nuckolls.bob(at)aeroelect
Guest
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 Posted: Fri Jan 16, 2009 7:08 am Post subject: Z-11 + aux battery and diode bridge rectifier problem |
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At 03:57 PM 1/15/2009, you wrote:
| Quote: | I have an RV9A wired as per Z-11 with a 7A aux battery as an EFIS keep alive
during start. This has worked well for 200 hours. Lately the EFIS has been
graying out during engine starts which implies that the aux battery is being
tapped for other than the electronics during engine start.
The batteries are isolated using two diode bridge rectifiers from B&C. The
E bus which feed the EFIS and other electronics gets it's power from the
main bus through one of the bridge rectifiers. Both of the batteries power
the main bus through individual contactors. The E bus is also powered
through the second bridge rectifier by both batteries direct and then
controlled by the E bus switch. Normal start is main battery contactor on,
aux battery contactor off, and E bus switch on. This should isolate the aux
battery to the E bus until the aux battery contactor is turned on after
engine start.
I have checked both diode assemblies to see that they are allowing current
to flow in the correct direction and they are not allowing backfeed.
Everything checks out properly using the voltmeter. However it seems to me
that the problem must lie with the diodes since they are the only link
between the batteries with the aux battery contactor off. Can a diode
function correctly under low load conditions and then temporarily break down
under start conditions.
Any ideas as to how I should proceed. Please keep in mind that I have read
the AeroElectric Connection and wired my RV9 but have no formal electrical
knowledge beyond this.
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Diodes don't "go bad" in ways that would produce the
symptoms you're seeing. The only thing that comes to mind
is that the aux battery isn't being properly charged or
has departed for the happy hunting grounds. You need to
load and cap check the battery.
Bob . . .
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( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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