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08-31-2019, 02:04 PM
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Join Date: Dec 2018
Location: Granada Hills
Posts: 820
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Finding battery discharged, again.
Friend of mine owns a 2016 RV-12 he built... N836BL, and he's having difficulty with the battery, quite new, being found in a state of discharge.
Today's voltage read 11.7V, battery was bought new at Aircraft Spruce in May, 2019.
Any suggestions on where to look for phantom drain of this battery such that it goes dead? Any relays?
We believe, currently, that the electrical problem may be intermittent.
Are 20-25 minute flights enough 1x a week for the voltage regulator to go into full 14.4V charge rates in that amount of time, or are longer flights necessary? Is a different Ducati brand VR worth looking into?
Last edited by NinerBikes : 09-02-2019 at 06:52 PM.
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08-31-2019, 04:13 PM
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Join Date: Sep 2006
Location: Windsor, California
Posts: 924
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While monitoring for parasitic drain at the battery (GOOGLE: Parasitic Drain) deactivate individual circuits by pulling individual fuses to identify suspect drain.
You could also disconnect the battery (remove negative terminal cable) after a flight and reattach the cable at the next flight. If the battery is still strong, it is likely a parasitic drain issue and not a weak battery or defective charging system.
In my experience, those short flights should be sufficient for a stock Odyssey PC-680/Ducati RR system to substantially recharge. Longer flights would likely be better for more thorough battery charging. I have found that frequent flying does wonders for the battery and IMHO trickle chargers are to be avoided.
__________________
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 (circa 1965) - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B 2020) - N124DH flying since March 2014 - 940+ hours (as of September 2020)! 
V AF donation through June 2021.
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08-31-2019, 04:35 PM
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Join Date: Mar 2014
Location: Prescott, AZ
Posts: 739
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A cheap DVM with a DC current range can show you if you have any drain on the battery while the system is shut off.
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Beech D17S Staggerwing
Lancair 360
Cessna 120
A&P IA
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08-31-2019, 05:07 PM
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Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,070
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Many Ducati voltage regulators put out less than 14 volts. My Ducati put out
13.8 volts. A friend's Ducati puts out 13.7 volts. I now have a John Deere
voltage regulator that puts out 14.1 when the RPM is above 4000.
If your friend's 20 minute flight includes 10 minutes of warm up and taxiing and
another 5 minutes of closed throttle for landing and taxiing, then that does not
leave very much time to recharge the battery.
Usually a battery maintainer is not recommended. But there are exceptions.
__________________
Joe Gores
RV-12 Flying
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08-31-2019, 06:07 PM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,247
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Also check for anything (like a USB power plug) in the 12V power socket. The socket is wired to the battery, not the master, so if you have a USB power supply plugged in it will suck current from the battery even with the master off.
I moved mine to the switched side of the master, took all of 10 minutes while we had the top cowl off.
__________________
Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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08-31-2019, 06:12 PM
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Join Date: Dec 2018
Location: San Diego
Posts: 403
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Quote:
Originally Posted by DaleB
Also check for anything (like a USB power plug) in the 12V power socket. The socket is wired to the battery, not the master, so if you have a USB power supply plugged in it will suck current from the battery even with the master off.
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I wouldn't necessarily say that the socket *IS* wired to the battery, not the master.. But rather that it *MIGHT* be. Good suggestion though.
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RV-9A, Fallbrook Ca (L18)
Paid, Jan 2020
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08-31-2019, 06:24 PM
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Join Date: Nov 2007
Location: Mississippi
Posts: 282
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Odyssey Technical Manual, ninth Ed. 2016 (page 16)
Chart shows for deep cycle operations,...charging at 14.7 volts more than doubles the life of the battery, compared to 14.2 volts....
....wonder where 13.7 volts would lie on the graph, ....(and how far the parasitic load is draining the battery)
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Wallace & Marietta Goodloe
9A -QB
N211LV
Phase 2 has started! 
Thanksgiving time, is dues time for us
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08-31-2019, 06:43 PM
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Join Date: Nov 2007
Location: Mississippi
Posts: 282
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Odyssey TM on parasitic load
Regardless of the application, it is important to make sure your battery does not have a parasitic load; if there is a slow drain, connect the battery to a float (trickle) charger that puts out between 13.5V and 13.8V at the battery terminals. Physically disconnecting one of the battery cables is an alternate method to eliminate the drain.
__________________
Wallace & Marietta Goodloe
9A -QB
N211LV
Phase 2 has started! 
Thanksgiving time, is dues time for us
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08-31-2019, 07:00 PM
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Join Date: Apr 2014
Location: Racine, WI
Posts: 194
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Stay alive circuits
Some avionics have a stay alive circuit wired directly to the battery, or to seperate fuse block which is then wired directly to the battery. Dynon D-10 for example. Or maybe a clock.
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RV-7A
IO-360 Hartzell CSP
Purchased
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08-31-2019, 07:05 PM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,247
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Quote:
Originally Posted by SPX
I wouldn't necessarily say that the socket *IS* wired to the battery, not the master.. But rather that it *MIGHT* be. Good suggestion though.
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Ah -- yeah, I see they changed that a couple years after mine was built.
__________________
Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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