BQ24650: can not reach the set voltage

Gene Qiu

Part Number: BQ24650

Hi team,

Question 1:
This is the case, using a 40W solar panel (output voltage 18V, current 2A MAX) as the input of the BQ24650,output is 4.2V, current 2A to charge the 18650 battery 
pack, and found that when the sun is not good (at this time due to MPPT, the measured input voltage is also higher than 14V, there will be about 14.7V)), 
the output voltage will not reach the normal output voltage of 4.2V, and the VFB voltage will be around 1.7V at this time and can not charge the battery pack properly.

Question 2:
When the sun is strong, the voltage of the MPPT chip pin will be very high, sometimes reaching 2.7V, not 1.2V in the chip manual. I wonder if there will be any problems.

Here attached the circuit diagram as below

BQ24650.pdf



Best Regards,
Gene Qiu

over 7 years ago

0 Ning T over 7 years ago

TI__Guru 59601 points

Gene,

What is the MPPT voltage and Voc (open circuit voltage) for your solar panel?

Thanks,

Ning.

0 Vickers over 7 years ago in reply to Ning T

Intellectual 980 points

MPPT 14V,Voc 18V

0 Ning T over 7 years ago in reply to Vickers

TI__Guru 59601 points

Hi,

1. When the sun is not good, what are the input voltage, input current and battery voltage, battery charge current?
2.When input voltage is higher than MPPT voltage (14V), it is normal for MPPSET pin voltage being higher than 1.2V. The absolute max voltage for MPPSET pin is 7V.

Thanks,

Ning.
Please click "This Resolved my issue" button if this post answer your question.

0 Vickers over 7 years ago in reply to Ning T

Intellectual 980 points

Hello Ning,
We also suspect that it is caused by power.Solar panel output current is not easy to measure.We use DC power to simulate.When the input current under 200mA,output voltage is under 4.2V.
When the sun is not good,the input voltage is also stable above MPPT.

0 Ning T over 7 years ago in reply to Vickers

TI__Guru 59601 points

Hi,

Is the battery connected? If yes, the output voltage should be equal to the battery voltage. If not, the output does battery detection as described in section 8.3.21 Battery Detection on the d/s.

Thanks,

Ning.
Please click "This Resolved my issue" button if this post answer your question.

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BQ24650: can not reach the set voltage