I was all geared up to make my first solar node, got a rak and a solar panel, put an 18650 in it. I was doing some testing to see how long it would last on my bench without sun. I got distracted and the voltage got lower than the rak liked, and then it just... Never came back. Wouldn't wake up again, not with solar power or adding additional external power. I'd probably need to disconnect and reconnect the battery. But I never tried that, because the point was that I wouldn't be able to.
Before this, I had already been researching and thinking about different methods, and I had already wasted some money on some ill-planned hybrid lithium capacitors. I also had some disappointing range tests from the local hill. Plus I was trying to get my buddies on board and they were dragging their feet.
So this was the last nail in the coffin. You can't have a device enter a non recoverable state when it's 40 feet up in a tree at the top of the tallest hill in town. Just bad design.
That stupid thing is still sitting on my desk, almost a year now. I lost all interest, unfortunately.
I'm sure I'll come back to it, eventually.
But yes, in my experience, rak doesn't like low voltages, and will likely get stuck in an unrecoverable state.
I would love to have a copy of this circuit!
I imagine adding more capacitance not only increases the run time at night under a light, but also the charge time. How did you decide on a good value?
Very cool!
Have you looked into lithium capacitors? Here's one built into a charging circuit. Kind of interesting