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WAS: Sizing a B-lead ANL now "master fuse" on the battery b

 
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stuart(at)stuarthutchison
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PostPosted: Mon Feb 28, 2022 11:52 pm    Post subject: WAS: Sizing a B-lead ANL now "master fuse" on the battery b Reply with quote
G’day Bob,
In anticipation of the in-rush and persistent current through that wire during prolonged starting, a pretty large gauge fusible link would be needed … do you really want that much current available at the site of a short hoping the large slow-blow fuse will eventually isolate power?  Weight is obviously at a premium, but it seems to me like a solenoid and master switch are a much safer bet.

Kind regards, Stuart
Quote:
On 1 Mar 2022, at 5:02 pm, Bob Verwey <bob.verwey(at)gmail.com (bob.verwey(at)gmail.com)> wrote:
Sort of related query.

A J3 Cub is being converted to accommodate an 0-200 engine with electric start.  
The battery box is behind the baggage compartment, and for the sake of simplicity, there is no master solenoid back there, so there is a hot #4 wire all the way top the firewall. 

The only electrical load is the radio and intercom, for which there is a switch and circuit breaker.

I want to add a fuse of some kind at the battery box to prevent a "shower of sparks" welding event if there is an incident which causes the steel bits to cut into the hot battery cable. 

What is the likely current draw on a typical lightweight starter for an 0-200, and what is the suggested "fuse " mechanism?







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bob.verwey(at)gmail.com
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PostPosted: Tue Mar 01, 2022 1:01 am    Post subject: WAS: Sizing a B-lead ANL now "master fuse" on the battery b Reply with quote
..of course when someone else points that out it makes perfect sense...lol..thanks!

On Tue, 01 Mar 2022, 09:54 Stuart Hutchison, <stuart(at)stuarthutchison.com.au (stuart(at)stuarthutchison.com.au)> wrote:

Quote:
G’day Bob,

In anticipation of the in-rush and persistent current through that wire during prolonged starting, a pretty large gauge fusible link would be needed … do you really want that much current available at the site of a short hoping the large slow-blow fuse will eventually isolate power?  Weight is obviously at a premium, but it seems to me like a solenoid and master switch are a much safer bet.


Kind regards, Stuart

Quote:
On 1 Mar 2022, at 5:02 pm, Bob Verwey <bob.verwey(at)gmail.com (bob.verwey(at)gmail.com)> wrote:

Sort of related query.


A J3 Cub is being converted to accommodate an 0-200 engine with electric start.  
The battery box is behind the baggage compartment, and for the sake of simplicity, there is no master solenoid back there, so there is a hot #4 wire all the way top the firewall. 


The only electrical load is the radio and intercom, for which there is a switch and circuit breaker.


I want to add a fuse of some kind at the battery box to prevent a "shower of sparks" welding event if there is an incident which causes the steel bits to cut into the hot battery cable. 


What is the likely current draw on a typical lightweight starter for an 0-200, and what is the suggested "fuse " mechanism?













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bob.verwey(at)gmail.com
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PostPosted: Tue Mar 01, 2022 1:54 am    Post subject: WAS: Sizing a B-lead ANL now "master fuse" on the battery b Reply with quote
But....the master solenoid is actuated by a negative wire right? So now if the thinner switching wire is earthed forceably to the fuselage, then rhe fat wire is live? What am I missing?

On Tue, 01 Mar 2022, 11:01 Bob Verwey, <bob.verwey(at)gmail.com (bob.verwey(at)gmail.com)> wrote:

Quote:
..of course when someone else points that out it makes perfect sense...lol..thanks!

On Tue, 01 Mar 2022, 09:54 Stuart Hutchison, <stuart(at)stuarthutchison.com.au (stuart(at)stuarthutchison.com.au)> wrote:

Quote:
G’day Bob,

In anticipation of the in-rush and persistent current through that wire during prolonged starting, a pretty large gauge fusible link would be needed … do you really want that much current available at the site of a short hoping the large slow-blow fuse will eventually isolate power?  Weight is obviously at a premium, but it seems to me like a solenoid and master switch are a much safer bet.


Kind regards, Stuart

Quote:
On 1 Mar 2022, at 5:02 pm, Bob Verwey <bob.verwey(at)gmail.com (bob.verwey(at)gmail.com)> wrote:

Sort of related query.


A J3 Cub is being converted to accommodate an 0-200 engine with electric start.  
The battery box is behind the baggage compartment, and for the sake of simplicity, there is no master solenoid back there, so there is a hot #4 wire all the way top the firewall. 


The only electrical load is the radio and intercom, for which there is a switch and circuit breaker.


I want to add a fuse of some kind at the battery box to prevent a "shower of sparks" welding event if there is an incident which causes the steel bits to cut into the hot battery cable. 


What is the likely current draw on a typical lightweight starter for an 0-200, and what is the suggested "fuse " mechanism?














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yellowduckduo(at)gmail.co
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PostPosted: Tue Mar 01, 2022 4:36 am    Post subject: WAS: Sizing a B-lead ANL now "master fuse" on the battery b Reply with quote
Exactly.  A fuse would not really add any safety since the resistance of
the contactor coil limits the possible current to less than 1 amp which
would not warm up even a small gauge wire.
Ken

On 01-Mar.-22 5:20 a.m., Stuart Hutchison wrote:
Quote:
No, the master contactor interrupts the positive side of the circuit
between the battery positive lead and the main power feeder wire. 
 The Master Switch connects a thin positive wire from an insulated
post on the contactor body to ground when closed, energising the
master contactor solenoid.  Obviously this small wire needs to be
physically protected, but I’ve never seen that wire fused (I could be
wrong) … potentially because it is small enough to burn through
without starting a fire. You certainly wouldn’t want nuisance CB or
fuse trips on Master Switch power.

> On 1 Mar 2022, at 8:54 pm, Bob Verwey <bob.verwey(at)gmail.com> wrote:
>
> But....the master solenoid is actuated by a negative wire right? So
> now if the thinner switching wire is earthed forceably to the
> fuselage, then rhe fat wire is live? What am I missing?
>
> On Tue, 01 Mar 2022, 11:01 Bob Verwey, <bob.verwey(at)gmail.com> wrote:
>
> ..of course when someone else points that out it makes perfect
> sense...lol..thanks!
>
> On Tue, 01 Mar 2022, 09:54 Stuart Hutchison,
> <stuart(at)stuarthutchison.com.au> wrote:
>
> G’day Bob,
>
> In anticipation of the in-rush and persistent current through
> that wire during prolonged starting, a pretty large gauge
> fusible link would be needed … do you really want that much
> current available at the site of a short hoping the large
> slow-blow fuse will eventually isolate power?  Weight is
> obviously at a premium, but it seems to me like a solenoid
> and master switch are a much safer bet.
>
> Kind regards, Stuart
>
>> On 1 Mar 2022, at 5:02 pm, Bob Verwey <bob.verwey(at)gmail.com>
>> wrote:
>>
>> Sort of related query.
>>
>> A J3 Cub is being converted to accommodate an 0-200 engine
>> with electric start.
>> The battery box is behind the baggage compartment, and for
>> the sake of simplicity, there is no master solenoid back
>> there, so there is a hot #4 wire all the way top the firewall.
>>
>> The only electrical load is the radio and intercom, for
>> which there is a switch and circuit breaker.
>>
>> I want to add a fuse of some kind at the battery box to
>> prevent a "shower of sparks" welding event if there is an
>> incident which causes the steel bits to cut into the hot
>> battery cable.
>>
>> What is the likely current draw on a typical lightweight
>> starter for an 0-200, and what is the suggested "fuse "
>> mechanism?
>>
>>
>



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