Hey guys. Senior year is coming up and I will be focusing on power and taking a few course in signals aswell.

I want to create a solar power battery pack. The idea is simple and I would like to challenge myself. I also want to add a Arduino with a screen which give me real time calculations of the solar panel and battery status. I want the screen to display the power/current being gernerated by the solar panel. For the battery I want to give me a percentage or value of how far the battery has charged. I want to connect the battery to a 5V USB discharger so I can connect a device to be charged.

The setup.

Solar Panel - Current IC 1 - Battery;
Battery-Current IC 1// Current IC 2
Current IC 2 - 5v USB discharge

Current IC 1 & 2 are connected to the Arduino which connects to the LCD screen to display the calculations.
I don't know how I want to supply the Arduino with power, preferable to the battery but I'm a little confused if a rechargeable battery can charge and discharge at the same time.

 

The panel can charge a battery and power the Arduino at the same time, as long as it supplies enough power. So don't worry about that. If the supply is inadequate, power for the Arduino will come from the battery with maybe some from the panel. The battery will never be charging and discharging at the same time.

The biggest challenge I see is trying to display the state of charge. Some battery chemistries (such as lead-acid) allow a pretty good estimation of SOC from voltage, which is easily measured at any time. But it's essentially impossible with Li-ion such as in a laptop. That's why battery monitoring software in a laptop keeps track of and totalizes charging and discharging currents, and compares to a "calibration" to estimate SOC for the battery pack. The software does not make a single point measurement.

I think an Arduino can probably totalize the currents in and out. But it will need to have a reference calibration. Out of my league.

 

When the battery is charging the solar should power both the battery and Arduino + LCD

{ed}
wayneh beat me to it.