Today's Message Index:
----------------------
1. 05:23 AM - Re: Rotax PM regulator (Robert L. Nuckolls, III)
2. 07:43 AM - Re: Rotax PM regulator (Jim Kale)
3. 09:22 AM - Re: Rotax PM regulator (C&K)
4. 09:28 AM - Re: Rotax PM regulator (Robert L. Nuckolls, III)
5. 09:48 AM - Re: Rotax PM regulator (rayj)
6. 03:04 PM - Re: Rotax PM regulator (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Rotax PM regulator |
>"The power being transmitted per burst, voltage ripples are more
>important. This can affect all powered systems and instruments but
>it is the battery that will suffer the most. To avoid premature
>aging, Hawker advocates RMS voltage ripple of less than 1% (battery
>not connected) ..."
I've reviewed several papers on the topic of
charger ripple. While technically accurate
I'm not seeing much significance with respect
to how we use the SLVA battery.
Here are two exemplar documents . . .
http://tinyurl.com/pprktbt
http://tinyurl.com/lkfrwzy
It's clear that these papers speak to
SLVA batteries as standby power where they
are 'floated' on a charger set for the
system operating voltage. I.e.
well above the open circuit voltage for
the cells. It's also clear that the
effects of poorly filtered charger output
are continuous and potentially deleterious
to battery performance when the stresses are
being impressed 24/7/365 by a 'charger'
that is also the ac mains power source
for the system.
Batteries on storage in the OBAM aviation
community should be "maintained" in a
fully charged state just above open
circuit voltage for the battery. The
maintainer is not an power source for
anything beyond simple offset of leakage
currents in the battery.
The conditions more nearly approximating those
explored in these papers are present during
normal operations where the engine drive
power sources are both CHARGERS and ENERGY
suppliers to the ship's systems. The duty
cycle for ripple stresses is exceedingly
low. A few hours per week for a total of
perhaps 100/year. A tiny fraction of that
imposed by un-interruptible power systems
in terrestrial, ac mains powered applications.
I'm skeptical of the notion that adding capacitance
across the output of the Ducati-style PM rectifier/
regulator will produce any observable improvement
in battery life. I'm acquiring test equipment
to quantify and qualify the performance
of PM R/R and will have some better ripple/
noise numbers to offer on the topic later his year.
Bob . . .
Message 2
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| Subject: | Rotax PM regulator |
I have also studied batteries for many years, although, I am not a battery
engineer. I too feel that ripple current has no effect on battery life.
It could affect avionics a lot though. On simple systems, the battery is
often used as the only device to reduce ripple current, and it does a fair
job at that. I have never seen any sign of short battery life, where ripple
current is high.
Jim
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Saturday, January 3, 2015 7:22 AM
Subject: Re: AeroElectric-List: Rotax PM regulator
--> <nuckolls.bob@aeroelectric.com>
>"The power being transmitted per burst, voltage ripples are more
>important. This can affect all powered systems and instruments but it
>is the battery that will suffer the most. To avoid premature aging,
>Hawker advocates RMS voltage ripple of less than 1% (battery not
>connected) ..."
I've reviewed several papers on the topic of
charger ripple. While technically accurate
I'm not seeing much significance with respect
to how we use the SLVA battery.
Here are two exemplar documents . . .
http://tinyurl.com/pprktbt
http://tinyurl.com/lkfrwzy
It's clear that these papers speak to
SLVA batteries as standby power where they
are 'floated' on a charger set for the
system operating voltage. I.e.
well above the open circuit voltage for
the cells. It's also clear that the
effects of poorly filtered charger output
are continuous and potentially deleterious
to battery performance when the stresses are
being impressed 24/7/365 by a 'charger'
that is also the ac mains power source
for the system.
Batteries on storage in the OBAM aviation
community should be "maintained" in a
fully charged state just above open
circuit voltage for the battery. The
maintainer is not an power source for
anything beyond simple offset of leakage
currents in the battery.
The conditions more nearly approximating those
explored in these papers are present during
normal operations where the engine drive
power sources are both CHARGERS and ENERGY
suppliers to the ship's systems. The duty
cycle for ripple stresses is exceedingly
low. A few hours per week for a total of
perhaps 100/year. A tiny fraction of that
imposed by un-interruptible power systems
in terrestrial, ac mains powered applications.
I'm skeptical of the notion that adding capacitance
across the output of the Ducati-style PM rectifier/
regulator will produce any observable improvement
in battery life. I'm acquiring test equipment
to quantify and qualify the performance
of PM R/R and will have some better ripple/
noise numbers to offer on the topic later his year.
Bob . . .
Message 3
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| Subject: | Re: Rotax PM regulator |
The references to "with the battery disconnected" threw me as then any
charging source with a diode in it will "ideally" prevent any discharge
at the low point of the ripple.
I believe I have a decent grasp of charging voltage constraints and
system voltage ripple but never really thought much about battery
charging current ripple from AC chargers or my single phase PM alternator.
Seems I don't need to give it much more thought either :)
As I recall, common large capacitors alone do next to nothing for
smoothing ripple on AC chargers and presumably my relatively low
frequency single phase PM alternator anyway. Perhaps less true of modern
AC chargers that use high frequency transformers. And then there are
the desulphaters that intentionally add ripple (spikes actually)... ;)
thanks
Ken
On 03/01/2015 10:42 AM, Jim Kale wrote:
>
> I have also studied batteries for many years, although, I am not a battery
> engineer. I too feel that ripple current has no effect on battery life.
> It could affect avionics a lot though. On simple systems, the battery is
> often used as the only device to reduce ripple current, and it does a fair
> job at that. I have never seen any sign of short battery life, where ripple
> current is high.
> Jim
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
> Nuckolls, III
> Sent: Saturday, January 3, 2015 7:22 AM
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Rotax PM regulator
>
> --> <nuckolls.bob@aeroelectric.com>
>
>
>> "The power being transmitted per burst, voltage ripples are more
>> important. This can affect all powered systems and instruments but it
>> is the battery that will suffer the most. To avoid premature aging,
>> Hawker advocates RMS voltage ripple of less than 1% (battery not
>> connected) ..."
>
>
> I've reviewed several papers on the topic of
> charger ripple. While technically accurate
> I'm not seeing much significance with respect
> to how we use the SLVA battery.
>
> Here are two exemplar documents . . .
>
> http://tinyurl.com/pprktbt
>
> http://tinyurl.com/lkfrwzy
>
> It's clear that these papers speak to
> SLVA batteries as standby power where they
> are 'floated' on a charger set for the
> system operating voltage. I.e.
> well above the open circuit voltage for
> the cells. It's also clear that the
> effects of poorly filtered charger output
> are continuous and potentially deleterious
> to battery performance when the stresses are
> being impressed 24/7/365 by a 'charger'
> that is also the ac mains power source
> for the system.
>
> Batteries on storage in the OBAM aviation
> community should be "maintained" in a
> fully charged state just above open
> circuit voltage for the battery. The
> maintainer is not an power source for
> anything beyond simple offset of leakage
> currents in the battery.
>
> The conditions more nearly approximating those
> explored in these papers are present during
> normal operations where the engine drive
> power sources are both CHARGERS and ENERGY
> suppliers to the ship's systems. The duty
> cycle for ripple stresses is exceedingly
> low. A few hours per week for a total of
> perhaps 100/year. A tiny fraction of that
> imposed by un-interruptible power systems
> in terrestrial, ac mains powered applications.
>
> I'm skeptical of the notion that adding capacitance
> across the output of the Ducati-style PM rectifier/
> regulator will produce any observable improvement
> in battery life. I'm acquiring test equipment
> to quantify and qualify the performance
> of PM R/R and will have some better ripple/
> noise numbers to offer on the topic later his year.
>
>
> Bob . . .
>
>
Message 4
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| Subject: | Rotax PM regulator |
At 09:42 2015-01-03, you wrote:
I have also studied batteries for many years, although, I am not a battery
engineer. I too feel that ripple current has no effect on battery life.
It could affect avionics a lot though. On simple systems, the battery is
often used as the only device to reduce ripple current, and it does a fair
job at that. I have never seen any sign of short battery life, where ripple
current is high.
One of the difficulties we face with making
such determinations is data . . . laboratory
data in particular. The ripple vs. service life
effects are going to be bounded by the single
digit percentages . . . in an operational
environment where the effects of other variables
are several times greater thus smothering any
ripple/life studies in 'noise'.
We used to teach that the battery was the ship's
best filter for small perturbations in bus
voltage . . . it was taught to me and I repeated
it faithfully until I began to study system
integration and design regulators.
Numbers refuting the 'best filter' assertions
were laying out on the table in profusion but
there was a predominant notion that batteries,
like capacitors, were these huge energy storage
devices with similar characteristics. But aside
from being able to store energy, similarities
end there . . .
An SVLA battery delivers energy at 12.5 and below.
It gets charged at 13.8 and above. In that gray
area between deliverance and acceptance of Joules,
the SVLA becomes 'soggy' as mitigator of
noise. Unlike the capacitor that presents a
relatively constant reactance at any voltage,
reactance of the battery rises sharply in the
gray area between charge and discharge voltages.
This means that batteries are not good 'filters'
of small (+/-5%) excursions in bus voltage. This
is why DO160 suggests that we expect and plan
to deal with certain noises on the DC bus. See:
http://tinyurl.com/pt36wsb
They tend to be a little better at the top
end of the gray area (at nominal bus voltage)
but in no instance does any salt-worthy
system integrator rely on battery presence
for anything but energy storage.
During the planned studies for this year,
I'll gather and publish data that supports
these notions . . .
Bob . . .
Message 5
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| Subject: | Re: Rotax PM regulator |
Kinda sounds like: Be given a fair trial, and then executed. :>)
Raymond Julian
Kettle River, MN
The things we admire in men, kindness and generosity, openness, honesty,
understanding and feeling are the concomitants of failure in our system.
And those traits we detest, sharpness, greed, acquisitiveness, meanness,
egotism and self-interest are the traits of success. And while men
admire the quality of the first they love the produce of the second.
-John Steinbeck, novelist, Nobel laureate (1902-1968)
On 01/03/2015 11:26 AM, Robert L. Nuckolls, III wrote:
-------------------SNIP--------------------------
>
> During the planned studies for this year,
> I'll gather and publish data that supports
> these notions . . .
>
>
> Bob . . .
>
>
Message 6
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| Subject: | Re: Rotax PM regulator |
>As I recall, common large capacitors alone do next to nothing for
>smoothing ripple on AC chargers and presumably my relatively low
>frequency single phase PM alternator anyway.
Even the smallest capacitor will do something . . . albeit
tiny. One way to put a sanity check on any recommended
capacitor is to consider the rate-of-change for voltage
across a capacitor based on current being drawn out of or
pumped into it.
A good estimation can be made by calculating
the drop between half-cycles of the full wave rectified
ac. Assume 200 Hz alternator. Assume capacitor gets
charged to 10V at top of each half-cycle. Let's say
we want the capacitor to hold the output at no less than
9.5 volts between half-cycle periods of 2.5mS.
1 Amp impressed on 1 Farad will change its voltage
by 1 Volt every Second or 2.5mV every 2.5mS. We're
trying to stay in a 500mV window so the CURRENT
can go up 200 times or 200A. To support 20A we can
cut it to 0.1F (100K uF).
This ball-parking exercise suggests that a 20A alternator
would have to be 'smoothed' with 100,000mF at 200Hz
operation to keep the ripple under 5% peak-to-peak. Of
course, a higher frequency of operation helps as does
a lower operating current. But that 0.1F capacitor
estimation illustrates your assertion nicely . . .
10 or 22KuF on a 20A Rotax alternator is not going
to be a robust 'smoother'.
Bob . . .
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