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  #11  
Old 05-23-2020, 05:31 AM
rjcthree's Avatar
rjcthree rjcthree is offline
 
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Default Strap and starter

Alan, if I understand your comments correctly, you added a strap without any improvement, then changed the starter and found happiness? I am using the lightweight plane power starter at the moment, so I find your experience interesting.
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  #12  
Old 05-23-2020, 08:07 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by rjcthree View Post
I clarified the orig post.

John, I donít measure resistance, but do give them a tug to check the crimp and an eyeball for corrosion, so good there.

Joe, I have parallel grounds, I am not depending on the mount to ground the engine to anything. I recognize itís a ground loop potential, I was trying to not let it float.

Carl, your comment gets to the root of my question...is grounding on a boss anywhere on the crankcase the same as to a bolt or stud used to mount the starter?

Iíve got #2ga to the starter. My ground strap engine to battery is equiv to #0, itís a fist full of nickel plated copper, so unless there is potential between the case halves, I should be in good shape?

After doing a bunch of forum search-fu, Iím leaning toward a less than awesome PC680 life cycle, more than grounding. I do see voltages fall pretty quick at first attempt of start. This battery was only ever fed by an oddyessy brand charger with a max current rating of 4A, with maybe 60 flight hours on it, but two winters. Itís not ever been drained or on a traditional charger.
If you have a lot of hours, look at the starter solenoid. They can wear internally and as they do, they can limit the current that can pass through them.

Larry
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  #13  
Old 05-23-2020, 11:01 AM
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JonJay JonJay is offline
 
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Measuring resistance via meter is really only going to catch a grossly inadequate or open circuit. You typically will have symptoms way before you see measurable resistance under no load. Slow cranking at the very least.
If you want to use a meter to check your grounding, measure voltage from engine case to battery ground. This must be done with a load applied, ie, while cranking.
Obviously, take extreme care. I am sure very few do this until they have a problem and I wouldn't recommend it as a pre-emptive practice.
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  #14  
Old 05-23-2020, 11:17 AM
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rjcthree rjcthree is offline
 
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Default Sigh...

I’m at the airport now. Three days ago I left with a fully charged battery ( having run for at least 20 minutes at 14.7 solid volts after being on the charger for a while. With just the master and the Dynon EFIS running (less than 2A) I see 12.3 volts from the battery. More damning is that it won’t charge above 13.1 volts on an approved AGM charger. Methinks the battery (PC680) is toast. It was installed October 2018, and has about 70 flight hours on it. It’s funny that I removed the previous one for time (7 years installed, through a good part of construction and 60 hours of flight) and it’s still starting my buddy’s ZTR mower. This battery was not abused. Master never left on. The only time it saw a charger until recently was when I was doing avionics work - I put the charger on during the work session. I never left the charger overnight, even though it’s an approved model to do so.

Apex? Earthx? Decision time. I like the idea of losing another ten pounds off the nose, W&B will allow it, but the BMC makes me flinch a bit.
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Last edited by rjcthree : 05-23-2020 at 12:09 PM. Reason: Clarified to address Carl’s question of abuse below.
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  #15  
Old 05-23-2020, 11:50 AM
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Carl Froehlich Carl Froehlich is offline
 
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Default

Quote:
Originally Posted by rjcthree View Post
SNIP

Carl, your comment gets to the root of my question...is grounding on a boss anywhere on the crankcase the same as to a bolt or stud used to mount the starter?
This will start a flame war, but for me the answer is no. Why go through all the pain of case grounds, big braided straps and such and wonder if that is causing startling problems or not? I especially do not like the RV-14 ďground the engine to the engine mount, not the firewallĒ instructions.

But shoot fire - what do I know other than I never had a engine cranking issue over the last couple of decades and three RVs.

For you, the first thing Iíd do is swap out the battery. If you ever abused it (e.g. left the master on) and gave it CPR with a battery charger to bring it back to life, most cases you caused damage and it needs to be replaced. You can always use it in your lawn tractor. For me I replace one battery (two PC-625s) every three years. As neither battery is more than six years old I get some confidence of reserve battery capacity at my design margin.

If you find yourself chasing your tail, swap out the starter solenoid. Odds are this is not your issue, but if you have the same issue with a new battery this would be suspect.

Side note - if you routinely use a charger I find many people end up with short battery lives. I never use a charger, but I do use a regulated 30 amp power supply to bring up the panel in the hangar when needed. I adjust the output voltage to match the alternator. Watching the supply current drop down after connecting gives me good indication of battery health as well.

Carl
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  #16  
Old 05-23-2020, 01:13 PM
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bjdecker bjdecker is offline
 
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Default Just one...

Hmm...

I've always used a single, 2AWG wire from the engine case to the firewall as shown in DWG OP-31, Zones D-7,8,9 and OP-30, Zone B-10. The only caveat was to remove the paint on the engine case where the wire attached, and burnish the firewall at the location where the wire attaches.

I ran an Odyssey PC-680 for a number of years, and recently upgraded to the EarthX ETX-680. It spins the engine exuberantly...and the 10+ lbs wasn't missed

As always, your mileage may vary.
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  #17  
Old 05-23-2020, 07:46 PM
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JonJay JonJay is offline
 
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Quote:
Originally Posted by bjdecker View Post
Hmm...

I've always used a single, 2AWG wire from the engine case to the firewall as shown in DWG OP-31, Zones D-7,8,9 and OP-30, Zone B-10. The only caveat was to remove the paint on the engine case where the wire attached, and burnish the firewall at the location where the wire attaches.

I ran an Odyssey PC-680 for a number of years, and recently upgraded to the EarthX ETX-680. It spins the engine exuberantly...and the 10+ lbs wasn't missed

As always, your mileage may vary.
I think most of us have a "per plans" set up and are swimming along just fine.
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  #18  
Old 05-23-2020, 10:18 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by JonJay View Post
I think most of us have a "per plans" set up and are swimming along just fine.
I have used a 2 gauge strap from block to firewall on both planes and have no issues. I used the engine mount on the 10. Though I took care to remove paint from the f/w mounting points of the mount and used dielectric grease. no issues here.
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  #19  
Old 05-24-2020, 08:33 AM
TS Flightlines TS Flightlines is offline
 
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What ever you do, DONT try to use a stainless braided hose as a ground strap.
Sound crazy? Yep was tried--inadvertently.

Yeah I know. nope wasnt me
Tom
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  #20  
Old 05-24-2020, 02:52 PM
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rjcthree rjcthree is offline
 
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Default Yikes!

Given the right - and not so implausible - situation, that could be a real mess!
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