On Sunday, June 21, 2020 at 12:13:51 AM UTC-4, SoaringXCellence wrote:
Another item on your list has a very high current draw: The Stratux is based on a Raspberry Pi and those have more current draw than most of the rest of your panel!

I have a 15000mAh LimeFuel external pack I run with my Stratux (Pi 3 based). It goes too low for effective operation of the Pi in about 4.5 hours. The spec for the Pi says it needs a 2.5 Amp 5-volt power supply.

But I have found that some of the Pi devices have lower current needs, and especially if you are making your own Stratux, you should check out a few different units and pick the one with the lowest power draw.

The Stratux software will run on a Pi 2 or 3. The Pi 4 is definitely over kill and uses the most power of the bunch.

Mike

Be careful when you evaluate the capacity of "power banks". The AH rating is often misleading, even if it is true. E.g., if it has one 3.7V lithium-ion cell (or several in parallel) then when it converts that up (internally) to 5V the AH would be less, by the factor 3.7/5 (plus some energy loss in the conversion). If the power bank has cells in series, e.g., 2 cells, 7.4V, then the voltage conversion to 5V is downwards, and the AH at 5V should be higher - unless (and likely) they rated it at 5V, or simply added up the AH of the cells in series. But all the (smaller) power banks I've seen just had one cell (or two in parallel). The best way to rate them is in watt-hours not amp-hours, but the sellers prefer to make the rating sound better.

Talking about watt-hours, a "12V" LFP battery outputs 13.x volts through most of its discharge, thus outputs somewhat more watt-hours than an SLA that yields the same amp-hours. Most of our modern avionics use less current when fed a higher voltage, very unlike ye olde light bulb. I've measured that behavior in my Portable PowerFLARM, for example.