MP2672A charge current low

Battery Management
1

I’m using the Mikroe Balancer 4 Click which is based on the MP2672A chip.
I have 2 Li-On batteries in series and hooked up correctly.
I’m powering the eval board with a USB plug hooked up to a USB charger (capable up to 3A for fast charge devices).
The STAT and ACOK are pulled low, so both lights are on indicating it is charging. The battery voltage for each is around 3.9v. The problem I’m seeing is the current is only 120mA even though ISET has a 12k resistor and the device is in standalone mode. Is this some sort of pre-charge cycle?
I should note that I am not using any NTC thermistor, but this doesn’t seem to be an issue as mentioned before, STAT and ACOK are low.

3

I re-flowed the chip and set it to host control mode. I’m still seeing low current
The status register reads 101000, which means it’s in constant current/voltage charge and in VIN PPM. What is VIN PPM? Could this be why the current is so low.
I have the settings cofigured as such:

writeRegister(BALANCER4_REG_CONFIG0, 0b00111000);
writeRegister(BALANCER4_REG_CONFIG1, 0b10000101);
writeRegister(BALANCER4_REG_TIMER, 0b10000011);

4

Hi Sean,
Thank you for utilizing MPS Technical Forum!

Can you please confirm you are getting 5V Vin and check for the following:

  1. Can you please clarify how are you probing/sensing the charge current?
  2. How long have you measured for the current during the charge profile?
  3. Have you tried varying the Iset resistance to see any changes on the charge current?
  4. Do you have SYS connected to a load?

For reference on charge profile, its 4 seconds per division:
image

Thanks,
Nouman

5

Hello,
I have tried two ways to test current, both yielding the same result. First is by positioning my bench meter between the positive side of VIN. The second is using my DC power supply to provide 5v/2A to the eval board.
I left it charging for over an hour with the same current reading.
I switched from a 12K resistor to a 6.8K with similar results.
Nothing is connected to SYS.

At the time of the picture, the charger has been running for 10minutes and battery voltage at 7.85v.

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6

Hello Sean -
I believe you are observing the end of the charge cycle for your batteries.

The current of 120mA you are measuring is called termination current. You can refer to datasheet for further explanation of I_term.

With 3.9V battery cells, your measured series voltage is 7.85V for the 2 Li-ion cells. It seems you have reached max pack voltage. No need for further charging on those cells.

Hope this assists and provides clarity,

Regards,
Nouman