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  #1  
Old 06-01-2018, 03:36 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,149
Default How to Start Rotax 912 if Odyssey Battery Fails…

I don’t want to get stranded with a dead battery caused by either the battery itself or the voltage regulator going on the fritz. The Rotax 912 uses capacitance discharge (CD) ignitions vs. magnetos as used on most other aircraft engines. The consequence is that you cannot hand prop the engine if the electric starter doesn’t do its job. The CD ignitions need ~ 500 rpm to self-generate enough voltage to create spark. You’re not going to hand prop (read: backdrive) a 2.4:1 gearbox – ain’t going to happen.

So, I’ve been thinking about what to do if the Odyssey battery ever lets me down in a remote location. No problem if battery goes dead in flight – engine keeps running. But can’t restart if you shut engine off.

For total cost of $70.40 I bought the following items on eBay to put a starter package together:
  • LED 82800mAh Portable Car Jump Starter Pack Booster Charger Battery Power Bank J
  • 8 Gauge Silicone Wire 10 feet (2x5') 8 AWG Silicone Wire Flexible Silicone Wire
  • Jumper Cable EC5 Connector Alligator Clamp Booster Battery for Car Jump Starters

The RV-12 Odyssey PC680 is rated 12 Volt / 16 Ah / 170 CCA. The 82800mAh Lithium Starter Pack with advertised 200A Starting Current is able to start up to 5L gas or 2L diesel engine. The 912ULS is 1.35L so the Starter pack should crank it just fine. I used 8 AWG silicone wire to allow the battery to sit on ground and still connect to the Odyssey airplane battery. Then I added a second set of clamps just in case a Good Samaritan would come along and provide a 12-volt power source.

When completed, I tested the starter pack by jumping a totally dead 26 HP garden tractor. Cranked fast and fired right up...


82800mAh Portable Car Jump Starter Pack


Battery Clamps w/ Fuse


Ring Terminal for 8AWG


Remove Plastic Insulation


Crimp Wire and Insert Under Copper Jaw


Finished Battery Clamp with 8AWG Extension Wire


Completed Assembly


82800mAh Lithium Battery


99% Remaining After Cranking/Starting Dead 26HP Tractor


Ready for RV-12 Baggage Compartment
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Jim Stricker
Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 406

LSRM-A Certificate 2016
Special Thanks to EJ Trucks

Last edited by Piper J3 : 06-01-2018 at 03:39 PM.
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  #2  
Old 06-01-2018, 03:42 PM
HarryL HarryL is offline
 
Join Date: Jun 2015
Location: Woking UK
Posts: 45
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This guy seems to think you can hand-start a Rotax:

https://m.youtube.com/watch?v=-JUBrHYsh4E
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  #3  
Old 06-01-2018, 04:10 PM
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Mel Mel is offline
 
Join Date: Mar 2005
Location: Dallas area
Posts: 10,144
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Quote:
Originally Posted by HarryL View Post
This guy seems to think you can hand-start a Rotax:
https://m.youtube.com/watch?v=-JUBrHYsh4E
I see a couple problems with this guy's procedure.
#1, You should never lift that leg. If your other foot should slip, the momentum of that leg will pull your body through the prop arc.
#2, When propping a carbureted engine, the fuel should be turned off. There will be plenty of fuel in the carburetor bowl to keep the engine running until you can turn the fuel on.
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Mel Asberry..DAR since last century
A&P/EAA Tech Counselor/Flight Advisor/Nat'l Test Pilot School
Specializing in Amateur-Built and Light-Sport Aircraft
<rvmel(at)icloud.com>
North Texas (8TA5)
RV-6 Flying since 1993, 172hp O-320, 3-Blade Catto (since 2003)
Legend Cub purchased 12/2017
FRIEND of the RV-1
Eagle's Nest Mentor
Recipient of Wright Brothers "Master Pilot" Award
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  #4  
Old 06-01-2018, 04:37 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
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Quote:
Originally Posted by HarryL View Post
This guy seems to think you can hand-start a Rotax
Yes, he is starting a 80 hp 912 UL which has compression ratio of 9.1:1. Might also have 2.27:1 gearbox.

912ULS is 100 hp and compression ratio of 10.8:1 with 2.43:1 gearbox.

Give it a shot and let me know how it works...
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Jim Stricker
Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 406

LSRM-A Certificate 2016
Special Thanks to EJ Trucks
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  #5  
Old 06-01-2018, 11:33 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,357
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I’ve been thinking about a similar rig, but I’m trying to figure out he best location for a positive post so I can jump it from the cockpit.
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  #6  
Old 06-02-2018, 07:31 AM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 4,871
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Maybe it's just me but no way I'm carrying a rather large cheap LI battery in the airplane.
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Walt Aronow, Dallas, TX (52F) RV7A, IO360, C/S, 1500+hrs

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #7  
Old 06-02-2018, 08:27 AM
AirHound AirHound is offline
 
Join Date: Oct 2006
Location: OFallon IL now, everywhere before
Posts: 243
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I’ve been lucky so far and have not been stuck out of town yet! Thank you for sharing a field expedient remedy for when the battery gives out. All lessons learned and fixes are truly valued by most of us,
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  #8  
Old 06-02-2018, 09:09 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
Posts: 1,149
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Quote:
Originally Posted by Walt View Post
Maybe it's just me but no way I'm carrying a rather large cheap LI battery in the airplane.
I understand your concern. Airlines can no longer accept bulk shipment of Lithium batteries in cargo hold. Likelihood of a major incident is magnified with thousands of tightly packed batteries. Individual Lithium batteries are allowed in the cabin and in carryon luggage.

Actually the LiPo (Lithium Polymer) here is same used for large scale radio control airplanes. Chemistry and battery construction is mature. Battery will only be charged perhaps twice a year to top it off. Self-discharge for LiPo is very slow reaching 70% in 3-4 months. Chemistry is similar as EarthX, however, unlike charge/discharge cycling of main battery in aircraft this battery will sit at full charge unless needed. LiPo's are designed for very heavy discharge - sometimes as much as 50-60 times rated capacity. Charging is done at low current and very controlled. This will be accomplished on a bench and not in the airplane.

These Portable Car Jump Starter Packs have been thrown around by tow truck drivers, highway patrol, and AAA road assist for years.
__________________
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Jim Stricker
Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 406

LSRM-A Certificate 2016
Special Thanks to EJ Trucks
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  #9  
Old 06-02-2018, 03:14 PM
jones jones is offline
 
Join Date: Apr 2015
Location: Portage la Prairie, Manitoba, Canada
Posts: 9
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I carry a similar battery pack in my RV6 when away from home. They advertise the compact battery pacs will start a healthy discharged battery, but not one that has issues like a dead cell or internal short. I had a one year old PC680 that crapped out on me and the lithium ion pac overheated trying to start the plane. It has however started many airport loaner cars so worth having and may someday hide the embarrassment of leaving the master on.
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  #10  
Old 06-02-2018, 04:10 PM
moosepileit moosepileit is offline
 
Join Date: Dec 2010
Location: Floyds Knobs, IN
Posts: 300
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Assuming the cells inside are cylinders like common 18650s, the main hazard is crushing them verically in shipping type handling. The negative contact is everything but the top and the insulator between the top and the balance of the shell case.

Cells can be dumb and managed by the device like a laptip battery or each cell can have a control chip.

Recharge it outside the plane away from easy igniteables just in case.

Easy to google if interested.

My concern in upping cable size is though more efficient, the smaller cable may be done on purpose to limit current. I would make sure the unit does not overheat using the larger cables. If 10 feet of 8 gauge acts like the thinner, shorter OEM cable, nice flexibility added.
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Last edited by moosepileit : 06-02-2018 at 04:14 PM.
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