First, I hope you are all doing well.
I am currently working on a project that will be using a solar panel interface as well as, for now, a 3.7V lipo battery (at night). So the Solar panel would supply the system and charge te battery in daytime, and the battery will take over at night.
So I thought that the BQ24650 would be adequate for this use case. But I am a little worried as I've seen many posts (without final answers) where people, using a 6V solar panel had trouble charging the battery, and I am using solar panels for the first time.
I need your help in order to answer some questions, and to be sure I am using the right components and values.
1- Does MPPSET voltage must be 1.2V sharp? Or is 1.2V a minimum? Couldn't there be fluctuations in the voltage supplied by the solar panel so that the voltage is not always the same depending on the sunlight intensity? (I think the fluctuation might be in current not in voltage)
2- Here are the characteristics of the Solar panel I am thiking of using:
- Open Circuit Voltage: 7.7V
- Peak Voltage: 6.5V
- Peak Current: 930mA
- Peak Power: 6.0W
- Power Tolerance: +/-10%
So for MPPSET, I should use a divider to get 1.2V from 6.5V right? We calculate using the peak voltage?
3- As the Max charge voltage for 3.7V Lipo batteries is usually 4.2V, then I shoud set VFB to 4.2V (or 4.1V for safety), correct?
4- As I said, I want to use the solar panel at day, and the battery at night (or couldy day) to power the rest of the board, so I should make the same setup as the EVM with D3 between VBAT and VSYS, correct?
That means that VSYS (and I mean the supply going to the board) will vary between 6V (from solar panel) and about 3.1V to 3.7V (with D3 voltage drop, and depending on how much the battry is charged), correct?
4- In this case, as my system uses 3.3V, I was thinking Ishould place a regulator to drop 6V to 3.3V before D3. But in that case, when the battery is charged and the solar panel is still working, wouldn't VBAT take over as 3.7V is greater than 3.3V? I am a little stuck on this issue.
Thank you for your help.