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wdaniell.longport(at)gmai
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 Posted: Tue May 12, 2020 4:48 pm Post subject: Is there any reason to have a separate battery and alt swit |
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Thanks for your wisdom Bud
(Hope youre well)
I was under the impression that you weren't supposed to run the alt without batt although it is ok to run the bat without the alt. Is this incorrect?
Will
William Daniell
+1 786 878 0246
On Tue, May 12, 2020, 19:55 budyerly(at)msn.com (budyerly(at)msn.com) <budyerly(at)msn.com (budyerly(at)msn.com)> wrote:
| Quote: | --> Europa-List message posted by: "budyerly(at)msn.com (budyerly(at)msn.com)" <budyerly(at)msn.com (budyerly(at)msn.com)>
Will and other builders,
It seems like the department of redundant redundancy to have a separate alternator and master switch. For many it is a matter of "That's the way we've always done it!" .
The Rotax manual actually implies a switch breaker not just a fuse/circuit breaker (aka Off Load Fuse Switch). The Europa manual shows a switch or solenoid of course as does Bob Knuckles in Aeroelectric Connections (aircraft electrical bible).
Rational for a Rotax: In the event of a battery problem, the battery has a switch we use to control power to and from the alternator and bus via a master contactor "kerchunk" solenoid or relay. Others have used a manual marine battery switch or as I call them "Igor Switches" which can be very heavy. Batteries normally do not give problems today, but if overcharged, they can. If a cell shorts, one may detect nasty odors, high amps, and isolating the battery helps shorten the problem by isolating the battery from the charging and aircraft bus system. In the event of a imminent crash landing, one should consider isolating the battery from the electrical system and cockpit as a spark prevention measure since we occupy the same space as the fuel tank.
The Alternator system has had a switch for three reasons in my opinion. To eliminate the chance of an overcharging alternator which can damage avionics and over-charge a battery. Or in the event of a battery problem or master solenoid failure the alternator will still allow electrical power without the battery. Or the need to disconnect the alternator due to electrical fires/forced landing situation as above to kill all power. Hence, there is a separate alternator switch to kill any spark in our fuel filled cockpit from that electrical source even forward of the firewall. Normally we separate the alternator from the bus via the C or control voltage bus feed switch or a 30 amp solenoid/relay controlled by a DC switch.
Why control the C or control voltage from the bus through a switch is, if the C wire is open, the regulator is shut down. Typically most in the US wired the alternator in this way. I have a 914 so my R,Band C wires go to a relay, on the firewall controlled by the cockpit alternator switch to simply remove the alternator power from the charge circuit on the firewall. (The alternator output goes through the firewall plug to the 914 Aux Boost Pump in the panel still, so I can't really kill all power in the panel. UGH!) In the event of a runaway Ducati regulator, a C wire of higher voltage from the bus, signals the regulator to decrease the voltage normally. Although highly unlikely in a B&C type alternator this can happen (but I haven't seen it ever). Kill the C voltage and you kill the faulty regulator output if the regulator is working. That said, Duati regulators don't tend to over volt and a crowbar or any type of over volt protection is not necessary either. However!
, if using a power management system for your bus, the bus will never run at full alternator output voltage going to the bus, therefore, a C wire off one of these PTC controlled bus outputs will input a C voltage that is lower (nominally a half a volt) than the actual output from the regulator and the regulator will be forced to charge at a higher rate. Not bad for a LiFe type battery or even some AGM types, but could be harder on the poor Ducati in my opinion. In a low amp draw aircraft a little overcharge (14.5 volts) helps some of the AGM and LiFe batteries charge better. (Note, supposedly there are two instances of the Schicke GR6 with LiFe has had a steady "voltage creep" issue in the Remos and Pipistrel climbing to 15 volts, but not the Ducati). Today's avionics can take up to 30 volts without worry, it's the battery that normally can't. So I'm not a fan of crowbars or experimenting with alternators without switch protection and extensive testing. Another topic o!
f contention we won't go to.
With a 914, wired via the Rotax manual, one can isolate the battery in the event of a short or smoking panel and with the battery off, the alternator will supply power through the aux boost pump switch preventing a flame out. For those with the 912 series, this is not a problem.
The Ducati type voltage regulator normally fails in a safe mode (dead) preventing a potential sparking mess on your firewall from the AC current being supplied by the engine stator. So very safe from runaway problems.
For a simple 912 with the battery located forward of the firewall, in a protective battery box, AND the regulator is wired to the same contactor as the alternator output (R,B and C connected together) the system would be safe for most automotive thinking types. One switch, ON or OFF forward of the firewall like a auto. This system is car like as you in the cockpit have no control over the electrical system. It is either ON or OFF. Backup batteries in avionics keep power alive so one must plan how to shut that off quickly in an emergency also. Another topic we won't go in to.
Normally a split master switch from suppliers has tabs to make the two switches work in unison. Those of us who are control freaks, cut these tabs and create a true split master/alternator.
My vote is do a split master in any aircraft so one has modest control over the electrical system. Especially if the battery is in the baggage bay or essential power is necessary in the event of a master contactor failure or battery issue. I can run both battery and alternator or one or the other to isolate a problem in foreseeable emergencies.
Best Regards,
Bud Yerly
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gilles(at)elixir-aircraft
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| Posted: Tue May 12, 2020 5:13 pm Post subject: Is there any reason to have a separate battery and alt swit |
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Le 13/05/2020 à 01:48, budyerly(at)msn.com a écrit :
| Quote: | That said, Duati regulators don't tend to over volt and a crowbar or any type of over volt protection is not necessary either.
[...]
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| Quote: |
The Ducati type voltage regulator normally fails in a safe mode (dead) preventing a potential sparking mess....
|
Bud and all,
Not to interfere, but I'm taking the liberty of asking whether actually
real data do exist to support the above statements. Or are they just
opinions ?
What if a regulator "fails abnormally", or a sense or control wire gets
severed ? The alternator voltage can climb to 100V peak in millseconds
if something goes wrong.
As in the past some builders reported different modes of failures for
their Ducati voltage regulator, I was wondering...
An overvoltage protection is no big deal, I would advise to better play
safe.
BTW, just in case; some electro wizard homebuilders here might find
information on the Rotax/Ducati alternator here :
http://contrails.free.fr/elec_alt_rotax_en.php
Our study of the Rotax/Ducati voltage regulator will soon be fully
translated.
Any hard data to complement these webpages will be warmly welcomed.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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gilles(at)elixir-aircraft
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| Posted: Tue May 12, 2020 5:23 pm Post subject: Is there any reason to have a separate battery and alt swit |
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Le 13/05/2020 à 02:46, William Daniell a écrit :
| Quote: |
I was under the impression that you weren't supposed to run the alt without batt although it is ok to run the bat without the alt. Is this incorrect?
|
Will,
Your impression is correct.
Some people say that the famous "Rotax" capacitor could replace the battery, but during our experiments on the voltage regulator, we found that in certain cases, it would not start - or continue - supplying power without having first a battery connected.
So with an electrically dependent engine, the Rotax suggested circuit is to be taken with a grain of salt.
I'll translate the detailed study within the next few weeks.
It would be interesting to ask those questions on the Aeroelectric List, where we meet builders of many horizons interested - and some very knowledgeable - in electricity.
FWIW,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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wdaniell.longport(at)gmai
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| Posted: Tue May 12, 2020 6:22 pm Post subject: Is there any reason to have a separate battery and alt swit |
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GilesThank you.
So i will follow the z16 recommendation having a switch for off , bat and alt-bat.
Fortunately my 912 turbo will run at low boost on just the mechanical pump so i am not electrically dependant.
On another note what is the max possible amps produced by the rotax alt?
Will
William Daniell
+1 786 878 0246
On Tue, May 12, 2020, 21:26 Gilles Thesee <gilles(at)elixir-aircraft.com (gilles(at)elixir-aircraft.com)> wrote:
| Quote: | Le 13/05/2020 à 02:46, William Daniell a écrit :
| Quote: |
I was under the impression that you weren't supposed to run the alt without batt although it is ok to run the bat without the alt. Is this incorrect?
|
Will,
Your impression is correct.
Some people say that the famous "Rotax" capacitor could replace the battery, but during our experiments on the voltage regulator, we found that in certain cases, it would not start - or continue - supplying power without having first a battery connected.
So with an electrically dependent engine, the Rotax suggested circuit is to be taken with a grain of salt.
I'll translate the detailed study within the next few weeks.
It would be interesting to ask those questions on the Aeroelectric List, where we meet builders of many horizons interested - and some very knowledgeable - in electricity.
FWIW,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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gilles(at)elixir-aircraft
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| Posted: Wed May 13, 2020 2:39 am Post subject: Is there any reason to have a separate battery and alt swit |
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Le 13/05/2020 à 04:17, William Daniell a écrit :
| Quote: |
Fortunately my 912 turbo will run at low boost on just the mechanical pump so i am not electrically dependant.
On another note what is the max possible amps produced by the rotax alt?
|
Will,
We found that the alternator can easily supply its short circuit limit current of 21A without thermal distress.
The limiting item is the voltage regulator.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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wdaniell.longport(at)gmai
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| Posted: Wed May 13, 2020 4:54 am Post subject: Is there any reason to have a separate battery and alt swit |
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Mmmm thanks
So where did the question come from?
I have a 912 turbo with a skyview.
About once a flight my amps go up off the chart - 70a - ending up with a red x on the screen (no sparks or smoke  ). After which the instrument comes alive and the amps reduce to normal 7-10 depending on the load. And remain normal thereafter.
When the amps are climbing the reading can be "reset" by turning off the alternator and then turning it back in again.
I have a hall effect sensor on the thick wire which charges the battery and this changes very little as on would expect.
I asked the europa and the aeroelectric forums and dynon. Several people said they had similar events. So having checked the wiring i assumed that this was a dynon bug.
AND ....I always understood that the alternator was unable to produce more than 18A hence people adding external alternator. But is thus a fair assumption?
Could it be a faulty regulator?
Will
William Daniell
+1 786 878 0246
On Wed, May 13, 2020, 06:41 Gilles Thesee <gilles(at)elixir-aircraft.com (gilles(at)elixir-aircraft.com)> wrote:
| Quote: | Le 13/05/2020 à 04:17, William Daniell a écrit :
| Quote: |
Fortunately my 912 turbo will run at low boost on just the mechanical pump so i am not electrically dependant.
On another note what is the max possible amps produced by the rotax alt?
|
Will,
We found that the alternator can easily supply its short circuit limit current of 21A without thermal distress.
The limiting item is the voltage regulator.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
|
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wdaniell.longport(at)gmai
Guest
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| Posted: Wed May 13, 2020 5:11 am Post subject: Is there any reason to have a separate battery and alt swit |
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PS:
1. this was a new rectifier 3 years ago and has 225 hours on it
2. Thanks to your and other comments on the forum although it is on the engine side of the firewall, it does have its own cooling air supply via a scat hose from a small scoop in the cowling inlet.
William Daniell
LONGPORT
+1 786 878 0246
On Wed, May 13, 2020 at 8:52 AM William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | Mmmm thanks
So where did the question come from?
I have a 912 turbo with a skyview.
About once a flight my amps go up off the chart - 70a - ending up with a red x on the screen (no sparks or smoke ). After which the instrument comes alive and the amps reduce to normal 7-10 depending on the load. And remain normal thereafter.
When the amps are climbing the reading can be "reset" by turning off the alternator and then turning it back in again.
I have a hall effect sensor on the thick wire which charges the battery and this changes very little as on would expect.
I asked the europa and the aeroelectric forums and dynon. Several people said they had similar events. So having checked the wiring i assumed that this was a dynon bug.
AND ....I always understood that the alternator was unable to produce more than 18A hence people adding external alternator. But is thus a fair assumption?
Could it be a faulty regulator?
Will
William Daniell
+1 786 878 0246
On Wed, May 13, 2020, 06:41 Gilles Thesee <gilles(at)elixir-aircraft.com (gilles(at)elixir-aircraft.com)> wrote:
| Quote: | Le 13/05/2020 à 04:17, William Daniell a écrit :
| Quote: |
Fortunately my 912 turbo will run at low boost on just the mechanical pump so i am not electrically dependant.
On another note what is the max possible amps produced by the rotax alt?
|
Will,
We found that the alternator can easily supply its short circuit limit current of 21A without thermal distress.
The limiting item is the voltage regulator.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
|
|
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wdaniell.longport(at)gmai
Guest
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| Posted: Wed May 13, 2020 5:12 am Post subject: Is there any reason to have a separate battery and alt swit |
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PPS - I have the OVP as required on the Z16 and this has not tripped.
William Daniell
LONGPORT
+1 786 878 0246
On Wed, May 13, 2020 at 9:09 AM William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | PS:
1. this was a new rectifier 3 years ago and has 225 hours on it
2. Thanks to your and other comments on the forum although it is on the engine side of the firewall, it does have its own cooling air supply via a scat hose from a small scoop in the cowling inlet.
William Daniell
LONGPORT
+1 786 878 0246
On Wed, May 13, 2020 at 8:52 AM William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | Mmmm thanks
So where did the question come from?
I have a 912 turbo with a skyview.
About once a flight my amps go up off the chart - 70a - ending up with a red x on the screen (no sparks or smoke ). After which the instrument comes alive and the amps reduce to normal 7-10 depending on the load. And remain normal thereafter.
When the amps are climbing the reading can be "reset" by turning off the alternator and then turning it back in again.
I have a hall effect sensor on the thick wire which charges the battery and this changes very little as on would expect.
I asked the europa and the aeroelectric forums and dynon. Several people said they had similar events. So having checked the wiring i assumed that this was a dynon bug.
AND ....I always understood that the alternator was unable to produce more than 18A hence people adding external alternator. But is thus a fair assumption?
Could it be a faulty regulator?
Will
William Daniell
+1 786 878 0246
On Wed, May 13, 2020, 06:41 Gilles Thesee <gilles(at)elixir-aircraft.com (gilles(at)elixir-aircraft.com)> wrote:
| Quote: | Le 13/05/2020 à 04:17, William Daniell a écrit :
| Quote: |
Fortunately my 912 turbo will run at low boost on just the mechanical pump so i am not electrically dependant.
On another note what is the max possible amps produced by the rotax alt?
|
Will,
We found that the alternator can easily supply its short circuit limit current of 21A without thermal distress.
The limiting item is the voltage regulator.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
|
|
|
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gilles(at)elixir-aircraft
Guest
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| Posted: Wed May 13, 2020 5:23 am Post subject: Is there any reason to have a separate battery and alt swit |
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Le 13/05/2020 à 14:52, William Daniell a écrit :
| Quote: |
I have a 912 turbo with a skyview.
About once a flight my amps go up off the chart - 70a - ending up with a red x on the screen (no sparks or smoke ). After which the instrument comes alive and the amps reduce to normal 7-10 depending on the load. And remain normal thereafter.
When the amps are climbing the reading can be "reset" by turning off the alternator and then turning it back in again.
I have a hall effect sensor on the thick wire which charges the battery and this changes very little as on would expect.
I asked the europa and the aeroelectric forums and dynon. Several people said they had similar events. So having checked the wiring i assumed that this was a dynon bug.
AND ....I always understood that the alternator was unable to produce more than 18A hence people adding external alternator. But is thus a fair assumption?
Could it be a faulty regulator?
|
Will,
Understand your concern.
I'd say an ammeter is not very useful as a *cockpit* instrument. An alternator is physically incapable of supplying more than its short-circuit current (21A for the Rotax).
What counts is *voltage* : under 12V, no charging, above 13+ V, system is charging, above ~15V, overvoltage etc.
I cannot help you on the Dynon, since I never installed or used one, and never bothered to read its manual.
Nevertheless, anytime you have an odd looking *instrument indication*, the first thing to do is check what the *actual value* of the indicated parameter is.
So the first thing to do is record or take note of the ship circuits voltage with an idependent instrument. If you don't have a panel voltmeter, your VHF certainly provides a voltage indication. Otherwise you'll need a portable voltmeter or datalogger.
Only then will come the time to make assumptions as to what actually occurs and what is at fault.
FWIW,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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wdaniell.longport(at)gmai
Guest
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| Posted: Wed May 13, 2020 10:03 am Post subject: Is there any reason to have a separate battery and alt swit |
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My voltage is a steady 13.8 so going back to my school electricity assuming a constant load and constant voltage the amps should be constant as well.
My second ammeter on the bat + fat wire shows a consistent charge once the starting energy has been recovered.
In any case I will follow your advice and measure V and A with a separate instrument.
thanks
Will
William Daniell
LONGPORT
+1 786 878 0246
On Wed, May 13, 2020 at 9:25 AM Gilles Thesee <gilles(at)elixir-aircraft.com (gilles(at)elixir-aircraft.com)> wrote:
| Quote: | Le 13/05/2020 à 14:52, William Daniell a écrit :
| Quote: |
I have a 912 turbo with a skyview.
About once a flight my amps go up off the chart - 70a - ending up with a red x on the screen (no sparks or smoke ). After which the instrument comes alive and the amps reduce to normal 7-10 depending on the load. And remain normal thereafter.
When the amps are climbing the reading can be "reset" by turning off the alternator and then turning it back in again.
I have a hall effect sensor on the thick wire which charges the battery and this changes very little as on would expect.
I asked the europa and the aeroelectric forums and dynon. Several people said they had similar events. So having checked the wiring i assumed that this was a dynon bug.
AND ....I always understood that the alternator was unable to produce more than 18A hence people adding external alternator. But is thus a fair assumption?
Could it be a faulty regulator?
|
Will,
Understand your concern.
I'd say an ammeter is not very useful as a *cockpit* instrument. An alternator is physically incapable of supplying more than its short-circuit current (21A for the Rotax).
What counts is *voltage* : under 12V, no charging, above 13+ V, system is charging, above ~15V, overvoltage etc.
I cannot help you on the Dynon, since I never installed or used one, and never bothered to read its manual.
Nevertheless, anytime you have an odd looking *instrument indication*, the first thing to do is check what the *actual value* of the indicated parameter is.
So the first thing to do is record or take note of the ship circuits voltage with an idependent instrument. If you don't have a panel voltmeter, your VHF certainly provides a voltage indication. Otherwise you'll need a portable voltmeter or datalogger.
Only then will come the time to make assumptions as to what actually occurs and what is at fault.
FWIW,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
|
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brian.davies44(at)gmail.c
Guest
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| Posted: Thu May 14, 2020 12:37 am Post subject: Is there any reason to have a separate battery and alt swit |
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“Assuming a constant load”—a very rare condition in an aircraft.
Brian Davies
From: owner-europa-list-server(at)matronics.com <owner-europa-list-server(at)matronics.com> On Behalf Of William Daniell
Sent: 13 May 2020 19:00
To: europa-list(at)matronics.com
Subject: Re: Re: Is there any reason to have a separate battery and alt switc
My voltage is a steady 13.8 so going back to my school electricity assuming a constant load and constant voltage the amps should be constant as well.
My second ammeter on the bat + fat wire shows a consistent charge once the starting energy has been recovered.
In any case I will follow your advice and measure V and A with a separate instrument.
thanks
Will
William Daniell
LONGPORT
+1 786 878 0246
On Wed, May 13, 2020 at 9:25 AM Gilles Thesee <gilles(at)elixir-aircraft.com (gilles(at)elixir-aircraft.com)> wrote:
| Quote: |
Le 13/05/2020 à 14:52, William Daniell a écrit :
| Quote: |
I have a 912 turbo with a skyview.
About once a flight my amps go up off the chart - 70a - ending up with a red x on the screen (no sparks or smoke ). After which the instrument comes alive and the amps reduce to normal 7-10 depending on the load. And remain normal thereafter.
When the amps are climbing the reading can be "reset" by turning off the alternator and then turning it back in again.
I have a hall effect sensor on the thick wire which charges the battery and this changes very little as on would expect.
I asked the europa and the aeroelectric forums and dynon. Several people said they had similar events. So having checked the wiring i assumed that this was a dynon bug.
AND ....I always understood that the alternator was unable to produce more than 18A hence people adding external alternator. But is thus a fair assumption?
Could it be a faulty regulator?
|
Will,
Understand your concern.
I'd say an ammeter is not very useful as a *cockpit* instrument. An alternator is physically incapable of supplying more than its short-circuit current (21A for the Rotax).
What counts is *voltage* : under 12V, no charging, above 13+ V, system is charging, above ~15V, overvoltage etc.
I cannot help you on the Dynon, since I never installed or used one, and never bothered to read its manual.
Nevertheless, anytime you have an odd looking *instrument indication*, the first thing to do is check what the *actual value* of the indicated parameter is.
So the first thing to do is record or take note of the ship circuits voltage with an idependent instrument. If you don't have a panel voltmeter, your VHF certainly provides a voltage indication. Otherwise you'll need a portable voltmeter or datalogger.
Only then will come the time to make assumptions as to what actually occurs and what is at fault.
FWIW,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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budyerly@msn.com
Joined: 05 Oct 2019
Posts: 282
Location: Florida USA
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| Posted: Fri May 15, 2020 5:52 am Post subject: Re: Is there any reason to have a separate battery and alt |
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Sorry for the long delay. My virus protection doesn't like the matronics site.
As for the ROTAX alternator. It is a dynamo so it does not require electrical excitation of the field circuit as there is none. Even the ignition coils in the stator are self generating. Pretty simple, basically a big lawn mower electrical system. So either battery, dynamo (ROTAX alternator), or both is not going to hurt a thing.
Your automotive or standard alternator (even certified aircraft) require voltage to excite a field current before the rotating coils can provide power. Alternators are lighter, more powerful and cheaper to make watt to watt.
An alternator is dependent on the battery to initiate the field. Cut the field and battery in a Cessna, then turn on only the battery, and the alternator will not fire, unless there is residual voltage stored in a capacitor in the system with enough energy to excite the field coil. To my limited knowledge of all solid state equipment currently available, that power backup to the main bus to excite an alternator field is no longer available. All backup batteries simply power the box only.
Best Regards,
Bud Yerly
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h&jeuropa
Joined: 07 Nov 2006
Posts: 635
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| Posted: Fri May 15, 2020 9:45 am Post subject: Re: Is there any reason to have a separate battery and alt |
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Will,
As Gilles pointed out above, the weak point of the Rotax system is the Ducatti rectifier/regulator. The electrical design is fine, the problem is the construction. Early ones, P/N 343620, had diodes that unsoldered internally. There is an easy work around for this (2 external diodes). Later ones, P/N 362001, are poorly manufactured with cold solder joints, unsoldered joints and mechanical failures. Either one seems to work pretty well if the load is kept low, certainly less than 10 amps and best if closer to 5 amps.
Silent Hektik regulators, made in Germany have been used by many Rotax owners. They are difficult to purchase in the US, although they may be available from Vans Aircraft as an alternate on the RV12.
Some owners have purchased John Deere garden tractor regulators and used them with success. Part number AM101406 is usually the one mentioned.
B&C Speciality has just developed a replacement for Ducatti, the part number is AVC1. You can find an install manual on their website but it's not yet listed for sale.
I built a Mike Miller replacement. Mike is an electrical engineer with a RV12. Ducatti failures are pretty common in them. He inspected many failed Ducatti units and summarized the problems as stated above. He designed a replacement that is electrically identical but has more robust components and most importantly larger heat sink. His will operate at 20 amps all day!
Our Europa draws about 8 amps in flight. We used an early Ducatti with external diodes for many years. At some point we purchased the later model Ducatti and used that for a couple years. Finally a year ago I built the MM replacement and have had no problems.
I hope this offers some insight and maybe solutions. Your 70A spike sounds like an instrumentation problem, but other than temporarily installing a second ammeter, I don't have a solution in mind.
Jim Butcher
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wdaniell.longport(at)gmai
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| Posted: Fri May 15, 2020 1:37 pm Post subject: Is there any reason to have a separate battery and alt swit |
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Jim
thanks
YES - I have to say I was quite alarmed by 70A! Since I was in the air some way from a suitable place to land I carried on figuring that all I had heard indicated that the rotax would be hard put to produce a consistent 18A let alone 70A. The sparks and smoke stayed in the wire.
Of course I checked and rechecked everything but could never replicate the fault on the ground. This suggests that this is something to do with a warm engine and high power. As a reuslt of this discussion it occurred to me that the fault might be the voltage regulator showing signs of failing? Mine is mounted on the engine side of the firewall so heat could be a factor.
I have a hall effect sensor on the battery wire and this has never shown major fluctuations.
So yes Im guessing that its a fault in the dynon or my installation or a loose connection or a bit of all three.
My next item is to check the output of the alt using an independent instrument.
Will
William Daniell
LONGPORT
+1 786 878 0246
On Fri, May 15, 2020 at 1:52 PM h&jeuropa <butcher43(at)att.net (butcher43(at)att.net)> wrote:
| Quote: | --> Europa-List message posted by: "h&jeuropa" <butcher43(at)att.net (butcher43(at)att.net)>
Will,
As Gilles pointed out above, the weak point of the Rotax system is the Ducatti rectifier/regulator. The electrical design is fine, the problem is the construction. Early ones, P/N 343620, had diodes that unsoldered internally. There is an easy work around for this (2 external diodes). Later ones, P/N 362001, are poorly manufactured with cold solder joints, unsoldered joints and mechanical failures. Either one seems to work pretty well if the load is kept low, certainly less than 10 amps and best if closer to 5 amps.
Silent Hektik regulators, made in Germany have been used by many Rotax owners. They are difficult to purchase in the US, although they may be available from Vans Aircraft as an alternate on the RV12.
Some owners have purchased John Deere garden tractor regulators and used them with success. Part number AM101406 is usually the one mentioned.
B&C Speciality has just developed a replacement for Ducatti, the part number is AVC1. You can find an install manual on their website but it's not yet listed for sale.
I built a Mike Miller replacement. Mike is an electrical engineer with a RV12. Ducatti failures are pretty common in them. He inspected many failed Ducatti units and summarized the problems as stated above. He designed a replacement that is electrically identical but has more robust components and most importantly larger heat sink. His will operate at 20 amps all day!
Our Europa draws about 8 amps in flight. We used an early Ducatti with external diodes for many years. At some point we purchased the later model Ducatti and used that for a couple years. Finally a year ago I built the MM replacement and have had no problems.
I hope this offers some insight and maybe solutions. Your 70A spike sounds like an instrumentation problem, but other than temporarily installing a second ammeter, I don't have a solution in mind.
Jim Butcher
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496382#496382
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wdaniell.longport(at)gmai
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| Posted: Fri May 15, 2020 1:39 pm Post subject: Is there any reason to have a separate battery and alt swit |
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Bud - So just to check that I understood, I could have the ALT ON and the BAT OFF without harming the electrical system?
Will
William Daniell
LONGPORT
+1 786 878 0246
On Fri, May 15, 2020 at 9:56 AM budyerly(at)msn.com (budyerly(at)msn.com) <budyerly(at)msn.com (budyerly(at)msn.com)> wrote:
| Quote: | --> Europa-List message posted by: "budyerly(at)msn.com (budyerly(at)msn.com)" <budyerly(at)msn.com (budyerly(at)msn.com)>
Sorry for the long delay. My virus protection doesn't like the matronics site.
As for the ROTAX alternator. It is a dynamo so it does not require electrical excitation of the field circuit as there is none. Even the ignition coils in the stator are self generating. Pretty simple, basically a big lawn mower electrical system. So either battery, dynamo (ROTAX alternator), or both is not going to hurt a thing.
Your automotive or standard alternator (even certified aircraft) require voltage to excite a field current before the rotating coils can provide power. Alternators are lighter, more powerful and cheaper to make watt to watt.
An alternator is dependent on the battery to initiate the field. Cut the field and battery in a Cessna, then turn on only the battery, and the alternator will not fire, unless there is residual voltage stored in a capacitor in the system with enough energy to excite the field coil. To my limited knowledge of all solid state equipment currently available, that power backup to the main bus to excite an alternator field is no longer available. All backup batteries simply power the box only.
Best Regards,
Bud Yerly
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496378#496378
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gilles(at)elixir-aircraft
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| Posted: Fri May 15, 2020 4:08 pm Post subject: Is there any reason to have a separate battery and alt swit |
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Le 15/05/2020 à 23:33, William Daniell a écrit :
Will,
There is a law in physics measurements : the more parameters you measure, the more you scratch your head^^!
That said, you wrote that your bus - or battery - voltage remained within the "green" limits during each of the events. So no reason to suspect the voltage regulator.
The only item capable of supplying more than the 21 amps of the alternator is the battery, but while doing this its voltage would sag due to internal resistance (Cf Ohm's law for a generator). 70 amp is no trifle.
So the main probabilty is an ammeter artefact. The best way to measure currents is with a Hall effect sensor, as the shunt may induce side effects in your circuits with high currents.
But first things first, without independent and reliable voltage and possibly current measurements or logging, no assumptions can be made.
Concerning disconnecting the battery while running, not sure it would be a safe thing to do, especially in flight :
[img]cid:part1.EB5D0C5A.7EC7D6BC(at)elixir-aircraft.com[/img]
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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gilles(at)elixir-aircraft
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| Posted: Sat May 16, 2020 5:55 am Post subject: Is there any reason to have a separate battery and alt swit |
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Le 16/05/2020 à 13:46, h&jeuropa a écrit :
| Quote: |
Attached is the main instruction document. It explains what is involved in the construction and also gives an excellent explanation of how the circuit operates. Let me know if you are interested in proceeding as there have been a few minor changes.
Jim,
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Great document, thanks for sharing !
Any chances to PM you, I'm afraid your displayed address doesn't work ?
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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h&jeuropa
Joined: 07 Nov 2006
Posts: 635
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| Posted: Sat May 16, 2020 6:35 am Post subject: Re: Is there any reason to have a separate battery and alt |
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Gilles,
Sure, send me PM here on Matronics. Use h&jeuropa
Jim
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h&jeuropa
Joined: 07 Nov 2006
Posts: 635
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| Posted: Sat May 16, 2020 6:45 am Post subject: Re: Is there any reason to have a separate battery and alt |
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Will,
Are you using a GRT Hall sensor? If so, my old Skyview manual shows it can be connected to any of three pins. If you switch it to a different input and the 70 A spike does not recur, it’s likely a Skyview problem. If it still happens it could still be either a Skyview or probe problem. You could put another Hall sensor in place and run wires to a temporary meter in cockpit but it’s tough to notice a spike. You say others have had similar experience. What does Dynon say?
Jim
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