Gas Gauge and Fast Charge
The EV2014x evaluation system provides a development
and evaluation environment for the bq2014 Gas Gauge
IC and the bq2004 Fast Charge IC. The EV2014x incor-
porates a bq2014, a bq2004, and all the external compo-
nents required to accurately monitor the capacity and
reliably fast charge 4 to 10 NiCd or NiMH cells. The
evaluation system includes a PC/AT interface to allow
the monitoring of battery parameters. The board fea-
n Jumper configuration for number of series cells and
n Complete fast charge control
n Battery capacity monitoring - LED display of avail-
The EV2014x provides two main functions: fast charge
control and battery capacity monitoring. The actual im-
plementation of a bq2004/bq2014 design will be signifi-
cantly smaller in size. See the bq2004 and the bq2014
data sheets for device functional descriptions.
Battery fast charge is terminated by any of the follow-
ing: ∆T/∆t (the change in temperature versus time), -∆V
(negative voltage change) or PVD (peak voltage detect),
maximum temperature, maximum time, and maximum
voltage. The board provides a direct connection for an
NTC thermistor for temperature charge terminations
and safety qualifications. It also includes an RS232 in-
terface for easy access to the battery state of charge in-
formation via the serial port of the bq2014. The menu
driven gas gauge software provided displays charge/dis-
charge activity and allows user interface to the bq2014
from any standard DOS PC.
The user supplies the power supply and the batteries.
Onboard LEDs indicate charging status and remaining
capacity. The capacity LEDs are activated by the push
An onboard voltage regulator supplies the bq2004 fast
charge chip with power from the DC charge input. The
bq2014 derives its VCC from the battery connected to the
BAT+ (J1) and BAT- (J2) terminal blocks. The bias re-
sistor (R17) for the bq2014 voltage regulator is 300K.
For less than 6 cells, this value should be 100K. Refer to
Table 4 in the application note entitled “Using the
bq2010-A Tutorial for Gas Gauging” for a more detailed
description of the bq2014 voltage regulator.
The bq2014 uses a sense resistor (R16) on the negative
terminal of the battery to measure charge and discharge
activity. This resistor may be changed if necessary.
The system load is connected between the BAT+ (J1)
and PACK-(J2) terminal blocks (see the schematic in
During charge, the bq2004 buck mode regulator also
uses a sense resistor to regulate the charge current. The
board is shipped with a value of 0.100ohm which corre-
sponds to a charge current of 2.25A. This resistor can
be changed depending on the application.
The EV2014x is programmed with jumpers JP1-JP3 and
JP6-JP10. The programming pins determine:
n Charge timeout limits
n Fast charge termination mode
n Programmed full count
n Scale factor
n Self-discharge rate