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  #11  
Old 08-27-2016, 09:01 PM
rv7charlie rv7charlie is offline
 
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The AH rating (which is basically the total energy in the battery; not power) is at a discharge rate that runs the battery down over 20 hours. Higher discharge rates will result in being able to extract less total energy from the battery. Confusing, but that's the way it is. Look at the PC680 discharge curves, in the document linked earlier by another poster. 1st link I found that describes relationships of the various ratings:

https://www.batterystuff.com/kb/arti...-basics.html#4

Charlie
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  #12  
Old 08-27-2016, 11:22 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by PIN 37 View Post
. I wonder why the label on the top of the battery says 16ah
Because its an industry standard and used for comparative purposes. Generally speaking, a 16 ah battery will deliver more energy in a similar current draw than a 14 ah battery. It's like listing a car's MPG. MPG is infinitely variable, but by comparing all cars against a common standard testing methodology, you can draw valuable comparison across different cars.

As you have learned, its not really meant to help you plan your available energy.

Larry
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  #13  
Old 02-13-2018, 03:05 PM
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Champ Champ is offline
 
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Default Time to Replace my PC680?

My PC680 let me down twice in the last two days. Engine usually starts fine with a couple blades. Now if it dosen't start after a couple blades the battery seems to give up. I charge it and then I get a to blade start again.

Info:
RV-8 with dual PMags, CS, rear mounted battery.
Skytec 149-NL starter.
Vans supplied starter solenoid.
Battery is 14 yr old, was used during construction and run down a least a half dozen times. has been good the last year flying.
Odyssey 12V 6a charger. Never use for trickle charging.
Voltage on D10 still shows 11.9 to 12v after start failure.
Local auto parts store load test: CCA 193a (170 rated). Voltage under load drops to 10.5V.

I have read thru a bunch of posts and will do more tonight. Just wondered if anyone can say if I need to replace the battery? I am on my way to ACS Canada neighbourhood tomorrow so it would be a good time to pick one up. Annual is due end of Feb. 70 Hr Tach Time so far. Please forgive me if the answer has already been posted.
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Bellanca Champ 7ACA since 1986, restored 1990.
RV-8 IO375, Hartzell CS, dual PMags.
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  #14  
Old 02-13-2018, 03:47 PM
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Mike S Mike S is online now
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Quote:
Originally Posted by Champ View Post
My PC680 let me down twice in the last two days.

Battery is 14 yr old, was used during construction and run down a least a half dozen times.
Methinks you should count your blessings---------14 years might be a record.
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Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

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  #15  
Old 02-13-2018, 04:11 PM
rv7charlie rv7charlie is offline
 
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I'd have to agree with Mike. But poor connections anywhere in the start circuit can lead to some seemingly inconsistent symptoms. You don't want to have the same problems after battery replacement.

Measure voltage *on the battery posts* (not the terminal ends, screws, etc) while it's failing to start the engine. If the voltage there is anything above the 8.5-9 volt range, you probably have a high resistance issue somewhere in the system. Even if the voltage is dropping lower than that, you could still have a high resistance issue that's limiting the charging system's ability to get adequate voltage/current into the battery. If it's not getting fully charged while flying, one start attempt might be all you get before capacity drops too low to spin the starter.

But you still should replace that battery....

Charlie
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  #16  
Old 02-13-2018, 05:05 PM
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Sam Buchanan Sam Buchanan is offline
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Odyssey ought to pay you for a testimonial......

Wow....14 years.....
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  #17  
Old 02-13-2018, 07:15 PM
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Champ Champ is offline
 
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Thanks guys. I guess the PC680 doesnít owe me much so Iíll replace it - lawn tractor needs a new battery anyway. Iíll also go thru the whole system at annual and make sure nothing else is causing a problem.
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  #18  
Old 02-13-2018, 08:58 PM
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airguy airguy is offline
 
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14 years - yeah, you made it about 9 years longer than you have any right to expect.
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  #19  
Old 02-13-2018, 09:32 PM
gasman gasman is offline
 
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Aero Electric Connection has this about checking battery condition....... http://www.aeroelectric.com/articles/battest.pdf
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  #20  
Old 02-13-2018, 09:36 PM
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RV7A Flyer RV7A Flyer is offline
 
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Quote:
Originally Posted by airguy View Post
14 years - yeah, you made it about 9 years longer than you have any right to expect.
And been discharged fully and recharged a few times? Wow!

I just replace mine after about 2.5-3 years when I notice a bit of sluggishness on starts. It's one of the cheapest things on the plane to replace at, what, a hundred bucks? Not worth messing with.
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