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stuart(at)stuarthutchison
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 Posted: Mon Feb 28, 2022 11:52 pm Post subject: WAS: Sizing a B-lead ANL now "master fuse" on the battery b |
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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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| Posted: Tue Mar 01, 2022 1:01 am Post subject: WAS: Sizing a B-lead ANL now "master fuse" on the battery b |
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..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. Â
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.Â
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.Â
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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| Posted: Tue Mar 01, 2022 1:54 am Post subject: WAS: Sizing a B-lead ANL now "master fuse" on the battery b |
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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. Â
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.Â
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.Â
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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| Posted: Tue Mar 01, 2022 4:36 am Post subject: WAS: Sizing a B-lead ANL now "master fuse" on the battery b |
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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.Â
 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. Â 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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