As a Noob to this I am putting this question here simply because the pi2grover is as confusing as the USB PowerControler (At least to me).
This is what was recommended to me and what I purchased.
1 - SunAIrPlus 4 Solar Panels 330mA 1- PI2Grover 1 - USB PowerControl Board V2 1 - MultiSolar Panel Connector 1 - 6600maH Battery Pack 5 - Extra grove cables Easy setup was the Panels to the MultiSolar and Battery to the SunAirPlus and a USB Cable to the Raspberry PI (That works). What is next and what should be obvious is where to connect the USB PowerControl and the PI2Grover (HAT). I know that the USB PowerController goes between the SunAirPlus and the PI via a cable. I just have know Idea how to wire them. What wires go from and to on both the PI2Grover and USB PowerControler.
You connect the USB Power Control to a Grove Data plug (D) on the Pi2Grover. That is the GPIO you would use to control the USB PowerCOntrol. You would only connect that if you want to turn the power off or disable the Hysteresis on the USB PowerControl. Look in the USB PowerControl specification and look at the truth table for the Grove connector.
Do you want to control the USB Power Control with the battery voltage? Connect a jumper between LIPOBATIN on the USB PowerControl to the JP4 pin on SunAirPlus. Read the spec on USB PowerControl to see what that does.
The Pi3 may not be the best choice for your setup. It consumes large amounts of energy and will suck your 6600mAh battery dry in no time. Consider a Pi A, A+, or Zero W. they use about 30% or less of the Pi 3.
I'd say "No time" is about 8 to 12 hours (max) from a full battery.
Think of the Raspberry Pi as someone sitting on a branch and sawing off the thicker side. In order for the Raspberry Pi to safely turn off it should run a "shutdown" command (via sudo). But after it did that there's no more way for the Pi to actuate the USB power control. Something else will need to do that.
One example would be the Watchdog, but used in reverse. So the Pi would pat the dog while it is running, and once that stops and the dog barks, that bark signal can be used to switch OFF the USB power control (normally the watchdog is used to restart something)
Another example would be an Arduino or other low power computer that can survive the Pi shutdown and then control the USB Power control.
And lastly, you _can_ use the USB Power control as a Powerswitch. But it won't be "safe" for the Pi. Most of the time the Pi will be just fine when power is yanked, but there certainly is a risk of SD card corruption. (you can mitigate that somewhat by making Raspbian as read-only as possible, using /dev/shm for temp files etc.)
That is way more than enough time for my need. And issuing a sudo halt or shutdown via putty isn't a problem either. Then I can use SW1 on SunAirPlus to shut the Raspberry off (and then back on when needed) Right? So if this is correct (and I hope it is)... what kind of load can I put on the Raspberry PI USB ports? For example an external Solid State drive or a Pendrive? And by the way, Thank You for responding...
Once the device is in a case, the lights will be hard to see. But if the Pi2Grove is on top of the Pi a clear panel would allow visibility. I did see that Grove LED are available in the store. How can I use these to replicate the LEDs on Raspberry and the AirSunPlus?
There's another (decidedly low tech) option. Remember the clear plastic waveguides of old? Basically use a piece of optical fiber that you strategically place over the LED, and then route to end flush with the case