On 6/21/20 6:56 AM, Martin Gregorie wrote:
On Sat, 20 Jun 2020 21:13:49 -0700, SoaringXCellence wrote:

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.

Don't forget that that's a peak rating, and that most Pis only hit that
value during boot or when working continuously on a compute-intensive
task.

The Pi Zero uses 140mA during boot and 50-70mA when idle, but may not
have the connectivity to run, say, a navigation system which will need a
serial connection to a GPS receiver and, maybe, another to a FLARM.

The model A+ peak consumption is 500Ma peak and typically 180MA but, like
the Zero, may not have the connectivity needed for some applications.

The model B+ uses 600Ma peak and 330mA average, but you're unlikely to
want its Ethernet connection in your glider, but it does have 4 USB
sockets.

Its only the models 3 and 4 that start to use serious amounts of power.

All models can drive touch-sensitive displays that connect via the 40 pin
GPIO header. You can now find these using both multi-colour TFT displays
and eInk display technology with decent display resolution (I have a 4"
TFT display with 480x400 pixels) and, of course, a TFT screen turned up
bright will use quite a lot of amps too. Advantage, eInk.



Since we're talking about a Stratux, it requires two rather high-powered
Software Defined Radios and a GPS to make it work, which adds
considerably to the power drain. You should use a high-current charging
cable to supply power, as short as possible, as you can lose several
tenths of a volt in the cable due to IR drop.

You might look at a uAvionix pingUSB as a better alternative, somewhat
more expensive though.


-Dave