Today's Message Index:
----------------------
1. 07:05 AM - Re: Re: fuses in series (Robert L. Nuckolls, III)
2. 07:21 AM - Re: fuses in series (GLEN MATEJCEK)
3. 08:34 AM - Re: Re: fuses in series (Matthew S. Whiting)
4. 10:36 AM - Re: Re: fuses in series (Sebastien)
5. 12:40 PM - Re: Re: fuses in series (Matthew S. Whiting)
6. 01:04 PM - PIDG Crimping Tool (Sebastien)
7. 01:18 PM - Re: PIDG Crimping Tool (Matthew S. Whiting)
8. 01:37 PM - Re: Re: fuses in series (Alec)
9. 05:36 PM - Re: Re: fuses in series (ashleysc@broadstripe.net)
10. 05:56 PM - Re: Re: fuses in series (Charlie England)
Message 1
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| Subject: | Re: fuses in series |
At 08:00 AM 2/24/2023, you wrote:
I could see someone following the architecture used in home and
building electrical distribution systems where series fuses/breakers
are very common. Electric utilities have fuses on their distribution
lines. Most buildings have a main breaker on the incoming
service. And then each circuit has a breaker. And finally many end
devices have their own internal fuses or breakers. So,
fuses/breakers in series are common in many applications.
In large scale distribution systems, failure mode effects
analysis will define the risks to conductors and equipment
based on known and anticipated failures.
Needless to say, the power grid is LARGE scale and
fraught with risks for faults. So indeed, from power
plant down to your wall outlet, there will be
many protective devices.
Our airplanes are very small scale systems. Fault
risks are pretty well understood by virtue of a
century of experience that gives rise to a
volumes of standard practices.
I don't recall seeing that in a vehicle though, although
I think my new Equinox does have a fuse on the main positive
battery lead, which is a first.
Yeah, my Sedona has a cluster of current limiters
built into a rather busy battery(+) terminal.
Why would one not want to have a fuse on the main battery lead to
protect a short of the battery cable? I know this isn't common,
but I also have seen battery cables contact ground a few
times and the results are generally fairly impressive.
Is the issue just one of not wanting an additional point of
failure? Or the cost of a large fuse and fuse holder?
Experience has demonstrated that such faults
are exceedingly rare and generally limited to
accidents of human origin. Hence the admonition
to unhook the battery (-) terminal before
swinging a wrench on your car. Airplanes
uniquely enjoy battery master switches . . .
very convenient for making the system 'cold'.
They are demonstrably immune to hard faults
that might be expected to trip active protection.
A robust wire's inadvertent connection with
ground is more likely to be a soft fault that
burns structure rather than the wire itself.
I've cited an example incident waaayyy back when
where a Beech C90 on short final to New Mexico airport
suddenly found the elevator mechanically disconnected
from the control column. They managed to land the
aircraft using pitch trim.
Subsequent investigation found the elevator
cables completely slack.
It seems that during maintenance activity
some time ago, some wire bundles under the floorboard
were mis-positioned for access but not properly
returned to as-manufactured.
One of the wires was feeder to the copilot's
windshield electric de-ice inverter . . . a relatively
fat wire protected at 75A or so. This wire was
being rubbed against the elevator control cables
until insulation was penetrated.
The intermittent arcing was so subtle that the
breaker never opened . . . and nothing untoward
was noticed by crew. Over a period of time
the steel control cable was eroded to failure
while copper wire strands were barely marked.
A similar thing would happen if a rear mounted
battery feeder were to become inappropriately
involved with the edge of a bulkhead lightening
hole under the floorboard . . . A little
insulation might smell bad but subsequent electrical
effects are more likely to burn away the aluminum
as opposed to over-stressing the wire.
Battery cable protection in cars goes to crash
safety. Batteries are generally mounted right
up front and exceedingly vulnerable to major
munching of sheet metal. Those protective
devices will be of the current-limiter/fusible-link
variety.
In airplanes, experience has demonstrated that
the lest destructive of unplanned arrivals with
the earth are controlled . . . i.e. pilot shuts
off fuel and master before striving to minimize
violence of the following events. The other
side of the coin is a completely unanticipated
termination of flight at high speed . . . wherein
condition of the electrical and fuel systems is
probably not relevant to the outcome.
Many moons ago I did some analysis of the bits-n-
pieces left of a King Air that hit a mountain in the Swiss
Alps at cruise. There were few chunks of
debris that would not fit into a 1-square foot
box. The thing they asked me to look at was
an Avionics Master switch that was missing some
wires . . . disconnected causing loss of nav aids
or ripped off as result of crash? The wires had
been 'tack soldered' as opposed to standard
practice of wrapping through the terminal's
wiring hole. Microscopic examination of exposed solder
surfaces showed that the wires were pulled off
and did not fall off due to joint failure.
The short answer is a study of power distribution
systems in hundreds of thousands of type
certified aircraft will reveal a minimalist
philosophy for power distribution current
limiting.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 2
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| Subject: | Re: fuses in series |
> Re: fuses in series
>
> I could see someone following the architecture used in home and building
> electrical distribution systems ...
>
A couple more data points:
My 1970's VW Rabbit had a fusible link in the battery cable, and I guess I
wouldn't be shocked to learn many cars were so equipped without it being
general knowledge.
There are transport category aircraft with current limiters geographically
distributed around the system to prevent hard faults from taking out the
whole system.
No clue if that strategy is based upon crashworthiness considerations,
maintenance considerations, corporate history, or some combination.
In my aft-battery RV-8, the fat wire runs through the crushable structure
under the cabin floor, making it susceptible to pinching and a hard fault
in a crash, especially given the model's tendency to shed its main gear.
Not sure the practicality of trying to size a current limiter that would
not open under cranking loads but still open with a hard fault. The
guestimated risk for me centers on the probability of hitting the planet
without knowing it's coming and thereby not getting the master off in
time. Given how I operate, I judge that to be a low very order threat and
one I can live with.
YMMV-
Message 3
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| Subject: | Re: fuses in series |
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Message 4
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| Subject: | Re: fuses in series |
We definitely need SOME way to cut electrical power to the aircraft for
several different emergency situations. A battery contactor solves this for
all but the most sudden and catastrophic situations. A friend of mine
crashed his F1 rocket at during a go-around at full throttle and ended up
trapped upside down. He could smell the fuel from the damaged wing tank but
couldn't reach the master switch. Fortunately the electrical system stayed
intact and the fuel never ignited. I don't know of a single crash where a
battery fuse could have changed the outcome.
As for current limiters rated for short starting loads, I flew King Airs
for years with current limiters. We carried spares because they blew on
engine start more than once. Beech eventually replaced them with bus ties.
When Cessna starts producing single engine aircraft with battery fuses, I
think it will be worth another look. In the meantime I don't see a benefit
to adding odds and ends to a proven system.
On Sat, 25 Feb 2023, 08:38 Matthew S. Whiting, <m.whiting@frontier.com>
wrote:
> I agree that the likelihood of a direct short of a main battery cable is
> small. However, it is not zero and the localized heating from such a sho
rt
> could ignite combustibles. As long as the cable is kept away from
> combustibles, this isn=99t an issue.
>
> The difference in current between starting and a significant short is
> pretty large so viable overcurrent protection is feasible. For example,
> most engines in EA-B aircraft probably draw 100 amps or less during
> starting. It takes a fairly large engine to draw 200 amps (think diesel
> pickup truck or larger). Yes, the initial current when the starter is no
t
> turning can be twice or more the normal cranking current, but that is ver
y
> short duration and is not likely to blow/trip a 200 A fuse or breaker. A
> short circuit of a battery can easily draw 1000 amps or more which would
> blow a 200 A fuse fairly quickly.
>
> [image: preview.png]
>
> VRLAshortCurrentsStorageBatterySystems
> <https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystems.p
df>
> PDF Document =C2=B7 163 KB
> <https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystems.p
df>
>
> <https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystems.p
df>
>
> [image: 03224d1fcb0108937e9b07deb18cf473_M.jpg]
>
> Cessna Flyer Association - Save your Starter
> <https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-starter
.html>
> cessnaflyer.org
> <https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-starter
.html>
>
> <https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-starter
.html>
>
> youtu.be <https://youtu.be/d2nPHWNoDSA>
> <https://youtu.be/d2nPHWNoDSA> <https://youtu.be/d2nPHWNoDSA>
>
>
> I believe overcurrent protection on a battery is easily accomplished, but
> I tend to agree with Bob that the likelihood of needing this is small.
> Then again, you can make a similar argument for the battery contactor. Y
ou
> don=99t see these in the automobile world as they are deemed unnece
ssary and
> for good reason. One could argue the same for aircraft.
>
> Matt
>
> Sent from my iPad
>
> On Feb 25, 2023, at 10:23 AM, GLEN MATEJCEK <fly4grins@gmail.com> wrote:
>
> =EF=BB
>
>
>> Re: fuses in series
>>
>> I could see someone following the architecture used in home and building
>> electrical distribution systems ...
>>
>
> A couple more data points:
>
> My 1970's VW Rabbit had a fusible link in the battery cable, and I guess
I
> wouldn't be shocked to learn many cars were so equipped without it being
> general knowledge.
>
> There are transport category aircraft with current limiters geographicall
y
> distributed around the system to prevent hard faults from taking out the
> whole system.
> No clue if that strategy is based upon crashworthiness considerations,
> maintenance considerations, corporate history, or some combination.
>
> In my aft-battery RV-8, the fat wire runs through the crushable structure
> under the cabin floor, making it susceptible to pinching and a hard fault
> in a crash, especially given the model's tendency to shed its main gear.
> Not sure the practicality of trying to size a current limiter that would
> not open under cranking loads but still open with a hard fault. The
> guestimated risk for me centers on the probability of hitting the planet
> without knowing it's coming and thereby not getting the master off in
> time. Given how I operate, I judge that to be a low very order threat an
d
> one I can live with.
>
> YMMV-
>
>
Message 5
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| Subject: | Re: fuses in series |
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Message 6
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| Subject: | PIDG Crimping Tool |
My friend is rewiring his boat and after using my ratcheting crimp tool has
decided he needs one of his own. Any current recommendations for an
e-bay or amazon cheap crimp tool that works well?
Thank you
Message 7
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| Subject: | Re: PIDG Crimping Tool |
I bought this one and it works fairly well and is about $50 with one die set
. I bought both die sets so I can do terminals as well as coax.
https://www.steinair.com/product/ratcheting-crimper-frame-only/
Sent from my iPad
> On Feb 25, 2023, at 4:05 PM, Sebastien <cluros@gmail.com> wrote:
>
> =EF=BB
> My friend is rewiring his boat and after using my ratcheting crimp tool ha
s decided he needs one of his own. Any current recommendations for an e-bay o
r amazon cheap crimp tool that works well?
>
> Thank you
Message 8
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| Subject: | Re: fuses in series |
You can start a very healthy fire with a 10 or 20 amp short circuit, as evid
enced by the old fashioned cigarette lighters, as it will apply sustained he
at for long enough to ignite nearby materiel.
A short circuit that takes out a 200A fusible link is more like a small fast
explosion and as Bob points out, the structure to which the short circuit i
s made will evaporate, acting as it=99s own fusible device
A 200 amp breaker won=99t stop a cabin fire.
Sent from my iPhone
> On Feb 25, 2023, at 15:41, Matthew S. Whiting <m.whiting@frontier.com> wro
te:
>
> =EF=BBThat is the beauty of EA-B. We can evaluate the risks and reward
s and make our own decision. I am still on the fence, but leaning against o
vercurrent protection at the battery. Mainly since I am hoping to fit both b
atteries on the firewall. A battery under the baggage compartment or in the
cockpit would most likely get an overcurrent protection device at the batte
ry as I=99d rather not have a 1,000 amp hot spot in the cabin area sho
uld a cable wear through the insulation.
>
> Matt
>
> Sent from my iPad
>
>>> On Feb 25, 2023, at 1:39 PM, Sebastien <cluros@gmail.com> wrote:
>>>
>> =EF=BB
>> We definitely need SOME way to cut electrical power to the aircraft for s
everal different emergency situations. A battery contactor solves this for a
ll but the most sudden and catastrophic situations. A friend of mine crashed
his F1 rocket at during a go-around at full throttle and ended up trapped u
pside down. He could smell the fuel from the damaged wing tank but couldn't r
each the master switch. Fortunately the electrical system stayed intact and t
he fuel never ignited. I don't know of a single crash where a battery fuse c
ould have changed the outcome.
>>
>> As for current limiters rated for short starting loads, I flew King Airs f
or years with current limiters. We carried spares because they blew on engin
e start more than once. Beech eventually replaced them with bus ties.
>>
>> When Cessna starts producing single engine aircraft with battery fuses, I
think it will be worth another look. In the meantime I don't see a benefit t
o adding odds and ends to a proven system.
>>
>>> On Sat, 25 Feb 2023, 08:38 Matthew S. Whiting, <m.whiting@frontier.com> w
rote:
>>> I agree that the likelihood of a direct short of a main battery cable is
small. However, it is not zero and the localized heating from such a short
could ignite combustibles. As long as the cable is kept away from combusti
bles, this isn=99t an issue.
>>>
>>> The difference in current between starting and a significant short is pr
etty large so viable overcurrent protection is feasible. For example, most e
ngines in EA-B aircraft probably draw 100 amps or less during starting. It t
akes a fairly large engine to draw 200 amps (think diesel pickup truck or la
rger). Yes, the initial current when the starter is not turning can be twic
e or more the normal cranking current, but that is very short duration and i
s not likely to blow/trip a 200 A fuse or breaker. A short circuit of a bat
tery can easily draw 1000 amps or more which would blow a 200 A fuse fairly q
uickly.
>>>
>>>
>>> VRLAshortCurrentsStorageBatterySystems
>>> PDF Document =C2=B7 163 KB
>>>
>>>
>>> Cessna Flyer Association - Save your Starter
>>> cessnaflyer.org
>>>
>>> youtu.be
>>>
>>>
>>>
>>> I believe overcurrent protection on a battery is easily accomplished, bu
t I tend to agree with Bob that the likelihood of needing this is small. Th
en again, you can make a similar argument for the battery contactor. You do
n=99t see these in the automobile world as they are deemed unnecessary
and for good reason. One could argue the same for aircraft.
>>>
>>> Matt
>>>
>>> Sent from my iPad
>>>
>>>>> On Feb 25, 2023, at 10:23 AM, GLEN MATEJCEK <fly4grins@gmail.com> wrot
e:
>>>>>
>>>> =EF=BB
>>>>
>>>>
>>>>>
>>>>> Re: fuses in series
>>>>>
>>>>> I could see someone following the architecture used in home and buildi
ng
>>>>> electrical distribution systems ...
>>>>
>>>> A couple more data points:
>>>>
>>>> My 1970's VW Rabbit had a fusible link in the battery cable, and I gues
s I wouldn't be shocked to learn many cars were so equipped without it being
general knowledge.
>>>>
>>>> There are transport category aircraft with current limiters geographica
lly distributed around the system to prevent hard faults from taking out the
whole system.
>>>> No clue if that strategy is based upon crashworthiness considerations, m
aintenance considerations, corporate history, or some combination.
>>>>
>>>> In my aft-battery RV-8, the fat wire runs through the crushable structu
re under the cabin floor, making it susceptible to pinching and a hard fault
in a crash, especially given the model's tendency to shed its main gear. N
ot sure the practicality of trying to size a current limiter that would not o
pen under cranking loads but still open with a hard fault. The guestimated r
isk for me centers on the probability of hitting the planet without knowing i
t's coming and thereby not getting the master off in time. Given how I oper
ate, I judge that to be a low very order threat and one I can live with.
>>>>
>>>> YMMV-
>>
>> <03224d1fcb0108937e9b07deb18cf473_M.jpg>
>> <preview.png>
Message 9
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| Subject: | Re: fuses in series |
Hi All;
I suppose it's a matter of opinion, but I think two fuses in series confuse
s diagnosis and increases the time for replacement, when that time sometime
s may not be available.
Cheers! Stu.
From: "Matthew S. Whiting" <m.whiting@frontier.com>
Sent: Saturday, February 25, 2023 12:40:02 PM
Subject: Re: AeroElectric-List: Re: fuses in series
That is the beauty of EA-B. We can evaluate the risks and rewards and make
our own decision. I am still on the fence, but leaning against overcurrent
protection at the battery. Mainly since I am hoping to fit both batteries o
n the firewall. A battery under the baggage compartment or in the cockpit w
ould most likely get an overcurrent protection device at the battery as I
=99d rather not have a 1,000 amp hot spot in the cabin area should a
cable wear through the insulation.
Matt
Sent from my iPad
On Feb 25, 2023, at 1:39 PM, Sebastien <cluros@gmail.com> wrote:
BQ_BEGIN
We definitely need SOME way to cut electrical power to the aircraft for sev
eral different emergency situations. A battery contactor solves this for al
l but the most sudden and catastrophic situations. A friend of mine crashed
his F1 rocket at during a go-around at full throttle and ended up trapped
upside down. He could smell the fuel from the damaged wing tank but couldn'
t reach the master switch. Fortunately the electrical system stayed intact
and the fuel never ignited. I don't know of a single crash where a battery
fuse could have changed the outcome.
As for current limiters rated for short starting loads, I flew King Airs fo
r years with current limiters. We carried spares because they blew on engin
e start more than once. Beech eventually replaced them with bus ties.
When Cessna starts producing single engine aircraft with battery fuses, I t
hink it will be worth another look. In the meantime I don't see a benefit t
o adding odds and ends to a proven system.
On Sat, 25 Feb 2023, 08:38 Matthew S. Whiting, < [ mailto:m.whiting@frontie
r.com | m.whiting@frontier.com ] > wrote:
BQ_BEGIN
I agree that the likelihood of a direct short of a main battery cable is sm
all. However, it is not zero and the localized heating from such a short co
uld ignite combustibles. As long as the cable is kept away from combustible
s, this isn=99t an issue.
The difference in current between starting and a significant short is prett
y large so viable overcurrent protection is feasible. For example, most eng
ines in EA-B aircraft probably draw 100 amps or less during starting. It ta
kes a fairly large engine to draw 200 amps (think diesel pickup truck or la
rger). Yes, the initial current when the starter is not turning can be twic
e or more the normal cranking current, but that is very short duration and
is not likely to blow/trip a 200 A fuse or breaker. A short circuit of a ba
ttery can easily draw 1000 amps or more which would blow a 200 A fuse fairl
y quickly.
[ https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystems.pd
f ] [ https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystem
s.pdf | VRLAshortCurrentsStorageBatterySystems ]
[ https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystems.pd
f | PDF Document =C2=B7 163 KB ]
BQ_END
[ https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-starter.
html ] [ https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-s
tarter.html | Cessna Flyer Association - Save your Starter ]
[ https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-starter.
html | cessnaflyer.org ]
[ https://youtu.be/d2nPHWNoDSA ] [ https://youtu.be/d2nPHWNoDSA | youtu.be
]
[ https://youtu.be/d2nPHWNoDSA ]
BQ_END
I believe overcurrent protection on a battery is easily accomplished, but I
tend to agree with Bob that the likelihood of needing this is small. Then
again, you can make a similar argument for the battery contactor. You don
=99t see these in the automobile world as they are deemed unnecessary
and for good reason. One could argue the same for aircraft.
Matt
Sent from my iPad
BQ_BEGIN
On Feb 25, 2023, at 10:23 AM, GLEN MATEJCEK < [ mailto:fly4grins@gmail.com
| fly4grins@gmail.com ] > wrote:
BQ_END
BQ_BEGIN
BQ_BEGIN
Re: fuses in series
I could see someone following the architecture used in home and building
electrical distribution systems ...
BQ_END
A couple more data points:
My 1970's VW Rabbit had a fusible link in the battery cable, and I guess I
wouldn't be shocked to learn many cars were so equipped without it being ge
neral knowledge.
There are transport category aircraft with current limiters geographically
distributed around the system to prevent hard faults from taking out the wh
ole system.
No clue if that strategy is based upon crashworthiness considerations, main
tenance considerations, corporate history, or some combination.
In my aft-battery RV-8, the fat wire runs through the crushable structure u
nder the cabin floor, making it susceptible to pinching and a hard fault in
a crash, especially given the model's tendency to shed its main gear. Not
sure the practicality of trying to size a current limiter that would not op
en under cranking loads but still open with a hard fault. The guestimated r
isk for me centers on the probability of hitting the planet without knowing
it's coming and thereby not getting the master off in time. Given how I op
erate, I judge that to be a low very order threat and one I can live with.
YMMV-
BQ_END
<03224d1fcb0108937e9b07deb18cf473_M.jpg>
<preview.png>
Message 10
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| Subject: | Re: fuses in series |
So, you're pressed for time because you're flying IFR and about to fly
an approach? Kinda violates the whole idea of saving troubleshooting
until you're on the ground.
On 2/25/2023 7:36 PM, ashleysc@broadstripe.net wrote:
> Hi All;
> I suppose it's a matter of opinion, but I think two fuses in series
> confuses diagnosis and increases the time for replacement, when that
> time sometimes may not be available.
> Cheers! Stu.
>
> ------------------------------------------------------------------------
> *From: *"Matthew S. Whiting" <m.whiting@frontier.com>
> *To: *aeroelectric-list@matronics.com
> *Sent: *Saturday, February 25, 2023 12:40:02 PM
> *Subject: *Re: AeroElectric-List: Re: fuses in series
>
> That is the beauty of EA-B. We can evaluate the risks and rewards and
> make our own decision. I am still on the fence, but leaning against
> overcurrent protection at the battery. Mainly since I am hoping to
> fit both batteries on the firewall. A battery under the baggage
> compartment or in the cockpit would most likely get an overcurrent
> protection device at the battery as Id rather not have a 1,000 amp
> hot spot in the cabin area should a cable wear through the insulation.
> Matt
>
> Sent from my iPad
>
> On Feb 25, 2023, at 1:39 PM, Sebastien <cluros@gmail.com> wrote:
>
> We definitely need SOME way to cut electrical power to the
> aircraft for several different emergency situations. A battery
> contactor solves this for all but the most sudden and catastrophic
> situations. A friend of mine crashed his F1 rocket at during a
> go-around at full throttle and ended up trapped upside down. He
> could smell the fuel from the damaged wing tank but couldn't reach
> the master switch. Fortunately the electrical system stayed intact
> and the fuel never ignited. I don't know of a single crash where a
> battery fuse could have changed the outcome.
>
> As for current limiters rated for short starting loads, I flew
> King Airs for years with current limiters. We carried spares
> because they blew on engine start more than once. Beech eventually
> replaced them with bus ties.
>
> When Cessna starts producing single engine aircraft with battery
> fuses, I think it will be worth another look. In the meantime I
> don't see a benefit to adding odds and ends to a proven system.
>
> On Sat, 25 Feb 2023, 08:38 Matthew S. Whiting,
> <m.whiting@frontier.com> wrote:
>
> I agree that the likelihood of a direct short of a main
> battery cable is small. However, it is not zero and the
> localized heating from such a short could ignite
> combustibles. As long as the cable is kept away from
> combustibles, this isnt an issue.
> The difference in current between starting and a significant
> short is pretty large so viable overcurrent protection is
> feasible. For example, most engines in EA-B aircraft probably
> draw 100 amps or less during starting. It takes a fairly
> large engine to draw 200 amps (think diesel pickup truck or
> larger). Yes, the initial current when the starter is not
> turning can be twice or more the normal cranking current, but
> that is very short duration and is not likely to blow/trip a
> 200 A fuse or breaker. A short circuit of a battery can
> easily draw 1000 amps or more which would blow a 200 A fuse
> fairly quickly.
>
> preview.png
>
> <https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystems.pdf>VRLAshortCurrentsStorageBatterySystems
> <https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystems.pdf>
> PDF Document 163 KB
> <https://www.sbsbattery.com/PDFs/VRLAshortCurrentsStorageBatterySystems.pdf>
>
> 03224d1fcb0108937e9b07deb18cf473_M.jpg
>
> <https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-starter.html>Cessna
> Flyer Association - Save your Starter
> <https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-starter.html>
> cessnaflyer.org
> <https://www.cessnaflyer.org/maintenance-tech/item/1151-save-your-starter.html>
>
>
> <https://youtu.be/d2nPHWNoDSA>youtu.be <https://youtu.be/d2nPHWNoDSA>
> <https://youtu.be/d2nPHWNoDSA>
>
>
> I believe overcurrent protection on a battery is easily accomplished,
> but I tend to agree with Bob that the likelihood of needing this is
> small. Then again, you can make a similar argument for the battery
> contactor. You dont see these in the automobile world as they are
> deemed unnecessary and for good reason. One could argue the same for
> aircraft.
>
> Matt
>
> Sent from my iPad
>
> On Feb 25, 2023, at 10:23 AM, GLEN MATEJCEK <fly4grins@gmail.com>
> wrote:
>
>
> Re: fuses in series
>
> I could see someone following the architecture used in home
> and building
> electrical distribution systems...
>
>
> A couple more data points:
>
> My 1970's VW Rabbit had a fusiblelink in the battery cable, and I
> guess I wouldn't be shocked to learn many cars were so equipped
> without it being general knowledge.
>
> There are transport category aircraft with current limiters
> geographically distributed around the system to prevent hard
> faults from taking out the whole system.
> No clue if that strategy is based upon crashworthiness
> considerations, maintenance considerations, corporate history, or
> some combination.
>
> In my aft-battery RV-8, the fat wire runs through the crushable
> structure under the cabin floor, making it susceptibleto pinching
> and a hardfault in a crash, especially given the model's
> tendencyto shed its main gear. Not sure the practicality of
> trying to size a current limiter that would not open under
> cranking loads but still open with a hard fault. The
> guestimatedrisk for me centers on the probability of hitting the
> planet without knowing it's coming and thereby not getting the
> master off in time. Given how I operate, I judge that to be a low
> very order threat and one I can live with.
>
> YMMV-
>
> <03224d1fcb0108937e9b07deb18cf473_M.jpg>
> <preview.png>
>
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