I have a few solar panels I wanted to play around with and charge some 18650s till I get a little more comfortable that I won’t blow something up. My main goal is to understand how to charge batteries, use solar panels, diodes, and learn more about electronics on this side.
The plan is to take come 5v solar panels in parallel, then run them to my little voltage regulator, and from there a diode is run off the + side to a 18650 and the - is bare. I will set the regulator to have a continuous output of ~4.1v so I don't blow anything up or charge too fast.
This brings me to asking things I don't understand, can’t really google, and think I know but I just am not brave enough assume.
1) Battery a 18650 generally has a low end of 3.6V and a high end of 4.3V. Outside of that will damage it/catastrophe.
Question - If I set a controller to feed 4.1V from a solar panel continuously, could I damage a battery or cause it to go over 4.2V? When I think of voltage, I think of it more like the width of a river. If you keep feeding something 4.2V 100ma, won’t the item go over 4.2V eventually? It would just take longer to “charge” given the lower voltage? (like a 2mm straw to fill a glass vs a 4mm one?)
2) Diode I get that a Diode controls the flow making it go only 1 way, so if I use one on the + side then the power cant back feed, but do I need one for the – side?
I can see this being a waste of a diode and you would need to invert the direction to make it useful at all, but I feel like leaving it open like that is bad mojo? Someone please tell me it would 100% be a waste to use one on both + and – to prevent back feed drain?
3) Theoretical Question If you had a 12v battery and a 12v solar panel in parallel leading to a motor or device of some sort, and used a diode on the + side of the solar panel (preventing back feed and forcing a charge only situation, would this cause any catastrophes? In my head, it would work so that when the motor ran, it would draw from the battery and the solar panel. If the motor were cut, the panel would charge the battery. Is this how it would work? I feel like I am 100% wrong and this would cause a short or something having a panel in parallel with a battery.
note None of my batteries have a Protection Circuit, which is why I feel so scared of trial and error with this kind of stuff.
If anyone has any related info to topics I asked about, Please post it, I find it difficult to google anything related to charging/batteries/solar panels on google unless it is raw statistics. Real life applications, experience, and lessons learned are really hard to find.