Other Parts Discussed in Thread: BQSTUDIO, EV2400
Dear Sirs,
as first please let me shortly introduce myself - my name is Mr. Ivelin Nenkov from Tractive GmbH sitting in Austria. Our company produces pet tracker devices mostly for both USA and European markets.
We equipped our last product with the Fuel Gauge bq27421-G1. This product is now in a beta testing phase and we see there is a problem with the estimated battery capacity computation.
Many devices in use by end customer report low and critical battery level even when the cell voltage is high enough (above 3.75V). As an example a device reports 5% at 3.81V and 62% at 4.34V
Our observation is as following:
- Qmax register never changes. It remains 16384 after configuration
- Measured voltage is always correct, but all capacity registers still show wrong values
- Full discharge/charge cycle does not help to get into proper range
- No gauge resets observed during continuous operation
Your assistance is very appreciated!
Below the technical details for reference:
- Fuel gauge configuration for Class Gauging, subclass State:
Qmax:16384
Design battery capacity: 810 (mAh)
Design battery energy computed as follow: 3.8*810
Terminate Voltage: 3520
Taper Rate: 144
Taper Voltage: 4100
- Built in battery cell:
Typical Capacity (Cell) 870mAh From 4.35V to 3.0V by discharge current 0.2C.
Min. Capacity (Cell) 810mAh 1.0C=810mA, nC=n*810mA.
Nominal Voltage 3.80V
Limited charging voltage 4.35V
- Percentage computation
The firmware uses the readout of memory address 0x0C (RemainingCapacity) to execute following:
(100.0 * RemainingCapacity) / 810
Looking forward for your feedback! Thank you very much in advance!
Kind Regards
Ivelin Nenkov
Embedded Systems Engineer
www.tractive.com
