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kenryan
Joined: 20 Oct 2009
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 Posted: Thu Dec 11, 2014 3:37 pm Post subject: fuse or breaker for OVP? |
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I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ?
[quote][b]
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jluckey(at)pacbell.net
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| Posted: Thu Dec 11, 2014 10:29 pm Post subject: fuse or breaker for OVP? |
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The idea behind feeding the Regulator with a circuit breaker is that it gives the pilot the ability to shut-down the alternator (by pulling the breaker) if that becomes necessary.
A few reasons you might want to shut down the alternator are:1. a failed regulator that is giving full field (if you don't have an over voltage module)2. a failed over-voltage module3. testing purposesA breaker is simply more practical in this situation.
On Thursday, December 11, 2014 3:35 PM, Ken Ryan <keninalaska(at)gmail.com> wrote:
I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ?
[quote][b]
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Fri Dec 12, 2014 8:04 am Post subject: fuse or breaker for OVP? |
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Thanks Jeff. Are you saying that it would be okay to use the OVP device to blow a fuse? Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?
On Thu, Dec 11, 2014 at 9:28 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote:[quote]
The idea behind feeding the Regulator with a circuit breaker is that it gives the pilot the ability to shut-down the alternator (by pulling the breaker) if that becomes necessary.
A few reasons you might want to shut down the alternator are:1. a failed regulator that is giving full field (if you don't have an over voltage module)2. a failed over-voltage module3. testing purposesA breaker is simply more practical in this situation.
On Thursday, December 11, 2014 3:35 PM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ?
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[b]
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jluckey(at)pacbell.net
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| Posted: Fri Dec 12, 2014 1:20 pm Post subject: fuse or breaker for OVP? |
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Ken,
To answer your question directly: Yes, it's okay to use a fuse w/ an OVM. It will just be more difficult to reset ( and it does not give you a convenient way to turn-off the alternator ).
However, I'm not sure I'm following you...
The best way to shut-down a standard, externally-regulated alternator is to turn-off its regulator. The regulator usually draws less than 1 amp, so you will commonly see a 1 or 2 amp Tyco Series 23 circuit breaker feeding the regulator. Like this:
The Over Voltage Modules we've been talking about are designed to create a short circuit on the field breaker when high voltage is present, thus popping it and shutting-down an errant regulator/alternator.
In this scenario, there is no big circuit breaker in the output of the alternator because it's not needed. The output of the alternator is controlled by the regulator & its circuit breaker. (And therein lies the beauty of this system: no big breaker required and no big wires running to that breaker in the panel.)
So, I'm a little confused by your question: "... Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?"
Perhaps I'm missing something? Are you referring to one of BobN's Z drawings? Do you have a schematic of the system you are talking about? (a schematic is worth a thousand words)
-Jeff
On Friday, December 12, 2014 8:23 AM, Ken Ryan <keninalaska(at)gmail.com> wrote:
Thanks Jeff. Are you saying that it would be okay to use the OVP device to blow a fuse? Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?
On Thu, Dec 11, 2014 at 9:28 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote: | Quote: |
The idea behind feeding the Regulator with a circuit breaker is that it gives the pilot the ability to shut-down the alternator (by pulling the breaker) if that becomes necessary.
A few reasons you might want to shut down the alternator are:1. a failed regulator that is giving full field (if you don't have an over voltage module)2. a failed over-voltage module3. testing purposesA breaker is simply more practical in this situation.
On Thursday, December 11, 2014 3:35 PM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ?
| Quote: |
_blank">www.aeroelectric.com
.com" target="_blank">www.buildersbooks.com
="_blank">www.homebuilthelp.com
="_blank">www.mypilotstore.com
ank">www.mrrace.com
_blank">http://www.matronics.com/contribution
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
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[quote][b]
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Fri Dec 12, 2014 2:29 pm Post subject: fuse or breaker for OVP? |
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Thanks Jeff. Your reply is very helpful. I am developing schematics, but have no easy way of scanning them. My system (Rotax) will have two engine driven current producers. One of them is a more traditional alternator with the internal regulator, and the other a permanent magnet affair with an external regulator that the Z diagrams like to refer to as a "Dynamo."
I understand how the over voltage protection device is (differently) wired for each of these two current producers, how for the alternator it cuts the field circuit and for the dynamo it disconnects the regulator.
But I was unaware that the use of the OVP device eliminates the need for a breaker in the high current charging wire. Now, looking again at the Z drawings, I see that the "fuse" in the high current alternator wire is marked by "note 10" which makes reference to something called a "fuse like device called a current limiter."
How is this "current limiter" different from a fuse or breaker and why is it preferable to a fuse or breaker?
Now, when I look at the Rotax specific drawing, I see the high current wire from the "dynamo" seems to be protected by a 16 gauge fusible link. The "dynamo" is rated at 22 amps. Is the 16 gauge fusible link up to the task? Why would I want to use a fusible link, rather than a fuse or a breaker?
Ken
On Fri, Dec 12, 2014 at 12:18 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote:[quote]Ken,
To answer your question directly: Yes, it's okay to use a fuse w/ an OVM. It will just be more difficult to reset ( and it does not give you a convenient way to turn-off the alternator ).
However, I'm not sure I'm following you...
The best way to shut-down a standard, externally-regulated alternator is to turn-off its regulator. The regulator usually draws less than 1 amp, so you will commonly see a 1 or 2 amp Tyco Series 23 circuit breaker feeding the regulator. Like this:
The Over Voltage Modules we've been talking about are designed to create a short circuit on the field breaker when high voltage is present, thus popping it and shutting-down an errant regulator/alternator.
In this scenario, there is no big circuit breaker in the output of the alternator because it's not needed. The output of the alternator is controlled by the regulator & its circuit breaker. (And therein lies the beauty of this system: no big breaker required and no big wires running to that breaker in the panel.)
So, I'm a little confused by your question: "... Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?"
Perhaps I'm missing something? Are you referring to one of BobN's Z drawings? Do you have a schematic of the system you are talking about? (a schematic is worth a thousand words)
-Jeff
On Friday, December 12, 2014 8:23 AM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
Thanks Jeff. Are you saying that it would be okay to use the OVP device to blow a fuse? Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?
On Thu, Dec 11, 2014 at 9:28 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote: | Quote: |
The idea behind feeding the Regulator with a circuit breaker is that it gives the pilot the ability to shut-down the alternator (by pulling the breaker) if that becomes necessary.
A few reasons you might want to shut down the alternator are:1. a failed regulator that is giving full field (if you don't have an over voltage module)2. a failed over-voltage module3. testing purposesA breaker is simply more practical in this situation.
On Thursday, December 11, 2014 3:35 PM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ?
|
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_blank">www.aeroelectric.com
.com" target="_blank">www.buildersbooks.com
="_blank">www.homebuilthelp.com
="_blank">www.mypilotstore.com
ank">www.mrrace.com
_blank">http://www.matronics.com/contribution
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
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[b]
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ceengland7(at)gmail.com
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| Posted: Fri Dec 12, 2014 3:37 pm Post subject: fuse or breaker for OVP? |
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I'm not Jeff, but,
A very short length (4"-6") of wire will carry much more current than its 'rated' capacity (which is for much longer lengths), and that's the basis on which the fusible link idea arises.
Fusible links are common in cars these days for wire runs that have a very low likelihood of overcurrent due to their load, but still need to be protected from catastrophic faults (like pinched insulation causing a short to ground). You can buy silicone-protected fusible link wire in bulk on line in various sizes for protecting heavier wire. Common practice is to make the link smaller by 4 numbers than the wire it protects (a 16ga link protects a 12ga wire). Like a fuse or breaker, it should be placed on the current source end of the wire. Properly installed, they are much less prone to defect-induced failure than circuit breakers or fuses (and much, much cheaper than a/c circuit breakers). Somewhere in 'the book' you should find a reference to making your own fusible link. It basically amounts to sliding a woven fiberglass sleeve over the smaller gauge wire link and the joint between link & wire. Download the book in digital form & use Acrobat Reader's search function to find the references. If that isn't clear, just ask for more detail.
Charlie
On 12/12/2014 4:27 PM, Ken Ryan wrote:
[quote] Thanks Jeff. Your reply is very helpful. I am developing schematics, but have no easy way of scanning them. My system (Rotax) will have two engine driven current producers. One of them is a more traditional alternator with the internal regulator, and the other a permanent magnet affair with an external regulator that the Z diagrams like to refer to as a "Dynamo."
I understand how the over voltage protection device is (differently) wired for each of these two current producers, how for the alternator it cuts the field circuit and for the dynamo it disconnects the regulator.
But I was unaware that the use of the OVP device eliminates the need for a breaker in the high current charging wire. Now, looking again at the Z drawings, I see that the "fuse" in the high current alternator wire is marked by "note 10" which makes reference to something called a "fuse like device called a current limiter."
How is this "current limiter" different from a fuse or breaker and why is it preferable to a fuse or breaker?
Now, when I look at the Rotax specific drawing, I see the high current wire from the "dynamo" seems to be protected by a 16 gauge fusible link. The "dynamo" is rated at 22 amps. Is the 16 gauge fusible link up to the task? Why would I want to use a fusible link, rather than a fuse or a breaker?
Ken
On Fri, Dec 12, 2014 at 12:18 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote: | Quote: | Ken,
To answer your question directly: Yes, it's okay to use a fuse w/ an OVM. It will just be more difficult to reset ( and it does not give you a convenient way to turn-off the alternator ).
However, I'm not sure I'm following you...
The best way to shut-down a standard, externally-regulated alternator is to turn-off its regulator. The regulator usually draws less than 1 amp, so you will commonly see a 1 or 2 amp Tyco Series 23 circuit breaker feeding the regulator. Like this:
The Over Voltage Modules we've been talking about are designed to create a short circuit on the field breaker when high voltage is present, thus popping it and shutting-down an errant regulator/alternator.
In this scenario, there is no big circuit breaker in the output of the alternator because it's not needed. The output of the alternator is controlled by the regulator & its circuit breaker. (And therein lies the beauty of this system: no big breaker required and no big wires running to that breaker in the panel.)
So, I'm a little confused by your question: "... Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?"
Perhaps I'm missing something? Are you referring to one of BobN's Z drawings? Do you have a schematic of the system you are talking about? (a schematic is worth a thousand words)
-Jeff
On Friday, December 12, 2014 8:23 AM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
Thanks Jeff. Are you saying that it would be okay to use the OVP device to blow a fuse? Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?
On Thu, Dec 11, 2014 at 9:28 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote: | Quote: |
The idea behind feeding the Regulator with a circuit breaker is that it gives the pilot the ability to shut-down the alternator (by pulling the breaker) if that becomes necessary.
A few reasons you might want to shut down the alternator are: 1. a failed regulator that is giving full field (if you don't have an over voltage module) 2. a failed over-voltage module 3. testing purposes A breaker is simply more practical in this situation.
On Thursday, December 11, 2014 3:35 PM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ?
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[b]
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jimkale(at)roadrunner.com
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| Posted: Fri Dec 12, 2014 8:59 pm Post subject: fuse or breaker for OVP? |
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I’d like to down load “the book” if anyone can tell me what it is????
Jim Kale
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Charlie England
Sent: Friday, December 12, 2014 5:39 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: fuse or breaker for OVP?
I'm not Jeff, but,
A very short length (4"-6") of wire will carry much more current than its 'rated' capacity (which is for much longer lengths), and that's the basis on which the fusible link idea arises.
Fusible links are common in cars these days for wire runs that have a very low likelihood of overcurrent due to their load, but still need to be protected from catastrophic faults (like pinched insulation causing a short to ground). You can buy silicone-protected fusible link wire in bulk on line in various sizes for protecting heavier wire. Common practice is to make the link smaller by 4 numbers than the wire it protects (a 16ga link protects a 12ga wire). Like a fuse or breaker, it should be placed on the current source end of the wire. Properly installed, they are much less prone to defect-induced failure than circuit breakers or fuses (and much, much cheaper than a/c circuit breakers). Somewhere in 'the book' you should find a reference to making your own fusible link. It basically amounts to sliding a woven fiberglass sleeve over the smaller gauge wire link and the joint between link & wire. Download the book in digital form & use Acrobat Reader's search function to find the references. If that isn't clear, just ask for more detail.
Charlie
On 12/12/2014 4:27 PM, Ken Ryan wrote:
| Quote: |
Thanks Jeff. Your reply is very helpful. I am developing schematics, but have no easy way of scanning them. My system (Rotax) will have two engine driven current producers. One of them is a more traditional alternator with the internal regulator, and the other a permanent magnet affair with an external regulator that the Z diagrams like to refer to as a "Dynamo."
I understand how the over voltage protection device is (differently) wired for each of these two current producers, how for the alternator it cuts the field circuit and for the dynamo it disconnects the regulator.
But I was unaware that the use of the OVP device eliminates the need for a breaker in the high current charging wire. Now, looking again at the Z drawings, I see that the "fuse" in the high current alternator wire is marked by "note 10" which makes reference to something called a "fuse like device called a current limiter."
How is this "current limiter" different from a fuse or breaker and why is it preferable to a fuse or breaker?
Now, when I look at the Rotax specific drawing, I see the high current wire from the "dynamo" seems to be protected by a 16 gauge fusible link. The "dynamo" is rated at 22 amps. Is the 16 gauge fusible link up to the task? Why would I want to use a fusible link, rather than a fuse or a breaker?
Ken
On Fri, Dec 12, 2014 at 12:18 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote: | Quote: |
Ken,
To answer your question directly: Yes, it's okay to use a fuse w/ an OVM. It will just be more difficult to reset ( and it does not give you a convenient way to turn-off the alternator ).
However, I'm not sure I'm following you...
The best way to shut-down a standard, externally-regulated alternator is to turn-off its regulator. The regulator usually draws less than 1 amp, so you will commonly see a 1 or 2 amp Tyco Series 23 circuit breaker feeding the regulator. Like this:
[img]cid:~WRD000.jpg[/img]
The Over Voltage Modules we've been talking about are designed to create a short circuit on the field breaker when high voltage is present, thus popping it and shutting-down an errant regulator/alternator.
In this scenario, there is no big circuit breaker in the output of the alternator because it's not needed. The output of the alternator is controlled by the regulator & its circuit breaker. (And therein lies the beauty of this system: no big breaker required and no big wires running to that breaker in the panel.)
So, I'm a little confused by your question: "... Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?"
Perhaps I'm missing something? Are you referring to one of BobN's Z drawings? Do you have a schematic of the system you are talking about? (a schematic is worth a thousand words)
-Jeff
On Friday, December 12, 2014 8:23 AM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
Thanks Jeff. Are you saying that it would be okay to use the OVP device to blow a fuse? Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?
On Thu, Dec 11, 2014 at 9:28 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote: | Quote: |
The idea behind feeding the Regulator with a circuit breaker is that it gives the pilot the ability to shut-down the alternator (by pulling the breaker) if that becomes necessary.
A few reasons you might want to shut down the alternator are:
1. a failed regulator that is giving full field (if you don't have an over voltage module)
2. a failed over-voltage module
3. testing purposes
A breaker is simply more practical in this situation.
On Thursday, December 11, 2014 3:35 PM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ?
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ceengland7(at)gmail.com
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| Posted: Fri Dec 12, 2014 9:43 pm Post subject: fuse or breaker for OVP? |
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user9253
Joined: 28 Mar 2008
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nuckolls.bob(at)aeroelect
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| Posted: Sat Dec 13, 2014 9:27 am Post subject: fuse or breaker for OVP? |
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At 17:38 2014-12-12, you wrote:
| Quote: | I'm not Jeff, but,
A very short length (4"-6") of wire will carry much more current than its 'rated' capacity (which is for much longer lengths), and that's the basis on which the fusible link idea arises.
Fusible links are common in cars these days for wire runs that have a very low likelihood of overcurrent due to their load, but still need to be protected from catastrophic faults (like pinched insulation causing a short to ground). You can buy silicone-protected fusible link wire in bulk on line in various sizes for protecting heavier wire. Common practice is to make the link smaller by 4 numbers than the wire it protects (a 16ga link protects a 12ga wire). Like a fuse or breaker, it should be placed on the current source end of the wire. Properly installed, they are much less prone to defect-induced failure than circuit breakers or fuses (and much, much cheaper than a/c circuit breakers). Somewhere in 'the book' you should find a reference to making your own fusible link. It basically amounts to sliding a woven fiberglass sleeve over the smaller gauge wire link and the joint between link & wire. Download the book in digital form & use Acrobat Reader's search function to find the references. If that isn't clear, just ask for more detail. |
It's not described in the book . . . but a search at
aeroelectric.com on "fusible link" will produce a
comic book on its fabrication . . .
Bob . . . [quote][b]
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Sat Dec 13, 2014 9:52 am Post subject: fuse or breaker for OVP? |
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On something like a generator charging wire that is connected to the battery, since either end of the wire can be the power source, would it make sense to put a fusible link at each end of the wire?
On Sat, Dec 13, 2014 at 8:22 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:[quote] At 17:38 2014-12-12, you wrote:
| Quote: | I'm not Jeff, but,
A very short length (4"-6") of wire will carry much more current than its 'rated' capacity (which is for much longer lengths), and that's the basis on which the fusible link idea arises.
Fusible links are common in cars these days for wire runs that have a very low likelihood of overcurrent due to their load, but still need to be protected from catastrophic faults (like pinched insulation causing a short to ground). You can buy silicone-protected fusible link wire in bulk on line in various sizes for protecting heavier wire. Common practice is to make the link smaller by 4 numbers than the wire it protects (a 16ga link protects a 12ga wire). Like a fuse or breaker, it should be placed on the current source end of the wire. Properly installed, they are much less prone to defect-induced failure than circuit breakers or fuses (and much, much cheaper than a/c circuit breakers). Somewhere in 'the book' you should find a reference to making your own fusible link. It basically amounts to sliding a woven fiberglass sleeve over the smaller gauge wire link and the joint between link & wire. Download the book in digital form & use Acrobat Reader's search function to find the references. If that isn't clear, just ask for more detail. |
It's not described in the book . . . but a search at
aeroelectric.com on "fusible link" will produce a
comic book on its fabrication . . .
Bob . . . | Quote: |
_blank">www.aeroelectric.com
.com" target="_blank">www.buildersbooks.com
="_blank">www.homebuilthelp.com
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nuckolls.bob(at)aeroelect
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| Posted: Sat Dec 13, 2014 10:00 am Post subject: fuse or breaker for OVP? |
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At 17:35 2014-12-11, you wrote:
| Quote: | | I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ? |
Either device will function as-intended . . . open the alternator field circuit when an ov condition is detected. Suggest you review the discussions unique to "crowbar" ov protection on aeroelectric.com
http://tinyurl.com/q48agpd
You will discover both the reasoning behind adoption of this technique along with recommendations for its use on your airplane.
If your project includes a circuit breaker panel, then the choice for fuse vs. breakers is moot. If your choice of circuit protection leans toward fuses, then the breaker is recommended for (1) convenient inflight reset (ONLY ONE TIME) in case of a nuisance trip, (2) ground maintenance operations where you'd like to stop a non-rotating alternator from draining the battery. The later is applicable only if you use the simple, two-pole, two-position DC master that brings battery and alternator on at the same time. If you choose to use the three-position, on-on-on switch shown on various z-figures, OFF, BAT, BAT+ALT then the pullable breaker for ground ops is not necessary.
But in terms of OV protection, either fuse or breaker will do the job.
Bob . . . [quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Sat Dec 13, 2014 10:03 am Post subject: fuse or breaker for OVP? |
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At 11:47 2014-12-13, you wrote:
| Quote: | | On something like a generator charging wire that is connected to the battery, since either end of the wire can be the power source, would it make sense to put a fusible link at each end of the wire? |
Not normally needed. An alternator is magnetically incapable of blowing it's own b-lead protection. You need protect only the battery-end of the b-lead.
Bob . . . [quote][b]
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