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What's are my batteries trying to tell me?

E. D. Eliot

Well Known Member
I have two PC680 batteries - one that a kind gentleman gave me as he retired it i n serviceable shape from his RV-7 after three years and the other is one point five years old - came from Van's with my finish kit. I've been charging them with the Odyssey recommended charger once a month and both start out before charging about 12.95 and end up after 20 or so hours on the charger at about 13.04.

Question is - what are they trying to tell me? The older one takes a few hours to show fully charged on the charger and the newer one from Van's shows as fully charged on the charger in about one hour.

Second question is should I continue to charge these batteries after they register 'fully charged' on the Odyssey charger or ? Thanks for your knowledgeable replies.
 
What they are trying to tell you is "Get these chargers away from us!"

PC680's will hold most of their charge for many months. Frequent charging can kill an AGM battery quicker than about anything else. Unless they are subject to a parasitic drain, charge them a couple of times a year.
 
What they are trying to tell you is "Get these chargers away from us!"

PC680's will hold most of their charge for many months. Frequent charging can kill an AGM battery quicker than about anything else. Unless they are subject to a parasitic drain, charge them a couple of times a year.

To build on Sam's comment, I'll try to be Captain Obvious. :D

The PC680 is NOT a flooded lead-acid battery. It should NOT be treated like a flooded lead-acid battery!

If you installed a turbine engine in your RV, would you treat it like a Lycoming piston-banger? NO. You would learn how this new-fangled turbine should be treated and you would apply that new knowledge to your new engine.

Take a few minutes to brush up on your new-fangled battery technology. It's not like your lawn tractor or car battery. It needs to be treated differently because it is totally different technology.

As far as storage goes, recharging a PC680 twice a year is plenty, as Sam mentioned. I've gone over a year. The self-discharge rate of AGM batteries is so much less than flooded lead-acid batteries that the old "charge it once a month" advice from your granddad is completely wrong for these new batteries.
 
I was just reading the manual for my Odyssey battery. Some good points from it:

You can leave it on a trickle charger for extended periods. The trickle charge voltage measured at the battery terminals must be between 13.5V and 13.8V

They don't need to be charged during storage unless the voltage drops below 12V. As others have said, they have low self discharge, so it's unlikely you'll need to charge them much at all.
 
Uh, I don't think that the docs say you can leave them on a 'trickle charger'. That's an almost guaranteed kill shot.

edit: I should expand on that. Many, if not most 'trickle chargers' are just very low current transformers followed by a diode block, with no filtering or regulation. Because of their low current ability & the varying load of the battery, they'll start out at substantially less than 12V on a discharged battery, and if left unattended, end up applying 16-18V to the fully charged battery.

IIRC (too lazy to pull up the doc at the moment), the docs *do* say you can leave them on Odyssey's own *smart charger*, a completely different animal.

But the docs also say that self-discharge is minimal, when stored in room temp conditions, for over a year. So why gamble?
 
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Agree with the "charge rarely" sentiments expressed here. Another interesting characteristic of the PC680 is they like the cold; the colder the temps, the happier they stay.
 
Different result with a battery charger

I have a different result than what is posted here. I have two PC680 batteries in an RV10. When I did fly regularly (several times a month) the batteries worked ok, but didn't spin the starter very well, and they wouldn't last more than 2 or 3 years. Then I quit flying, but ran the engine periodically (several times a month) to keep everything working well and to charge the batteries. I noticed my batteries would not last more than a year or 2 at most. When I replaced the batteries I bought 2 Yuasa automatic battery charger & maintainers and keep them attached to the batteries and powered whenever I'm not running the plane. Note that these are not continuous trickle chargers, but they apply a boost charge up to 14.7v and then a lower voltage maintenance charge when needed to keep the battery at the proper charge. The battery technical manual states that the battery voltage must be kept above 12.0 volts (35% state of charge) or they should be charged immediately to prevent permanent damage. It states that the best charger to use brings the battery up to 14.7v and then switches to a float voltage of 13.6v.
My starter now spins over faster than ever and these batteries have lasted 6 years. So using a charger continuously doesn't automatically kill batteries - it depends on the charger that is being used. What kills these batteries is letting them sit and allowing the voltage to drop too low, then they deteriorate and are never as good as they were. Also, the alternator voltage must be high enough to fully charge the batteries or they never reach full charge. The batteries can also be ruined by overcharging them with a charger that is not designed as a maintainer.
 
Another point is the self-discharge rate of the battery is not the only consideration - when installed in the plane and not used there are some equipment that require keep-alive power from the battery which will pull the battery down over time.
 
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