bq2016

GAS GAUGE IC FOR

HIGH DISCHARGE RATES

SLUS475A– JANUARY 2001 – REVISED NOVEMBER 2002

12

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

charge and discharge count counting (continued)

self-discharge estimation

The bq2016 continuously decrements NAC and increments DCR for self-discharge based on time and

temperature. The self-discharge count rate is programmed to be a nominal 1/80

 NAC rate per day for NiCd

and a nominal 1/60

× NAC for NiMH. This is the rate for a battery whose temperature is between 20°C–30°C.

The self-discharge rate doubles every 10

°C increase in temperature.

count compensations

The bq2016 compensates charge and discharge counting for temperature and rate before updating the NAC

and/or DCR. The bq2016 compensates self-discharge estimation for temperature before updating the NAC or

DCR.

charge compensations

The bq2016 compensates for charge efficiencies at a quick-charge and fast-charge rate at two different

temperature thresholds. The bq2016 applies the NiCd or NiMH factors based on the VPFC setting. For charge

compensation, quick charge is defined as a C/5 charge rate or less and fast charge is defined as a rate greater

than C/5.

The charge-compensation factors are shown in Tables 4 and 5.

charge compensations

Table 4. Charge Compensation for NiCd

CHARGE TEMPERATURE

QUICK CHARGE

(

≤ C / 5 ) COMPENSATION

FAST CHARGE

(

> C / 5 ) COMPENSATION

<40C

0.80

0.95

≥ 40

0.75

0.90

Table 5. Charge Compensation for NiMH

CHARGE TEMPERATURE

QUICK CHARGE

(

≤ C / 5 ) COMPENSATION

FAST CHARGE

(

> C / 5 ) COMPENSATION

<40C

0.80

0.90

≥ 40

0.75

0.85

discharge compensation

The bq2016 corrects for the rate of discharge by adjusting an internal discharge-compensation factor. The

discharge factor is based on the calculated discharge rate determined from the VSR potential and the PFC

setting. The table below shows the compensation factors for NiCd and NiMH during discharge:

DISCHARGE RATE

DISCHARGE EFFICIENCY

( FDE ) (%)

≤1C

100

>3C

100

>6C

95

>9C

95

>12C

90

NOTE: The C Rate determination is made from LMD.