高通BMS的理解

一： SOC（荷电状态）计算方法

名词：

FCC  Full-charge capacity      

UC     Remaining capacity

CC     Coulumb counter    

UUC  Unusable capacity

RUC   Remaining usable capacity //    RUC=RC-CC-UUC

SoC   State of charge    

OCV    Open circuit voltage

 SOC=(RC-CC-UUC)/(FCC-UUC)

以下是各个变量的计算方法：

1：FCC：

   在校准的电池profile中有定义,会随温度有变化；

static struct single_row_lut fcc_temp = {

 .x  = {-20, 0, 25, 40, 60},

 .y  = {3193, 3190, 3190, 3180, 3183},

 .cols = 5

};

2：RC: 开机通过开始获取的开路电压（ocv）来查表（电池校准的profile文件）计算百分比，来比对计算（电压与电荷量正比）；(ocv=vbatt+rbatt*i_ma)

内核计算方法：

static int calculate_remaining_charge_uah(struct pm8921_bms_chip *chip,

      struct pm8921_soc_params *raw,

      int fcc_uah, int batt_temp,

      int chargecycles)

{

 int  ocv, pc, batt_temp_decidegc;

 ocv = raw->last_good_ocv_uv;

 batt_temp_decidegc = chip->last_ocv_temp_decidegc;

 pc = calculate_pc(chip, ocv, batt_temp_decidegc, chargecycles);

 pr_info("ocv = %d pc = %d\n", ocv, pc);

 return (fcc_uah * pc) / 100;

}

但是通常情况下开机使用计算RC的ocv是上次关机存下的百分比，反向查表算出的ocv；

现在我们做法是通过判断开机时的ocv与关机的ocv如果偏差太大，我们将采用开机ocv来计算RC，所以开机的ocv对开机的百分比影响非常大；

3:CC:pmic库伦计获取到的：

内核获取方法：

/**

* calculate_cc_uah -

* @chip:  the bms chip pointer

* @cc:   the cc reading from bms h/w

* @val:  return value

* @coulumb_counter: adjusted coulumb counter for 100%

*

* RETURNS: in val pointer coulumb counter based charger in uAh

*        (micro Amp hour)

*/

static void calculate_cc_uah(struct pm8921_bms_chip *chip, int cc, int *val)

{

 int64_t cc_voltage_uv, cc_pvh, cc_uah;

 cc_voltage_uv = cc;

 pr_debug("cc = %d\n", cc);

 cc_voltage_uv = cc_to_microvolt(chip, cc_voltage_uv);

 cc_voltage_uv = pm8xxx_cc_adjust_for_gain(cc_voltage_uv);

 pr_debug("cc_voltage_uv = %lld microvolts\n", cc_voltage_uv);

 cc_pvh = ccmicrovolt_to_pvh(cc_voltage_uv);

 pr_debug("cc_pvh = %lld pico_volt_hour\n", cc_pvh);

 cc_uah = div_s64(cc_pvh, chip->r_sense_uohm);

 *val = cc_uah;

}

4:UUC:计算方法和UC一致，但是rbatt是动态变化的，会复杂点；

static int calculate_termination_uuc(struct pm8921_bms_chip *chip,

     int batt_temp, int chargecycles,

    int fcc_uah, int i_ma,

    int *ret_pc_unusable)

{

 int unusable_uv, pc_unusable, uuc;

 int i = 0;

 int ocv_mv;

 int batt_temp_degc = batt_temp / 10;

 int rbatt_mohm;

 int delta_uv;

 int prev_delta_uv = 0;

 int prev_rbatt_mohm = 0;

 int prev_ocv_mv = 0;

 int uuc_rbatt_uv;

 for (i = 0; i <= 100; i++) {

  ocv_mv = interpolate_ocv(chip->pc_temp_ocv_lut,

    batt_temp_degc, i);

  rbatt_mohm = get_rbatt(chip, i, batt_temp);

  unusable_uv = (rbatt_mohm * i_ma) + (chip->v_cutoff * 1000);

  delta_uv = ocv_mv * 1000 - unusable_uv;

  pr_debug("soc = %d ocv = %d rbat = %d u_uv = %d delta_v = %d\n",

    i, ocv_mv, rbatt_mohm, unusable_uv, delta_uv);

  if (delta_uv > 0)

   break;

  prev_delta_uv = delta_uv;

  prev_rbatt_mohm = rbatt_mohm;

  prev_ocv_mv = ocv_mv;

 }

 uuc_rbatt_uv = linear_interpolate(rbatt_mohm, delta_uv,

     prev_rbatt_mohm, prev_delta_uv,

     0);

 unusable_uv = (uuc_rbatt_uv * i_ma) + (chip->v_cutoff * 1000);

 pc_unusable = calculate_pc(chip, unusable_uv, batt_temp, chargecycles);

 uuc = (fcc_uah * pc_unusable) / 100;

 pr_debug("For i_ma = %d, unusable_rbatt = %d unusable_uv = %d unusable_pc = %d uuc = %d\n",

     i_ma, uuc_rbatt_uv, unusable_uv,

     pc_unusable, uuc);

 *ret_pc_unusable = pc_unusable;

 return uuc;

}

 高通的这套BMS算法运行起来由于ocv的校准和温度等等原因，会有一定的偏差，高通还有一套通过校准OCV来估算SOC（简称soc_est）的机制，下面就是使用这套来校准SOC；

二：校准SOC

 

 高通算法通过对soc与soc_est比较计算出ocv的差值，来改变last_ocv_uv的值，主要是改变RC，重新计算soc，将会使得soc与soc_est越来越接近，越来越准；

 但是只有在 soc_est小于等于15的情况下才会发生校准，而有时在 soc_est大于15的情况下就上报百分比等于0了，会出现关机电压过高的问题。所以函数adjust_soc里面许多地方需要我们自己微调；
 只有开机时库伦计RESET从0开始，RC在开机时就固定，但是当温度变化时由于FCC的几个值在变化，RC会随之变化；当校准SOC时才会引起ocv查表得到的pc变化而导致RC变化；
 所以还是开机ocv至关重要，不准到低电时才微调ocv，RC变化。但是电池电压偏高的时候微调ocv对百分比不敏感，所以方法中选择了在soc_est低于15的时候微调。

 

<6>[ 7796.038269] read_soc_params_raw: 333333333 last_good_ocv_uv= 3777000uV

<6>[ 7796.038360] read_soc_params_raw: last_good_ocv_raw= 0x943f, last_good_ocv_uv= 3777000uV

<6>[ 7796.038543] calculate_soc_params: FCC = 3190000uAh batt_temp = 300, cycles = 0

<6>[ 7796.038635] calculate_remaining_charge_uah: ocv = 3777000 pc = 35

<6>[ 7796.038665] calculate_soc_params: RC = 1116500uAh

<6>[ 7796.038726] calculate_soc_params: cc_uah = 394979uAh raw->cc = 5764312

<6>[ 7796.038818] calculate_state_of_charge: RUC(RC-CC-UUC) = 657721uAh RC = 1116500uAh CC= 394979uAh UUC= 63800uAh FCC= 3190000uAh SOC(RUC/FCC-UUC) =21

adjust_soc方法：

 static int last_soc_est = -EINVAL;

static int adjust_soc(struct pm8921_bms_chip *chip, int soc,

  int batt_temp, int chargecycles,

  int rbatt, int fcc_uah, int uuc_uah, int cc_uah)

{

 int ibat_ua = 0, vbat_uv = 0;

 int ocv_est_uv = 0, soc_est = 0, pc_est = 0, pc = 0;

 int delta_ocv_uv = 0;

 int n = 0;

 int rc_new_uah = 0;

 int pc_new = 0;

 int soc_new = 0;

 int m = 0;

 int rc = 0;

 int delta_ocv_uv_limit = 0;

 int correction_limit_uv = 0;

 rc = pm8921_bms_get_simultaneous_battery_voltage_and_current(

       &ibat_ua,

       &vbat_uv);

 if (rc < 0) {

  pr_err("simultaneous vbat ibat failed err = %d\n", rc);

  goto out;

 }

 very_low_voltage_check(chip, ibat_ua, vbat_uv);

 if (chip->low_voltage_detect &&

  wake_lock_active(&chip->low_voltage_wake_lock)) {

  if (is_voltage_below_cutoff_window(chip, ibat_ua, vbat_uv)) {

   soc = 0;

   pr_info("Voltage below cutoff, setting soc to 0\n");

   goto out;

  }

 }

 delta_ocv_uv_limit = DIV_ROUND_CLOSEST(ibat_ua, 1000);

 ocv_est_uv = vbat_uv + (ibat_ua * rbatt)/1000;

 calc_current_max(chip, ocv_est_uv, rbatt);

 pc_est = calculate_pc(chip, ocv_est_uv, batt_temp, last_chargecycles);

 soc_est = div_s64((s64)fcc_uah * pc_est - uuc_uah*100,

      (s64)fcc_uah - uuc_uah);

 soc_est = bound_soc(soc_est);

 /* never adjust during bms reset mode */

 if (bms_reset) {

  pr_debug("bms reset mode, SOC adjustment skipped\n");

  goto out;

 }

 if (ibat_ua < 0 && pm8921_is_batfet_closed()) {

  soc = charging_adjustments(chip, soc, vbat_uv, ibat_ua,

    batt_temp, chargecycles,

    fcc_uah, cc_uah, uuc_uah);

  goto out;

 }

 /*

  * do not adjust

  * if soc_est is same as what bms calculated

  * OR if soc_est > 15

  * OR if soc it is above 90 because we might pull it low

  * and  cause a bad user experience

  */

 if (soc_est == soc

  || soc_est > 15

  || soc >= 90)

  goto out;

 if (last_soc_est == -EINVAL)

  last_soc_est = soc;

 n = min(200, max(1 , soc + soc_est + last_soc_est));

 /* remember the last soc_est in last_soc_est */

 last_soc_est = soc_est;

 pc = calculate_pc(chip, chip->last_ocv_uv,

   chip->last_ocv_temp_decidegc, last_chargecycles);

 if (pc > 0) {

  pc_new = calculate_pc(chip, chip->last_ocv_uv - (++m * 1000),

     chip->last_ocv_temp_decidegc,

     last_chargecycles);

  while (pc_new == pc) {

   /* start taking 10mV steps */

   m = m + 10;

   pc_new = calculate_pc(chip,

      chip->last_ocv_uv - (m * 1000),

      chip->last_ocv_temp_decidegc,

      last_chargecycles);

  }

 } else {

  /*

   * pc is already at the lowest point,

   * assume 1 millivolt translates to 1% pc

   */

  pc = 1;

  pc_new = 0;

  m = 1;

 }

 delta_ocv_uv = div_s64((soc - soc_est) * (s64)m * 1000,

       n * (pc - pc_new));

 if (abs(delta_ocv_uv) > delta_ocv_uv_limit) {

  pr_debug("limiting delta ocv %d limit = %d\n", delta_ocv_uv,

    delta_ocv_uv_limit);

  if (delta_ocv_uv > 0)

   delta_ocv_uv = delta_ocv_uv_limit;

  else

   delta_ocv_uv = -1 * delta_ocv_uv_limit;

  pr_debug("new delta ocv = %d\n", delta_ocv_uv);

 }

 if (wake_lock_active(&chip->low_voltage_wake_lock)) {

  pr_debug("Low Voltage, apply only ibat limited corrections\n");

  goto skip_limiting_corrections;

 }

 if (chip->last_ocv_uv > 3800000)

  correction_limit_uv = the_chip->high_ocv_correction_limit_uv;

 else

  correction_limit_uv = the_chip->low_ocv_correction_limit_uv;

 if (abs(delta_ocv_uv) > correction_limit_uv) {

  pr_debug("limiting delta ocv %d limit = %d\n", delta_ocv_uv,

    correction_limit_uv);

  if (delta_ocv_uv > 0)

   delta_ocv_uv = correction_limit_uv;

  else

   delta_ocv_uv = -1 * correction_limit_uv;

  pr_debug("new delta ocv = %d\n", delta_ocv_uv);

 }

skip_limiting_corrections:

 chip->last_ocv_uv -= delta_ocv_uv;

 if (chip->last_ocv_uv >= chip->max_voltage_uv)

  chip->last_ocv_uv = chip->max_voltage_uv;

 /* calculate the soc based on this new ocv */

 pc_new = calculate_pc(chip, chip->last_ocv_uv,

   chip->last_ocv_temp_decidegc, last_chargecycles);

 rc_new_uah = (fcc_uah * pc_new) / 100;

 soc_new = (rc_new_uah - cc_uah - uuc_uah)*100 / (fcc_uah - uuc_uah);

 soc_new = bound_soc(soc_new);

 /*

  * if soc_new is ZERO force it higher so that phone doesnt report soc=0

  * soc = 0 should happen only when soc_est == 0

  */

 if (soc_new == 0 && soc_est >= the_chip->hold_soc_est)

  soc_new = 1;

 soc = soc_new;

out:

 pr_debug("ibat_ua = %d, vbat_uv = %d, ocv_est_uv = %d, pc_est = %d, "

  "soc_est = %d, n = %d, delta_ocv_uv = %d, last_ocv_uv = %d, "

  "pc_new = %d, soc_new = %d, rbatt = %d, m = %d\n",

  ibat_ua, vbat_uv, ocv_est_uv, pc_est,

  soc_est, n, delta_ocv_uv, chip->last_ocv_uv,

  pc_new, soc_new, rbatt, m);

 return soc;

}