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Odyessey PC680 Battery Rejuvenation

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I thought I might pass this tip along if anyone else might be chasing similar issues.

Background: I bought a PC680 in Sept 2012 from BatteryMart online for my plane. I also purchaced the recommended Ultimizer Charger from Odyssey as well. I don't have a alternator so I alway plug the plane in after my flights. After about a year half the battery started failing to pull the prop through the compression stroke. It always had troubles but once it got through the first blade it seemed to spin it just fine. I had some old electrical parts (starter contactor and master switch contactor) along with my weight saving choice of 6 AWG wire. When I started having problems I started thinking my choice of wire size was the problem so I replaced the 6 AWG with 2 AWG and also ran a 2 AWG ground from the engine back to the neg term on the battery. I thought that was working but I think it was the Placebo effect. I then thought it was the starter contactor. Relpaced that and again thought it helped some but only superficial. I then replaced the master switch contactor I thought it helped but after several weeks I realized it still wasn't the smoking gun I thought. Finally I thought it could be a bad starter so I started in on the troubleshooting step off Skytec Website which was to measure the loaded voltage across the battery while cranking. Turns out I was down in the mid to low 7.5 - 6.5 volts the more the blades when by. That suggested the battery.

I didn't think it was the battery as I had pretty good luck with getting 6+ years out of another PC680 used in a similar fashion. So I started in on looking for another to buy. When I came across numerous out of stock places I started searching to see if maybe there was a recall. I have been charging it just like the company told me too using their charger.

In my google searching I came across this tread: http://www.vansairforce.com/community/showthread.php?t=108220 It turns out many others in the RV community have had similar problems as I (cranks good but after a 1.5 to 2 years it can't swing a blade)

Solution: The above link talks about this but the bottom line it seems that in our usage (no alternator no normal loads just starting loads) The battery never depletes enough for the charger to go into an absorption phase what typically happens it the charger just goes into a maintain phase at 13.5 volts. This causes the battery to sulphate which takes hard working side down. The symptoms are good Open Circuit Voltage but no ass behind it for cranking a starter. To desulphate my battery I used a MR16 12Volt 50Watt halogen bulb I bought from Lowes for $5.50 I hooked it to my battery and drew the battery down to 10.5 OCV (this took my battery about 2 hours or so). I then connected my Odyssey Ultimizer charger and charged it back up (4 hours). Each time the draw down took a little bit longer (not much) but after 2 cycles I put it in my plane today. The first blade was tough but it when I bumped it again it never had a problem after that swinging the blades 4 starts later still going strong. I measured loaded Voltage of the battery during starting and it was up in the 10.5 volt range so that was way better not as good as the 11 volts that Skytec asks for. So I took it home for some more cycling tonight we'll see how it goes.
 
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