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08-04-2013, 08:25 PM
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Join Date: Nov 2010
Location: West Linn, Oregon
Posts: 1,351
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Expected Voltage for SD-8
I have an SD-8 installed as a backup alternator on my IO-540. I do not have a shunt installed on it's output so I am unable to see an Amperage draw on it when it is activated (and primary alternator is disabled). But when I load shed down my system down to about 3As, increase RPMs to 1800 the voltage goes from 14.7 (on primary alternator) down to 13.2V when on the SD-8.
Is this the expected voltage for the SD-8 when operating or is it possible the SD-8 isn't properly outputting to the main bus?
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CharlieWaffles - But you can call me " Mark"
RV-10
N928MT
Flying - AKA Still Tinkering
Build Project Site
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08-04-2013, 08:29 PM
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Join Date: Sep 2005
Location: Dothan, Alabama
Posts: 1,487
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Yep. The SD-8 external regulator is always on-line and picks up when voltage falls to the setpoint. On my SD-20, it is 13 volts.
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Alton DeWeese
N526RV RV7A Tip Up, IO360 180 W/Hartzel BA prop.
Flying ~950 hours since Aug 2010
N4IDH
Construction Log
?The secret of getting ahead is getting started. The secret of getting started is breaking your complex overwhelming tasks into small manageable tasks, and then starting on the first one.?
?Mark Twain
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08-05-2013, 01:46 PM
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Join Date: Dec 2005
Posts: 976
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NB @ 1800RPM [Engine] max Output of the SD-8 is ~3.5A, so if you are pulling about 3A you are near maxing the SD-8 out.
The -1 regulator [PMRIC-14] should push out nominal 14V and according to the diagram is adjustable. However, I would "load shed" everything you can to get a true reading, and/or do at Max RPM.
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08-11-2013, 10:49 AM
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Join Date: Oct 2007
Location: St-Jerome,Quebec,Canada
Posts: 1,125
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SD-20 INSTALLATION
Hi Alton
I just looked at your construction log to see how you mounted the Current Limiter/shunt of your SD-20 B/U Alternator but the pictures came out kind of fuzzy.
I'm installing one on my -4 as we speak and I wonder if it will be possible to see any pictures you may have.
Thank you for your help.
Cheers
Bruno
rv4@videotron.ca |
08-12-2013, 06:04 AM
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Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,068
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When a battery is first disconnected from a charger, or main alternator in this case, its voltage is expected to be slightly above 13 volts. A better test of the SD-8 would be to go flying at cruise RPM with the main alternator off. If the voltage remains above 13 for an extended period of time at reduced load, then yes, the SD-8 is working.
Joe Gores
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08-12-2013, 07:32 AM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,120
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Quote:
Originally Posted by Mich48041
When a battery is first disconnected from a charger, or main alternator in this case, its voltage is expected to be slightly above 13 volts. A better test of the SD-8 would be to go flying at cruise RPM with the main alternator off. If the voltage remains above 13 for an extended period of time at reduced load, then yes, the SD-8 is working.
Joe Gores
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And if you're going to do that - don't turn your main alternator back on with the engine at full RPM, you'll give the regulator fits and the resulting voltage spike is tough on it. Get your engine RPM down (either on the ground or slow speed flight) before re-energizing your main alternator field. Be kind to your electronics! 
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now. 
Last edited by airguy : 08-12-2013 at 07:35 AM.
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