STEVAL-ISV012V1 Setting up issues

[Khoi Ly]

Dear ST Community,

I am trying to use STEVAL-ISV012V1 to recharge my Lithium-ion battery using a benchtop power supply to evaluate it's charging efficiency. I really appreciate if you could point out where I do it wrong since I couldn't get to the claimed 80-90% efficiency.

Essentially, I measured the power from the power supply (1.5V) to the boost charger STEVAL device, and I also measured the power that goes to the lithium-ion battery. What I observed was a consistent 50-60% efficiency of charging, on top of the current fluctuation that I posted in this case. From the datasheet, it's stated that the efficiency is between 80-90% so I wonder what I missed.

I measured the voltage and current at the battery side to see the charging performance and I see a lot of fluctuation in current to the battery.

Current: 139.25 mA Bus Voltage: 3836.25 mV Power: 410.00 mW

Current: 114.25 mA Bus Voltage: 3836.25 mV Power: 500.00 mW

Current: 134.25 mA Bus Voltage: 3823.75 mV Power: 450.00 mW

Current: 109.25 mA Bus Voltage: 3838.75 mV Power: 490.00 mW

Current: 130.50 mA Bus Voltage: 3823.75 mV Power: 470.00 mW

Currnt: 128.00 mA Bus Voltage: 3841.25 mV Power: 490.00 mW

Current: 121.75 mA Bus Voltage: 3837.50 mV Power: 460.00 mW

Current: 131.75 mA Bus Voltage: 3840.00 mV Power: 500.00 mW

Current: 126.75 mA Bus Voltage: 3825.00 mV Power: 460.00 mW

Current: 128.00 mA Bus Voltage: 3841.25 mV Power: 470.00 mW

Current: 121.75 mA Bus Voltage: 3836.25 mV Power: 460.00 mW

Current: 121.75 mA Bus Voltage: 3826.25 mV Power: 450.00 mW

Current: 129.25 mA Bus Voltage: 3837.50 mV Power: 520.00 mW

Current: 141.75 mA Bus Voltage: 3837.50 mV Power: 420.00 mW

Current: 140.50 mA Bus Voltage: 3837.50 mV Power: 520.00 mW

Current: 134.25 mA Bus Voltage: 3827.50 mV Power: 500.00 mW

Current: 114.25 mA Bus Voltage: 3830.00 mV Power: 500.00 mW

Current: 140.50 mA Bus Voltage: 3833.75 mV Power: 400.00 mW

Current: 128.00 mA Bus Voltage: 3841.25 mV Power: 470.00 mW

Current: 118.00 mA Bus Voltage: 3838.75 mV Power: 510.00 mW

Current: 113.00 mA Bus Voltage: 3837.50 mV Power: 500.00 mW

Current: 106.75 mA Bus Voltage: 3830.00 mV Power: 400.00 mW

Current: 128.00 mA Bus Voltage: 3825.00 mV Power: 470.00 mW

Current: 119.25 mA Bus Voltage: 3822.50 mV Power: 510.00 mW

Current: 139.25 mA Bus Voltage: 3836.25 mV Power: 490.00 mW

This data log shows the current and voltage into the battery. And I wonder what causes the fluctuation?

Any help is appreciated and I look forward to hearing from you. I have not modified the evaluation board in anyway. I simply removed the solar panel and attach the inputs to the benchtop power supply.

Thank you very much,

Khoi Ly