributed to
car charging. Battery enters the morning at 20%, then imports from grid at 30.51p until solar eventually recovers it mid-afternoon.

Real example from last night: rain and heavy cloud all day today, currently only 1.5kW solar. Predbat's plan showed no Powerwall charging overnight. If I hadn't manually overridden it I'd be
drawing from grid at 30.51p all day.

Is Predbat's plan correct here — i.e. is it genuinely optimal to leave the Powerwall at 20% and let car charging take the cheap rate? Or is something wrong with how it's calculating the
trade-off?

---

Issue 3: battery_minimum_soc and Tesla SOC reporting

I've set battery_minimum_soc: 20 to match the Tesla 20% backup reserve. The Predbat settings page shows best_soc_min: 2.7 which is 20% of 13.5 kWh — looks right.

However the plan still shows the SOC floor at 4% not 20%. Is sensor.starlight_cottage_percentage_charged reporting 0–100% of total capacity or 0–100% of usable capacity above the reserve? I
want to make sure the 20% minimum is being applied correctly.

---

Issue 4: charge_stop_service — backup reserve

The default config had charge_stop_service setting the Tesla backup reserve to "0" when Predbat stops charging. I've changed this to "20" to preserve emergency backup power. Is this the
correct approach, or does Predbat manage the reserve differently and I'm interfering with something?

---

Summary

In monitor mode Predbat looks very promising — on good solar days it correctly skips cheap rate charging because Solcast predicts enough generation. But on poor solar days it appears to leave
the Powerwall uncharged because it thinks the car needs all the cheap rate capacity. Given my weekend EV usage that assumption is wrong 95% of the time.

Any advice on getting the car SOC/limit calculation working correctly so Predbat can properly balance Powerwall vs EV charging?
pred_bat.md