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Old 06-26-2018, 01:15 PM   #41
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For starting circuit fuses you might need to go higher than the size terminal fuses are available in. As far as fuse cost is concerned, the SAME MRBF (Buss brand) fuses are available at Del City for $7.58.

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Old 06-26-2018, 05:56 PM   #42
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So! I popped a 300 amp fuse into the port engines battery fuseholder; got one start out of it and it blew. I've taken the fuse out of the holder and replaced it with a...wait for it...a socket. So, I'm back to as safe as the original system was and, if the socket was ABYC approved, in accordance with ABYC standards.
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Old 06-27-2018, 02:39 PM   #43
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I run a 300A fuse on my single start battery that starts twin Perkins 4.236s. (My initial 200A fuse blew also.)

kchace, thanks for the tip on the Dell City MRBF fuse deals. Those are great prices.
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Old 08-15-2018, 07:57 AM   #44
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Well! It's been a long haul. Both engines start and run. And I've removed the sockets and put 300amp fuses in. The engines start and run.
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Old 08-15-2018, 10:24 AM   #45
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For general info....just read that this is the new ABYC standard (2018) ..


"11.10.1.2.3 For batteries or battery banks with a CCA rating greater than 2200 CCA, or 500 amp hours, battery overcurrent protection shall have a minimum ampere interrupting capacity (AIC) rating at least as great as the battery manufacturer’s short circuit rating or be rated at a minimum of 20kA at 125 VDC or higher."
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Old 08-15-2018, 11:53 AM   #46
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Originally Posted by psneeld View Post
For general info....just read that this is the new ABYC standard (2018) ..


"11.10.1.2.3 For batteries or battery banks with a CCA rating greater than 2200 CCA, or 500 amp hours, battery overcurrent protection shall have a minimum ampere interrupting capacity (AIC) rating at least as great as the battery manufacturer’s short circuit rating or be rated at a minimum of 20kA at 125 VDC or higher."

Interesting. I did a quick check and of common marine fuses I only found class T fuses would meet this spec.


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Old 08-15-2018, 12:03 PM   #47
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That is interesting. Nothing in that demands a fuse, though.
Bolted fuses take a bit of time to replace.
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Old 08-15-2018, 01:58 PM   #48
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Originally Posted by psneeld View Post
For general info....just read that this is the new ABYC standard (2018) ..


"11.10.1.2.3 For batteries or battery banks with a CCA rating greater than 2200 CCA, or 500 amp hours, battery overcurrent protection shall have a minimum ampere interrupting capacity (AIC) rating at least as great as the battery manufacturer’s short circuit rating or be rated at a minimum of 20kA at 125 VDC or higher."

I don't even understand what that means. Can anyone translate?
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Old 08-15-2018, 02:04 PM   #49
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Well! It's been a long haul. Both engines start and run. And I've removed the sockets and put 300amp fuses in. The engines start and run.
Great to hear! And the alternators each charge its battery bank??
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Old 08-15-2018, 03:46 PM   #50
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I don't even understand what that means. Can anyone translate?
I think that means... don't touch ends of wire with wet fingers having feet in same water as the bulk of wire travels through from its hot-point.
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Old 08-15-2018, 06:33 PM   #51
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With large battery banks you have enough power to melt down a circuit breaker there by making your circuit protection ineffective. The new standard requires your circuit breaker to not only trip at the correct amperage but to with stand the full onslaught of your battery bank with out failing. If you use components from quality manufacture like Bluesea you probably meet all the standards with out knowing it.

Take wire made by ancor marine. It says right on the wire the gauge and the tempeture. The minimum standard is 80C but anchor wire is built to 105C standard. Most people don’t know about the temperature standard and how it applies but end up safe because of the margin built in by the manufacture. However as one sources cheaper product the first thing that goes is the safety margin.
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Old 08-15-2018, 06:43 PM   #52
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With all due respect, not all battery switches have alt field disconnects, and few battery switches are wired with alt field disconnects.

While "things" happen, there is no logical reason to turn a battery switch to off with the engine(s) running. Also all popular battery switches are "make before break" which means when switching between 1-2- all the switch never disconnects.

While a nice feature to keep people out of trouble with their alternator, saying any switch with an off position MUST have an alt field disconnect is just not true or current practice. Just don't turn the switch to off with the engine(s) running, there is really no reason to.



Electrical fire?
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Old 08-15-2018, 07:27 PM   #53
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"Originally Posted by Keysdisease View Post
With all due respect, not all battery switches have alt field disconnects, and few battery switches are wired with alt field disconnects.

While "things" happen, there is no logical reason to turn a battery switch to off with the engine(s) running. Also all popular battery switches are "make before break" which means when switching between 1-2- all the switch never disconnects.

While a nice feature to keep people out of trouble with their alternator, saying any switch with an off position MUST have an alt field disconnect is just not true or current practice. Just don't turn the switch to off with the engine(s) running, there is really no reason to."




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Electrical fire?
That's exactly why I modified my big cable wiring to separate the charge from the load. All alternator charges goes directly to their respective batteries, appropriately fused with large cable, without regard to the HOUSE and START load switches.

If I have an alternator overcharge or short problem that does not get resolved by the fuses, I can turn off the alternator at the start key. The old Perkins engines continue to purr but my hourmeter loses power.

Each bank can be paralleled as needed and plus a charge combiner with ON-AUTO switched at the lower helm. If I lose one engine, the other alternator can run all systems.

If I have a serious short that the fuses do not properly handle, I have separate START and HOUSE switches on the LOAD side that are located outside the ER. These can be switched to OFF within 3 steps of the lower helm.

I patterned the system after airplanes that have similar layouts.
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Old 08-15-2018, 08:56 PM   #54
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FlyWright, each engine charges its own start batt and, via its own ACR, charges the house bank. If the house bank is sufficiently discharged, the 2 ACRs isolate the 2 start batts. The 110v charger charges each of the three banks through its own fuses. There are MRBFs on each bank so that no hot conductor is unfused. The ACRs are fused as required (each end). Additionally each alternator (now) has its own fuse on its output.
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Old 08-15-2018, 09:32 PM   #55
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FlyWright, each engine charges its own start batt and, via its own ACR, charges the house bank. If the house bank is sufficiently discharged, the 2 ACRs isolate the 2 start batts. The 110v charger charges each of the three banks through its own fuses. There are MRBFs on each bank so that no hot conductor is unfused. The ACRs are fused as required (each end). Additionally each alternator (now) has its own fuse on its output.
Is it a requirement to fuse alt output? If yes why?

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Old 08-16-2018, 08:41 AM   #56
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Lou, Our Perkins were supplied to FuHwa with a fuse in the alt-starter wire, part of the on-engine wiring harness. Of course, that connection at the starter is where the battery is also connected. So it is effectively fusing the alternator to battery connection. When some PO replaced the alternator on the starboard engine, the fuse was removed and that's the wire that melted in my son's miswiring. One of the modes of alternator failure is unregulated charging which would also heat that wire. Another mode of failure is that wire grounding through some fault.


I had the battery-starter wire ground to the engine in my 83 Volvo. Remarkable flames, destroyed the battery and some of the electronics in the car.
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Old 08-16-2018, 10:45 AM   #57
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"11.10.1.2.3 For batteries or battery banks with a CCA rating greater than 2200 CCA, or 500 amp hours, battery overcurrent protection shall have a minimum ampere interrupting capacity (AIC) rating at least as great as the battery manufacturer’s short circuit rating or be rated at a minimum of 20kA at 125 VDC or higher."


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I don't even understand what that means. Can anyone translate?

Yes, what it basically means if you have a battery bank of 500ah or more, any fuse or circuit breaker on that bank needs to be rated to be able to interrupt a minimum of 20,000Amps at 125V.


The reason for this is because in a really bad short circuit, when the fuse or breaker opens the current "wants" to keep flowing and will create an electrical arc between the two points that just opened - high current can continue to flow between the two OPEN points through this arc. Devices that are rated to be able to interrupt high current flow like this use various methods to "quench" the arc that forms and stop the current flow.


Hope that makes sense.


BTW - a quick check of commonly used marine fuses and breakers - I found no breakers and only "T class" fuses meet this spec.



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Old 08-16-2018, 10:56 AM   #58
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Is it a requirement to fuse alt output? If yes why?

L

Technically yes, but the fuse goes at the battery end which is the real source of power and is of course available at all times - not just when the alternator is running.


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Old 08-16-2018, 11:50 AM   #59
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I'll be honest with you guys... I opted NOT to fuse either of the starter runs, nor the alternator connection to the house bank. Is it wrong and a little dangerous? Yea maybe... even probably, but a blown fuse in either place, for even a minor error, renders the alternator toast or an inability to start the boat. Sure, you can (and probably will) argue that both are better than a fire, and you would be correct, however, I felt like I had to weigh the pros and cons. I may change it in the future, but for now, this is how it is.
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Old 08-16-2018, 01:48 PM   #60
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"11.10.1.2.3 For batteries or battery banks with a CCA rating greater than 2200 CCA, or 500 amp hours, battery overcurrent protection shall have a minimum ampere interrupting capacity (AIC) rating at least as great as the battery manufacturer’s short circuit rating or be rated at a minimum of 20kA at 125 VDC or higher."





Yes, what it basically means if you have a battery bank of 500ah or more, any fuse or circuit breaker on that bank needs to be rated to be able to interrupt a minimum of 20,000Amps at 125V.


The reason for this is because in a really bad short circuit, when the fuse or breaker opens the current "wants" to keep flowing and will create an electrical arc between the two points that just opened - high current can continue to flow between the two OPEN points through this arc. Devices that are rated to be able to interrupt high current flow like this use various methods to "quench" the arc that forms and stop the current flow.


Hope that makes sense.


BTW - a quick check of commonly used marine fuses and breakers - I found no breakers and only "T class" fuses meet this spec.



Ken
I spoke with Trojan battery tech and they say the short circuit rating for T-105 golf cart batteries is 2000 amps so if you have the Blue Seas battery terminal fuses, you are OK.

They have a 10000A interupt rating at 14V.
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