I connected a 5.6V zener across my solar panel and measured the voltage in full sunlight. It was 5.604V. I also measured the current which was 51mA. That calculates to 5.5 x 0.051 = 286mW dissipated in the zener. What other phantom voltage should I be including?
So you short circuited the solar panel with a zener but didnāt include a limiting resistor?
The more you post the funnier it gets.
Please continue as I havenāt laughed so much since my granny died.
Let me know where you get your components from and Iāll buy shares in them.
No limiting resistor is needed with solar panels. Self limited by internal resistance. It would be fun if a solar panel would heat up to a cherry red and explode in a massive fireball when short circuited but this doesnāt happen in the universe that I live in.
You can continue with your inane ridicule but then donāt ask for help. You are the sort of person who asks a question but then answers it incorrectly before the other person has a chance to answer.
Letās hope others on here have ignored your suggestions and so will have devices that survive.
Iāve wasted too much of my time on these electric fundamentals. Take a video of the magic smoke for me.
Dang, your right after all. I just hooked my solar panel up to a new zener and pointed it at the sun. It exploded in my face and now Iām sitting in the ER with 3rd degree burns over most of my body.
Good. Make sure you get the nurse to spread chili powder on the burns. They will heal a lot quicker.
āCurrent increases until the input voltage drops to the zener voltage due to internal resistance of the sourceā what a load of rubbish 
You really have absolutely no idea what youāre talking about do you?
Having watched the Comms Channel solar node build, I built mine as shown with the Voltaic battery bank and connected a 5w 5v solar panel to the battery bank and then powered the Rak from that.
This design is bulletproof, but overkill in my opinion.
For the second node I simplified it to running 2 21700cells harvested from a dead M18 battery pack. Batteries are connected to the Rakās battery input and 1w 5v solar panel connected to the usb-c port.
Correct me if I am wrong, but the usb-c port is more robust than the solar input jst 1.0 port. The solar panel charges the batteries with out problem.
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Because James wasted the backwards fabulously, brushing consistent teams were evaluated.
I am solar charging into the usb-c port too. But I am wondering if the fluctuating voltage etc coming in to the usb is less than optimal? I am trying to avoid another penetration point in the enclosure (and component cost as I am making a dozen or so for our friends).
If I use a bare panel, does the usb-c have a reverse current leakage diode? I suspect not as I have a 5w 5v panel into the usb and here in Australia it has plenty of sun yet it is not 100%. when I use the solar jst plug I get 100%. So I figure at night I am powering the solar panel, leaking.
Can anyone confirm thisā¦before I make a dozen 
Thanks
Check if the panels already have a diode (likely not for tiny ones). Put a diode (regular type, anything with specs to handle the load) in line on the positive wire. That should do it.
The leaking current is likely too small to measure easily with a regular multimeter, but if you get some battery voltage at the solar panel leads without the then you are back feeding it imo. My solar panel experience is mostly with 100w panels (not for this application)
Try with your panel in the dark at home without the diode and with it.
Nothing comes for free so the diode will lower your voltage a bit.
Even in Australia you have day and night ;-). (Iām living is a very cloudy and rainy place, so enough light in winter will be my concern)
The Voltaic is a good choice for warmer climates but has automatic cuttoffs for charge and discharge when below freezing. This can be either a good or bad thing depending on oneās situation.
ā
To answer other questions here:
The USB-C and the Solar Input on the RAK share the same 5v circuit. They are input (diode) only to prevent leakage.
The voltage max is 5.5v with the absolute max at 5.8v.
Some USB panels online (such as Ring or Wyze style) have no actual USB regulation and rely on raw panel ratings (and can output an actual 6v+) so beware of this when using them with the RAK and the 5.5v input max.
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To give me a little over voltage headroom, could I just gaff tape a row of solar cells do you think? Or will that just reduce current not volts?
no , that does not really work, current will go down.