diff --git a/README.md b/README.md
index b61881e..8d420ce 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@
 `pip install pygrocy`
 
 ## Usage
-Import the package: 
+Import the package:
 ```python
 from pygrocy import Grocy
 ```
@@ -38,4 +38,4 @@ for entry in grocy.stock():
 If you need help using pygrocy check the [discussions](https://github.com/SebRut/pygrocy/issues) section. Feel free to create an issue for feature requests, bugs and errors in the library.
 
 ## Development testing
-You need tox and Python 3.6/8/9 to run the tests. Navigate to the root dir of `pygrocy` and execute `tox` to run the tests.
+You need tox and Python 3.8/9/10 to run the tests. Navigate to the root dir of `pygrocy` and execute `tox` to run the tests.
diff --git a/pygrocy/grocy_api_client.py b/pygrocy/grocy_api_client.py
index 5a171c8..012a2d4 100644
--- a/pygrocy/grocy_api_client.py
+++ b/pygrocy/grocy_api_client.py
@@ -3,11 +3,11 @@
 import logging
 from datetime import datetime
 from enum import Enum
-from typing import Dict, List, Optional
+from typing import Dict, List, Optional, Any
 from urllib.parse import urljoin
 
 import requests
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, validator
 from pydantic.schema import date
 
 from pygrocy import EntityType
@@ -21,6 +21,17 @@
 _LOGGER.setLevel(logging.INFO)
 
 
+def _field_not_empty_validator(field_name: str):
+    """Reusable Pydantic field pre-validator to convert empty str to None."""
+    return validator(field_name, allow_reuse=True, pre=True)(_none_if_empty_str)
+
+
+def _none_if_empty_str(value: Any):
+    if isinstance(value, str) and value == "":
+        return None
+    return value
+
+
 class ShoppingListItem(BaseModel):
     id: int
     product_id: Optional[int] = None
@@ -76,7 +87,7 @@ class ProductData(BaseModel):
     id: int
     name: str
     description: Optional[str] = None
-    location_id: int
+    location_id: Optional[int] = None
     product_group_id: Optional[int] = None
     qu_id_stock: int
     qu_id_purchase: int
@@ -87,6 +98,9 @@ class ProductData(BaseModel):
     min_stock_amount: Optional[float]
     default_best_before_days: int
 
+    location_id_validator = _field_not_empty_validator("location_id")
+    product_group_id_validator = _field_not_empty_validator("product_group_id")
+
 
 class ChoreData(BaseModel):
     id: int
@@ -102,6 +116,10 @@ class ChoreData(BaseModel):
     next_execution_assigned_to_user_id: Optional[int] = None
     userfields: Optional[Dict]
 
+    next_execution_assigned_to_user_id_validator = _field_not_empty_validator(
+        "next_execution_assigned_to_user_id"
+    )
+
 
 class UserDto(BaseModel):
     id: int
@@ -113,8 +131,8 @@ class UserDto(BaseModel):
 
 class CurrentChoreResponse(BaseModel):
     chore_id: int
-    last_tracked_time: Optional[datetime]
-    next_estimated_execution_time: datetime
+    last_tracked_time: Optional[datetime] = None
+    next_estimated_execution_time: Optional[datetime] = None
 
 
 class CurrentStockResponse(BaseModel):
@@ -160,7 +178,7 @@ class ProductDetailsResponse(BaseModel):
 class ChoreDetailsResponse(BaseModel):
     chore: ChoreData
     last_tracked: Optional[datetime] = None
-    next_estimated_execution_time: datetime
+    next_estimated_execution_time: Optional[datetime] = None
     track_count: int = 0
     next_execution_assigned_user: Optional[UserDto] = None
     last_done_by: Optional[UserDto] = None
@@ -193,11 +211,14 @@ class TaskResponse(BaseModel):
     assigned_to_user: Optional[UserDto] = None
     userfields: Optional[Dict] = None
 
+    category_id_validator = _field_not_empty_validator("category_id")
+    assigned_to_user_id_validator = _field_not_empty_validator("assigned_to_user_id")
+
 
 class CurrentBatteryResponse(BaseModel):
     id: int
     last_tracked_time: Optional[datetime] = None
-    next_estimated_charge_time: datetime
+    next_estimated_charge_time: Optional[datetime] = None
 
 
 class BatteryData(BaseModel):
@@ -214,7 +235,7 @@ class BatteryDetailsResponse(BaseModel):
     battery: BatteryData
     charge_cycles_count: int
     last_charged: Optional[datetime] = None
-    next_estimated_charge_time: datetime
+    next_estimated_charge_time: Optional[datetime] = None
 
 
 class MealPlanSectionResponse(BaseModel):
@@ -223,6 +244,8 @@ class MealPlanSectionResponse(BaseModel):
     sort_number: Optional[int] = None
     row_created_timestamp: datetime
 
+    sort_number_validator = _field_not_empty_validator("sort_number")
+
 
 class StockLogResponse(BaseModel):
     id: int
@@ -620,7 +643,7 @@ def get_recipe(self, object_id: int) -> RecipeDetailsResponse:
             return RecipeDetailsResponse(**parsed_json)
 
     def get_batteries(self) -> List[CurrentBatteryResponse]:
-        parsed_json = self._do_get_request(f"batteries")
+        parsed_json = self._do_get_request("batteries")
         if parsed_json:
             return [CurrentBatteryResponse(**data) for data in parsed_json]
 
diff --git a/test/test_product.py b/test/test_product.py
index 86e5446..8619b1c 100644
--- a/test/test_product.py
+++ b/test/test_product.py
@@ -26,7 +26,7 @@ def test_product_get_details_valid(self, grocy):
         assert product.qu_factor_purchase_to_stock == 1.0
         assert product.default_quantity_unit_purchase.id == 5
         assert product.default_quantity_unit_purchase.name == "Tin"
-        assert product.default_quantity_unit_purchase.description == None
+        assert product.default_quantity_unit_purchase.description is None
         assert product.default_quantity_unit_purchase.name_plural == "Tins"
 
         assert len(product.product_barcodes) == 2