 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
nuckolls.bob(at)aeroelect
Guest
|
 Posted: Mon Jul 28, 2014 8:07 pm Post subject: Ni-Cad? |
 |
|
| Quote: |
Great article 9/14 Kitplanes
|
Thank you . . . I'm gathering info for the 4th chapter . . .
| Quote: |
Will you be doing a NiCad comparison article? The NiCal seems to take a lot
more punishment without problems and Air Bus said they were looking at
them.
|
There are very few companies that offer ni-cads
suited to engine cranking. The legacy wet-cells
are still made for replacement and refurbishment
of an existing installation but they're not
well liked in the general aviation community.
I suggested that the OBAM aviation community
take a look at wet ni-cads back about 1988 . . .
but that was based on the availability of surplus
cells that could be sorted and assembled into
a DIY battery.
Next time I talk to Skip Koss at Concorde, I'll
ask him what his take is on the current state
of the Ni-Cad market . . .
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
 |
peter(at)sportingaero.com
Guest
|
| Posted: Tue Jul 29, 2014 11:12 am Post subject: Ni-Cad? |
|
|
Back in the early 90s the Royal Navy fleet of SeaKing helicopters (S-61
derivative) used NiCad batteries. We were pretty much banned from using
them to start and made sure ground power was always available. They
didn't turn the engine over quickly enough to get a reliable start -
usually too much fuel and not enough rpm resulted in a hot start with
sheets of flame out the exhaust - and potentially an overheated turbine.
The batteries were a lot of trouble, I remember several being float
tested after aircraft landed back on-board with over heating or smoking
battery compartments (now not an option as nothing is allowed over the
side). We could also swap out individual cells if a battery went down. I
guess the technology has moved on in 20 years, but I still would not be
rushing to fit one.
Peter
On 29/07/2014 05:06, Robert L. Nuckolls, III wrote:
| Quote: |
<nuckolls.bob(at)aeroelectric.com>
>
> Great article 9/14 Kitplanes
Thank you . . . I'm gathering info for the 4th chapter . . .
>
> Will you be doing a NiCad comparison article? The NiCal seems to
> take a lot
> more punishment without problems and Air Bus said they were looking at
> them.
There are very few companies that offer ni-cads
suited to engine cranking. The legacy wet-cells
are still made for replacement and refurbishment
of an existing installation but they're not
well liked in the general aviation community.
I suggested that the OBAM aviation community
take a look at wet ni-cads back about 1988 . . .
but that was based on the availability of surplus
cells that could be sorted and assembled into
a DIY battery.
Next time I talk to Skip Koss at Concorde, I'll
ask him what his take is on the current state
of the Ni-Cad market . . .
Bob . . .
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Wed Jul 30, 2014 7:16 am Post subject: Ni-Cad? |
|
|
At 02:10 PM 7/29/2014, you wrote:
| Quote: | --> AeroElectric-List message posted by: Peter Pengilly <peter(at)sportingaero.com>
Back in the early 90s the Royal Navy fleet of SeaKing helicopters (S-61 derivative) used NiCad batteries. We were pretty much banned from using them to start and made sure ground power was always available. They didn't turn the engine over quickly enough to get a reliable start - usually too much fuel and not enough rpm resulted in a hot start with sheets of flame out the exhaust - and potentially an overheated turbine. The batteries were a lot of trouble, I remember several being float tested after aircraft landed back on-board with over heating or smoking battery compartments (now not an option as nothing is allowed over the side). We could also swap out individual cells if a battery went down. I guess the technology has moved on in 20 years, but I still would not be rushing to fit one. |
The hot-start phenomenon would not have root cause in the chemistry of the batteries, only the sizing- to-task irrespective of chemistry.
The volumetric and power density numbers for ni-cad are superior to lead-acid . . . i.e. a PROPERLY SIZED ni-cad will be smaller and lighter than the lead-acid capable of the same starting performance.
But as others have noted, ni-cads are not very friendly to the cost of ownership. Their alkaline electrolyte is antagonistic to lead-aced which prompts maintenance operators to have separate shops for dealing with the two technologies . . . which could probably be dispensed with today . . . nobody has to 'maintain' electrolyte in a lead-acid battery any more.
The thermal runaway thing was the byproduct of some rather un-creative design decisions. The smaller, lighter cells were very capable of cranking engines but when those engines started, generators rated at hundreds of amps would stuff energy back into the little batteries causing them to warm up. Ni-Cad temperature coefficient of voltage causing them to draw more current from a fixed voltage bus as their temperature rises . . . which causes them to warm up still faster . . . you get the picture.
Quoting from Wikipedia at:
http://tinyurl.com/7zm7xee
"One of the biggest disadvantages is that the battery exhibits a very marked negative temperature coefficient. This means that as the cell temperature rises, the internal resistance falls. This can pose considerable charging problems, particularly with the relatively simple charging systems employed for lead–acid type batteries. Whilst lead–acid batteries can be charged by simply connecting a dynamo to them, with a simple electromagnetic cut-out system for when the dynamo is stationary or an over-current occurs, the Ni–Cd battery under a similar charging scheme would exhibit thermal runaway, where the charging current would continue to rise until the over-current cut-out operated or the battery destroyed itself."
People who understood batteries published reams of data on how to get the best performance from Ni-Cads . . . data which said "constant current charge" . . . but those- who-know-more-about-airplanes-than-we-do decided that it would be too much to expect an air-framer to install ni-cad friendly starter-generator controllers. They decreed that thermometers be added to ni-cads with displays on the panel along with warning lights for battery overheat.
Instead of crafting a battery management system totally transparent to the pilots . . . the pilots were burdened with rudimentary system management duties to offset poor regulatory judgement.
Hence, the ni-cad gets this bad rap for being higher risk . . . risks driven by inelegant design. As a chemical energy storage system, ni-cads have a lot going for them. But as we've discussed here on the List . . . there is no such creature as an alternative chemistry, drop-in lead-acid replacement. THERE ARE DIFFERENCES that beg understanding and deference in design, fabrication, installation, operation and maintenance.
Whether lead-acid, ni-cad or lithium-ion . . . failure to pay homage to the physics gods is at best just expensive . . . at worst it sets airplanes on fire. Every technology comes with its own constellation of challenges.
http://tinyurl.com/kxu3s6j
Bob . . . [quote][b]
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
jloram
Joined: 07 Nov 2009
Posts: 54
Location: United States
|
| Posted: Thu Jul 31, 2014 4:28 pm Post subject: Ni-Cad? |
|
|
Well Said! –john-
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Wednesday, July 30, 2014 8:15 AM
To: aeroelectric-list(at)matronics.com
Subject: Re: Ni-Cad?
….
People who understood batteries published reams of data
on how to get the best performance from Ni-Cads . . . data
which said "constant current charge" . . . but those-
who-know-more-about-airplanes-than-we-do decided that it
would be too much to expect an air-framer to install
ni-cad friendly starter-generator controllers. They decreed
that thermometers be added to ni-cads with displays
on the panel along with warning lights for battery overheat.
Instead of crafting a battery management system totally
transparent to the pilots . . . the pilots were burdened
with rudimentary system management duties to offset
poor regulatory judgement.
Hence, the ni-cad gets this bad rap for being higher
risk . . . risks driven by inelegant design. As a chemical
energy storage system, ni-cads have a lot going for them.
But as we've discussed here on the List . . . there is
no such creature as an alternative chemistry, drop-in
lead-acid replacement. THERE ARE DIFFERENCES that
beg understanding and deference in design, fabrication,
installation, operation and maintenance.
Whether lead-acid, ni-cad or lithium-ion . . . failure
to pay homage to the physics gods is at best just
expensive . . . at worst it sets airplanes on fire.
Every technology comes with its own constellation of
challenges.
http://tinyurl.com/kxu3s6j
Bob . . . | Quote: | | http://www.matronics.com/Navigator?AeroElectric-List |
01234567
[quote][b]
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
