diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 4cd7072..3f19a28 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -94,6 +94,14 @@ jobs:
           cmake --build build/debug --target ds5-bridge
           cp build/debug/ds5-bridge.uf2 artifacts/ds5-bridge-debug.uf2
 
+      - name: Build no-batt-led firmware (compile check only)
+        run: |
+          cmake -S . -B build/no-batt-led -G Ninja \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DPICO_SDK_PATH="$PICO_SDK_PATH" \
+            -DENABLE_BATT_LED=OFF
+          cmake --build build/no-batt-led --target ds5-bridge
+
       - name: Upload standard UF2 artifact
         uses: actions/upload-artifact@v7
         with:
diff --git a/README.md b/README.md
index 088e370..3e29bbd 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,12 @@ The Pico device will only be visible to the system after the controller is conne
 
 Some behaviors depend on reconnection cycles to take effect
 
+### Low-battery LED indicator
+
+When the connected DualSense reports its battery at or below 10% (and it is not charging), the Pico onboard LED switches from solid-on to a 1 Hz blink so you can see the warning at a glance. The LED returns to solid-on as soon as the controller is plugged in or its reported level rises again. The blink also fires when `disable_pico_led` is set — the warning is treated as critical and overrides the LED-off preference; the LED returns to its disabled (off) state once the battery recovers or the controller starts charging.
+
+To opt out at build time, configure with `-DENABLE_BATT_LED=OFF`. Default is ON.
+
 ## Known Issues
 
 - ⚠️ Audio may experience slight stuttering
diff --git a/src/battery_led.cpp b/src/battery_led.cpp
new file mode 100644
index 0000000..7e457a2
--- /dev/null
+++ b/src/battery_led.cpp
@@ -0,0 +1,73 @@
+//
+// Low-battery LED indicator. See battery_led.h.
+//
+
+#include "battery_led.h"
+
+#include <cstdint>
+
+#include "config.h"
+#include "pico/cyw43_arch.h"
+#include "pico/time.h"
+
+extern uint8_t interrupt_in_data[63];
+
+namespace {
+
+constexpr uint64_t REPORT_STALE_US = 2'000'000;  // assume disconnected if no report for 2 s
+constexpr uint64_t BLINK_PERIOD_US =   500'000;  // 1 Hz, 50% duty
+constexpr uint8_t  THRESHOLD_LEVEL = 1;          // PowerPercent <= 1 (i.e. <= 10%)
+constexpr uint8_t  POWER_STATE_DISCHARGING = 0x0;
+
+uint64_t last_report_us = 0;
+uint64_t last_toggle_us = 0;
+bool     blinking       = false;
+bool     led_state      = false;
+
+}  // namespace
+
+void battery_led_init(void) {
+    last_report_us = 0;
+    last_toggle_us = 0;
+    blinking = false;
+    led_state = false;
+}
+
+void battery_led_note_report(void) {
+    last_report_us = time_us_64();
+}
+
+void battery_led_tick(void) {
+    const uint64_t now = time_us_64();
+    if (last_report_us == 0 || (now - last_report_us) >= REPORT_STALE_US) {
+        // No fresh data — bt.cpp owns the LED while disconnected.
+        blinking = false;
+        return;
+    }
+
+    const uint8_t b   = interrupt_in_data[52];
+    const uint8_t pct = b & 0x0F;
+    const uint8_t st  = (b >> 4) & 0x0F;
+    const bool low    = (st == POWER_STATE_DISCHARGING) && (pct <= THRESHOLD_LEVEL);
+
+    if (low) {
+        // Critical warning: override disable_pico_led so the user always sees it.
+        if (!blinking) {
+            blinking = true;
+            led_state = true;
+            last_toggle_us = now;
+            cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, true);
+            return;
+        }
+        if ((now - last_toggle_us) >= BLINK_PERIOD_US) {
+            led_state = !led_state;
+            last_toggle_us = now;
+            cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, led_state);
+        }
+    } else if (blinking) {
+        blinking = false;
+        // Battery recovered or now charging — restore steady-state LED per the user
+        // preference flag (LED off when disabled, otherwise the bt.cpp connected = on state).
+        cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, !get_config().disable_pico_led);
+    }
+}
diff --git a/src/battery_led.h b/src/battery_led.h
new file mode 100644
index 0000000..8100a5f
--- /dev/null
+++ b/src/battery_led.h
@@ -0,0 +1,18 @@
+//
+// Low-battery LED indicator for the Pico onboard LED.
+// Reads PowerPercent / PowerState from interrupt_in_data[52]
+// (DualSense BT 0x31 report, see USBGetStateData in utils.h).
+//
+
+#pragma once
+
+void battery_led_init(void);
+
+// Call once per main-loop iteration. Drives the LED blink while the
+// battery is low and the controller is connected; otherwise no-op.
+void battery_led_tick(void);
+
+// Call from the BT input-report callback whenever a fresh 0x31 report
+// has been copied into interrupt_in_data. Used to detect disconnection
+// via stale-report timeout.
+void battery_led_note_report(void);
diff --git a/src/bt.cpp b/src/bt.cpp
index cc4c4f1..f0b19c4 100644
--- a/src/bt.cpp
+++ b/src/bt.cpp
@@ -17,8 +17,8 @@
 #include "config.h"
 #include "pico/util/queue.h"
 
-#define MTU_CONTROL 256
-#define MTU_INTERRUPT 1691
+#define MTU_CONTROL 672
+#define MTU_INTERRUPT 672
 
 using std::unordered_map;
 using std::vector;
@@ -395,6 +395,9 @@ static void l2cap_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t
                 if (psm == PSM_HID_CONTROL) {
                     printf("[L2CAP] HID Control opened cid=0x%04X\n", local_cid);
                     hid_control_cid = local_cid;
+
+                    const auto mtu = l2cap_get_remote_mtu_for_local_cid(hid_control_cid);
+                    printf("[L2CAP] Remote Control MTU: %d\n",mtu);
                 } else if (psm == PSM_HID_INTERRUPT) {
                     printf("[L2CAP] HID Interrupt opened cid=0x%04X\n", local_cid);
                     hid_interrupt_cid = local_cid;
@@ -429,6 +432,9 @@ static void l2cap_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t
                     memcpy(report32 + 2, packet_0x10, sizeof(packet_0x10));
                     bt_write(report32, sizeof(report32));
 
+                    const auto mtu = l2cap_get_remote_mtu_for_local_cid(hid_interrupt_cid);
+                    printf("[L2CAP] Remote Interrupt MTU: %d\n",mtu);
+
                     // tud_connect();
                 } else {
                     printf("[L2CAP] Unknown Channel psm: 0x%02X", psm);
diff --git a/src/main.cpp b/src/main.cpp
index ed635b6..38f2ae3 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -17,6 +17,9 @@
 #endif
 #include "config.h"
 #include "cmd.h"
+#if ENABLE_BATT_LED
+#include "battery_led.h"
+#endif
 
 // Pico SDK speciifically for waiting on conditions
 #include "pico/critical_section.h"
@@ -85,6 +88,9 @@ void on_bt_data(CHANNEL_TYPE channel, uint8_t *data, uint16_t len) {
 
         if (get_config().polling_rate_mode != 2) {
             memcpy(interrupt_in_data, data + 3, 63);
+#if ENABLE_BATT_LED
+            battery_led_note_report();
+#endif
             return;
         }
 
@@ -98,6 +104,9 @@ void on_bt_data(CHANNEL_TYPE channel, uint8_t *data, uint16_t len) {
         memcpy(interrupt_in_data, data + 3, 63);
         report_dirty = true;
         critical_section_exit(&report_cs);
+#if ENABLE_BATT_LED
+        battery_led_note_report();
+#endif
     }
 }
 
@@ -204,6 +213,10 @@ int main() {
     }
     cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, false);
 
+#if ENABLE_BATT_LED
+    battery_led_init();
+#endif
+
 #if !ENABLE_SERIAL
     if (watchdog_caused_reboot()) {
         printf("Rebooted by Watchdog!\n");
@@ -243,5 +256,8 @@ int main() {
         tud_task();
         audio_loop();
         interrupt_loop();
+#if ENABLE_BATT_LED
+        battery_led_tick();
+#endif
     }
 }