 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
wdaniell.longport(at)gmai
Guest
|
 Posted: Mon May 04, 2020 2:22 pm Post subject: Is there any reason to have a separate battery and alt switc |
 |
|
I know this might put the cat among the pigeons...
I have self powered back ups
- dynon has its own battery
- Back iLevil with its own battery
- hand held radio
I have a crowbar and I believe that the rotax alt will generate a maximum of 18 amps on a very good day. The only things that dont have their own backup power is trim and prop.
So would having everything wired into a single ON OFF switch present any drawback?
This arises out of reaching out to my GPS and a sudden bump causing me to miss the GPS and turn off the bat (which I immediately turned back on). I have separate bat and alt switches .(which is probably not in an case the best arrangement I admit but leaving that argument aside for now).
Th obvious thing to do is what is recommended by Bob N in the Z16 which is to have an OFF - ON (BAT) - ON (BAT+ALT) switch..but Im curious.
Will
William Daniell
LONGPORT
+1 786 878 0246
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
 |
h&jeuropa
Joined: 07 Nov 2006
Posts: 645
|
| Posted: Mon May 11, 2020 4:53 am Post subject: Re: Is there any reason to have a separate battery and alt s |
|
|
Will,
I have Z16 configuration in my Europa but what you suggest, a single switch is exactly what Rotax shows in their install manual. Likewise, the Europa 914 install manual (I don't have the Europa 912 install manual) has the same setup.
Jim
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
budyerly@msn.com
Joined: 05 Oct 2019
Posts: 288
Location: Florida USA
|
| Posted: Tue May 12, 2020 3:48 pm Post subject: Re: Is there any reason to have a separate battery and alt s |
|
|
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 of 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
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
