Today's Message Index:
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1. 04:56 AM - Re: Z14 with different bus voltages ? (C&K)
2. 05:39 AM - Re: Z14 with different bus voltages ? (Robert L. Nuckolls, III)
3. 08:46 AM - Re: Z14 with different bus voltages ? (Bill Watson)
4. 06:45 PM - Electrical System with Dual Batteries & Brownout Prevent (user9253)
Message 1
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| Subject: | Re: Z14 with different bus voltages ? |
I do not close the crossfeed unless one alternator has quit and
therefore don't have any concern about running the same voltage on both
systems. Seems little point of having dual systems if a failure in one
can affect the other. My crossfeed does auto close during cranking but
again not an issue.
Ken
On 28/01/2015 9:53 PM, bobbarrow wrote:
>
> I have a Vans RV7A (finished but not yet flying) with the Z14 architecture (dual
buses with crossfeed contactor). The only deviation from Z14 is that the system
does not automatically crossfeed between buses at engine start).
>
> Bus 1 has a B&C LR3C voltage regulator, a B&C L40 alternator and an Odyssey PC680
AGM battery (17 Amphours). The aircraft starts on Bus 1 and all heavy current
users are on this bus.
>
> Bus 2 has a B&C LR3C voltage regulator, a B&C SD20 alternator and an Odyssey
PC310 AGM battery (8 Amphours). This bus supports only the primary EFIS and one
LightSpeed EI (magneto on the other ignition side).
>
> The LR3C regulators are both factory set to approx 14.4 volts but there is likely
to be a very small difference in the settings. In practical terms this means
that when the crossfeed contactor is activated one alternator will tend to
hog the load but the other alternator will tend to flicker on and off. I think
that this cannot be desirable.
>
> Odyssey Batteries have advised me that the optimum bus voltage for charging either
the PC310 or PC680 is 14.4 volts but that the recommended min/max is 13.6
to 14.8 volts. The B&C installation manual for the LR3C regulator says that
the voltage can be manually adjusted up and down. So here are my questions:
>
> 1. Should I create a voltage spread between the LR3C regulators such that when
the crossfeed contactor is activated the L40 takes all the load and the SD20
justs sit idle in the background as a true standby alternator. In other words
Bus 1 and Bus 2 would run at different voltages when the crossfeed is NOT activated.
>
> 2. If the answer to question 1 is YES then what would be the optimum differential
voltages for the alternators to achieve a satisfactory outcome. Would say
running the L40 at 14.6 volts and the SD20 at 14.1 volts (thus creating a spread
of 0.5 volts) be desirable.
>
> Bob Barrow
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=437794#437794
>
>
Message 2
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| Subject: | Re: Z14 with different bus voltages ? |
At 06:55 2015-01-29, you wrote:
>
>I do not close the crossfeed unless one alternator has quit and
>therefore don't have any concern about running the same voltage on
>both systems. Seems little point of having dual systems if a failure
>in one can affect the other. My crossfeed does auto close during
>cranking but again not an issue.
>Ken
That was the spirit and intent of the Z-14 architecture.
Two batteries for cranking . . . if useful . . . but
if the failure gods smile on your airplane with benevolence,
the cross-feed contactor is never closed in flight.
They are intended to be separate, independent systems
with the capability to share if needed . . . but no
more.
If you DO operate with the contactor closed, then you
have Z-12 with two batteries. In that case the smaller
alternator should be regulated with an SB-1 regulator
set up to conduct operations as an always-on but
relaxed, stand-by alternator with active notification
of activation.
In that case, the standby regulator is set for 13.5
volts and never intended to charge batteries.
Bob . . .
Message 3
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| Subject: | Re: Z14 with different bus voltages ? |
On 1/29/2015 8:38 AM, Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 06:55 2015-01-29, you wrote:
>>
>> I do not close the crossfeed unless one alternator has quit and
>> therefore don't have any concern about running the same voltage on
>> both systems. Seems little point of having dual systems if a failure
>> in one can affect the other. My crossfeed does auto close during
>> cranking but again not an issue.
>> Ken
>
> That was the spirit and intent of the Z-14 architecture.
> Two batteries for cranking . . . if useful . . . but
> if the failure gods smile on your airplane with benevolence,
> the cross-feed contactor is never closed in flight.
It took me awhile to fully understand the spirit and intent of a
straight up Z-14 but I have been operating that way for over year now
and am very satisfied. The (2) 960s give me what I need to reliably
turnover my cold IO540 with the lightweight starter....
>
> They are intended to be separate, independent systems
> with the capability to share if needed . . . but no
> more.
...and the peace of mind of having 2 separate electrical systems that
can be linked if ever needed.
Given the (3) EFISs and the rest of the 'kitchen sink' panel I have, I
can turn the key parts on, do all my flight plan entry and clearance
work, and know that I still have at least 1 fresh battery to cross feed
with the somewhat discharged 2nd battery for a reliable start. This
capability was very important to me and my flying based on previous
experience with my Maule.
FWIW, I don't have any auto cross feed function during the start. That
would have been undesirable based on early experiences with the EFISs
re-booting due to low voltage during some cross feed starts. I learned
to do single battery starts in certain situations to avoid the (longish)
reboots - the same situations where a 2 battery start would otherwise be
most desirable. I eliminated that situation by adding a power
stabilizer to maintain adequate voltage levels during the start for the
EFISs. Now, an auto cross feed during the start would be nice but not
necessary.
>
Bill "the happy RV10 driver" Watson
Message 4
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| Subject: | Electrical System with Dual Batteries & Brownout Prevent |
Attached is a diagram that I drew of an electrical system with two engine-cranking
batteries and brownout prevention. It is intended for a seaplane that will
fly into remote lakes. Either battery can crank the engine. One of the batteries
will run a bilge pump. If the engine is cranked using only one battery,
then the other battery will provide 12 volts to avionics to prevent brownout.
The electrically dependent engine will be powered by the same bus as the avionics.
With multiple current paths through two contactors and two relays, the
chances of this bus losing power are slim. Good workmanship will prevent short
circuits.
Go ahead and point out any faults with this diagram or give suggestions. You
will not hurt my feelings. I want to fix any shortcomings or design errors.
I used Bob N's Z-19/RB as a staring point, although you might not see any resemblance.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=437846#437846
Attachments:
http://forums.matronics.com//files/dual_bat_brownout_prevention__202.pdf
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