After the production, we conducted a test on the product.  We found some problems that need to fix:

  1. It can be slow to change due to the lack of converted power from solar panels.
  2. In the evening, when you charge your phone with a lithium battery, you may have less storage space.
  3. When the lithium-ion battery becomes too low, the charger will reverse the process and drain the electric energy from the phone.
  4. Sometimes the solar power bank works in reverse to drain the battery from the phone
  5. If there is no sunlight for a long time, the battery bank will not be able to charge after the backup power of the Lead-acid storage battery is used up.

Based on Problem 1, our group decide to have multiple solar panels connected togather to generate electricity and increase power. Based on Porblem 2 and 5, we decided connect motiple Lead-acid storage batteries to increase its capacity. In order to make the connection of two obejcts, we need to learn the series connections. This technology is different with the normal parallel connection. The series connections means that we need to connect the positive pole of one object to the negative pole of another object to achieve the effect of adding the power of the device. Through this technology, we fixed the first two problem.

According to the thrid and fourth problems, we found that the USB interface provided by the school is not the common interface. This USB port is a safe-down port, so it lowers the voltage in the Lead-acid storage batteries, which is the reason why the phone charges the solar bank in reverse. When the voltage in the phone exceeds the voltage provided by the charging point device, the electricity in the phone automatically flows into the charging bank. When the voltage in the phone exceeds the voltage provided by the charging point device, the electricity in the phone automatically flows into the charging bank. To stop the backflow of electricity in the phone, we need to place an LED light between the lead-acid battery and the USB port, which makes the current flow in only one direction. Later, we found that the LED light did not turn on due to the high voltage. So we installed a resistor in front of the LED lamp to make the LED light on.