diff --git a/eg4battery/bin/eg4-battery b/eg4battery/bin/eg4-battery
index 292b631..dfbbd67 100755
--- a/eg4battery/bin/eg4-battery
+++ b/eg4battery/bin/eg4-battery
@@ -433,6 +433,12 @@ class ModbusActivePoller:
                 bytesize=8, parity="N", stopbits=1,
             )
 
+    # Some pack/FTDI combos (observed on 2026-05-11 batch) emit one or two
+    # line-idle bytes before the real Modbus frame, e.g. "00 f0 40 03 4e …".
+    # Tolerate up to this many leading non-frame bytes by sliding the
+    # window and CRC-checking each candidate offset.
+    _MAX_LEADING_IDLE = 4
+
     def _read_block(self, start: int, count: int) -> list[int]:
         body = bytes([self._address, 0x03,
                       start >> 8, start & 0xFF, count >> 8, count & 0xFF])
@@ -443,7 +449,8 @@ class ModbusActivePoller:
         self._ser.reset_input_buffer()
         self._ser.write(frame)
 
-        expected = 3 + count * 2 + 2
+        # Read enough bytes to also cover any leading idle bytes.
+        expected = 3 + count * 2 + 2 + self._MAX_LEADING_IDLE
         buf = bytearray()
         deadline = time.monotonic() + self._timeout_s
         while time.monotonic() < deadline and len(buf) < expected:
@@ -454,15 +461,21 @@ class ModbusActivePoller:
         log.debug("pack 0x%02x [%d@%d] tx=%s rx=%s",
                   self._address, count, start, frame.hex(" "), raw.hex(" "))
 
-        if len(raw) < 5 or raw[0] != self._address or raw[1] != 0x03:
-            raise RuntimeError(f"no/bad response ({len(raw)} B) for read({count}@{start})")
-        bc = raw[2]
-        if len(raw) < 3 + bc + 2:
-            raise RuntimeError(f"truncated response for read({count}@{start})")
-        if not _crc_ok(raw, 0, 3 + bc + 2):
-            raise RuntimeError(f"CRC mismatch for read({count}@{start})")
-        data = raw[3:3 + bc]
-        return [(data[i] << 8) | data[i + 1] for i in range(0, len(data), 2)]
+        # Locate the real frame: address byte + fn=0x03 + valid CRC, at
+        # offset 0..MAX_LEADING_IDLE. Reject any candidate whose CRC fails.
+        for off in range(min(self._MAX_LEADING_IDLE + 1, max(len(raw) - 4, 0))):
+            if raw[off] != self._address or raw[off + 1] != 0x03:
+                continue
+            bc = raw[off + 2]
+            frame_end = off + 3 + bc + 2
+            if frame_end > len(raw):
+                continue
+            if not _crc_ok(raw, off, 3 + bc + 2):
+                continue
+            data = raw[off + 3:off + 3 + bc]
+            return [(data[i] << 8) | data[i + 1] for i in range(0, len(data), 2)]
+
+        raise RuntimeError(f"no valid frame in {len(raw)} bytes for read({count}@{start})")
 
     def poll(self) -> list[int]:
         self._open()