BQ24230 charging current issue

What is the battery voltage when you measuring the current? The battery voltgae will have to be over 3V and below VBATREG to be in fast charge mode. The current will taper down when the battery voltage rise close to VBAT_REG and continue to decrease until reach the termination threshold.

Also, how are you measuring the charge current? we recommand to use current probe to obtain an acurate current measurement.

Hi Jing ,

Thanks for the reply!

My battery voltage was 3.8 V and i was measuring the current of Riset ressitor , which is 17.4 K , using this formula ( V ISET =(I CHARGE / 400)×R ISET)) given into the datasheet of this ic . i measured the current in both precharge and CC fast charge both mode.

Now let me tell you the whole scenario. I am using a 108 mAh li-ion battery, i deep discharge the battery using a load to 0 Volt , then i connect the battery into the prototype with charge current rate of 50 mAh , so by calculation it should not take more than 3 hours to full charge the battery , but is taking approximately 8 hours to full charge the battery and i put TMR pin floating so pre-charge period is 30 minutes and fast charge period is 5 hours.

Now please tell me how to debug this issue?

Thanks in advance!

Regards,

Hitesh B

The TMR is the safety timer programming input, which means the charge will be suspended when the timer expires. With 30 minutes precharge safety timer, the timer fault will occur if the battery voltage has not reach the VLOWV in 30 minutes.Charge will be suspended. Looks like in your case, the safety timer is either extended or disabled.

During the fast-charge phase, several events increase the timer durations.

1. The system load current activates the DPPM loop which reduces the available charging current

2. The input current is reduced because the input voltage has fallen to VIN(LOW)

3. The device has entered thermal regulation because the IC junction temperature has exceeded TJ(REG)

During each of these events, the internal timers are slowed down proportionately to the reduction in charging current. 

I recommend you first check the setting of TD. When termination is disabled, the timers are also disabled. Corresponding to the above events,

1. make sure no load is connect at OUT 

2. Check the input current limit setting, make sure the input current is greater than the some of the load current and the preset charge current.

3. Make sure the junction temperature has not exceed the TJ(REG)

Hi Jing,

I am working on this with Hitesh. We have checked based on your recommendation following things but no positive result.

1. make sure no load is connect at OUT  - Our load is very light while charging less than 5 mA.

2. Check the input current limit setting, make sure the input current is greater than the some of the load current and the preset charge current. - We checked charging current is 50mA which is much greater than our load

3. Make sure the junction temperature has not exceed the TJ(REG) - We tested it room temp and IC was cool so not exceed greater than 35-40 degree.

We achieved 5 hrs charging time  from 8 hrs after doing below modification:

1.  Reduced VIN pin capacitor value to 1uF from 4.7uF.

2. Reduced Fast charging time period to 3 hrs by tuning resistor value at TMR pin.

Could you please help us to reduce more charging time ? Our target to complete full battery charge time is 2-3 hrs.

P.S. : We are checking CHG# pin of IC to detect full charging status.

Thanks.

Best Regards,

Hitesh Gambhava

 

The resistor on TMR sets the safety timer which does not control the fast charge time. Refer to datasheet 24 for the explaination of the functionality.
What I meant regarding on 2 is check the input current limit setting, and make sure IIN-MAX > ICHG+ILOAD where IIN-MAX = KILIM/RILIM.
Please also check is the voltage on TS pin. Please make sure it is within the operating window. Refer to datasheet page 20.
Checking the /CHG will help to determin the charge status. You can refer to datasheet page 25 for detail.
Some batteries may have its internal protection circuit which limits the charge current. Please check the battery spec sheet. When you mention deeply discharge the battery, what voltage did the battery discharge to?

Hi Jing,

Thanks for reply. As I told, we have IIN-MAX > ICHG+ILOAD and since we are not using TS pin, we have grounded it with 10K resistor. Voltage across TS pin is 0.7V and it is within limit.

Our battery do not have any protection circuit . Battery can discharge up to 1.8V. Let me put some points here to get better clue if any.....

1. Our Battery capacity is 100mAh and we have fast charging current is 50mA. Adjustable input current set to 495mA.

Thanks.

Hitesh Gambhava

Can you provide more information on the battery spec? For most of the 3.7V (nominal) lithium-ion/ LI-PO batteries, they should not be discharge down to 1.8V. Most likely the discharge voltage limit should be 3V.

Have you checked the /CHG status? it should indicate if a falt occured.

Anyway, I have done a charge cycle with the bq24230EVM and a 100mAh LiPo battery. The charge current is set to around 80mA and the battery is able to reach full charge within  1 hour and 40 minutes.