Solar model for KW

Model PV solar system design.

My goal here is to design, build and test a model working electrical system the simulates a typical off grid PV system. Using small scale components to represent the load, the battery, the charge controller and the PV input. The purpose is to gain a better understanding the technical electrical requirements and limits of todays bigger and more complex home PV grid tied electrical systems. 

Pictured above (L to R) a load, a battery and a solar panel. The charge controller is not shown.

 Some questions that should come up if the system is to function are:

1. Can this battery light the load and for how long?

2. Can the solar PV panel recharge the battery and at what speed?

The drawing above uses water in a bucket (at the top) to run a load (shown in green). The water flows out of the top bucket straight down to the green load turning the shaft and then out on to the ground. Depending on the flow of water through the green load (controlled by the green valve above the load) some or all of the water will flow past the red valve and into the storage at the bottom. The red valve will control the flow of water into the storage at the bottom and can be shut off to protect the storage from being over filled (the storage area will be damaged if filled to fast or overfilled).  If the flow out of the top bucket slows or goes dry then the water from the storage at the bottom will be used to make up the difference to keep the green load running to meet the demand until the water in storage (below) is used up.

If this makes sense then I would direct students on to the drawing on the right using the parts from a $15 Ace hardware rechargeable solar powered landscape lighting unit with a  6 volt dc solar panel and single 1865 Lithium ion 3.4 volt cell. I replaced the units charge controller with a $2.00  5v 1A Lithium battery module charging board that had a type C interface USB. This allowed me to plug in a $10 Diymore USB C Tester Power Meter to collect data (Voltage and Current, Power Bank Capacity and working Time) for the model PV system during charging and discharging of the 1865 Lithium cell. I started testing using my LED shop light. The LED worked and I could collect all the data to confirm the performance of the model system, but was to slow. I then replaced the 6 volt dc solar panel with a $25 Radio Shack Universal AC adapter to provide the 6 volt dc input needed. This increased the speed of the battery charge performance when measured. I also used two 12 volt dc automotive type running lights (in parallel) to speed up the discharge of the 1865 Lithium ion cell.

This is my progress on the PV model system to date.