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1. 03:06 PM - Re: Schottky Diode (Peter Pengilly)
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Hello Bob & all, thanks for your replies.
I am reluctant to go to LiPos as I have a ready supply of =91gelcels=92
(or
whatever they are really!) I know it could be dumb to avoid spending a
couple of hundred =A3=A3/$$ on a $100K aircraft, but if I can make the
gelcels
work I would like to. Getting the system working on the bench is
probably a
good idea, I have nearly all the equipment to hand so should get
something
running in a week or two. At present I am inclined to use a plain on-off
switch on all the batteries, and to switch the 2 main batteries and the
fin
battery on together at the start of a flight, I should have a minimum of
8.5
hrs endurance with the engine battery available if required.
A single main battery is not possible due to the battery trays provided
by
the manufacturer ' this is a certified aircraft, but the electrical
system
is not well defined (no circuit diagram provided as almost all
installations
are bespoke).
The engine battery is used only to extend the engine into the airflow,
run a
fuel pump used during starting and to run the control box.
Extend/retract
cycle times are typically 5 to 7 seconds. The control unit has a 7.5A
c/b,
so that must be approximately the max current. Yes, it is a large
battery
for the task, but it fits the battery tray and is a certified system
(circuit diagram provided this time!) so I am loathe to mess with it.
This
is a top level description of the system
https://www.schempp-hirth.com/en/individual/engine-options/turbo-sustaine
r-e
ngine.html.
Once I have measured the load for each item I will report back.
Regards, Peter
The equipment list is (current draw assumes 12v):
Item
Current (mA)
Notes
LX Nav LX9000 glide computer
500
Max brightness
Flap positioner
30
Provides flap angle - always operating
Trig bridge
20
Interfaces to radio
Remote stick
20
Multi-function stick top
V8 electric vario
150
Sensitive rate of climb +much more
Vario audio
50
estimate
Power FLARM Core ***
165
Proximity warning
Oudie (PDA running gliding s/w)
150
estimate - on-board battery
Radio Trig TY91 ***
240
Unknown speaker load
Transponder Trig TT21 ***
420
Likely to be off for some of flight
TOTAL
1745
Entries marked *** have an unpredictable duty-cycle, load may vary
From: owner-aeroelectric-list-server@matronics.com
<owner-aeroelectric-list-server@matronics.com> On Behalf Of Robert L.
Nuckolls, III
Sent: 28 December 2018 03:03
Subject: Re: AeroElectric-List: Schottky Diode
4. Since knowing your exact loads are a bit more critical than a typical
a/c, rather than look at mfgr data sheets, consider directly measuring
each
item's current in actual operation. Most data sheets will show you a
conservative number, to be sure the installer doesn't 'short change' the
device's needs.
BINGO!
Bob . . .
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