I am using the BQ24010 to charge a single cell 4.2v Lithium Ion battery. The battery is being used in an Intrinsically Safe environment so it has a fixed 3.6 ohm resistor on the output terminal to limit short circuit current. A separate sense line is also provided out of the battery with a fixed 1K ohm in series.
The 3.6 ohm battery terminal is connected to the BQ24010 OUT pin and circuit load. The 1K ohm battery terminal is connected to the BQ24010 BAT pin for sensing.
Rset = 5.2K in hopes of keeping charge current under 170mA or so.
The circuit seems to charge well when the battery is near empty, but as it becomes more charged the current into the battery can exceed 500mA.
Shorting the OUT and BAT pins, the battery (with its 3.6ohm series resistor) charges at a rate well under 170mA. Placing a 2k resistor between OUT and BAT seems to do the trick but is not consistent from battery to battery. Similarly varying Rset can get us closer to the desired charge current, but seems to vary from battery to battery.
The BQ2401x is one of the few charger families that has separate OUT and BAT pins so it seemed well suited to charge this IS battery configuration. Any suggestions or advice you could provide would be greatly appreciated.
Thanks,
Mark
