Mauledriver(at)nc.rr.com
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 Posted: Tue Sep 06, 2011 5:58 am Post subject: Initial experience with dual Odyssey PC680s powering RV-10 |
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(my original post seems to have been blank - pardon if this is a re-post with some additional info)
Some data:
Using the HF Battery Load Tester with a 200amps load applied at the disconnected starter lead, I got 7.5 volts on one battery, 8 volts with both batteries. That is short of the 9 volts you suggested I should get,
I used a 6" 8awg lead for the ground attached to one of the starter's mounting bolts.
I saw a similar results when I went to a ground block directly on the firewall (I think this block has a 8awg line running back to the batteries in addition to it's airframe connection).
My plan is to repeat this test tomorrow after re-charging the batteries. I'll also test the battery directly. Assuming I get the same result, and the battery is good, it appears that I have some deficiency in either the ground or power circut for the starter.
I'll try to use the tester to work my way from the starter back thru the power circuit and the ground connections.
Some more data:
After charging overnight and working my way back towards the battery, I hooked up the tester to the battery side of the starter solenoid and the ground stud on the firewall. I got 8.5 volts going to 8.0 volts after 15 seconds with a 200 amp load.
Then I took the tester directly to the battery - 8.5 volts with a 200amp load (??!!). Bad Battery? I think not, so...
Yesterday, I went out an bought Schumacher charger at Walmart. I had been using another 'maintainer' type charger (I'll get the brand and specs later). With all this electrical work, I felt like I needed something with more options like fast/slow charge. I charged up some older batteries including my old 680s. One battery was clearly bad per the tester and wouldn't take a charge. The other one seemed good. And after a full charge, it tested 10 volts (at) 200amps for 15 seconds. That's more than I was getting with my 'fully charged' new battery.
I think I have some charging issues. I suspect at this point that the 'maintainer' type charger is not fully charging my 2 batteries for some reason. That combined with the fact that almost every flight is followed by much battery draining panel work followed by charging.
So, right now I'm using the new charger on the batteries in the aircraft. I suspect when finished, I'll be getting 10 volts (at)200 amps at the terminals, and close to that at the starter.
Will report later.
Bill "transitioning from building to operating mode" Watson
On 9/4/2011 5:53 PM, Robert L. Nuckolls, III wrote: [quote] At 03:28 PM 9/4/2011, you wrote:
| Quote: | --> AeroElectric-List message posted by: "Richard E. Tasker" <retasker(at)optonline.net> (retasker(at)optonline.net)
Have you measured the voltage at the starter and an adjacent ground point and compared it to the same measurement at the battery terminals, both while cranking?
Possibly you have a bad or loose connection somewhere that is contributing to your hard cranking.
Certainly worth a try (if you haven't already done this) to avoid replacing the battery and battery holder.
Dick Tasker |
Absolutely. These batteries have a DEMONSTRATED ability
to do the job for which you've installed them. You need
DATA on where energy from the batteries is being lost
before it reaches the starter motor.
Unfortunately, the current draw of a starter motor
is so wiggly, it's difficult to get meaningful measurements
on a starter while standing behind a swinging prop. Suggest
you acquire the use of a battery load tester like this
Harbor Freight product
--
Unhook the starter feed wire at the starter and put
a bolt through the lug end with a nut to get a good
grip. Clip the red test lead to the bolt (you don't
want an imperfect connection to burn your lug).
Similarly, fabricate a short piece of 4AWG with
a lug-bolt assembly on one end and a lug on the
other suitable for grounding to your engine . . .
preferably the same bolt that attaches the starter.
The voltmeter on this tester reads voltage
right at the test clips . . . so you don't need
to worry about votlage drop in the long fat-wires.
Simulate an engine cranking event while cranking
the load tester up to 200A . . . you should have
9V+
Use the same tester to load each battery until
the voltage drops to 9V. Each battery should
be capable of delivering 9V at 400 amps or more.
Bob . . . [b]
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