We have a design that uses the LTC2942 fuel gauge and the value in the accumulated register is ~80% when the battery is fully discharged.
When charge completes (as indicated by MCP73113 charger) the MCU writes 0xFFFF to the accumulated charge register. After multiple charge/discharge cycles the fuel gauge reliably reports a minimum accumulated charge of 78%.
The battery is PKCell ICR14500 and we're using a prescaler of 128,
Vnominal = 3.7 V
Capacity = 750 mAh
Q_total = 2700 C [Q = 0.75 Ah * 3600 sec/h]
Rsense = 75 mOhm
M = 2^(4*[b2] + 2*[b1] + [b0])
0b111 -> M = 128
Q_lsb = 56.7 mC [Q = 0.085 mAh * (50 mOhm / 75 mOhm) * (128 / 128)]
Q_max = 3713.7 C [Q = Q_lsb * 2^16]
What needs to be done to get the accumulated charge register to use the full range?
As a work-around, we're currently re-scaling the accumulated charge register value from 78-100% to 0-100%, and sanity checking the result with battery voltage.
