I was inspired by another post to do some general testing. Here is the panel another member is using and it seems to work well for him.
I started doing some math assuming that the panel is running at 5 Watt as was mentioned.
The panel is 5v and 5 watt. That means it should give us 1 amp while there is good sunlight.
In my area an average day with that solar panel should deliver about 4 amps.
Look up your own area if you like: Hours * 1amp = Total amps
Of course some days will be more and others less.
Next I tested the Gotenna mesh to see how much of that energy it could actually use.
With the power off the Gotenna will charge at 0.27 amps when the battery is low.
In 2 1/2 hours the Gotenna was full.
It took about 607mah or about 0.6 amps total.
Keep in mind Lithium-ion batteries charge more slowly when they are close to being fully charged. I think they typically start slowing the charge rate at around 80% capacity.
Example: After 2 hours charging the Gotenna reduced the charge rate to only 0.14 amps. That’s just over half the speed it charged at when the battery was below the 80% mark.
I then tested the Gotenna to see how much power it could take well turned on.
It still only accepts 0.27 amps which was not surprising.
This time with the Gotenna was still accepting 0.19 amps at the two and a half hour mark.
At 3 hours it accepted 0.08 amps.
At the 4 hour mark it accepted around 0.07 amps average.
This is with the unit on but not sending any messages.
My primary conclusion at this point is that the panel @ShootAnyAngle recommended should work for a great many of us and any bigger panel would probably be a waste unless you added another battery into the equation. Under peak conditions that panel produces 0.73 amps more then the Gotenna can use.
I will have to do some more testing with simulated traffic to see how much energy message passing will eat. I plan to test over a 24 hour period.
A Gotenna could theoretically pass around 4320 messages in that time if it were very busy. I won’t push the Gotenna that hard however since I just want a baseline to predict overall power consumption.
EDIT: Some typos… oops.