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BQ24753A: Battery Charger Operation

Pradeep N52
Prodigy 190 points
Part Number: BQ24753A
Other Parts Discussed in Thread: BQ34110

The Circuit is attached . Let's say we are using two cell Li-ion battery 7.4V (Max. voltage 8.4V). 

As per my understanding while charging this voltage is gradually increases at BATTERY_PACK+ and the same is sensed by BAT pin of IC. The default charging voltage is 4.2 V per cell. Now we are using 2 cell battery the BAT pin senses the voltage 8.4(when battery is completely charged)and once system is achieved that voltage the IC switches to discontinuous mode. is that correct??

Also can we directly connect two cells(Eg. LG18650) in series without any extra circuits to charge them??The charging voltage of 4.2 recommended by battery cell manufacturer.

We want to measure the voltage at BATTERY_PACK+ terminal to determine the percentage of battery while charging if some voltage variations at in BATTERY_PACK+ occurs because of the IC, that may cause problem in calculating the percentage of the battery. We just want to know our concept of calculating battery percentage by just sensing the voltage at BATTERY_PACK+ terminal will work or not while Charging.

Regards,

  • 0
    TI__Guru**** 155606 points
    Hi Pradeep,

    Yes, once the BAT pin sense the battery voltage is 8.4V, the charge enters constant voltage (CV) mode and regulates its voltage no higher than 8.4V. Yes, you can connect two cells in series. Determining battery capacity by simply measuring battery pack + while charging is difficult. For an accurate measurement, I recommend using a series, system-side battery gauge product like BQ34110. If not using a gauge, then I recommend periodically stopping charge, waiting briefly for the battery to relax and then measure battery voltage.