Gary856I thought a bit more and realized I missed something earlier, and this gadget just might work in principle.
As you already saw, you measured 0-19V as the light intensity changed. This is “open circuit” voltage that you measured with a dc meter, with no current flow. The analogy for “open circuit voltage” (i.e., no electrical current flow) is static pressure in a pipe, with no water flow.
Let’s say your battery is at 12.5V, and charging would occur when your charger’s output voltage rises above 12.5V. So:
– When the charger’s output voltage is at or below 12.5V, no current will flow, i.e., no charge. The charger just needs to have a diode (like a one-way valve for current) to prevent draining the battery, since the battery, being at a higher voltage than the charger, would attempt to force current back into the charger without the diode (one-way valve).
– When the charger’s output voltage start to rise above 12.5V, current starts to flow from the charger to the battery, i.e., charging. The more intense the light is, more current would flow from the charger to the battery, but the voltage would only go up gradually as the battery charges. Why? A charger is like an electrical pump. Think about an air pump analogy here. A small bicycle pump can pump up a skinny bike tire to over 100psi quickly. But, if you try to use it to pump up an air mattress, no matter how fast/hard you pump, the pressure will build up extremely slowly, since the there’s a lot of air volume to fill. On a solar charger, with very limited current producing capability, charging the battery is like using a bicycle pump to fill a mattress. It’ll slow charge/fill, and the voltage/pressure would only build up slowly.
I hope this makes some sense, since I struggled to put this into words. Please, no more electrical questions; let’s go back to talking bikes.
