BQ27426: Reserve Capacity

Hi Onyx
Please answer the above question?
Best regards,
C.Endo

Hi Onyx

Thank you for your reply
(1)Although charging / discharging is repeated three days with 3.7V 700mAh battery (set Cehm ID1202), both res_up and qmax_up are not set.
In order to confirm whether the chemical properties of the battery are close to the default chemical ID, what kind of information (such as electrode and electrolyte material) should be obtained from the battery maker?
(2)How can I shut down correctly when the Reserve Capacity is not available (res_up, qmax_up is not set)? For example, until res_up and qmax_up are set, Terminate Voltage is set to 3.3 V in consideration of the guard band, and Terminate Voltage is set to 3.0 V of the battery discharge lower limit voltage after res_up, qmax_up setting.
(3)I heard that there is a 5% error in the capacity measurement of bq 27426. In this case, is it also necessary to consider a 5% error in the set value of Reserve Capacity?
For example, if 100 mAh is required for shutdown and consider the error of 5% of capacity, should we set the Reserve Capacity be "100 mAh + 100 mAh * 5% = 105 mAh"?
(4) Are the voltages at which SOC = 0% as following?
・ Reserve Cacity not set: "Terminate Voltage"
・ Reserve Cacity set, no load spike: "Terminate Voltage" + "Voltage for Reserve Capacity"
・ Reserve Cacity set, load spike: "Terminate Voltage" + "Reserve Capacity Voltage" + "Voltage Considering Load Spikes"
(5) When replacing the battery, it is assumed that the charge in the product remains and learning state remains in the RAM of bq 27426 (res_up, qmax_up remains set).
Is there a way to clear the learning state in such a case?

Thanks
Chiaki

Hi Onyx

I will measure the chemical characteristics of the battery refer to the quick start guide.
Please answer the above (2) to (5) other than that.
Thanks
Chiaki

Hi, Onyx -san,

In your comment  at Feb,28th :
> Do you have qmax and resistances updated in your test to indicate the gauge has learned Ra and qmax properly? 

Could you please let me know how to learned Ra and qmax properly?
He use Learning cycle in bqStudio as below and use the battery which voltage is 3257mV. Once push the start in GUI, the learning start from Discharging as below. Could you please check the procedure to run learning?
- Should use use fully-charged battery?
- How much time should user wait for Relax -> Charge -> Relax -> Discharge -> Relax ?
(I cannot find the document how to learn the battery.)

Regards,
Nagata.

Hi, Onyx -san,

Thank you very much for your support.
Let me check the manually Learning procedure. Is below correct? if not , could you please correct it?

1. Use the fully-discharged battery (Vbat = 3000mV)
2. Insert the battery to apprication board ( and reset command (=0x0041) )
3. Relax for a least 5 hours
4. Charge at C/2 rate until fully charge
5. Relax for a leaset 2 hours
6. Discharge at C/5 - C/10 rate until fully - discharge
7. Relax for a leaset 5 hours

And How should user know if the learning process done correctly?
Can user get the updated Ra_table and Qmax infomation? ( I believe flash infomation will not update during learning cycyle.)


Regards,
Nagata.

Hi, Onyx -san,

User would like to use reserve capacity. When he update some data in gg file to RAM of bq27426, will the reserve capacity be used? If  QMAX_UP bit and RES_UP bit should be set for using the reserve capacity, how does user set the bits?

Regards,
Nagata.

Hi Onyx-san

From your reply on the following thread "Feb 28, 2019 8:30 PM", I thought that the gauge should report 0% at a voltage higher than the termination voltage, and for which the qmax and resup bits need to be set (complete learning).
Is this correct?

And I understood that "discharge to empty, rest 2 hours charge to full, rest 2 hours then discharge to empty" is required to complete learning.
However, the product can not execute this cycle.
What conditions does the product complete learning?

Thanks,
Endo

Hi Onyx-san,

Thank you for your reply.

I will evaluate gauge matching of our cell.
When Reserve Capacity is set, what is the condition for reporting 0% above the termination voltage (ex. gauge matching of our cell, flags set of resup and qmaxup...etc)?

Thanks
Chiaki

Hi, Onyx -san,

Below is Chiaki -san setting for reserve capacity:

Unfortunately, the gauge report Remaining Capacity = 0 at Terminate voltage with above setting. 

Is his setting correct?

Regards,
Nagata.

Hi, Onyx -san,

The Load mode is already 0. The Load Mode bit is located at bit 7 in Load Select / mode register.

This meaning of his setting "1"  is Load Mode = 0, Load Select =1.

Regards,
Nagata.

Is your meaning that the load mode  load select register should be 0?

Regards,

Nagata.

Why does user not use the reserve capacity with load select = 1 when Load Mode = 0?

Regards,
Nagata