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Alternator/shunt question
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art(at)zemon.name
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PostPosted: Fri Jan 04, 2019 5:14 am    Post subject: Alternator/shunt question Reply with quote

Ernest,
I used LibreOffice Draw. Here are the drawings: https://github.com/azemon/N114AC_wiring
Cheers,
    -- Art Z.
On Thu, Jan 3, 2019 at 4:12 PM Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:

Quote:

How did you manage that with LibreOffice, Art?  I've never been able to get anything other than the most rudimentary drawings out of it.  I'd appreciate you sharing your source files.  I would definitely use it to improve my POH.

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supik



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PostPosted: Fri Jan 04, 2019 11:32 am    Post subject: Re: Alternator/shunt question Reply with quote

Art, that's my concern.. I think that's not enough Volts to charge the battery..

art(at)zemon.name wrote:
Igor,
The backup voltage regulator came preset to 13.0 volts. Per a discussion here, I am going to increase it to 13.5 volts.
You might want to look at the manual for the regulator on B&C Aero's website. It is available here: http://www.bandc.aero/standbyalternatorcontroller14vhomebuilt.aspx
Cheers,
    -- Art Z.
On Fri, Jan 4, 2019 at 3:49 AM supik <bionicad> wrote:

Quote:
--> AeroElectric-List message posted by: "supik" <bionicad>

Art, at what voltage did you setup your Aux Alt? What is the max Voltage the Standby Regulator will allow?

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PostPosted: Fri Jan 04, 2019 1:28 pm    Post subject: Alternator/shunt question Reply with quote

At 01:32 PM 1/4/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "supik" <bionicad(at)hotmail.com>

Art, that's my concern.. I think that's not enough Volts to charge the battery..


One does not CHARGE a battery with the standby
alternator . . . you only support the bus
at some level that prevents DISCHARGING
the battery.

The idea is to minimize loads to some
level at or below what the standby
alternator will deliver thus holding
the battery in reserve for approach
to landing



Bob . . .


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PostPosted: Fri Jan 04, 2019 3:34 pm    Post subject: Re: Alternator/shunt question Reply with quote

nuckolls.bob(at)aeroelect wrote:
At 01:32 PM 1/4/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "supik" <bionicad>

Art, that's my concern.. I think that's not enough Volts to charge the battery..


One does not CHARGE a battery with the standby
alternator . . . you only support the bus
at some level that prevents DISCHARGING
the battery.

The idea is to minimize loads to some
level at or below what the standby
alternator will deliver thus holding
the battery in reserve for approach
to landing



Bob . . .


Bob,

I don't get it. B&C says the standby alt can be configured with both the normal or the standby regulator. Therefore I assume that this 30A alt is able to charge a battery.

Flipping 1 switch I am able to shed loads immediately to 19amps (that's what the e-bus typically consumes). Now I have approx. 11amps left depending on RPM -why not use that power to charge the battery?

thanks,


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PostPosted: Fri Jan 04, 2019 4:13 pm    Post subject: Alternator/shunt question Reply with quote

OK - this may be my first "contribution" to the discussion, based on
what I've learned here. Here goes:

Igor,

If I understand correctly, other than briefly after starting (when the
60-amp alternator would be handling the duties), the battery should
already be fully charged, and operating strictly as a "backup" to the
dual-alternator system. Thus, if the primary (60Amp) alternator were to
fail, the backup (30Amp) alternator would take over powering the
aircraft's electrical system. It is only if BOTH the primary (60Amp)
and backup (30Amp) alternators were to fail that the battery would begin
to be discharged.

If both alternators were to fail while the battery was still being
recharged, you'd likely still be on the ground taxiing, and I would
think that would constitute enough of an 'emergency' to scrub the
flight...

Bob, et al, how'd I do?

Jim Parker (Complete rookie at all things electrical, but hopefully
beginning to have a clue...)
------


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PostPosted: Fri Jan 04, 2019 4:18 pm    Post subject: Alternator/shunt question Reply with quote

If your primary alt failed in the first ten minutes of flight your battery may not be fully charged. If this is true just return to the departure airport.  If the battery was fully charged before take off and the alt failure was more than 10 to 15 minutes later your battery is fully recharged anyway. Either way you do not need to charge the battery with the secondary alt.

On Fri, Jan 4, 2019, 15:39 supik <bionicad(at)hotmail.com (bionicad(at)hotmail.com) wrote:

Quote:
--> AeroElectric-List message posted by: "supik" <bionicad(at)hotmail.com (bionicad(at)hotmail.com)>


nuckolls.bob(at)aeroelect wrote:
> At 01:32 PM 1/4/2019, you wrote:

> > --> AeroElectric-List message posted by: "supik"
> >
> >  Art, that's my concern.. I think that's not enough Volts to charge the battery..
> >
> > 
>
>    One does not CHARGE a battery with the standby
>    alternator . . . you only support the bus
>    at some level that prevents DISCHARGING
>    the battery.
>
>    The idea is to minimize loads to some
>    level at or below what the standby
>    alternator will deliver thus holding
>    the battery in reserve for approach
>    to landing
>


>    Bob . . .


Bob,

I don't get it. B&C says the standby alt can be configured with both the normal or the standby regulator. Therefore I assume that this 30A alt is able to charge a battery.

Flipping 1 switch I am able to shed loads immediately to 19amps (that's what the e-bus typically consumes). Now I have approx. 11amps left depending on RPM -why not use that power to charge the battery?

thanks,

--------
Igor

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PostPosted: Fri Jan 04, 2019 4:39 pm    Post subject: Re: Alternator/shunt question Reply with quote

jim(at)PoogieBearRanch.co wrote:
OK - this may be my first "contribution" to the discussion, based on
what I've learned here. Here goes:

Igor,

If I understand correctly, other than briefly after starting (when the
60-amp alternator would be handling the duties), the battery should
already be fully charged, and operating strictly as a "backup" to the
dual-alternator system. Thus, if the primary (60Amp) alternator were to
fail, the backup (30Amp) alternator would take over powering the
aircraft's electrical system. It is only if BOTH the primary (60Amp)
and backup (30Amp) alternators were to fail that the battery would begin
to be discharged.

If both alternators were to fail while the battery was still being
recharged, you'd likely still be on the ground taxiing, and I would
think that would constitute enough of an 'emergency' to scrub the
flight...

Bob, et al, how'd I do?

Jim Parker (Complete rookie at all things electrical, but hopefully
beginning to have a clue...)
------


Jim,

That's exactly my idea. thanks!

Normal flight starts with a healthy battery and 2 alternators.

Main alternator fails: load shedding follows, Stby alternator takes over the reduced load & keeps the battery charged. I land, refuel and continue home in Day VFR with load shedded and battery maintained charged. I am not forced to replace or repair the Main alt after my first landing.

In case the Stby alternator fails too (dual alt failure) -land ASAP (emergency)


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PostPosted: Fri Jan 04, 2019 5:08 pm    Post subject: Alternator/shunt question Reply with quote

On 1/4/2019 6:39 PM, supik wrote:
Quote:

jim(at)PoogieBearRanch.co wrote:
> OK - this may be my first "contribution" to the discussion, based on
> what I've learned here. Here goes:
>
> Igor,
>
> If I understand correctly, other than briefly after starting (when the
> 60-amp alternator would be handling the duties), the battery should
> already be fully charged, and operating strictly as a "backup" to the
> dual-alternator system. Thus, if the primary (60Amp) alternator were to
> fail, the backup (30Amp) alternator would take over powering the
> aircraft's electrical system. It is only if BOTH the primary (60Amp)
> and backup (30Amp) alternators were to fail that the battery would begin
> to be discharged.
>
> If both alternators were to fail while the battery was still being
> recharged, you'd likely still be on the ground taxiing, and I would
> think that would constitute enough of an 'emergency' to scrub the
> flight...
>
> Bob, et al, how'd I do?
>
> Jim Parker (Complete rookie at all things electrical, but hopefully
> beginning to have a clue...)
> ------

Jim,

That's exactly my idea. thanks!

Normal flight starts with a healthy battery and 2 alternators.

Main alternator fails: load shedding follows, Stby alternator takes over the reduced load & keeps the battery charged. I land, refuel and continue home in Day VFR with load shedded and battery maintained charged. I am not forced to replace or repair the Main alt after my first landing.

In case the Stby alternator fails too (dual alt failure) -land ASAP (emergency)

--------
Igor
I think one tripping point for some, is that the lower setpoint for the

standby alt is so that it will automatically come on line if the primary
fails. (The lower setpoint means that the standby regulator sees no need
to supply field current, since the system is already above its setpoint.
A byproduct is that when the system voltage drops to the standby
setpoint, the low voltage monitor will notify the pilot that he's now
running on 'backup' alternator power. If the standby had the same
setpoint, you'd never get a notification of the primary's failure. So,
you get multiple uses from one adjustment, instead of extra hardware.

Another tripping point is 'keeping the battery charged'. That's not
what's happening on a typical flight. We crank up (slight discharge),
then the alternator picks up all the a/c loads plus recharges the
battery. Once the battery is fully charged (fairly quickly for a healthy
battery and an uneventful start), the alternator isn't 'keeping the
battery charged'; it's just supplying the electrical loads of the a/c.
(Over the course of a typical flight, and for quite a while afterward,
the battery doesn't need to be kept charged. I've had normal starts from
a no-name generic SLA battery after it's been sitting in the plane for a
month or more.) So.... once you've been flying for 10-15 minutes, in all
probability your battery is fully charged. At any point in the flight
after that, you have a fully charged battery on board if the primary alt
fails. The standby then takes over at 13+ volts, running the a/c
appliances, which will operate just fine on 12V. Since you're operating
above the fully charged voltage level of the battery, it will not
discharge during the flight.

You always have the option to use the same regulator setpoints for both
alternators, and set up some other monitoring system to notify you
and/or switch to the backup. I'm running two identical alternators on my
alternative engine and will be doing just that.

Charlie

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PostPosted: Fri Jan 04, 2019 6:00 pm    Post subject: Re: Alternator/shunt question Reply with quote

[quote="ceengland7(at)gmail.com"]On 1/4/2019 6:39 PM, supik wrote:
Quote:

If the standby had the same
setpoint, you'd never get a notification of the primary's failure.

The Stby setpoint would be 14.1V (good enough for bat recharge and monitoring function of the Stby alt coming online) and the Main alt's setpoint 14.7V. Does that make sense?


[quote="ceengland7(at)gmail.com"]On 1/4/2019 6:39 PM, supik wrote:
Quote:

Another tripping point is 'keeping the battery charged'. That's not
what's happening on a typical flight. We crank up (slight discharge),
then the alternator picks up all the a/c loads plus recharges the
battery. Once the battery is fully charged (fairly quickly for a healthy
battery and an uneventful start), the alternator isn't 'keeping the
battery charged'; it's just supplying the electrical loads of the a/c.
(Over the course of a typical flight, and for quite a while afterward,
the battery doesn't need to be kept charged.


That's correct, we are not talking about a typical flight. It's a 'get aircraft home mode' in good weather and day conditions (sorry for repeating myself again). The calculated typical e-bus draw is supposed to be at 19Amps.

With intermittent loads (engine start, flaps extension/retraction etc) the loads might get above 30Amps for a short period of time where the battery's capacity will take over. After the peak draw is over, the Stby alternator would be able to recharge the battery again. This assures that I land with a fully charged battery -good for another engine start.

Shall the Stby alt fail in flight (dual alt failure), this would leave me with a fully charged (full capacity in ideal world) battery for 'emergency land ASAP mode' anytime except shortly after the battery took over to supply some peak draw, where I expect the peak draws to happen during take off and landing, not so much during cruise..

Am I missing something?

Thanks,


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PostPosted: Fri Jan 04, 2019 6:28 pm    Post subject: Alternator/shunt question Reply with quote

It seems that you want to do something that a standby system was never meant to do. If you insist on being able to make multiple departures after the primary alt quits, maybe you should use 2 60 amp alternators with independant controls. a better plan would be to use tje secondary system as dezigned and continue your flight as far as the fuel on board allows, land and make repairs and then continue on. Irf your car breaks down do stop for repairs or try to drive it home?

On Fri, Jan 4, 2019, 18:06 supik <bionicad(at)hotmail.com (bionicad(at)hotmail.com) wrote:

Quote:
--> AeroElectric-List message posted by: "supik" <bionicad(at)hotmail.com (bionicad(at)hotmail.com)>

[quote="ceengland7(at)gmail.com"]On 1/4/2019 6:39 PM, supik wrote:


> If the standby had the same
> setpoint, you'd never get a notification of the primary's failure.
>



The Stby setpoint would be 14.1V (good enough for bat recharge and monitoring funciton of the Stby alt comming online) and the Main alt's setpoint 14.7V. Does that make sense?



[quote="ceengland7(at)gmail.com"]On 1/4/2019 6:39 PM, supik wrote:


> Another tripping point is 'keeping the battery charged'. That's not
> what's happening on a typical flight. We crank up (slight discharge),
> then the alternator picks up all the a/c loads plus recharges the
> battery. Once the battery is fully charged (fairly quickly for a healthy
> battery and an uneventful start), the alternator isn't 'keeping the
> battery charged'; it's just supplying the electrical loads of the a/c.
> (Over the course of a typical flight, and for quite a while afterward,
> the battery doesn't need to be kept charged.
>


That's correct, we are not talking about a typical flight. It's a 'get aircraft home mode' in good weather and day conditions (sorry for repeating myself again). The calculated typical e-bus draw is supposed to be at 19Amps.

With intermittent loads (engine start, flaps extension/retraction etc) the loads will get above 30Amps for a short period of time where the battery's capacity will take over. After the peak draw is over, the Stby alternator would be able to recharge the battery again. This assures that I land with a fully charged battery -good for another engine start.

Shall the Stby alt fail in flight (dual alt failure), this would leave me with a fully charged battery for 'emergency land ASAP mode' anytime except shortly after the battery took over to supply some peak draw, where I expect the peak draws to happen during take off and landing, not so much during cruise..

Am I missing something?

Thanks,

--------
Igor

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PostPosted: Fri Jan 04, 2019 6:52 pm    Post subject: Alternator/shunt question Reply with quote

On 1/4/2019 8:00 PM, supik wrote:
Quote:


[quote="ceengland7(at)gmail.com"]On 1/4/2019 6:39 PM, supik wrote:

>
> If the standby had the same
> setpoint, you'd never get a notification of the primary's failure.
>
The Stby setpoint would be 14.1V (good enough for bat recharge and monitoring funciton of the Stby alt comming online) and the Main alt's setpoint 14.7V. Does that make sense?

[quote="ceengland7(at)gmail.com"]On 1/4/2019 6:39 PM, supik wrote:

>
> Another tripping point is 'keeping the battery charged'. That's not
> what's happening on a typical flight. We crank up (slight discharge),
> then the alternator picks up all the a/c loads plus recharges the
> battery. Once the battery is fully charged (fairly quickly for a healthy
> battery and an uneventful start), the alternator isn't 'keeping the
> battery charged'; it's just supplying the electrical loads of the a/c.
> (Over the course of a typical flight, and for quite a while afterward,
> the battery doesn't need to be kept charged.
>

That's correct, we are not talking about a typical flight. It's a 'get aircraft home mode' in good weather and day conditions (sorry for repeating myself again). The calculated typical e-bus draw is supposed to be at 19Amps.

With intermittent loads (engine start, flaps extension/retraction etc) the loads will get above 30Amps for a short period of time where the battery's capacity will take over. After the peak draw is over, the Stby alternator would be able to recharge the battery again. This assures that I land with a fully charged battery -good for another engine start.

Shall the Stby alt fail in flight (dual alt failure), this would leave me with a fully charged battery for 'emergency land ASAP mode' anytime except shortly after the battery took over to supply some peak draw, where I expect the peak draws to happen during take off and landing, not so much during cruise..

Am I missing something?

Thanks,

--------
Igor
Well, the designer is a pretty sharp dude. I suspect that if the system

operation would be stable at those settings, he'd have used them. I
suspect that you'll find that system voltage in an a/c isn't
particularly stable, and setting the margin that close will give lots of
'nuisance trips'. But this is experimental aviation; give it a shot &
let us know how it goes.

Charlie

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PostPosted: Fri Jan 04, 2019 7:02 pm    Post subject: Re: Alternator/shunt question Reply with quote

donvansanten(at)gmail.com wrote:
It seems that you want to do something that a standby system was never meant to do. If you insist on being able to make multiple departures after the primary alt quits, maybe you should use 2 60 amp alternators with independant controls. a better plan would be to use tje secondary system as dezigned and continue your flight as far as the fuel on board allows, land and make repairs and then continue on. Irf your car breaks down do stop for repairs or try to drive it home?


I understand, the system wasn't designed with my plan in mind. The question is: Is it possible to apply my idea as requested or won't physics allow it?

When I look at the gear driven main B&C 462H (60amp) alternator -it is supposed to deliver 41.3Amps at cruise RPM 2450. This is 11.3 Amps more than the 30Amps Stby Alt. This would not leave me with 2 identical alternators either.

One can wait for a week or more before the replacement unit arrives in Europe. We have a completely different network here. Further, you will hardly find a service center willing to touch an experimental.

It is quite common in airlines that items get on MEL (minimum equipment list) if they fail and the airplane can depart for another flight although limited by weather or any other restriction. It doesn't mean that you are grounded as soon as something fails, provided there is a backup system available and functional. Not to compare to cars..


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PostPosted: Fri Jan 04, 2019 7:18 pm    Post subject: Re: Alternator/shunt question Reply with quote

ceengland7(at)gmail.com wrote:
:

operation would be stable at those settings, he'd have used them. I
suspect that you'll find that system voltage in an a/c isn't
particularly stable, and setting the margin that close will give lots of
'nuisance trips'. But this is experimental aviation; give it a shot &
let us know how it goes.

Charlie

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That's a good point Charlie, it might trigger the Stby Alt (online) warning light for example right after engine start, taxiing with all el. equipment on. The same might happen in an aircraft with single battery and single alternator setup when after engine start and on idle rpm a lot of el. equipment is turned on (low volts warning light comes on).

Anything else to consider?


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PostPosted: Fri Jan 04, 2019 7:47 pm    Post subject: Alternator/shunt question Reply with quote

On 1/4/2019 9:18 PM, supik wrote:
Quote:

ceengland7(at)gmail.com wrote:
> :
>
> operation would be stable at those settings, he'd have used them. I
> suspect that you'll find that system voltage in an a/c isn't
> particularly stable, and setting the margin that close will give lots of
> 'nuisance trips'. But this is experimental aviation; give it a shot &
> let us know how it goes.
>
> Charlie
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus

That's a good point Charlie, it might trigger the Stby Alt (online) warning light for example right after engine start, taxiing with all el. equipment on. The same might happen in an aircraft with single battery and single alternator setup when after engine start and on idle rpm a lot of el. equipment is turned on.

Anything else to consider?

--------
Igor

With the exception of some of the really small alternators, like the

small Permanent Magnet 'dynamos', That doesn't happen. (Empirical
evidence, looking at virtually all planes flying (and cars driving) with
modern alternators.)

What I'm talking about is normal operation, as larger loads come & go in
the system, if the two setpoints are only .5V apart.


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PostPosted: Fri Jan 04, 2019 8:10 pm    Post subject: Alternator/shunt question Reply with quote

On 1/4/2019 9:02 PM, supik wrote:

Quote:
Quote:
--> AeroElectric-List message posted by: "supik" <bionicad(at)hotmail.com> (bionicad(at)hotmail.com)
donvansanten(at)gmail.com wrote:
Quote:
It seems that you want to do something that a standby system was never meant to do. If you insist on being able to make multiple departures after the primary alt quits, maybe you should use 2 60 amp alternators with independant controls. a better plan would be to use tje secondary system as dezigned and continue your flight as far as the fuel on board allows, land and make repairs and then continue on. Irf your car breaks down do stop for repairs or try to drive it home?



I understand, the system wasn't designed with my plan in mind. The question is: Is it possible to apply my idea as requested or won't physics allow it?

When I look at the gear driven main B&C 462H (60amp) alternator -it is supposed to deliver 41.3Amps at cruise RPM 2450. This is 11.3 Amps more than the 30Amps Stby Alt. This would not leave me with 2 identical alternators either.

One can wait for a week or more before the replacement unit arrives in Europe. We have a completely different network here. Further, you will hardly find a service center willing to touch an experimental.

It is quite common in airlines that items get on MEL (minimum equipment list) if they fail and the airplane can depart for another flight although limited by weather or any other restriction. It doesn't mean that you are grounded as soon as something fails, provided there is a backup system available and functional. Not to compare to cars..

--------
Igor

To address the supply chain delay issue, I'd suggest a consult with B&C about whether their regulators are 'married' to their alternators. There are *many* off-the-shelf automotive alternators that will fit on the forward mount of a Lyc. And with proper hookup to an alternator made for external regulation a regulator is just a regulator. So with the right automotive part # in hand, you should be able to local source a temporary replacement for the belt driven model.

To address the short term 'continue the mission' issue, I note that the 462H data sheet says that "may be used as either a Primary or a Standby Alternator, depending on your electrical system configuration."

With that knowledge in hand, and care in the regulator mounting locations and harness design, if you have a primary *alternator* failure you'd have the option upon next landing to move the standby alternator control to the primary regulator. Now the only failure that keeps you at 13.5V would be failure of the primary *regulator*. If it's that important to have 100% dispatch, carry a spare regulator.

Charlie

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Joined: 22 Aug 2018
Posts: 44

PostPosted: Fri Jan 04, 2019 8:20 pm    Post subject: Re: Alternator/shunt question Reply with quote

ceengland7(at)gmail.com wrote:
On 1/4/2019 9:18 PM, supik wrote:
Quote:

ceengland7(at)gmail.com wrote:
> :
>
> operation would be stable at those settings, he'd have used them. I
> suspect that you'll find that system voltage in an a/c isn't
> particularly stable, and setting the margin that close will give lots of
> 'nuisance trips'. But this is experimental aviation; give it a shot &
> let us know how it goes.
>
> Charlie
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus

That's a good point Charlie, it might trigger the Stby Alt (online) warning light for example right after engine start, taxiing with all el. equipment on. The same might happen in an aircraft with single battery and single alternator setup when after engine start and on idle rpm a lot of el. equipment is turned on.

Anything else to consider?

--------
Igor

With the exception of some of the really small alternators, like the

small Permanent Magnet 'dynamos', That doesn't happen. (Empirical
evidence, looking at virtually all planes flying (and cars driving) with
modern alternators.)

What I'm talking about is normal operation, as larger loads come & go in
the system, if the two setpoints are only .5V apart.


This might be indeed the limiting factor.. I'll check the battery's minimum charging voltage with the manufacturer.

Thanks,


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user9253



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PostPosted: Fri Jan 04, 2019 8:32 pm    Post subject: Re: Alternator/shunt question Reply with quote

14.7 volts is a little too much for continuous charging. You do not want to
damage the battery. Odyssey recommends 13.6 for continuous float charge.
There are hundreds of RV-12s flying whose Ducati regulators are set at 13.8
volts, enough to keep the battery charged. How about setting the main
regulator at 14.3 or 14.4 and set the standby regulator at 13.7 or 13.8 which
will keep the battery charged. And there will be enough voltage differential
spread to warn of low voltage if the main alternator fails.
Quote:
For this setup I need the Aux Alternator to be able to charge at min
14.1V to recharge the battery -correct?
No, 13.8 is enough.


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supik



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Posts: 44

PostPosted: Fri Jan 04, 2019 8:48 pm    Post subject: Re: Alternator/shunt question Reply with quote

user9253 wrote:
14.7 volts is a little too much for continuous charging. You do not want to
damage the battery. Odyssey recommends 13.6 for continuous float charge.
There are hundreds of RV-12s flying whose Ducati regulators are set at 13.8
volts, enough to keep the battery charged. How about setting the main
regulator at 14.3 or 14.4 and set the standby regulator at 13.7 or 13.8 which
will keep the battery charged. And there will be enough voltage differential
spread to warn of low voltage if the main alternator fails.
Quote:
For this setup I need the Aux Alternator to be able to charge at min
14.1V to recharge the battery -correct?
No, 13.8 is enough.

I am planing to go with the Concorde RG-25XC (12V, 24Ah)

Thanks for mentioning this, but still, 14.4 - 13.8 gives a 0.6V difference.


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supik



Joined: 22 Aug 2018
Posts: 44

PostPosted: Fri Jan 04, 2019 9:09 pm    Post subject: Re: Alternator/shunt question Reply with quote

In one of the previous posts, Bob replies to OP:

'SB-1 is set too low. It only needs to be 0.7v or
so below your main alternator set point.
Bob . . .'

So 0.6V difference might actually work.. ?? Empirical evidence will show during phase 1.

Thank you all for your replies! If something new comes to your mind, please share that info with me. I would love to know the answer before I go myself the trial error method Wink

My apologies to the OP for hijacking the thread.


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Kellym



Joined: 10 Jan 2006
Posts: 1570
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PostPosted: Fri Jan 04, 2019 9:34 pm    Post subject: Alternator/shunt question Reply with quote

No alternator should be run at greater than 80% of its rating for any
length of time. So don't figure the backup at more than 24 amps. Even an
AGM battery will charge (perhaps slowly) at any voltage over 13 volts.
Almost all 14 V aircraft electrowhizzies will operate fine on 13V.
If you intend to limp home on the back up alternator, know what you need
electrically and assume you get only partial recharge of battery after
starter draw. I don't know how high adjustable regulators will let you
go, but there really isn't much reason to have the primary operate above
14.5, and you probably want the standby to be at something more like
13.5-13.8.
Not sure what the mission is calling for two alternators with one
battery. I've been flying 2.5 years in my RV-10 with one alternator, one
Odyssey 925L battery, and a backup battery on each of two EFIS. The
Odyssey is considerably cheaper than a Concorde or Gill, has very
comparable capacity and better cranking. Also fits in the battery tray
with room to spare. Of course if battery fails where only certified
aircraft batteries are available, the Concorde will bolt right in.
If you are trying to power two electronic ignitions, you may want to
think about 2 batteries.
Kelly

On 1/4/2019 8:02 PM, supik wrote:
Quote:



donvansanten(at)gmail.com wrote:
> It seems that you want to do something that a standby system was never meant to do. If you insist on being able to make multiple departures after the primary alt quits, maybe you should use 2 60 amp alternators with independant controls. a better plan would be to use tje secondary system as dezigned and continue your flight as far as the fuel on board allows, land and make repairs and then continue on. Irf your car breaks down do stop for repairs or try to drive it home?
>


I understand, the system wasn't designed with my plan in mind. The question is: Is it possible to apply my idea as requested or won't physics allow it?

When I look at the gear driven main B&C 462H (60amp) alternator -it is supposed to deliver 41.3Amps at cruise RPM 2450. This is 11.3 Amps more than the 30Amps Stby Alt. This would not leave me with 2 identical alternators either.

One can wait for a week or more before the replacement unit arrives in Europe. We have a completely different network here. Further, you will hardly find a service center willing to touch an experimental.

It is quite common in airlines that items get on MEL (minimum equipment list) if they fail and the airplane can depart for another flight although limited by weather or any other restriction. It doesn't mean that you are grounded as soon as something fails, provided there is a backup system available and functional. Not to compare to cars..

--------
Igor

RV10 in progress




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=486724#486724











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