Other Parts Discussed in Thread: BQ40Z50
Tool/software:
Hi,
Customer is using BQ40Z50-R2 in a 4S1P LiFePo4 project. Customer would like to know if our device can support below custom conditions:
1.RC adjustment during discharging through terminals
Example: (a) Low Voltage Detect Voltage (LVD4) 15%
Set & Detect duration = 10sec (Discharge Current ≥ 150mA)
= 50sec (Discharge Current ≤ 150mA)
When voltage = 15% of remaining voltage, then set
RemainingCapacity = FullChargeCapacity * 15%
RSOC = 15%
If RSOC reaches 15% of FCC before cell voltage reaches
15% of remaining voltage then keep RSOC at 16% (of FCC)
until 15% Voltage is reached
(b) Low Voltage Detect Voltage (LVD3) 10%
Set & Detect duration = 10sec (Discharge Current ≥ 150mA)
= 50sec (Discharge Current ≤ 150mA)
When voltage = 10% of remaining voltage, then set
RemainingCapacity = FullChargeCapacity * 10%
RSOC = 10%
If RSOC reaches 10% of FCC before cell voltage reaches
10% of remaining voltage then keep RSOC at 11% (of FCC)
until 10% Voltage is reached。
2.RC adjustment by Self-Discharge
Remaining Capacity is adjusted by BQ40Z50 current and measured self-discharge of cells. Self-discharge will begin being calculated by assuming a 2mA/hr self-discharge.
The BQ40Z50 will, after 3 hours, check OCV to evaluate if the self-discharge is correct. If discharge is <2mA per hour then the BMU will correct down to 1mA per hour self-discharge
3.RC adjustment by OCV
BQ40Z50 adjusts RSOC based on minimum cell voltage measurements.
OCV Adjustment occurs when the fuel gauge starts up or detects all of the
following conditions :
10degC < Temp < 45degC
3.45V ≤ cell voltage ≤ 3.50V
Absolute current < 50mA for 1 hour
No error is detected
RSOC (0x0D command) – RSOC (OCV) >= 1%
Action: Set RSOC (0x0D command) = SOCOCV (and adjust Remaining
Capacity)
4.OCV Update
FCC is to be updated by partial charge & discharge, which is the
calculated capacity of the battery between two OCV conditions (OCV1,
OCV2). FCC is to be updated at the timing of detecting OCV2 if all the
following conditions are met:
o OCV detection: |current| < 50mA for 1hour (during charge)
o The amount of charge / discharge (gap between OCV1 and OCV2),
is > 20%
o Temperature: 10degC < cell temp. < 45degC
o Minimum cell voltage is more than 3.45 V
o Maximum cell voltage is less than
3.50 V
o OCV measurement is not performed when RSOC is less than 20%
o Cycle Count > 0
FCC calculated = (|OCV1-OCV2|) / ⊿RSOC, where ⊿RSOC =
|RSOC(OCV1) – RSOC(OCV2)|
FCC new = FCC old * (1-⊿RSOC)+ FCC calculated *⊿RSOC
Limitation: Updated value of FCC is limited to a change of
o Min: Previous value of FCC x 90%
o Max: DesignCapacity() x 125%
Best Rgds,
Stanley
