Hi,
I have a specific question regarding the learning cycle of the Bq27421-G1A when trying to do the initial charge from relaxed.
I have set the following configuration:
Design capacity = 1800
Design Energy = 6660
Taper rate = 180 x0.1Hr Rate (100mA for this capacity)
Opconfig = 0x05F8 (in order to send the software BAT_INSERT command).
So the gauge is setup with these parameters, the BAT_INSERT command is sent and the gauge has simulated its guess at the SOC. Then I discharged the battery to 3.24v and let it sit there for 10 minutes. At this time the important registers are:
relaxing:
Control status: 009E (INITCOMP | SLEEP | LDMD | RUP_DIS | VOK)
Flags: 018E (CHG | OCVTAKEN | BAT_DET | SOC1 | SOCF)
Volts: 3274
Current: 0
SOC: 0
The battery was then charged at max 500mA
0 min: (the sleep flag is cleared)
Control status: 008E (INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 018E (CHG | OCVTAKEN | BAT_DET | SOC1 | SOCF)
Volts: 3390
Current: 507
SOC: 0
7.6 min: (SOCF is cleared)
Control status: 008E (INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 018C (CHG | OCVTAKEN | BAT_DET | SOC1)
Volts: 3714
Current: 504
SOC: 5
26.8 min (SOC1 is cleared)
Control status: 008E (INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 0188 (CHG | OCVTAKEN | BAT_DET)
Volts: 3826
Current: 500
SOC: 15
194 min (CHG is cleared)
Control status: 008E (INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 0088 (OCVTAKEN | BAT_DET)
Volts: 4182
Current: 362 (current has been reducing since 183 minutes)
SOC: 99
241 min (CCA is set)
Control status: 088E (CCA | INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 0088 (OCVTAKEN | BAT_DET)
Volts: 4195
Current: 97
SOC: 100
241 min (CCA is cleared)
Control status: 008E (INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 0088 (OCVTAKEN | BAT_DET)
Volts: 4196
Current: 96
SOC: 100
243 min (FC is set)
Control status: 008E (INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 0288 (FC | OCVTAKEN | BAT_DET)
Volts: 4195
Current: 93
SOC: 100
253 min (OCVTAKEN is cleared)
Control status: 008E (INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 0208 (FC | BAT_DET)
Volts: 4197
Current: 70
SOC: 100
258.4 min (OCVTAKEN is set)
Control status: 008E (INITCOMP | LDMD | RUP_DIS | VOK)
Flags: 0288 (FC | OCVTAKEN | BAT_DET)
Volts: 4197
Current: 62
SOC: 100
258.8 min (VOK and RUP_DIS cleared)
Control status: 0088 (INITCOMP | LDMD)
Flags: 0288 (FC | OCVTAKEN | BAT_DET)
Volts: 4197
Current: 60
SOC: 100
The gauge then stays in this state and the charge current keeps tapering down. The gauge does another CCA at 331 minutes.
The current tapers down to 10mA a few seconds after the CCA and the gauge sets the sleep bit.
The gauge then stays in sleep mode for many hours, the charge current tapers off to zero.
During this time the registers are:
Control status: 0098 (INITCOMP | SLEEP | LDMD)
Flags: 0288 (FC | OCVTAKEN | BAT_DET)
Volts: 4199
Current: 0
SOC: 100
The gauge never sets QMAX_UP or RES_UP and it also never updates "Qmax cell 0" or the Ra tables.
That was a lengthy intro. Here is my question: Does the gauge need a "step" to zero on the charging current in order to consider this a charge termination? Obviously my charger just operates continuously and the current just tapers slowly to zero.
If it does need a step, under what conditions should this happen? I've read SLUA597 and the quick start guide SLUUAH7, and from these it seems that as soon as FC is set it is OK then to disable the charger. Is this correct or should there be a minimum time after FC sets before removing power to the charger?
I am going to make the necessary hardware modifications so that I can test this out, but I was hoping for a definitive answer on the subject in case I am still stuck after trying this.
Thanks
- Wayne