Hi Shuan,
One solution may be to go with a manual Hella battery switch. A website
which shows the item is :-
http://www.classicgarage.com/classicgarage/he-87181.html $16.49 !
seems a good deal to me, capacity seems very adequate and Hella is a
reputable manufacturer. The quarter turn red key can be removed in the
OFF position.
I spotted this switch in an auto parts store during my build sequence
but this was after I had committed to a standard contactor installation
so I do not have any experience with it. It would seem to be quite
practical to mount this item with a suitable seal through the firewall
shelf so that the key is accessible from the cockpit.
Does anyone see any problem with this idea ? If one has an all electric
panel such as mine, amperage conservation is important and the main
contactor 1 amp is just another straw on the camel's back. Only snag I
can see is that "Master Switch to OFF " in an emergency may be slower
than operating a regular Master Switch.
Cheers, John
N262WF, monoXS, 912S, WhirlWind prop
Shaun Simpkins wrote:
>All:
>
>Jim Nelson and a few others excepted, the XS cowl can't nicely fit a standard
"big"
>front-mounted alternator, so past "all-electric airplane" threads on this forum
have explored
>the possibility of a B&C SD-8 or SD-20 on the vac. pad PTO as a secondary
>alternator
a la
>Bob Nuckolls' Z-13 "all-electric airplane on a budget" concept.
>The Rotax-supplied alternator is of small capacity - 18A less
>whatever the fuel pumps and ECU computer draw - and the vac. pad RPM is slower
than
>Lycoming standard, so an SD-8 is derated to about 5A and an SD-20 to about 12A.
So good
>"amperage conservation" needs to be practiced.
>
>An annoyance is the 1A holding current of the battery contactor relay, which
>represents
appx. 8%
>of the net Rotax alternator capacity. If you choose to implement a fully
>redundant
system, with
>dual batteries and alternators, you'll have at least 2 battery contactors, plus
crossfeed contactors,
>so this drain can add up fast. Although one can use manual contactors ( as
>Tony
K. did for
>a while ) - possibly remotely activated via a Bowden cable - an alternative is
a power-managed
>contactor, one example of which is the cii technologies EV-200
> http://www.ciitech.com/doc_generator.asp?doc_id=1280
>This product was designed for battery-powered vehicles, can switch 200A DC
>indefinitely,
>and has a solenoid power-management circuit, which drops the hold current of
>the
relay
>actuator to 130mA - an 8:1 reduction from a conventional contactor relay, and
possibly low enough to be insignificant. It is highly reliable,
>lightweight, and an easy retrofit to a standard power system. Unfortunately,
it is a lot more expensive
>than a conventional contactor relay - $75 instead of $15. But it may make
>sense
if you don't want to go to
>heroic (Bowden cable) lengths to control alternator loads.
>
>I caution that this product has not been certified for the aircraft market, nor
have I actually tested it. But
>it's a tantalizing idea for those builders who'd like to try something new.
>
>If you would like to see how the big boys do all-electric, check out the SR-22
Pilot's Operating Handbook
>on the Cirrus Design website
> http://www.cirrusdesign.com
>Page 3-28 and Page 7-39 et. seq. are very interesting reading and a neat way of
implementing a dual-alt
>dual-bat dual-bus system without the need for a crossfeed switch. It's got Bob
Nuckolls' name all over it,
>but I don't think he was a part of its design. Warning: the POH is 320+ pages
and a 2.8MB download.
>
>Shaun Simpkins
>...no longer building but still scheming...
>
>
>
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