• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 64 subscribers
  • Views 565 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25713: BQ25713 unable to restart charging

Di Ma
Intellectual 420 points
Part Number: BQ25713

Hello team,

I'm using BQ25713 to charge 2S2P Li-ion battery pack. My problem is as follows:

I'm setting the charge current to 2432 mA and charge voltage to 8400 mV.

I have no problem charging the battery until the current drops to 550 mA and battery voltage 8.06 V.

Furtherly, while charging the battery, if I stop the charging (by turning OFF the power supply) and then start the charging again (by turning ON the power supply) the charging current drops to 100 mA.

I have found out that if I restart the charging with 12V (11.5 V for battery voltages of 8.18-8.2 V) from the power supply the charge current is normal (~500 mA), however for any other voltage the charging current drops to 100 mA.

Also an interesting thing I found is that while charging with 100 mA (which is supposed to be ~500 mA), if I connect the load (5 ohm) the charging current switches to 500 mA even though it has nothing to do with it. The load current should be provided directly from Power Source.

Until battery voltage is <8.24V and charging current is >250 mA the situation is similar, however when I try to recharge the battery after 8.24V, I'm unable to do it even if I connect the load or restart the charging from 12V.

In any case I can restart the charging following the procedure:

1. Charge the battery

2. Stop the charging

3. Connect the load (Battery voltage drops due to the load)

4. Restart the charging

5. Disconnect the load

6. Charging continues with normal charge current (~500 mA for battery voltage = 8.06 V)

Below you can find my schematics:

Is there any limit for the battery voltage that the charger understands that the battery is full and drops the current to 100mA even though it can still accept 500mA.

Let me know if you need any additional information.

Thanks in advance,

Dmitriy

  • 0
    TI__Mastermind 24075 points

    Hi Dimitriy,

       In the constant voltage phase of battery charging, the battery voltage is regulated and charge current is allowed to taper down. Instead of measuring the actual battery voltage, can you measure at SRN, for when you observe the charge current start to decrease from your set charging current? With regards to the input voltage, also verify the ChargeStatus register for if you are in VINDPM.

  • 0 in reply to Kedar Manishankar
    Intellectual 420 points

    Hi Kedar Manishankar,

    Regarding the battery voltage: Do you mean when chrager switches from CC to CV mode of charging?

    Regarding the VINDPM: Charger_Status.IN_VINDPM =0

    I forgot to say that I changed R14 (RSR) to 20 mOhm and now my charge current resolution is 32 mA. 

    Below I'm attaching the values of BQ25713 registers when the battery voltage is 8.256 (charging stopped, circuit is battery powered and consuming ~3 mA)

    I observe ADC_IBAT.I_CHG as '1' = 32 mA, from the ammeter connected in series with the battery I read 70 mA of charge current. From SRN I read 8.445 V (8.26 V without charging). From IBAT pin I read 0.025V (I_charge = 0.025V / (16 * 0.02 ohm = 78 mA).

    To get the actual charging current I proceed with the procedure described previously. Below I'm attaching the new register values:

     

    I observe ADC_IBAT.I_CHG as '6' = 192 mA, from the ammeter connected in series with the battery I read 203 mA of charge current. From SRN I read 8.39 V (8.26 V without charging). From IBAT pin I read 0.062V (I_charge = 0.062V / (16 * 0.02 ohm = 193.7 mA).

  • 0 in reply to Di Ma
    TI__Genius 10240 points

    Hi Dimitriy,

    You mentioned that you have a meter connected in series with the battery. The internal impedance of the meter has impact on the charging profile. Could you check the result without the meter in the loop?  

  • 0 in reply to ezhao
    Intellectual 420 points

    Hello Team, 

    Yes you were right, without the ammeter in series I can now charge the battery of 8.3 V with 400 mA charge current. Interestingly the ammeter was bloking this current, I have measured its input impedance as 0.4 ohm.

    Thank you very much for the support.

    Have a nice day!

    Dmitriy