Thank you very much everyone for the above replies and explanations!

The Apollo is now hashing away happily and I have a thousand more questions brewing.....

Can an Apollo BTC (or an Orange Pi) be operated on 12V DC from a lead acid battery?
The voltage would actually be 12.7V to 14V.
That would be a simple UPS when combined with some solar panels and a grid powered battery charger. I have no idea if computer components would be happy with the slightly higher voltage.

Is the power on the Orange Pi USB ports lower than on larger PC's? My keyboard and mouse only make connection from very close (1m or less) to the Apollo. On my laptop, the same mouse and USB receiver work well from at least 5m away.

The WiFi connection for my Apollo also seems to be much weaker than for my laptop. It does not find the WiFi network unless the modem is within a few meters of the Apollo. Is that normal?

Is the SD card quality important? I don't know if the old 16GB SD card which I put in the Apollo might be slowing it down. It seems very sluggish even when there is not much processor load.