creightonious
Joined: 10 Mar 2007
Posts: 40
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 Posted: Tue Jul 29, 2014 9:47 am Post subject: NiCd batteries that |
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When I flew PT-6 powered planes in the '80s they had NiCads. When executing a battery start we watched the generator current like a hawk and when it tapered down we could start the other engine. This was because deeply cycling the battery could cause a thermal runaway-the battery could melt-right through the bottom of the aircraft. This was taken so seriously that nothing essential was installed or routed under the battery.
Being NiCads they were also subject to charge memory.
At the 100hr check they were removed and each cell was completely discharged in a water bath-nothing could runaway in a heat sink that large.
We monitored battery temps in flight. Maintenance took higher than normal temps very seriously.
It was worth all this because you could get a lot of current out and back in very quickly, but we used a cart to start whenever possible.
Sent from my Galaxy S®III
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From: AeroElectric-List Digest Server
Date:07/29/2014 02:59 (GMT-05:00)
To: AeroElectric-List Digest List
Subject: AeroElectric-List Digest: 18 Msgs - 07/28/14
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Total Messages Posted Mon 07/28/14: 18
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Today's Message Index:
----------------------
1. 02:40 AM - Re: Schematic symbol (mmayfield)
2. 08:12 AM - Re: Schematic symbol (Eric M. Jones)
3. 08:24 AM - tachometer question (Sacha)
4. 08:39 AM - Re: tachometer question (Dj Merrill)
5. 08:57 AM - Re: Lithium Battery Experience - Sept. Kitplanes Article (Robert L. Nuckolls, III)
6. 09:21 AM - Re: tachometer question (David Lloyd)
7. 09:37 AM - Wiring a 2 dash 7 Two pole Switch for my flaps (AZFlyer)
8. 10:33 AM - Re: tachometer question (rayj)
9. 10:44 AM - Re: GNS430 Microphone/Sidetone Problem (Jared Yates)
10. 12:24 PM - Is Bob at Oshkosh? (David Saylor)
11. 01:06 PM - Re: Wiring a 2 dash 7 Two pole Switch for my flaps (Robert L. Nuckolls, III)
12. 01:06 PM - Re: Is Bob at Oshkosh? (Robert L. Nuckolls, III)
13. 01:07 PM - Re: speedometer, not tachometer question (Sacha)
14. 01:23 PM - Re: GNS430 Microphone/Sidetone Problem (Sacha)
15. 02:30 PM - Re: speedometer, not tachometer question (David Lloyd)
16. 06:40 PM - Re: LiFePo Battery (eschlanser)
17. 08:52 PM - Re: speedometer, not tachometer question (Sacha)
18. 09:07 PM - Ni-Cad? (Robert L. Nuckolls, III)
________________________________ Message 1 _____________________________________
Time: 02:40:03 AM PST US
Subject: AeroElectric-List: Re: Schematic symbol
From: "mmayfield" <mmayfield(at)ozemail.com.au>
Ah thanks Mike. I could've sworn I looked at every schematic in the AEC library
but must've missed it.
Yes Bob, that's the exact reason I want a different symbol for it. I have mainly
conventional breakers however I also have 2 switch breakers which power a couple
of low-cycle non flight-critical system circuits. I want to make sure the
circuit diagram accurately represents the system components for the benefit of
anyone who may happen to be working on it other than myself.
--------
Mike
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=427429#427429
________________________________ Message 2 _____________________________________
Time: 08:12:55 AM PST US
Subject: AeroElectric-List: Re: Schematic symbol
From: "Eric M. Jones" <emjones(at)charter.net>
There really are standards for this sort of thing; many many standards. Ugh...
See: http://symbols.radicasoftware.com/category/Circuit-Breakers.html
But you'd do almost as good drawing a little box with a label in it.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=427437#427437
________________________________ Message 3 _____________________________________
Time: 08:24:05 AM PST US
From: "Sacha" <uuccio(at)gmail.com>
Subject: AeroElectric-List: tachometer question
This is a non-aviation question but I hope relevant to this lists' interest.
The needle of my pickup truck's tachometer has started to vibrate
significantly more than it used to. Whereas it used to be only a few km/h,
now it goes from 50km/h to 60km/h and back incessantly with a period of
about 1 second. It seems excessive and I was wondering if it's the sign of
something wrong. Where would I start looking?
________________________________ Message 4 _____________________________________
Time: 08:39:04 AM PST US
Subject: Re: AeroElectric-List: tachometer question
From: Dj Merrill <deej(at)deej.net>
On 07/28/2014 11:22 AM, Sacha wrote:
| Quote: | Whereas it used to be only a few km/h,
now it goes from 50km/h to 60km/h and back incessantly with a period of
about 1 second. It seems excessive and I was wondering if it's the sign of
something wrong. Where would I start looking?
|
My Audi's speedometer does something similar. My guess is that it is
either the servo motor that controls the needle (common in the TT), or
the speed sensor on the transmission.
Might be something similar with your tach.
-Dj
--
Dj Merrill - N1JOV - VP EAA Chapter 87
Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Glastar Flyer N866RH - http://deej.net/glastar/
________________________________ Message 5 _____________________________________
Time: 08:57:03 AM PST US
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
Subject: Re: AeroElectric-List: Lithium Battery Experience - Sept. Kitplanes
Article
At 05:00 PM 7/27/2014, you wrote:
Bob requested in his recent article that those experimenting with
Lithium batteries relate their experiences. I built a Zenith STOL
CH750 with a Jabiru 3300 engine - a day/VFR, non-electrically
dependent aircraft - perfect for experimentation!
Thank you for taking the time to share . . .
I purchased a Ballistic 12-cell. Initially, things were fine - it
spun the 3300 as good or better than the PC680 (and saved about 12-13
lbs doing it!).
However, I began to get erratic tach readings and looked at the
alternator leads where the tach picks up and the Jabiru OEM female
spade leads appeared burned! After consulting Jabiru USA, I replaced
the rather flimsy leads with quality AMP female spade connectors.
According to the Jabiru wiring diagram for this
engine http://tinyurl.com/mpsmquh
the tachometer drives from a variable
reluctance pickup that looks at features
on the flywheel . . . gear teeth, bolt heads,
etc.
This is a TINY signal that is unlikely to
burn anything. What you may have observed in
terms of discoloration is corrosion. But in any
case, if you have spade terminal females getting
loose or corroded, be aware of the potential for
similar problems every other place you used this
same terminal . . . this particular failure
would not have been related to your battery
change-out.
THEN, my 20 amp alternator breaker began to trip!
Where was this breaker installed?
At this point, I did a lot of research and found that since the Jab
3300 doesn't output charging current 'til about 1800-1900 rpm,
. . . typical of ALL brands and sizes of permanent
magnet 'dynamos' . . .
. . . my theory was that the connectors were frying due to the surge
of charging current after take off and low internal resistance of the
battery, and once the connectors were corrected, the little Ballistic
battery was getting hit with a surge of charging current in excess of
20 amps and tripping the breaker.
Those connectors were not associated with any part of
the battery recharging current.
I did two things - I reviewed my wiring and found I was good for up
to a 35 amp breaker to protect it, so I replaced the breaker with a
35A, and switched to an EarthX ETX36D which supposedly has close to
the capacity of the PC680.
Why the battery change? When I'm informed as to the
location of 20/35A breakers, we can begin to figure
out root cause of the tripping phenomenon you observed.
It's not clear that the trip is related to the differences
in batteries. The alternator is rated for 200W continuous
which is 200/14 or about 14A. It MIGHT be that the lithium
battery's willingness to accept charge at 14v is greater
than the Lead-Acid . . . I'll need to explore that with
some lithium cells on the bench. If that's true, then
substitution of lithium for lead in your particular
installation may be putting your rectifier/regulator/
alternator at risk. These systems are generally not
current limited like wound-field alternators. So while
up-sizing the breaker may have fixed a symptom, it
doesn't answer the question as to why the 20A breaker
was popping. Do you have an alternator loadmeter . . .
if not, would you be willing to install one temporarily
to sort out the questions?
Time will tell as to durability and performance of the EarthX, but
for now I'm a happy camper!
It's not clear that the AeroVoltz would not be performing
as well as the EarthX . . . But the EarthX does feature
a full-up battery management system not unlike that
installed in the TrueBlue products presently finding
their way onto TC aircraft.
Bob . . .
________________________________ Message 6 _____________________________________
Time: 09:21:38 AM PST US
From: "David Lloyd" <skywagon(at)charter.net>
Subject: Re: AeroElectric-List: tachometer question
Sacha,
Can't help without knowing if the tach is driven by cable or electronics.
If cable, then lubricating the cable would probably stop the tach needle
from whipping.
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Creighton Smith
A 036 |
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