TIDA-010042: Charging with Electronics load

Hi Yin Min,

The ambient light sensor is not necessary for the circuit to operate.

When setting the electronic load in CV mode, always keep the CV setting around 0.5V higher than the parallel connected power supply so that it does not source any current. In this setting the electronic load should take all the power available from panel. Also, please check the set voltage of the CV load is not higher than the max. battery voltage set in the program.

Regards,

Salil

Hi Salil,

Thank you for your reply and suggestion.

In my case, once I powered on the Panel power supply (36V), the voltage (22.42V) was already at the battery terminal. So, however, I set the E load CV 24V and parallel connected power supply 23.5V, the voltage at the battery terminal is still 22.42V. It didn't change and not taking the power available from panel. Then, I set the E load CV 23V and parallel connected power supply 23.5V. And then, I tried again. But there is no difference.

According to design manual, panel voltage is 36V for 24V battery. I followed the same and I used the original source code downloaded from the website. The source code is default for 48V battery. Even though I changed for 24V battery system, there is no difference.

Anything did I miss? I still can't figure out why cannot charge.

Best regards,

Yin Min

Hi Yin Min,

The parallel connected power supply has to be turned on first. It should be kept lower than the CV load so that it will not sink current into the load. Then the CV load has to be turned on (the "LOAD" switch should be turned on so that it can absorb the panel power when it is turned). The panel should be connected only last. Otherwise the circuit might get into some protection mode.

Regards,

Salil

Hi Salil,

Thank you for your reply.

I was doing the same procedure: parallel power supply>>CV E-Load >> Panel Supply. 

Now, when I reduce the CV load voltage 20V which is less than battery terminal voltage (22.42V), then can start charge.

That means charging function is based on the battery terminal voltage and E-load CV comparison. It is not panel voltage and E-load CV comparison. Is that right?

In design manual, panel input is set at 36V for 24-V system.  But in my board, when panel input is 36V, battery terminal voltage is only 22.42V. Then, I cannot charge fully for 24V battery which is higher than battery terminal voltage (22.42V).

Please correct me if I am wrong. 

Best regards,

Yin Min

Hi Yin Min,

I still don't understand why you are not able to charge the battery in the way I suggested. I think there is some fault is getting triggered. You need to find this out and rectify it before continuing.

Regards,

Salil

Hi Salil,

Now, I am a bit confused. 

When I supply the solar panel (36V) to MPPT board, what voltage should have at the battery output terminal (J5) and load terminal (J7)?

In my case, when I supply the solar panel (36V) to MPPT board, I am getting 22V at the battery output terminal (J5). And I cannot set the CV E load voltage more than 22V. CV voltage with less than 22V can draw the current from the MPPT board without the use of additional power supply.

I think I got issue since starting. I found out that U15 (battery current sensor IC) doesn't work. but after I changed to new U15 IC, then no more voltage at the battery output terminal (J5) and input panel power is also not stable.

Best regards,

Yin Min 

Hi Yin Min,

Just to check - is this how you connect the set-up? The 23V PSU, and the 23.5V E-load together simulates the battery:

If this set-up fails to start, reduce the E-load CV setting to 23.2V. Still not able to get the 36V PSU to operate at the border of CC/CV, there is some problem with the board.

Regards,

Salil

Hi Salil,

Yes. Exact connection. But in my board, there is already 22V at J5 before I connect with (E-load and PSU with diode).

So, it doesn't matter whether I connect PSU with diode or not. Board can start to charge (means CV E-load can draw the current) as long as CV E-load setting is less than 22V.

So, getting 22V at J5 when I input the solar power is normal or not? 

Best regards,

Yin Min

Hi Yin Min,

You should turn on the 36V PSU the last. The sequence is like this: 23V PSU, 23.5V E-load and then 36V PSU. There is no possibility of getting voltage at J5 without connecting the 23V PSU. If the sequence is not correct, the system will detect a battery disconnect condition and stop working.

Regards,

Salil

Hi Salil,

I was getting voltage at J5 without connecting the 23V PSU. Now I come to know it is most likely U15 issue. 

I will get back you.  Thanks a lot.

Best regards,

Yin Min

Hi Salil,

After I changed new U15 IC, there is no more voltage at J5 without connecting 23V PSU. But still cannot start to charge with your setup connection. 

In my board, the only thing I left to solder is temperature sensing components which will not effect the output voltage. I have no idea now what actually is this issue.

Best regards,

Yin Min

Hi Yin Min,

I don't understand it when you say there is voltage at J5 without connecting the 23V PSU. There should not be any other power source connected to the board before connecting the 23V PSU. So how can you get a voltage at J5 without any power source connected to the board? And this is no way related to the presence or absence of U15.

The temperature senor is not a necessary component for the operation of the circuit.

Regards,

Salil

Hi Salil,

Ok. Let me explain my investigating.

First case: There is 22V at J5 when I input 36V solar panel supply at J6 before connecting 23V PSU, E-load and Batt current sense IC (U15).

Second case: After I soldered back U15, there is no 22V at J5 when I input 36V solar panel supply at J6 before connecting 23V PSU and E-load.

Then, I followed your set up connection and turn on procedure.

 Sequence : 23V PSU, 23.5V (CV) E-load and then 36V PSU.

It still cannot start to charge. Instead, 36V PSU (J6) increased to 48V and Batt output at J5 is 22.8V. And there is no current drawing. 

Then, I changed as per suggestion.

Sequence: 23V PSU, 23.2V (CV) E-load and then 36V PSU.

But there is no changes. Still cannot start to charge.

Best regards,

Yin Min