Car charging plan empty after v8.34.7 — optimizer finds 0 combinations on hybrid inverter, collapsing import threshold

[kuriandk]

Describe the bug

After upgrading from v8.34.7 to v8.34.8+, car charging stops working entirely: car_charging_slots is empty, "Car kWh" in the plan shows 0.0, and "Hold for car" never triggers. Downgrading to v8.34.7 with the same config and same energy rates immediately restores everything.

The prediction model changes in the v8.34.7→v8.34.8 diff (new battery_rate_max_charge_dc, calculate_export_on_pv, removal of battery_rate_max_charge_scaled) cause the optimizer to evaluate 0 combinations on my Kostal hybrid inverter setup. This means best_price_charge_level stays at the minimum import rate instead of being set by actual charge window discovery. The import threshold then equals the minimum rate, nothing qualifies as a "low rate" window, and plan_car_charging() receives an empty slot list.

The car charging is collateral damage — the real problem is the optimizer producing no plan at all for this inverter type.

Side-by-side evidence — same config, same rates

	v8.34.7 (working)	v8.34.16 (broken)
Import rates	min 31.1, max 242.5	min 31.1, max 242.5
Rate thresholds	242.0øre	242.0øre
Optimizer combinations tried	141 (13.5 sec)	0 (0.0 sec)
best_price_charge_level	33.4øre	31.1øre (= min rate)
best_cycle	20.76 kWh	0 kWh
best_import	0.0 kWh → 1.62 kWh	0 kWh
Import threshold	223.1øre	31.1øre
Low import rate windows	46 windows	[] (empty)
Car charging slots	6 slots, ~50 kWh	[] (empty)
Hold for car	Works	Never triggers

Key log lines

v8.34.7 (working)

Optimise levels pass ended, duration 13.5 seconds tried 141 combinations
Set best_price_charge_level 33.4øre, best_price_export_level 80.4øre, best_price_charge 31.1øre
Import threshold used for optimisation was 223.1øre
Low Import rate found rates in range 31.1øre to 238.8øre
Car 0 plan charging from 0.0 to 46.0, with slots [46 slots]
Car 0 charging plan is: [6 charging slots totalling ~50 kWh]
Completed run status Hold for car

v8.34.16 (broken)

Optimise levels pass ended, duration 0.0 seconds tried 0 combinations
Set best_price_charge_level 31.1øre
Import threshold used for optimisation was 31.1øre
No low rate period found
Low import rate windows []
Car 0 plan charging from 0.0 to 46.0, with slots [] from SoC 0.0% to 46.0%, ready by 07:00:00
Completed run status Demand

Root cause

The v8.34.7→v8.34.8 diff (https://github.com/springfall2008/batpred/compare/v8.34.7...v8.34.8) changed prediction.py significantly:

1. battery_rate_max_charge_scaled removed, replaced with battery_rate_max_charge_dc — different semantics
2. New DC charging model in prediction.py — changes how ECO-mode battery charging from PV is scored for hybrid inverters
3. calculate_export_on_pv added (defaults to True) — adds metric_keep penalty in prediction, changing plan scores

These changes alter how the optimizer evaluates plans for hybrid inverters. On my Kostal hybrid setup (which doesn't set inverter_limit_charge_dc), the optimizer now finds 0 valid combinations. Since the optimizer doesn't run, best_price_charge_level stays at the minimum rate, which becomes the import threshold, which empties low_rates, which gives plan_car_charging() zero slots.

The car plan and "hold for car" are downstream victims — the core issue is the optimizer finding nothing worth doing.

Steps to reproduce

1. Use a Kostal hybrid inverter (or likely any hybrid inverter without inverter_limit_charge_dc set)
2. Use EnergiDataService or any spot price tariff
3. Configure num_cars: 1 with car_charging_planned resolving to true
4. Run v8.34.8 or later — optimizer tries 0 combinations, threshold = min rate, car plan empty
5. Downgrade to v8.34.7 — optimizer runs 141 combinations, threshold = 223.1øre, car plan populated, hold for car works

Predbat version

• Broken on: v8.34.8 through v8.34.16 (confirmed)
• Working on: v8.34.7

Environment details

• Inverter: Kostal hybrid (inverter_hybrid: true, custom template)
• Energy rates: EnergiDataService (Danish spot prices, øre/kWh)
• No Octopus Intelligent
• No inverter_limit_charge_dc set (new setting from v8.34.8)
• Car charger has no HA integration — using manual input_select.car_charger_plugged_in for car_charging_planned
• car_charging_plan_smart: false (default)

Key config

num_cars: 1
car_charging_battery_size: 46.0
car_charging_limit: 46.0
car_charging_rate: 11
car_charging_hold: true
car_energy_reported_load: true
car_charging_planned: input_select.car_charger_plugged_in
car_charging_plan_time: 07:00:00
car_charging_plan_smart: false
car_charging_plan_max_price: 80
car_charging_from_battery: false
inverter_hybrid: true
# inverter_limit_charge_dc: NOT SET

Attachments

• predbat.log from v8.34.16 (broken) — shows 0 optimizer combinations
• predbat.log from v8.34.7 (working) — shows 141 optimizer combinations, car plan populated
• Screenshots of "Hold for car" notifications working on v8.34.7
• predbat_debug yaml from v8.34.16 run (renamed to .yaml.txt)

vv8.34.16.txt
vv8.34.7.txt

predbat_debug.yaml.txt

[huuub]

I also had no charging of the EV yesterday.
I still also want to mention that if charging is allowed from the homebattery there is a problem if the max price to charge the battery from the grid is also taken into account.
If slots are planned to charge the ev from the battery that max price must be ignored. (which is not at the moment)

[springfall2008]

There's a second PR here that likely relates to this: #3687

[kuriandk]

There's a second PR here that likely relates to this: #3687

Thanks for the reply, I will try and test when the fix is released