czechsix(at)juno.com
Guest
|
 Posted: Thu Mar 02, 2006 11:06 am Post subject: Backup battery - Lightspeed EI |
 |
|
Hi Doug,
My RV is setup for day/night VFR and I have dual Lightspeeds. I pondered the electrical system options extensively. I originally planned to go with two alternators and one battery. The thing I kept coming back to is that with one battery, you have a single-point failure for the entire electrical system. Notwithstanding the opinion of others to the contrary, it IS possible to have a battery lead break off or come loose. I know people who've had their car quit because of this. I don't know anyone who has had their Lycoming quit from this--yet--but one of the guys on the Aeroelectric List a couple years back did have a battery lead break (in his case it did not result in engine failure, but if he had been using a single battery architecture with dual elec igntion, it would have!). People can argue that it was improper installation or poor maintenance and that's fine, but it has happened and I prefer to design out the possibility in my airplane. Even with dual alternators, if the backup alternator is off and you lose connection to the battery, the alternator is not self-exciting for startup so it does you no good (or at least I wouldn't bank on it). So you lose everything including the engine at that point. I was not personally comfortable with this setup in my plane and decided to go with single alternator, dual battery setup instead.
Another advantage to the dual battery setup is that you can avoid the perceived weakness in the Lightspeed system with the Skytec starter that has resulted in damaging kickback with more than one installation. I won't get into the causes and fixes and who's-to-blame thing, but if you have a small backup battery that is isolated from the rest of the elec system, you can use it to power one ignition while cranking the engine from the main battery. This is exactly what I do on my plane with great results so far...I turn on only the ignition powered by the backup battery, leaving the main one off. Crank it and it starts great (even in winter in Iowa, with no primer system). Then I switch on the main ignition and I'm good to go with no chance of kickback from low voltages on the Lightspeed...
I wired mine pretty much like Klaus shows with a Schottky diode in between to isolate the backup battery from the rest of the elec system. I elected not to put in a switch like Klaus shows to switch the ignition between main and backup...I didn't see an advantage to it and didn't want to be flipping switches to get my engine started again (would prefer it doesn't quit to begin with!). I simply wired my second igntion directly to the +/- terminals of the backup battery. The main ignition is likewise wired directly to the +/- terminals of the main battery. The only other thing I have connected to the backup battery is a voltmeter just so I can monitor it (note: in my case the path to the voltmeter is switched on/off with the ignition....this is because the voltmeter draws a small current, so if you wired it always-on it would drain the battery while the airplane is powered down).
I used a PowerSonic 2.9 Ah battery (PS-1229). It's light and relatively cheap (I think about $25-30...you can Google it and get lots of hits). I plan to change the battery every two years to ensure that it's reasonably fresh. I know Klaus says 4.5 Ah but I thought that was overkill (unless you plan to be flying over some really rugged terrain/ocean with no alternates within an hour or two of flight). The 2.9 Ah batt is theoretically good for almost 3 hours of run time on one ignition (drawing ~ 1A at cruise RPM's). In the unlikely event that I ever find myself operating the engine soley on the backup battery, I will try to have it on the ground within an hour. Remember, if you're flying in that condition it means you've lost everything else in your panel so you're probably not going to be wanting to continue a long XC under those circumstances! If I upgrade to IFR I'll put the backup battery in the Dynon and make sure I have fresh batteries in my handheld comm and GPS.
One nice thing about the PS-1229 is that it can fit into the standard Vans battery tray along with an Odyssey PC-680. I have the PC-680 at the back of the tray against the firewall and a piece of angle in front of it (to keep it from sliding forward). The PS-1229 is in the front of the tray. There is about 3/4" of space between the two so any sort of melt down/overheat condition of one battery won't take out the other one.
FWIW, I made up a quick checklist in my POH for main alternator failure. If the main alternator quits and I plan to continue my flight for over an hour, I will turn OFF my backup-powered ignition to save the battery just in case it's needed. I will continue to planned destination running the main igntion and reduced panel loads (e-bus) and only turn the backup ignition ON when approaching to land. This way if the main battery craps out on me prior to arrival at my destination I will be able to keep the engine running with the fully-charged backup system.
Some may say my setup is overkill, others will think it's inadequate. But it's my airplane and this setup is one that I'm very comfortable with.
--Mark Navratil
Cedar Rapids, Iowa
RV-8A N2D flying 8.3 hours...
Subject: RV-List: Backup battery - Lightspeed EI
From: Doug Weiler <dcw(at)mnwing.org>
Fellow Listers:
I am contemplating converting my mag driven 0-360 to Lightspeed
electronic ignition. I may consider the dual Lightspeed installation.
Lightspeed calls for a 4.5 amp/hr backup battery (if I so choose). I need
something small and light to squeeze this installation in to my RV-4. For
those that have done this, what backup battery did you use?
Thanks
Doug Weiler
N722DW, 275 hrs
Hi Doug,
My RV is setup for day/night VFR and I have dual Lightspeeds. I pondered the electrical system options extensively. I originally planned to go with two alternators and one battery. The thing I kept coming back to is that with one battery, you have a single-point failure for the entire electrical system. Notwithstanding the opinion of others to the contrary, it IS possible to have a battery lead break off or come loose. I know people who've had their car quit because of this. I don't know anyone who has had their Lycoming quit from this--yet--but one of the guys on the Aeroelectric List a couple years back did have a battery lead break (in his case it did not result in engine failure, but if he had been using a single battery architecture with dual elec igntion, it would have!). People can argue that it was improper installation or poor maintenance and that's fine, but it has happened and I prefer to design out the possibility in my airplane. Even with dual alternators, if the backup alternator is off and you lose connection to the battery, the alternator is not self-exciting for startup so it does you no good (or at least I wouldn't bank on it). So you lose everything including the engine at that point. I was not personally comfortable with this setup in my plane and decided to go with single alternator, dual battery setup instead.
Another advantage to the dual battery setup is that you can avoid the perceived weakness in the Lightspeed system with the Skytec starter that has resulted in damaging kickback with more than one installation. I won't get into the causes and fixes and who's-to-blame thing, but if you have a small backup battery that is isolated from the rest of the elec system, you can use it to power one ignition while cranking the engine from the main battery. This is exactly what I do on my plane with great results so far...I turn on only the ignition powered by the backup battery, leaving the main one off. Crank it and it starts great (even in winter in Iowa, with no primer system). Then I switch on the main ignition and I'm good to go with no chance of kickback from low voltages on the Lightspeed...
I wired mine pretty much like Klaus shows with a Schottky diode in between to isolate the backup battery from the rest of the elec system. I elected not to put in a switch like Klaus shows to switch the ignition between main and backup...I didn't see an advantage to it and didn't want to be flipping switches to get my engine started again (would prefer it doesn't quit to begin with!). I simply wired my second igntion directly to the +/- terminals of the backup battery. The main ignition is likewise wired directly to the +/- terminals of the main battery. The only other thing I have connected to the backup battery is a voltmeter just so I can monitor it (note: in my case the path to the voltmeter is switched on/off with the ignition....this is because the voltmeter draws a small current, so if you wired it always-on it would drain the battery while the airplane is powered down).
I used a PowerSonic 2.9 Ah battery (PS-1229). It's light and relatively cheap (I think about $25-30...you can Google it and get lots of hits). I plan to change the battery every two years to ensure that it's reasonably fresh. I know Klaus says 4.5 Ah but I thought that was overkill (unless you plan to be flying over some really rugged terrain/ocean with no alternates within an hour or two of flight). The 2.9 Ah batt is theoretically good for almost 3 hours of run time on one ignition (drawing ~ 1A at cruise RPM's). In the unlikely event that I ever find myself operating the engine soley on the backup battery, I will try to have it on the ground within an hour. Remember, if you're flying in that condition it means you've lost everything else in your panel so you're probably not going to be wanting to continue a long XC under those circumstances! If I upgrade to IFR I'll put the backup battery in the Dynon and make sure I have fresh batteries in my handheld comm and GPS.
One nice thing about the PS-1229 is that it can fit into the standard Vans battery tray along with an Odyssey PC-680. I have the PC-680 at the back of the tray against the firewall and a piece of angle in front of it (to keep it from sliding forward). The PS-1229 is in the front of the tray. There is about 3/4" of space between the two so any sort of melt down/overheat condition of one battery won't take out the other one.
FWIW, I made up a quick checklist in my POH for main alternator failure. If the main alternator quits and I plan to continue my flight for over an hour, I will turn OFF my backup-powered ignition to save the battery just in case it's needed. I will continue to planned destination running the main igntion and reduced panel loads (e-bus) and only turn the backup ignition ON when approaching to land. This way if the main battery craps out on me prior to arrival at my destination I will be able to keep the engine running with the fully-charged backup system.
Some may say my setup is overkill, others will think it's inadequate. But it's my airplane and this setup is one that I'm very comfortable with.
--Mark Navratil
Cedar Rapids, Iowa
RV-8A N2D flying 8.3 hours...
Subject: RV-List: Backup battery - Lightspeed EI
From: Doug Weiler dcw(at)mnwing.org
-- RV-List message posted by: Doug Weiler dcw(at)mnwing.org
Fellow Listers:
I am contemplating converting my mag driven 0-360 to Lightspeed
electronic ignition. I may consider the dual Lightspeed installation.
Lightspeed calls for a 4.5 amp/hr backup battery (if I so choose). I need
something small and light to squeeze this installation in to my RV-4. For
those that have done this, what backup battery did you use?
Thanks
Doug Weiler
N722DW, 275 hrs
| | - The Matronics RV-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?RV-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
