Solar Testing model for KW

 Solar testing model for KidWind - first prototype 1-27-25

Ok so this $14 solar yard light represents an off grid solar PV system with battery storage. You have a solar PV collector, (inside) you have a battery (cell) and battery (cell) charge controller and then you have the load, a LED light. Everybody that is a consumer gets this. 

Let’s look at the detailed information that comes with it. 

PRODUCT SIZE: 41.5 H cm / 16.34 H clear enough but it is in metric (2.54 cm = 1”) 

BATTERY  1 (did you know that this should say CELL not battery because there is only one): 

1 X 18650 (did you know that this cell is 18 cm in diameter and 65 cm tall) 

3.7V (did you know that a standard carbon paste dry cell can only produce 1.5V)

1200mAh (did you know that this single 1865 cell could power a light drawing 1.2 amps for 1 hour)

Lithium Rechargable Battery (Cell) usually written Li-ion and if dead could be recharged if you applied 1.2 amps at a little over 3.7V for one hour.   

This information is a bit more technical. My point is that knowing or understanding these details is not necessary if you just want to be a consumer. Lay your $14 down at your local ACE Hardware and you have a working solar system!

However if you are a KidWinder want to be one of the people that DESIGN, BUILD and TEST a solar PV system with battery storage, read on…

To help answer some of the design question and understand what is going I have built this model. The blue 1865 Li-ion cell has been made visible as well as the charge controller (under the yellow tape). A set of four 1.5V D cells in series to get 6 Vdc has been added. These will be used when there is no sun or light on the PV panel. Each of the components that make up the system has contact points where voltage measurements can be made. Also each of the components has a connection that can be pulled apart and an ammeter can be inserted (in series) to measure the current flowing in each individual part.

This schematic shows the wiring of the different parts. Helpful when using that multimeter making measurements and collecting data.

These four switches are mounted in the from of the model. These allow you to set up different conditions and then measure voltage and amperage readings. Calculate the wattages and determine the charge going into the 1865 Li-ion cell or the amount of charge being drawn out of the cell. Then calculate the time needed to charge the cell or how long the cell will last before the light goes out. There is a lot more to it and after I work with this for a few more days I will post a follow up post.

Do you want to be a consumer of solar PV systems or do you want to be the person that Designs, Builds and Tests solar PV systems? 
  

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.