diff --git a/backend/tests/test_planning_charge_slot_selection.py b/backend/tests/test_planning_charge_slot_selection.py
index 346c1e3..bbc99b0 100644
--- a/backend/tests/test_planning_charge_slot_selection.py
+++ b/backend/tests/test_planning_charge_slot_selection.py
@@ -31,18 +31,26 @@ def _prague_date(s: PlanningSlot) -> date:
     return s.interval_start.astimezone(_PRAGUE).date()
 
 
-def _export_window_start(slots: list[PlanningSlot], degrad: float) -> datetime | None:
-    """Kopie R__063: sell > min(buy) téhož kalendářního dne (Prague) + degrad."""
-    result: datetime | None = None
+def _export_window_start_by_day(
+    slots: list[PlanningSlot], degrad: float
+) -> dict[date, datetime]:
+    """Kopie R__063: první sell > min(buy) téhož kalendářního dne (Prague) + degrad."""
+    out: dict[date, datetime] = {}
     for s in slots:
         day = _prague_date(s)
-        day_min = min(
-            float(x.buy_price) for x in slots if _prague_date(x) == day
-        )
+        day_min = min(float(x.buy_price) for x in slots if _prague_date(x) == day)
         if float(s.sell_price) > day_min + degrad:
-            if result is None or s.interval_start < result:
-                result = s.interval_start
-    return result
+            prev = out.get(day)
+            if prev is None or s.interval_start < prev:
+                out[day] = s.interval_start
+    return out
+
+
+def _before_day_export(
+    slots: list[PlanningSlot], t: int, export_by_day: dict[date, datetime]
+) -> bool:
+    start = export_by_day.get(_prague_date(slots[t]))
+    return start is not None and slots[t].interval_start < start
 
 
 def _future_sell(slots: list[PlanningSlot], t: int) -> float:
@@ -55,13 +63,13 @@ def _buy_min_next_n(
     t: int,
     n: int = _LOOKAHEAD_SLOTS,
     *,
-    export_window_start: datetime | None = None,
+    export_by_day: dict[date, datetime] | None = None,
 ) -> float | None:
-    tail = [
-        float(slots[i].buy_price)
-        for i in range(t + 1, min(t + 1 + n, len(slots)))
-        if export_window_start is None or slots[i].interval_start < export_window_start
-    ]
+    tail: list[float] = []
+    for i in range(t + 1, min(t + 1 + n, len(slots))):
+        day_start = export_by_day.get(_prague_date(slots[i])) if export_by_day else None
+        if day_start is None or slots[i].interval_start < day_start:
+            tail.append(float(slots[i].buy_price))
     return min(tail) if tail else None
 
 
@@ -100,7 +108,7 @@ def _select_charge_slots(
         default=min(float(s.buy_price) for s in slots),
     )
     ref_buy_global = min(float(s.buy_price) for s in slots)
-    export_window_start = _export_window_start(slots, degrad)
+    export_by_day = _export_window_start_by_day(slots, degrad)
     plan_day = _prague_date(slots[0])
 
     eta = float(getattr(battery, "charge_efficiency", 1.0) or 1.0)
@@ -161,12 +169,7 @@ def _select_charge_slots(
 
     def _grid_sort_key(t: int, pred: bool, price: float) -> tuple[int, int, int, float, int]:
         today_first = 0 if _prague_date(slots[t]) == plan_day else 1
-        before_export = (
-            0
-            if export_window_start is not None
-            and slots[t].interval_start < export_window_start
-            else 1
-        )
+        before_export = 0 if _before_day_export(slots, t, export_by_day) else 1
         return (today_first, before_export, int(pred), price, t)
 
     if purchase_pricing_mode != "fixed":
@@ -733,6 +736,38 @@ class FixedPurchasePricingTests(unittest.TestCase):
         night = {t for t in out if _prague_hour(slots[t]) < 8}
         self.assertGreater(len(night), 0, "očekáváno grid nabíjení v noci před večerním výkupem")
 
+    def test_fixed_nt_charge_after_yesterday_evening_peak(self) -> None:
+        """Včerejší večerní peak nesmí zablokovat dnešní 00–06 grid (per-day export okno)."""
+        base = datetime(2026, 5, 23, 20, 0, tzinfo=_PRAGUE)
+        slots: list[PlanningSlot] = []
+        for i in range(64):
+            t = base + timedelta(minutes=15 * i)
+            sell = 3.8 if t.hour >= 20 and t.date() == date(2026, 5, 23) else 2.9
+            if t.date() == date(2026, 5, 24) and t.hour >= 19:
+                sell = 3.7
+            slots.append(
+                _slot(
+                    buy=3.088,
+                    sell=sell,
+                    load=200,
+                    interval_start=t.astimezone(timezone.utc),
+                )
+            )
+        battery = _battery(charge_buf=1.3, uc_wh=12_500.0)
+        out = _select_charge_slots(
+            slots,
+            battery,
+            current_soc_wh=0.33 * battery.usable_capacity_wh,
+            purchase_pricing_mode="fixed",
+        )
+        may24_night = {
+            t
+            for t in out
+            if _prague_date(slots[t]) == date(2026, 5, 24)
+            and _prague_hour(slots[t]) < 6
+        }
+        self.assertGreater(len(may24_night), 0)
+
     def test_fixed_allows_discharge_on_high_sell(self) -> None:
         slots = [
             _slot(buy=3.09, sell=1.0, hour_utc=10),
diff --git a/db/routines/R__063_fn_load_planning_slots_full.sql b/db/routines/R__063_fn_load_planning_slots_full.sql
index 4d6639e..15235d3 100644
--- a/db/routines/R__063_fn_load_planning_slots_full.sql
+++ b/db/routines/R__063_fn_load_planning_slots_full.sql
@@ -304,24 +304,33 @@ begin
   from _ems_plan_slot_wk wk
   where extract(hour from wk.interval_start at time zone 'Europe/Prague') >= 12;
 
-  -- První výkupní okno: sell nad min(buy) **téhož kalendářního dne** (Prague), ne globální
-  -- min(buy) zítra (NT) — jinak okno začne už ~15:30 a dnešní PM grid dostane 1 slot.
-  select min(wk.interval_start)
-  into v_export_window_start
-  from _ems_plan_slot_wk wk
-  where wk.sell_price > (
-    select coalesce(min(w2.buy_price), wk.buy_price) + v_degrad_czk_kwh
-    from _ems_plan_slot_wk w2
-    where (w2.interval_start at time zone 'Europe/Prague')::date
-      = (wk.interval_start at time zone 'Europe/Prague')::date
-  );
-
   -- Lookahead min buy (VT→NT) a store_score pro vrstvu A.
   alter table _ems_plan_slot_wk
     add column if not exists future_sell_lookahead numeric,
     add column if not exists buy_min_next_n numeric,
     add column if not exists store_score numeric,
-    add column if not exists allow_grid_charge boolean default false;
+    add column if not exists allow_grid_charge boolean default false,
+    add column if not exists export_window_start_at timestamptz;
+
+  -- První výkupní okno **per kalendářní den** (Prague). Globální min přes dny by
+  -- zablokoval NT grid nabíjení (včerejší večerní peak → dnešní 00–06 už „po okně“).
+  update _ems_plan_slot_wk wk
+  set export_window_start_at = (
+    select min(wx.interval_start)
+    from _ems_plan_slot_wk wx
+    where (wx.interval_start at time zone 'Europe/Prague')::date
+        = (wk.interval_start at time zone 'Europe/Prague')::date
+      and wx.sell_price > (
+        select coalesce(min(w2.buy_price), wx.buy_price) + v_degrad_czk_kwh
+        from _ems_plan_slot_wk w2
+        where (w2.interval_start at time zone 'Europe/Prague')::date
+          = (wx.interval_start at time zone 'Europe/Prague')::date
+      )
+  );
+
+  select min(wk.export_window_start_at)
+  into v_export_window_start
+  from _ems_plan_slot_wk wk;
 
   update _ems_plan_slot_wk wk
   set
@@ -339,8 +348,8 @@ begin
       where w2.slot_ord > wk.slot_ord
         and w2.slot_ord <= wk.slot_ord + v_lookahead_slots
         and (
-          v_export_window_start is null
-          or w2.interval_start < v_export_window_start
+          wk.export_window_start_at is null
+          or w2.interval_start < wk.export_window_start_at
         )
     ),
     store_score =
@@ -431,8 +440,8 @@ begin
             else 1
           end,
           case
-            when v_export_window_start is not null
-              and wk.interval_start < v_export_window_start
+            when wk.export_window_start_at is not null
+              and wk.interval_start < wk.export_window_start_at
             then 0
             else 1
           end,
@@ -479,8 +488,8 @@ begin
             else 1
           end,
           case
-            when v_export_window_start is not null
-              and wk.interval_start < v_export_window_start
+            when wk.export_window_start_at is not null
+              and wk.interval_start < wk.export_window_start_at
             then 0
             else 1
           end,
@@ -522,8 +531,8 @@ begin
             else 1
           end,
           case
-            when v_export_window_start is not null
-              and wk.interval_start < v_export_window_start
+            when wk.export_window_start_at is not null
+              and wk.interval_start < wk.export_window_start_at
             then 0
             else 1
           end,
@@ -567,8 +576,8 @@ begin
             else 1
           end,
           case
-            when v_export_window_start is not null
-              and wk.interval_start < v_export_window_start
+            when wk.export_window_start_at is not null
+              and wk.interval_start < wk.export_window_start_at
             then 0
             else 1
           end,
diff --git a/docs/planning-changelog.md b/docs/planning-changelog.md
index 1f30df9..17d7960 100644
--- a/docs/planning-changelog.md
+++ b/docs/planning-changelog.md
@@ -108,6 +108,18 @@ where pr.site_id = (select id from ems.site where code='BA81') and pr.status='ac
 
 ---
 
+## 2026-05-24 (d) — BA81: grid jen 1 slot (globální export okno)
+
+**Problém:** Run **15820** — mírné zlepšení (1× ~4,5 kW grid+bat o půlnoci), ale **00:45–05:45 `allow_charge=false`**, max nabíjení pořád ~3,3 kW z FVE.
+
+**Příčina:** `v_export_window_start` = **min přes celý horizont** (včerejší večerní sell 3,7 → čas ~22:15). Grid vrstva B řadí „před oknem“ vůči tomuto **jednomu** času → dnešní NT sloty (00–06) už jsou „po okně“ a nedostanou `allow_grid_charge`.
+
+**Oprava:** Sloupec **`export_window_start_at` per kalendářní den** (Prague); grid AM/PM i `buy_min_next_n` používají `wk.interval_start < wk.export_window_start_at`.
+
+**Deploy:** `flyway migrate` (R__063) + replan.
+
+---
+
 ## Šablona pro další záznamy
 
 ```markdown