Issue #116

* Improve battery percentage calculation to work better for batteries of different voltages.
* Fix LVC limiting to work better for batteries of different voltages.
* Make battery soc value available earlier to display at boot.

src/firmware/app.c

@@ -51,7 +51,9 @@ typedef struct
 static uint8_t assist_level;
 static uint8_t operation_mode;
 static uint16_t global_max_speed_rpm;
-static uint16_t lvc_ramp_down_offset_volt_x10;
+
+static uint16_t lvc_voltage_x100;
+static uint16_t lvc_ramp_down_start_voltage_x100;
 
 static assist_level_data_t assist_level_data;
 static uint16_t speed_limit_ramp_interval_rpm_x10;
@@ -90,11 +92,16 @@ void app_init()
 	motor_disable();
 	lights_disable();
 
+	lvc_voltage_x100 = g_config.low_cut_off_v * 100u;
+
+	uint16_t voltage_range_x100 =
+		EXPAND_U16(g_config.max_battery_x100v_u16h, g_config.max_battery_x100v_u16l) - lvc_voltage_x100;
+	lvc_ramp_down_start_voltage_x100 = (uint16_t)(lvc_voltage_x100 +
+		((voltage_range_x100 * LVC_RAMP_DOWN_OFFSET_PERCENT) / 100));
+
 	global_max_speed_rpm = 0;
-	lvc_ramp_down_offset_volt_x10 = (uint16_t)((g_config.low_cut_off_v * 10 * LVC_RAMP_DOWN_OFFSET_PERCENT) / 100);
 	temperature_contr_c = 0;
 	temperature_motor_c = 0;
-
 	ramp_up_target_current = 0;
 	last_ramp_up_increment_ms = 0;
 	ramp_up_current_interval_ms = (g_config.max_current_amps * 10u) / g_config.current_ramp_amps_s;
@@ -674,45 +681,42 @@ void apply_low_voltage_limit(uint8_t* target_current)
 	if (system_ms() > next_voltage_reading_ms)
 	{
 		next_voltage_reading_ms = system_ms() + 125;
-		int32_t voltage_x100 = motor_get_battery_voltage_x10() * 10ul;
+		int32_t voltage_reading_x100 = motor_get_battery_voltage_x10() * 10ul;
 
-		if (voltage_x100 < flt_min_bat_volt_x100)
+		if (voltage_reading_x100 < flt_min_bat_volt_x100)
 		{
-			flt_min_bat_volt_x100 = EXPONENTIAL_FILTER(flt_min_bat_volt_x100, voltage_x100, 8);
+			flt_min_bat_volt_x100 = EXPONENTIAL_FILTER(flt_min_bat_volt_x100, voltage_reading_x100, 8);
 		}
 
 		if (eventlog_is_enabled() && system_ms() > next_log_volt_ms)
 		{
 			next_log_volt_ms = system_ms() + 10000;
-			eventlog_write_data(EVT_DATA_VOLTAGE, (uint16_t)voltage_x100);
+			eventlog_write_data(EVT_DATA_VOLTAGE, (uint16_t)voltage_reading_x100);
 		}
 	}
 
-	uint16_t voltage_x10 = flt_min_bat_volt_x100 / 10;
-	uint16_t start_limit_v_x10 = motor_get_battery_lvc_x10() + lvc_ramp_down_offset_volt_x10;
+	uint16_t voltage_x100 = flt_min_bat_volt_x100;
 
-	if (voltage_x10 <= start_limit_v_x10)
+	if (voltage_x100 <= lvc_ramp_down_start_voltage_x100)
 	{
-		uint16_t lvc_x10 = motor_get_battery_lvc_x10();
-
 		if (!lvc_limiting)
 		{
-			eventlog_write_data(EVT_DATA_LVC_LIMITING, voltage_x10);
+			eventlog_write_data(EVT_DATA_LVC_LIMITING, voltage_x100);
 			lvc_limiting = true;
 		}
 
-		if (voltage_x10 < lvc_x10)
+		if (voltage_x100 < lvc_voltage_x100)
 		{
-			voltage_x10 = lvc_x10;
+			voltage_x100 = lvc_voltage_x100;
 		}
 
 		// ramp down power until 20% when approaching lvc
 		uint8_t tmp = (uint8_t)MAP32(
-			voltage_x10,					// value
-			lvc_x10,						// in_min
-			start_limit_v_x10,				// in_max
-			LVC_LOW_CURRENT_PERCENT,		// out_min
-			100								// out_max
+			voltage_x100,						// value
+			lvc_voltage_x100,					// in_min
+			lvc_ramp_down_start_voltage_x100,	// in_max
+			LVC_LOW_CURRENT_PERCENT,			// out_min
+			100									// out_max
 		);
 
 		if (*target_current > tmp)

src/firmware/battery.c

@@ -17,9 +17,25 @@ static int16_t battery_full_x100v;
 
 static uint8_t battery_percent;
 static uint32_t motor_disabled_at_ms;
+static bool first_reading_done;
 
 #define BATTERY_NO_LOAD_DELAY_MS		2000
 
+#define BATTERY_FULL_OFFSET_PERCENT		8
+#define BATTERY_EMPTY_OFFSET_PERCENT	8
+
+//
+// No attempt is made to have accurate battery state of charge display.
+//
+// This is only a voltage based approch using configred max and min battery voltages.
+// The end values are padded (BATTERY_EMPTY_OFFSET_PERCENT, BATTERY_FULL_OFFSET_PERCENT).
+//
+// Battery voltage is measured when no motor power has been applied for at least 2 seconds
+// (to mitigate measuring voltage sag but is still problematic in cold weather).
+//
+// Battery SOC percentage is calculated from measured voltage using linear interpolation.
+//
+
 
 static uint8_t compute_battery_percent()
 {
@@ -32,35 +48,58 @@ static uint8_t compute_battery_percent()
 
 void battery_init()
 {
-	battery_percent = 0;
+	// default to 70% until first reading is available
+	battery_percent = 70;
 	motor_disabled_at_ms = 0;
+	first_reading_done = false;
+
+	uint16_t battery_min_voltage_x100v = g_config.low_cut_off_v * 100u;
+	uint16_t battery_max_voltage_x100v =
+		EXPAND_U16(g_config.max_battery_x100v_u16h, g_config.max_battery_x100v_u16l);
 
-	// Consider battery full if above 98% of configured max voltage
-	battery_full_x100v = (98l * EXPAND_U16(g_config.max_battery_x100v_u16h, g_config.max_battery_x100v_u16l)) / 100;
+	uint16_t battery_range_x100v = battery_max_voltage_x100v - battery_min_voltage_x100v;
 
-	// Consider battery empty at 5% above configured low voltage cutoff
-	battery_empty_x100v = 105l * g_config.low_cut_off_v;
+	// Consider battery full if above 95% (100 - BATTERY_FULL_OFFSET_PERCENT)
+	// of configured voltage range
+	battery_full_x100v = battery_max_voltage_x100v -
+		((BATTERY_FULL_OFFSET_PERCENT * battery_range_x100v) / 100);
+
+	// Consider battery empty if below 8% (BATTERY_EMPTY_OFFSET_PERCENT)
+	// of configured voltage range
+	battery_empty_x100v = battery_min_voltage_x100v +
+		((BATTERY_EMPTY_OFFSET_PERCENT * battery_range_x100v) / 100);
 }
 
 void battery_process()
 {
-	uint8_t target_current = motor_get_target_current();
-
-	if (motor_disabled_at_ms == 0 && target_current == 0)
+	if (!first_reading_done)
 	{
-		motor_disabled_at_ms = system_ms();
+		if (motor_get_battery_voltage_x10() > 0)
+		{
+			battery_percent = compute_battery_percent();
+			first_reading_done = true;
+		}
 	}
-	else if (target_current > 0)
+	else
 	{
-		motor_disabled_at_ms = 0;
-	}
-
-	if (target_current == 0 && (system_ms() - motor_disabled_at_ms) > BATTERY_NO_LOAD_DELAY_MS)
-	{
-		// Compute battery percent using linear interpolation between lvc
-		// and configured max voltage while under no load.
-
-		battery_percent = compute_battery_percent();
+		uint8_t target_current = motor_get_target_current();
+
+		if (motor_disabled_at_ms == 0 && target_current == 0)
+		{
+			motor_disabled_at_ms = system_ms();
+		}
+		else if (target_current > 0)
+		{
+			motor_disabled_at_ms = 0;
+		}
+
+		if (target_current == 0 && (system_ms() - motor_disabled_at_ms) > BATTERY_NO_LOAD_DELAY_MS)
+		{
+			// Compute battery percent using linear interpolation between lvc
+			// and configured max voltage while under no load.
+
+			battery_percent = compute_battery_percent();
+		}
 	}
 }
 

src/firmware/fwconfig.h

@@ -57,12 +57,12 @@
 #endif
 
 
-// Current ramp down starts at LVC + (LVC * LVC_RAMP_DOWN_OFFSET_PERCENT / 100)
+// Current ramp down starts at LVC + (VOLTAGE_RANGE * LVC_RAMP_DOWN_OFFSET_PERCENT / 100)
 // Example:
-// LVC is 42V
-// 42 * 0.06 = 2.5V
-// Ramp down starts at 42V + 2.5V
-#define LVC_RAMP_DOWN_OFFSET_PERCENT			6
+// LVC is 42V, max voltage at 58.8
+// Range = 58.8 - 42 = 16.8
+// Ramp down starts at 42V + Range * 0.09 = 43.5
+#define LVC_RAMP_DOWN_OFFSET_PERCENT			9
 
 // Maximum allowed motor current in percent of maximum configured current (A)
 // to still apply when LVC has been reached.

src/tool/Model/EventLogEntry.cs

@@ -201,7 +201,7 @@ public string Parse()
 				case EVT_DATA_LVC_LIMITING:
 					if (_data.Value != 0)
 					{
-						return $"Low voltage limiting activated, voltage={(_data / 10.0):0.0}";
+						return $"Low voltage limiting activated, voltage={(_data / 100f):0.0}";
 					}
 					else
 					{