feat(core): introduce battery cycle counter.

diff --git a/core/embed/io/power_manager/battery/battery.c b/core/embed/io/power_manager/battery/battery.c
index 7756e3bc6..be441fd88 100644
--- a/core/embed/io/power_manager/battery/battery.c
+++ b/core/embed/io/power_manager/battery/battery.c
@@ -24,6 +24,7 @@
 #include "battery.h"
 #include "battery_model.h"
 #include "fuel_gauge.h"
+#include "math.h"
 
 typedef struct {
   float voltage_V;
@@ -48,6 +49,8 @@ typedef struct {
   battery_model_t battery_model;
   bat_sample_buffer_t sample_buf;
 
+  float cycle_counter;
+
 } bat_driver_t;
 
 bat_driver_t g_bat_driver = {
@@ -60,7 +63,6 @@ void bat_init(void) {
   if (drv->initialized) {
     return;  // Already initialized
   }
-
   memset(drv, 0, sizeof(bat_driver_t));
 
   battery_model_init(&drv->battery_model);
@@ -197,6 +199,10 @@ ts_t bat_fg_update(uint32_t dt_ms, float voltage_V, float current_mA,
     return TS_EINVAL;
   }
 
+  drv->cycle_counter += (fabsf(current_mA) * ((float)dt_ms / 3600000.0f)) /
+                        (2 * battery_total_capacity(&drv->battery_model, 25.0f,
+                                                    current_mA >= 0.0f));
+
   fuel_gauge_update(&drv->fg_state, &drv->battery_model, dt_ms, voltage_V,
                     current_mA, temp_C);
 
@@ -224,6 +230,18 @@ ts_t bat_fg_compensate_soc(float* soc, uint32_t elapsed_s,
   return TS_OK;
 }
 
+float bat_fetch_cycle_increment(void) {
+  bat_driver_t* drv = &g_bat_driver;
+
+  if (!drv->initialized) {
+    return 0.0f;
+  }
+
+  float cycle_increment = (float)((uint16_t)drv->cycle_counter);
+  drv->cycle_counter = 0.0f;
+  return cycle_increment;
+}
+
 float bat_soc_to_ocv(float soc, float temp_C, bool discharging_mode) {
   bat_driver_t* drv = &g_bat_driver;
 
diff --git a/core/embed/io/power_manager/battery/battery.h b/core/embed/io/power_manager/battery/battery.h
index 9f99d0981..c811b204b 100644
--- a/core/embed/io/power_manager/battery/battery.h
+++ b/core/embed/io/power_manager/battery/battery.h
@@ -153,6 +153,21 @@ ts_t bat_fg_update(uint32_t dt_ms, float voltage_V, float current_mA,
 ts_t bat_fg_compensate_soc(float* soc, uint32_t elapsed_s,
                            float avg_bat_current_mA, float avg_temp_C);
 
+/**
+ * @brief Fetch battery cycle count increment from the fuel gauge.
+ *
+ * Battery driver maintains an internal cycle counter based on the accumulated
+ * current throughput. This function retrieves the number reflecting the number
+ * of full charge-discharge cycles completed since the last fetch.
+ *
+ * calculation example:
+ * cycle_count = sum(current_mA * dt_hours) / (2 *
+ * battery_total_capacity_mah(@25C))
+ *
+ * @return Number of full charge-discharge cycles completed since last fetch
+ */
+float bat_fetch_cycle_increment(void);
+
 /**
  * @brief Convert battery SOC to OCV according to the battery model at given
  * temperature point.
diff --git a/core/embed/io/power_manager/stm32u5/power_manager.c b/core/embed/io/power_manager/stm32u5/power_manager.c
index e8b89dea1..ab3a1d077 100644
--- a/core/embed/io/power_manager/stm32u5/power_manager.c
+++ b/core/embed/io/power_manager/stm32u5/power_manager.c
@@ -526,6 +526,15 @@ pm_status_t pm_store_data_to_backup_ram() {
     return PM_ERROR;
   }
 
+  /* Update battery cycle counter telemetry */
+  // float cycle_increment = bat_fetch_cycle_increment();
+  //
+  // Add cycle increment to telemetry
+  // #ifdef USE_TELEMETRY
+  //   telemetry_add_battery_cycle_increment(cycle_increment);
+  // #endif
+  //
+
   return PM_OK;
 }