MP2672 Cell Balancing Problem

Battery Management
1

image
image736×316 12.5 KB

I am currently working with the MP2672 IC in standalone mode for a project involving a two-cell Lithium-ion battery configuration. I am facing following issues:

  1. Cell Balancing Problem:
  • The IC is not correctly detecting cell imbalance despite the MID pin being properly connected to the midpoint of the cells.
  • The cell balancing feature appears to cause the cells to become unbalanced during charging, leading to a prolonged balancing loop.
  1. Charging Issue with Deeply Discharged Cells:
  • When both cells reach 0V, the IC only charges the upper cell, rather than balancing the charge between both cells.

I have verified my connections and configurations.
Any assistance or additional documentation would be greatly appreciated.

2

Hello, welcome to the MPS forums!

This is certainly a complex issue. There are many places to start when debugging an issue like this, but just to narrow things down, let us start at the beginning input stage.

A few questions to start:

  • Are the capacitors that you are using to bypass Vcc ceramic (they have a lower ESR and is the reason why they are suggested in datasheet)?
  • Have you verified that no more than 20mA is being pulled by this pin?
  • What is the reason that you are using 22uF and 2.2uF as opposed to the suggested 1uF as recommended by the datasheet?
  • Is the capacitor from SYS & BATT pins to PGND as close to the IC as possible?
  • Are you able to capture waveforms of the battery charge curve?
    LS_Cell Balance and HS_Cell Balance would be helpful to see charging behavior in your case.
  • There is a cell balancing threshold voltage as specified in the datasheet, so the balancing of this circuit wouldn’t be very complete.
  • What batteries are you using if you don’t mind me asking? Mismatched cells may be the culprit in that case.

The reason the following questions focus on Vcc is because this pin is responsible for powering all internal circuitry which regulates cell balancing capabilities. The rest of your schematic looks good which is why this is rather tricky.

I know I threw a lot of questions at you, but this would certainly narrow things down to get to the root cause of your issue

Best,
Krishan.