I've been messing with a street light that broke and I fixed it by replacing the PCB with a tiny85 circuit that i made.
It uses an 18650 3.7V Lithium cell. The Tiny does a great job and works reliably up to the lowest discharge voltage of the cell of about 3V.
So, wanting to stay on the cheap, I got a charging module from Amazon that takes 5V input.
My solar panel goes as high as 7V on full sun, so I added a buck converter to drop it to 5V.
So far, so good, it works, but doesn't charge fully, compared to a factory light.
I assume that it only charges while the solar panel voltage is higher than 5V, even though charging voltage is 4.2V for this cell.
Any thoughts of how to improve the charging circuit would be greatly appreciated.
This is a problem that may be better off discussed on the TinyCircuts Forum. We will try and fix your problem, but it seems that you are not using Arduino software or hardware, so it may be harder to find an answer here.
Not a good idea. DC-DC converters do not work well with a solar panel, which is best thought of as a current source, not a voltage source. The solar panel voltage will drop when loaded.
Thank you for replying, J. True, under load, the voltage will drop, but the battery charging module is intended for 5V (it even has a micro USB port), so max is 5.5V as specced. I was concerned that I will exceed that and fry it under the bright summer sun. 7V was what I got in direct sun, but in December, LOL.
This looks like the charging module I got: amazon link
Maybe the 5.5V limit is on the USB connector, the TP4056 should be able to take 8V. Worth trying without the buck?
Noah, thanks for replying. I actually am using the Arduino IDE with Dr Azzy’s Tiny core for my Tiny85, that is why I posted here.