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Old 09-26-2022, 02:20 AM
Tomas J's Avatar
Tomas J Tomas J is offline
Join Date: Jan 2008
Location: Ostersund in middle of Scandinavia
Posts: 49
Default My Odyssey needs to be woken up

I have a funny phenomenon with my three year old Odyssey PC680 battery. It can't pull the engine around even though it's been on maintenance charge. But if I then put it on charge for just ten minutes, it's suddenly like a new battery. Same thing if I manually start the engine and then just let it run for 3-4 minutes.
What is happening in the battery? It can't be that it charge in that short time. It seems like it just been waked up with a failed start attempt and a very short charge.
I usually change the battery when this happens and I think I'm on my fourth battery. But it feels unnecessary to have to change the battery when it really only needs to be "awakened" to work. Is there anything I can do to make it work better?
Tomas Johansson
Flying RV-4, and Super Cub on floats and skis
in Northern Sweden in Skandinavia
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Old 09-26-2022, 09:13 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 4,029

Originally Posted by Tomas J View Post
SNIP….It can't pull the engine around even though it's been on maintenance charge.
Stop doing this. I’ve flown Odyssey PC-625 batteries for over 20 years and never used any maintenance/tender/etc. on them and the engine cranks every time. In other words you may be killing your batteries. There are “approved” battery minders and such but why use them if not needed? For hangar flying I connect a real 30amp power supply to mimic the alternator. It provides clean power to the avionics and keeps the battery from discharging.

I replace one of the two batteries every three years - so oldest battery is six years old. I do this to have confidence in batteries reserve capacity. The pulled batteries go on for a few more years in lawn tractors or the neighbors’ John Deer.


Last edited by Carl Froehlich : 09-26-2022 at 10:05 AM.
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Old 09-26-2022, 09:52 AM
MacCool's Avatar
MacCool MacCool is offline
Join Date: Aug 2020
Location: central Minnesota
Posts: 1,499

If it was me, I’d start by load testing the battery which might give info regarding a bad cell and at least give an idea of overall battery health. Then I’d get out the multimeter and check for the amount of parasitic drain. Next, check all the wiring looking for bad crimps or loose connections…jiggle wiring in the primary circuit with multimeter attached. Maybe just empirically clean and tighten all the connections. Then, I take a hard look at the maintenance charger…there is a wide variety of quality and reliability in those things.

On my RV, I run two PC680s in parallel and keep them 24/7 on an Odyssey OBC-6A charger when in the hangar, and I have some kind of Amazon regulated power supply that I use for avionics updating etc. When I bought the airplane, the owner included the float charger he’d been using. I was getting some occasional low battery issues, threw that charger away and bought the (rather expensive) Odyssey charger. Never an issue since. I use Battery Tenders for maintaining all my seasonal home rolling stock and have never been disappointed but I went all out for these airplane batteries. I believe that the thing that kills lead-acid batteries is sulfation and the thing that causes sulfation is discharge. Hooking my airplane up to a good quality float charger when I put it in the hanger is a very, very simple way to eliminate that variable.
RV-9A, 2011, bought flying
IO-320D1A (factory new), C/S
Dual Pmags
IFR equipped
AFS 5400/3500, G5, IFD440 navigator,
bunch of other stuff
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