BQ27441-G1: BQ27441-G1

Hi Onyx

I am doing the configuration on every power on. And I am reading back the register. The guage is updating the battery voltage and temperature correctly,but not the battery capacity and the remaining battery capacity.

After updating the parameters I am reading back the check sum after the software reset it is same as that of previous.

I have provided the schematic if something I have missed please reply.

Regards

Harish

Hi Onyx

I am not using Bqstudio.

I am refering to Quickstart Guide for bq27441-G1 SLUUAP7–December 2013. 

Their is an algorithm mentioned at page 4 I am doing according to that.

1) I am unsealing the guage by sending 8000 twice.

2) Then configuration update 0013.

3) After that  Reading the flag register.

4) Then I read the initial checksum.

5) After that I read old battery capacity, terminate voltage and design energy.

6) And I subtract with the previous check sum.

7) Then I add the new battery capacity, terminate voltage and design energy.

8) Since maximum battery capacity is 8000mAh of this Ic and I am using 100000mAh in my design So I have configured the battery_capacity as 0x1f40.

9) And since I am using G1-A series my design energy will be 3.7 times of bat_capacity So I have configured the design energy as 0x73A0.

10) And Similarly the terminate voltage 0x0E74.

11) After this I am calculating the check sum and updating that also and making a soft reset and reading back the checksum.

12) If the checksum is same then I am sealing the guage and reading the battery capacity and remaining battery capacity which I am getting is default not the configured one.

Regards

Harish

Please read the CONTROL_STATUS register from the gauge. Is INITCOMP (bit 7) set?
Please read the FLAGS register from the gauge. Is BAT_DET (bit 3) set?

If these bits aren't set then the gauge didn't detect the battery and it will not report the actual remaining capacity. Did you configure the gauge to auto-detect the battery or is it configured so that it requires the BAT_INSERT command?

There are a few other issues with your design:

1. Just setting Design Capacity (and Design Energy by proxy) to 8000mAh for a 10000mAh cell won't work because the gauge will internally saturate some registers eventually if your cell has higher capacity (the gauge will update Qmax and if you cell is 10000mAh, Qmax will grow to reflect this number, which in turn will cause problems with various internal power calculations).

You can scale this down (e.g. divide CC_GAIN by 10 and scale all current and capacity related parameters (and impedances) by the same factor. Design Capacity would then be 1000mAh).

With a large battery, make sure that the max. current from your system doesn't saturate the current sense inputs.

2. Unless you physically disconnect the gauge from the battery, do not reconfigure the gauge at every power-up of your system. This defeats the adaptive behavior of the gauging algorithm. Only configure the gauge if the ITPOR bit in FLAGS is set (which indicates that the gauge was reset and lost it's configuration/learned parameters).

Hi Dominik

Thanks for the reply.

I just checked the control status for init comp and flags register value for Bat_det. It is working fine.

And thanks for the point number 2 so now I am configuring it only on POR.

But I didn't understand point number 1, how to change the cc_gain and if I do that the 10000mAh is represented as 1000mAh???

And I am able to read the discharging current but while charging it is still giving me discharge current value. But battery is getting charged I am measuring it but here remaining battery capacity is not increasing.

And my batteries Chemical composition is Lithium Nickel Manganese Cobalt Oxide. And my chem id is 0x0128 which Lithium Cobalt Oxide. Is that a problem ???

Regards

Harish

About #1: The gauge determines capacity with discharge simulations using a model of the battery together with actual discharge measurements (coulomb counter (via sense resistor) and battery voltage). If you use a cell that exceeds the maximum capacity limits for the gauge, you can adjust the model (impedance tables, design capacity) and the coulomb counter measurements by a common scaling factor (e.g. by 10 or by 2 or whichever gets you within the limits). cc_gain is a floating point value which is normally set so that a 10mOhm sense resistor will result in a 1mA current reading from the gauge for a 1mA current through the sense resistor. You can scale this by 10 so that a 10mA current will result in a 1mA reading from the gauge. If you do that you can then use a 1000mAh design capacity setting for your 10000mAh battery (and you'd also have to scale the impedance table entries and any other current/capacity related parameter accordingly).

If the gauge reports a discharge current when you charge the battery, then the charging current doesn't go through the sense resistor or something else is very wrong.

Hi Dominik

Sorry for the late reply, after seeing your previous post I changed the current flow path which was initially designed wrong so now I can monitor the charging as well as discharging through fuel guage.

But during configuring the fuel guage I connected supply also in the same time at that time the design capacity and remaining bat capacity were showing same which was highest but battery was not charged yet.

If I remove the supply and just put battery back after configuring it was working fine and I connected supply back it was working fine.So while configuring the guage shouldnt I connect the supply ?? Or am I doing something wrong...

Regards

Harish