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Improve battery handling #107

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Improve battery handling #107

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017dea4
Improve battery handling
pelle-c Aug 25, 2024
3cebb07
Modified default corrections values
pelle-c Sep 5, 2024
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47 changes: 38 additions & 9 deletions Firmware/LowLevel/src/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -62,12 +62,39 @@ SerialPIO uiSerial(PIN_UI_TX, PIN_UI_RX, 250);
#define R_SHUNT 0.003f
#define CURRENT_SENSE_GAIN 100.0f

// These are the absolute maximum voltage levels, for a 7S-pack with cells of 4.2V max the BATT_ABS_MAX will be 29.4V. Might be good
// with a safety margin here as well.
// 7S parameters:
#define BATT_ABS_MAX 28.7f
#define BATT_ABS_Min 21.7f
// 6S parameters:
// #define BATT_ABS_MAX 25.2f
// #define BATT_ABS_Min 19.2f

// We really want to avoid going higher than BATT_ABS_MAX. All battery packs should have a bms that safeguards against overvoltage,
// but in worst case overvoltage can lead to explossions.
// Since the ADC will not give you very accurate readings, it might be worth measuring the values and try to correct the figures.
// This can be done in the CORRECTION-defines.
// Another step to avoid danger which can also prolong the life of the pack is not to charge it up to 100%. The threshold is
// defined in BATT_FULL below.

#define BATT_FULL BATT_ABS_MAX - 0.3f
#define BATT_EMPTY BATT_ABS_Min + 0.3f

// Make some corrections to the ADC values. Assuming the error is linear the value from the adc is multiplied by the "FACTOR" and then "OFFSET" is added.
#define ADC_BATTERY_CORRECTION_FACTOR 1.0f
#define ADC_BATTERY_CORRECTION_OFFSET 0
#define ADC_CHARGE_CORRECTION_FACTOR 1.0f
#define ADC_CHARGE_CORRECTION_OFFSET 0
#define ADC_CHARGE_CURRENT_CORRECTION_FACTOR 1.0f
#define ADC_CHARGE_CURRENT_CORRECTION_OFFSET 0

// To avoid charge/discharge toggling don't restart charging until the battery voltage is below the value below.
#define BATT_FULL_HYSTERESIS BATT_FULL - 1.0f

// Will stop/won't start charging if the current is above this value.
#define MAX_CHARGE_CURRENT 1.5f

// Emergency will be engaged, if no heartbeat was received in this time frame.
#define HEARTBEAT_MILLIS 500

Expand Down Expand Up @@ -605,7 +632,7 @@ void onPacketReceived(const uint8_t *buffer, size_t size) {

// returns true, if it's a good idea to charge the battery (current, voltages, ...)
bool checkShouldCharge() {
return status_message.v_charge < 30.0 && status_message.charging_current < 1.5 && status_message.v_battery < 29.0;
return status_message.v_charge < (BATT_ABS_MAX + 1.3) && status_message.charging_current < MAX_CHARGE_CURRENT && status_message.v_battery < BATT_FULL;
}

void updateChargingEnabled() {
Expand All @@ -618,13 +645,14 @@ void updateChargingEnabled() {
} else {
// enable charging after CHARGING_RETRY_MILLIS
if (millis() - charging_disabled_time > CHARGING_RETRY_MILLIS) {
if (!checkShouldCharge()) {
digitalWrite(PIN_ENABLE_CHARGE, LOW);
charging_allowed = false;
charging_disabled_time = millis();
} else {
// Also check that battery voltage is not close to being full to avoid charge/discharge toggling
if ((checkShouldCharge()) && (status_message.v_battery < BATT_FULL_HYSTERESIS)) {
digitalWrite(PIN_ENABLE_CHARGE, HIGH);
charging_allowed = true;
} else { // Should already be disabled, so why do this?
digitalWrite(PIN_ENABLE_CHARGE, LOW);
charging_allowed = false;
charging_disabled_time = millis();
}
}
}
Expand Down Expand Up @@ -679,13 +707,14 @@ void loop() {
if (now - last_status_update_millis > STATUS_CYCLETIME) {
updateNeopixel();

// Read the ADCs and put the value through a filter to scrub off the peaks of values being off
status_message.v_battery =
(float) analogRead(PIN_ANALOG_BATTERY_VOLTAGE) * (3.3f / 4096.0f) * ((VIN_R1 + VIN_R2) / VIN_R2);
((float) analogRead(PIN_ANALOG_BATTERY_VOLTAGE) * (3.3f / 4096.0f) * ((VIN_R1 + VIN_R2) / VIN_R2) * ADC_BATTERY_CORRECTION_FACTOR + ADC_BATTERY_CORRECTION_OFFSET) * 0.2f + status_message.v_battery * 0.8f;
status_message.v_charge =
(float) analogRead(PIN_ANALOG_CHARGE_VOLTAGE) * (3.3f / 4096.0f) * ((VIN_R1 + VIN_R2) / VIN_R2);
((float) analogRead(PIN_ANALOG_CHARGE_VOLTAGE) * (3.3f / 4096.0f) * ((VIN_R1 + VIN_R2) / VIN_R2) * ADC_CHARGE_CORRECTION_FACTOR + ADC_CHARGE_CORRECTION_OFFSET) * 0.2f + status_message.v_charge * 0.8f;
#ifndef IGNORE_CHARGING_CURRENT
status_message.charging_current =
(float) analogRead(PIN_ANALOG_CHARGE_CURRENT) * (3.3f / 4096.0f) / (CURRENT_SENSE_GAIN * R_SHUNT);
((float) analogRead(PIN_ANALOG_CHARGE_CURRENT) * (3.3f / 4096.0f) / (CURRENT_SENSE_GAIN * R_SHUNT) * ADC_CHARGE_CURRENT_CORRECTION_FACTOR + ADC_CHARGE_CURRENT_CORRECTION_OFFSET) * 0.2f + status_message.charging_current * 0.8f;
#else
status_message.charging_current = -1.0f;
#endif
Expand Down