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Odyssey PC680 Solution

David Bell

Well Known Member
The slow cranking PC680.. many have been there. I reached out to the Marketing Director of Odyssey explaining the frustrations I have been through with their battery. He had a new one shipped to my home and gave shipping instructions to send my new weak cranking battery to their lab. Results revealed no problem with the battery. All circuitry, starter. etc in the aircraft checked out good.
On cross country flights, cranking amps work great, it’s the short “gotta run the plane” flights that the cranking amps aren’t there. Personally, I think it’s a heat issue causing the battery to not perform.
Well, I figured if I make a pigtail and route it into the cockpit, use the Noco GB40 Boost Plus, I won’t get left out with a weak crank. It works beautifully! 100$ we’ll spent! Obviously I created my own connectors for a clean installation.
 

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Neat solution.
Looking at the label on the boost unit - 12v 1000 amp - I was wondering if the wire run from the connector to the battery (about 3 ft) gets warm during use?
 
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So you're using this device for the start only?

Not to bash, but are you sure you're not masking the real problem with the booster pack? The battery manufacturer claims no issue with your old battery, and since others can crank with one PC680 ... Lots of discussion around about weak crank leading to a bad ground or other connection.

Good luck!
 
‘Not to bash’… many post around the PC680, Earthx solved there problems. As said, mine works fine in cross country flights, obviously not a ground issue.
 
I use two PC-680s in parallel that I can use for starting if I need it for that but I’ve never had any cranking issues. I will usually start with both batteries on but take #2 offline after engine start and use it as an avionics backup. I'll put it back in the circuit if I ever have an alternator failure (never happened yet). In the meantime, both batteries are on an Odyssey OB6A float charger 24/7/365 while in my hangar.
 
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The slow cranking PC680.. many have been there. I reached out to the Marketing Director of Odyssey explaining the frustrations I have been through with their battery. He had a new one shipped to my home and gave shipping instructions to send my new weak cranking battery to their lab. Results revealed no problem with the battery. All circuitry, starter. etc in the aircraft checked out good.
On cross country flights, cranking amps work great, it’s the short “gotta run the plane” flights that the cranking amps aren’t there. Personally, I think it’s a heat issue causing the battery to not perform.
Well, I figured if I make a pigtail and route it into the cockpit, use the Noco GB40 Boost Plus, I won’t get left out with a weak crank. It works beautifully! 100$ we’ll spent! Obviously I created my own connectors for a clean installation.

When you are starting you RV, how does the battery know if it is going to be a local flight or a cross country flight??

There are thousands of RV's using the PC680 with no problem. You do have an issue with your starting system, and it will let you down some day if you don't address it now in your hangar, instead of at a tie down 1000 miles from home.
 
I used PC680 on several aircraft fitted with AEIO-580 and never had a slow cranking issue. I used the very same battery on both RV-8s I owned and never got an issue.
If you have slow cranking experience prior and after swapping your battery, you may have an issue with your electrical system. While the booster helps, it is not solving the issue you may have.

My $0.02
 
Determine Root Cause

David,

Can you post some pictures of your starter, the wiring at the starter, the wiring from/to the engine crankcase, the wiring at the master relay, starter relay (CH 24021 or equivalent).

Also, can you provide voltage measurements that you are seeing when the master is OFF, master is ON, starter is energized?

As others have indicated, the battery doesn't "know" if it's on a short hop around the pattern or a long x-country flight. A battery provides electrical energy storage and potential into a circuit -- motors (inductive), lightbulbs (resistive), etc.

A slow cranking engine is typically caused by a low voltage potential seen at the starter motor -- this can be caused by losses in either the supply (+) or the return (-) legs of the circuit. Things we have all seen -- mis-sized/mis-matched wires in the high current circuits (e.g. bad things -- 6ga wire instead of 2ga), faulty windings in the starter motor, faulty contacts in some/all of the relays in the circuit ( master, starter relay, starter solenoid. Very common - I just replaced a friends starter relay), weak/shoddy terminations on the "BFW"s (big-fat-wires).

I suspect your jump pack works so well is because of the higher voltage it provides -vs- the PC680 ( 13.3Vdc vs ~12 ), the additional voltage overcomes loses seen in the system.

Cheers!

B
 
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Do this

I couldn’t find my text version of this so follow the steps in this link;

https://skytec.aero/aircraft-starter-performance-issues/

Most likely, something is restricting the current flow. Less likely I’d cable gage since it works well sometimes. Even odds for bad connection versus starter contactor going south. Voltage measurements are an easy way to get to the bottom of it. Best of luck.
 
This is what caused my starter problem in my 7A. The plastic portion cracked allowing the inner portion to malfunction.
 

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6 RV's, 2000 hours and only two cranking issues

over the last 20 years of flying 6 RVs and almost 2000 hours, I have only experienced cranking issues two times. the first was poor crimping of the terminal ends, my first build, and was easily solved with soldering each terminal end to wire on all builds. the second was a weak battery that severely struggled in 35 deg temps, which required battery replacement to fix the issue.
how does it go, treat the cause not the symptom.
good luck
 
But at least the cables were tight enough....
Cracked sol.jpg

The first nut is installed at the factory. It "clocks" the contact foot. Very important that is is never rotated from that spot.

The second nut is used to secure cable. And in doing so, installer must keep a wrench on the first nut and not let move during tightening of the second nut.

De-Ox should be used on all of your big contact terminals...alternator, master sol, starter sol, starter, power center terminal, all big grounds... batt, batt to firewall, firewall to motor case (two straps, two different locations).

De-Ox seals the connection from oxygen and moisture. I crimp, solder and heat shrink every connection 20ga and bigger for the same reason..... I am not doing it for a living, so I have the time.
 
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When you are starting you RV, how does the battery know if it is going to be a local flight or a cross country flight??

My take is this is a second start issue, i.e. after a short or a long flight. If that's the case, I'd look at charging issues as well. Although a good battery should be able to handle multiple starts without recharging.
 
My take is this is a second start issue, i.e. after a short or a long flight. If that's the case, I'd look at charging issues as well. Although a good battery should be able to handle multiple starts without recharging.

My sense was that this is a first start of the day issue. I wonder if the OP has some sort of parasitic drain that is discharging his battery in the days/weeks between flights?
 
I recently fixed a weak starting issue that developed slowly into being unable to reliably spin past compression. I suspected battery, but battery checked out. Found a loose crimp on the wire from starter contactor to starter. It was not obvious, just a small amount of "wiggle", but I was able to pull the terminal off with pliers.
 
My sense was that this is a first start of the day issue. I wonder if the OP has some sort of parasitic drain that is discharging his battery in the days/weeks between flights?

The only electric load that should not go through the master solenoid would be electronic ignition. But you never know what the builder did till you check it out.

Your theory is easy to confirm.
 
Unless I missed it, I did not see what starter you have. If the skytech solenoid type, the contacts in the solenoid could be the problem, or starter contactor, or power/ground.
 
Ok.. have a magnaflite starter which was serviced by an alternator/starter company 100 hours ago. He put four new brushes, two were shot, was only getting half the starter capacity. It worked perfectly for about 30 hours, then the battery replacement started. Replaced solenoids, both on firewall per vans specs.
Inspected cables/connectors, which are vans specs. Measure 13 volts at the starter/cranking.
Plane Power Alternator puts out 14.4 volts while running, amps start out at 10 and settle around 6, turn everything on, amps rise to 20 for a while.
Pulled the starter again, had service company check it again, all good.
 
Ok.. have a magnaflite starter which was serviced by an alternator/starter company 100 hours ago. He put four new brushes, two were shot, was only getting half the starter capacity. It worked perfectly for about 30 hours, then the battery replacement started. Replaced solenoids, both on firewall per vans specs.
Inspected cables/connectors, which are vans specs. Measure 13 volts at the starter/cranking.
Plane Power Alternator puts out 14.4 volts while running, amps start out at 10 and settle around 6, turn everything on, amps rise to 20 for a while.
Pulled the starter again, had service company check it again, all good.

Are the brushes getting stuck and not feeding out as they wear?
 
I questioned the alternator/starter shop brush replacement in my mind since the second time I direct jumped the starter with a a 14 volt charged PC680 I experienced the same slow crank over the first compression stroke. I pulled the starter, opened it up and found one braided brush tails rubbing on the armature.
I guess the shop failed to perform a perfect installation.
https://vansairforce.net/community/attachment.php?attachmentid=31316&stc=1&d=1663793435
 

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Kinda hard to be sure, but it looks like the brush wiring may have gotten pretty hot at some time. Silver area could be solder that has let go of its original bond.

Zoom in on the tab where the brush leads attach.

If so, this could surely cause high resistance.
 
Done with Odyssey

Well my solution of a jump worked a while.. continued to replace Odyssey PC680 until enough is enough! Odyssey can’t take heat… I’m done with them! EarthX ETX680 is a drop in for Vans battery box.. no mods needed. Check them out!
 
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