diff --git a/src/case.py b/src/case.py
index 76f106f..48e088f 100644
--- a/src/case.py
+++ b/src/case.py
@@ -46,8 +46,9 @@ class CaseOps:
     battery_harness_shell_thickness = 1.2
     battery_harness_margin_bottom = 22.3
     battery_harness_margin_top = 0.0
+    battery_margin_leftright = 4.0  #< how much room to reserve on each of the left and right sides of the battery
     # optionally, force a specific number of columns instead of radii
-    n_columns = 0
+    n_columns = None
 
     dark_gray = cq.Color(95/256, 87/256, 79/256)
     mid_gray = cq.Color(128/256, 118/256, 108/256)
@@ -62,7 +63,12 @@ class CaseOps:
 
     def __init__(self, config: Config):
         self.battery_harness_height = max(self.battery_harness_height, config.min_feature_z)
-        self.n_columns = config.battery_harness_shell_columns
+        if config.battery_margin_leftright is not None:
+            self.battery_margin_leftright = config.battery_margin_leftright
+        if config.battery_harness_shell_columns is not None:
+            self.n_columns = config.battery_harness_shell_columns
+        if config.battery_harness_shell_thickness is not None:
+            self.battery_harness_shell_thickness = config.battery_harness_shell_thickness
 
     def make_shell(self, body: cq.Workplane) -> cq.Workplane:
         p = self
@@ -286,6 +292,8 @@ class CaseOps:
         ))
         # shift to desired position
         battery = battery.translate((0, p.battery_shift_y, 0))
+
+        battery = thicken(battery.faces("<X or >X"), p.battery_margin_leftright, combine=True).union(battery)
         return battery
 
     # def battery_straps(phone, battery):
diff --git a/src/config.py b/src/config.py
index 224dc6a..ac6fbe3 100644
--- a/src/config.py
+++ b/src/config.py
@@ -12,7 +12,9 @@ class Config:
     min_feature_z: float = 0.0
 
     battery: str = DEFAULT_BATTERY
-    battery_harness_shell_columns: int = 0
+    battery_harness_shell_columns: int | None = None
+    battery_harness_shell_thickness: float | None = None
+    battery_margin_leftright: float | None = None
 
     # TODO: these should really be lifted out, as they don't impact the model
     render_phone: bool = False
@@ -40,6 +42,14 @@ class Config:
         if battery_harness_shell_columns is not None:
             self.battery_harness_shell_columns = int(battery_harness_shell_columns)
 
+        battery_harness_shell_thickness = os.environ.get("CASE_BATTERY_HARNESS_SHELL_THICKNESS_MM")
+        if battery_harness_shell_thickness is not None:
+            self.battery_harness_shell_thickness = float(battery_harness_shell_thickness)
+
+        battery_margin_leftright = os.environ.get("CASE_BATTERY_MARGIN_LEFTRIGHT_MM")
+        if battery_margin_leftright is not None:
+            self.battery_margin_leftright = int(battery_margin_leftright)
+
         min_feature_z = os.environ.get("CASE_MIN_FEATURE_Z_MM")
         if min_feature_z is not None:
             self.min_feature_z = float(min_feature_z)