Mauledriver(at)nc.rr.com
Guest
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 Posted: Tue Dec 25, 2012 6:43 am Post subject: Problem with the Harbor Freight Carbon Pile battery teste |
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All is well now. Not exactly sure what my problem was but I suspect
that 1) at some point I had completely unscrewed the knob and 2) one of
the carbon disk got out of position and got jammed. But I can't be
sure. For those interested, I made some additional notes among those
already made at the bottom of this note.
So I proceeded on with the task I had in mind.
I run a Z-14 with dual PC680s. It seemed that one of my batteries is
below par. In cold weather 1 of my 3 GRT HX screens will not boot up
before engine start and the alternator comes on line. The plan has
always been to keep the best battery on the starter circuit so I figured
it may be time to get a new one and swap the starter battery to the GRT
circuit.
In addition, I get a solid warning light from the LRC3 regulator on that
circuit. I'm not sure that is a battery problem at all but hoping it
may clear up too.
Even though I've only been flying the RV10 for 1.5 years, I've been
playing with PC680s for 6 or 7 years now. With the latest purchase, I
now have 5 batteries (!!). I've hurt 1 or 2 of them by using them
heavily and recharging them exclusively with a trickle charger before I
learned better. By the time the plane was flying, they wouldn't charge
up to full capacity.
But the task at hand was to test the performance of all 5 batteries to
confirm selection of the best two. Here is the test and the results.
The battery numbers reflect the sequence of purchase. (Temp = 62F)
Initial Voltage Voltage 30min after load
Battery 24hrs after charge 120amps for 15 sec
Batt1 12.71 12.56
Batt2 13.10 13.02
Batt3 13.00 12.84
Batt4 12.99 12.86
Batt5 13.15 13.08
I had been using Batts 2&3. Now I will be moving 3 out of the plane,
putting 2 in it's place and using Batt5 on the starter circuit.
Interestingly, I would have come to same conclusions using the first
column of numbers (without load testing) that I would have based on the
load testing.
Battery 4 is the 'aviation version' of the PC680. Right out of the box,
It never performed as well as the standard PC680s, even though there is
no apparent external difference other than mention of "PMA" and it's all
orange color. In the end, it's never been in the plane.
Thanks Bob and everyone!
Bill Watson
On 12/24/2012 10:09 AM, Robert L. Nuckolls, III wrote:
| Quote: |
<nuckolls.bob(at)aeroelectric.com>
At 06:25 PM 12/23/2012, you wrote:
>
> <Mauledriver(at)nc.rr.com>
>
> I've used this unit a few times without a problem. Then it suddenly
> stopped working. I couldn't seem to apply a load though the exact
> symptoms I don't quite remember.
is it failing to APPLY a load or failing to
INDICATE what that load is? Does the voltmeter
behave as expected? Can you depress the voltmeter
reading and get it to smell hot by cranking the
load knob down?
Voltmeter was working fine. Cranking the knob resulted in no change, no
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smell. I think the know was jammed by a disk being out of position.
| Quote: |
> Today, I pulled the unit apart and found
> 1) a fuse on a small circuit board which had not blown (not easily
> replaceable either)
> 2) the carbon disks that presumably supplies the variable resistance
> seem to be stacked between two steel plates but the carbon disks
> appeared to be loose or askew.
Those are classically not tightly captive.
A carbon pile rheostat is a PRESSURE device
wherein once the slack is taken out of the
stack height by the first turn of load knob
rotation, the pile doesn't physically move
much after that. It's behavior is a response
to pressure not motion.
That makes sense.
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| Quote: |
> If I screw the big knob down and shake things a bit, I can get the
> stack of carbon plates lined up and it seems that increased
> resistance results from placing more pressure on the stack.
>
> Does that sound right?
No, the resistance between the fat wires to hte
battery should drop markedly. To load a battery
to 500A at 8 volts requires a resistance on
the order of 16 MILLIOHMS.
My mistake here - I was referring to physical resistance on the knob,
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not electrical resistance
| Quote: |
> Furthermore, it would seem for consistent operation, it would be best
> to lie the unit on its back to insure the carbon plates remain flat.
Doesn't matter.
> Tomorrow I will attempt to use it again to see if it works now that
> the plates are back in position.
>
> Any insight or tips welcome. I will report further tomorrow.
I've got two of these critters and they've
performed as expected for 5+ years. Sounds
like something may be unhooked. Tell us what
behaviors you see on the voltmeter while trying
to get the load increased.
Bob . . .
-----
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