TIDA-00120: Regarding Output Voltage

Hi Naresh,

Thanks for your post. I need some time to find the owner of this TI Design and get back to you later.

B.R
Winter

Naresh,
Are you using the software provded with the TIDesign as is? Any other changes to the design?

Hi Bart,

Thanks for the reply. I Didn't make any changes to the design. I am using same software provided by TI

regards

Naresh

Hi Winter ,

Thanks for the reply. Please try to find ASAP

Naresh,
The design should be attempting to track to the maximum power point. With no load or battery connected, it will just increase the output voltage in attempts to get there.

When you connect the battery, where are you measuring the output voltage at? At the load terminal? Are you also able to determine what state hte software is in (in the charging profile).

Regards,
Bart

Hi Bart,

I am measuring the output voltage at Battery terminal and also Load Terminal.

With No load the voltage is 13.5V and when i connect the battery , it is increasing to 15V. 

Please advice me one more thing. I want to use this for 48V system. Do i need to change only the MOSFETs or any other components? Please confirm

regards

Naresh

Naresh,

Could you provide more information about the battery you are using? If the battery's internal resistance is high (typically due to age), the voltage will begin to rise when the system starts pumping current into it. If this is the case, it can only be charged in CV mode.

Regards,

Bart

Hi Bart,

I am using 12V, 65Ah Lead acid battery. This battery we are using from more than a year. I hope my MPPT is working fine

regards

Naresh

Naresh,
I have a few other things things I'd like you to check if possilbe.

In the firmware (main.c), on lines 125 to 131 (the battery configuration parameters), have you changed any of these values? By default the firmware should switch to CV mode before 15V.

Can you validate the value of the resistor divider networks for the voltage sensing?

Do you have the GUI connected? If so, can you send a screenshot of it when it's operating at 15V so I can see the other parameters as well?

Regards,
Bart

Bart ,

I didn't change anything in the firmware.

The voltage sensing resistor divider network values are R56 = 178K and R55 = 13.3K.

I am unable to connect to GUI. I don't have the MSP430 launchPad. Is it possible to connect to GUI with MSP430FET?

regards
Naresh

Naresh,
No, the MSP-FET does not have a UART-SerialUSB converter integrated into it. Even just a generic converter you might have hanging around will work though.

If the GUI isn't connected though, there are a few parameters when you have the battery connected you might be able to share that will help me here:
1. The input supply (PV) voltage
2. The input supply current
3. The load voltage
4. The battery voltage

It is also possilbe to run the software in debug mode so you can see what state the charging system is in (CV or CC). Just be sure to double check the power path for the 3.3V rail so that there is no loops that might damage the FET or your computer.

Regards,
Bart

Bart,

Below are the details when i connect my Battery(12V, 65Ah) to MPPT

Input supply Voltage = 17.5V(DC Source)
Input supply current = 5.2A
Load Voltage = 15.2V(at LOAD +, LOAD - terminals)
Battery Voltage = 15.2V(at BAT+, BAT- terminals)

regards
Naresh