Fusing Hi-Ouput Alternator?

[nautikaljeeper]

I have installed a 140 amp Electromaxx alternator on my Yanmar 3YM30. The
2/0 cables to the battery selector from the 420 amp hour AGM house battery
bank and the 200 amp hour AGM starter battery are both currently protected
with 300 amp class T fuses within 7” of each battery positive terminal. The
wire runs from battery selector to starter are also 2/0. The negative
cables are all also 2/0.

The + wire from the alternator to starter is 2ga with 18 inch length.

The round trip length from the starter to selector switch
and on to the batteries is 50’ so at 14.2V and 100 amps I expect about a
2.7% voltage drop with 2/0 cable.

I will be installing a Balmar MC-614-H external regulator with temperature
sensors for both batteries and alternator.

I normally set the selector switch to “both” and discharge and charge the
battery banks simultaneously.

My understanding from reading much of the information is that I need to fuse
the wire run from alt to starter or the 15 feet from starter to battery
selector, which of course runs to battery banks.

Questions:

1) Should I put a fuse between the alternator and the starter or between
the starter and selector switch ?

2) Which is the best kind of protection (Class T, ANL, ANN) for the wire
from the alternator ?

I am confused how to protect the alternator from being damaged when the
protection fuse is blown in the alternator-starter-battery switch run.

Is it suggested that a zap-stop (zener diode) protection is used on +
alternator output?

Will a single zap-stop be able to sink the 140amp/14V (~1.9kWatts) output
for a second without failing?

The “new” Balmar TSP (transient spike protection) device looks to be the
same as the “old” zap-stop but with a fuse in line. If the TSP is trying to
sink 1.9kW won’t that poor old fuse blow and defeat the purpose of the TSP,
which is to provide a path to ground for the un-dissipated energy in the
spinning alternator?

 

[Maine Sail]

I'd suggest running the alternator directly to the house bank and fuse it there.

Let an ACR or Echo type charger take care of charging the second bank or feel free to use BOTH....

Wire the batts you use as house permanently in parallel. (it seems you are using the house bank in parallel with a switch)

With the MC-614 you will then lead the voltage sense wire direct to the house bank, you can't do this with the alt running through a 1/2/BOTH switch, and the alt reg can then compensate for any voltage drop.

Fusing always goes within a few inches of the "source" which in this case is the battery bank. If you step down in wire size and the fuse is outside the 150% of max ampacity range then you can opt for an additional fuse at the step down.

 

[Stu Jackson]

Here is some backup material to help you wire the alternator output to the house bank. Add a switch in the output line to be able to work on the engine and avoid a "live" alternator.

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

 

[nautikaljeeper]

Wire the batts you use as house permanently in parallel. (it seems you are using the house bank in parallel with a switch)

I appreciate your suggestion but I don't think I made myself clear as to how my system is wired. I will try to post a diagram soon tomorrow.

There is a separate 2/0 wire run from each bank to the 1/2/all switch that is fused at each battery bank. From the switch runs a 2/0 to the starter. If I do what you suggest I still am confused how to fuse from the starter to the batt. That run would be 10 plus feet.

 

[nautikaljeeper]

Wire the batts you use as house permanently in parallel. (it seems you are using the house bank in parallel with a switch)

I appreciate your suggestion but I don't think I made myself clear as to how my system is wired. I will try to post a diagram soon tomorrow.

There is a separate 2/0 wire run from each bank to the 1/2/all switch that is fused at each battery bank. From the switch runs a 2/0 to the starter. If I do what you suggest I still am confused how to fuse from the starter to the batt. That run would be 10 plus feet.

Sorry for the confusion the top part of this reply is from Maine Sail's response. I meant to hit the edit button.

 

[nautikaljeeper]

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowner...d.php?t=137615

The first diagram that is shown is what I currently have. I fully understand this system and do appreciate the issues you raise about the system. However, my question was how to fuse the alt-starter- C Post path.

Please refer back to my 5 questions I asked in my original post.
Thanks again for your response and I appreciate all your feedback.

 

[Maine Sail]

Questions:

1) Should I put a fuse between the alternator and the starter or between
the starter and selector switch ?

Neither the fuse goes at the battery. Technically the 2GA wire is a tad small to be protected by a 300A fuse but in a dead short it will still blow. I have blown 15' of 8GA wire with a 300A fuse and a LiFePO4 lithium bank capable of well over 20,000A into a dead short. The wire never even got warm. You could always bump the 18" alt wire to 1GA, 1/0 or 2/0 and then the 300A fuse would meet the ABYC guidelines..

2) Which is the best kind of protection (Class T, ANL, ANN) for the wire
from the alternator ?

You already have Class T fuses. These are excellent. ANN fuses are not ideal where starting loads will be used but ANL and MRBF's are. If using ANL please use the ignition protection rated fuses like those sold by Blue Sea and manufactured by Cooper Bussman..

I am confused how to protect the alternator from being damaged when the
protection fuse is blown in the alternator-starter-battery switch run.

The fuse is at the battery and this fuse should never blow. If it does you have much larger issues than an alt rebuild. There is no protection fuse for the alt the protection is for the wire. Alternators are self limiting devices and do not require any fusing at the alt end of the wire. The fuse goes at the battery end closest to the source..

Is it suggested that a zap-stop (zener diode) protection is used on +
alternator output?

Will a single zap-stop be able to sink the 140amp/14V (~1.9kWatts) output
for a second without failing?

The “new” Balmar TSP (transient spike protection) device looks to be the
same as the “old” zap-stop but with a fuse in line. If the TSP is trying to
sink 1.9kW won’t that poor old fuse blow and defeat the purpose of the TSP,
which is to provide a path to ground for the un-dissipated energy in the
spinning alternator?

The best protection for the alt is to run it direct to the house bank with its own dedicated fuse. This way no load dumps via the 1/2/BOTH switch are possible. TSP's often do not work IME. I still have to rebuild alts that blew with Zap Stops etc..

I would not personally wire a 140A alt without a direct run to the bank and the ability for proper voltage sensing.

 

[TacomaSailor]

I am somewhat confused by several of these responses.

MaineSail says:
"The fuse is at the battery and this fuse should never blow. If it does you have much larger issues than an alt rebuild. There is no protection fuse for the alt the protection is for the wire. Alternators are self limiting devices and do not require any fusing at the alt end of the wire. The fuse goes at the battery end closest to the source.."

What is being protected if the fuse in the alternator-starter-battery path is at the + battery terminal? That fuse would only blow if the draw from the battery exceeded the fuse rating and there is already a 300A Class T fuse on the load side of the battery circuit to the C Post. Isn't the recommended fuse in the alternator-battery path redundant? What circumstance would cause your recommended fuse to blow?

What protects the 15' of 2/0 wire in the starter-battery path when the fuse is at the battery end? If that 2/0 cable were to ground between the starter and the battery the battery side fuse would not see the ground and would not blow. The alternator would then be connected to a dead short and would be putting over 2kW into the boat. What would stop the alternator from continuing to supply that power to the ground?

My understanding of circuit protection is, as you say "the protection is for the wire.", yet the fuse you recommend seems to ignore the 15' of cable.

Even more confusing is your statement "The best protection for the alt is to run it direct to the house bank with its own dedicated fuse. This way no load dumps via the 1/2/BOTH switch are possible."

If your recommended dedicated fuse blows - then the alternator will see an open circuit and will suffer a load dump just as it would with a 1/Both/2/Off switch since the blown fuse exactly duplicates a Off switch.

What am I mis-understanding here?

19 years ago I wired my boat as suggested with a direct path from my 135 amp alternator to my 625 amp hour house bank and do use an echo charger. The system has worked flawlessly through years of cruising and live aboard. But, I am still puzzled by a couple of your answers.

 

[nautikaljeeper]

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615[/QUOTE]

Ok so the first diagram that is shown is the way my boat was wired. All I did was to upgrade wire run from 1/2/both switch to alternator to 2/0 and a 140 amp alternator. I will be installing the Balmar MC-614-H external regulator hoping it will work on MY system the way it is wired. I like to use my house bank and starter bank combine so I don't draw batteries as low as if only house bank is used. I constantly monitor my batteries so I don't worry about running battery too low so motor won't start.

I understand running alternator straight to house bank but still confused as to what would happen if there is a short in that run. Fuse would blow at battery bank but now what would stop power running from the alternator to the short. Hence my concern for alternator damage or possible fire.

 

[Stu Jackson]

If the alternator is running and the fuse blows, the alternator diodes blow. This is just like having it wired to the 1-2-B switch and turning the switch off. The advantage of having the AO going direct to the house bank is that it avoids having it go through the switch, as discussed in detail in the link.

If the fuse blows, and it's wired to the house bank, you have other problems.

Also, using the switch as a charging selector is also discussed in the link, in great detail. Using both to start your engine is unnecessary, but since you have it set up as a charging as well as use source, and don't have an echo charger yet, it's the only way to charge your reserve bank.

"Hoping" that a regulator will work makes little sense. It would be preferable to purchase and install equipment "knowing" it will work, not "hoping." Unless I'm missing your emphasis.

Why not KISS and follow the suggestions made in the links? Maine Sail and I wrote those many, many years ago, and many, many skippers have followed those suggestions with good reason: you can turn the 1-2-B switch off when the AO goes to the house bank and you'll never damage anything.

Good luck. I hope this answered your question. If not, please let us know.

 

[Maine Sail]

What is being protected if the fuse in the alternator-starter-battery path is at the + battery terminal? That fuse would only blow if the draw from the battery exceeded the fuse rating and there is already a 300A Class T fuse on the load side of the battery circuit to the C Post. Isn't the recommended fuse in the alternator-battery path redundant? What circumstance would cause your recommended fuse to blow?

The recommended fuse is to protect the large GA battery/starter/alt cables. A wire chafing, loose terminal etc. creating a dead short is what these are for. Your "loads" should never exceed the fuse. If they can the fuse is sized improperly. They are there for catastrophic shorts in the large gauge wiring and to protect this wiring from the batteries..

What protects the 15' of 2/0 wire in the starter-battery path when the fuse is at the battery end?

The fuse..

If that 2/0 cable were to ground between the starter and the battery the battery side fuse would not see the ground and would not blow.

How would it not see ground if that is where it grounded to..? The banks are always connected to grnd/earth/eng to complete the circuit. If you short the battery cable to ground it is shorting to ground....

The alternator would then be connected to a dead short and would be putting over 2kW into the boat. What would stop the alternator from continuing to supply that power to the ground?

Even if the alt continued to work it can not exceed its rating. This is called a "self limiting device. The wire is sized to handle 140A continuously so the wire can handle all the alternators current safely and no fire. The max allowable ampacity of 2/0 wire, inside an engine space, and under ABYC E-11 is 420A @ 150% and 280A @ 100%. So the alt can't even touch with wires max ampacity with its 140A.

What the wires can not handle is the short circuit current that can be created by an AGM battery bank. With some AGM batteries this can approach 5000A of short circuit current for each parallel wired battery. As single group 31 AGM by Odyssey/Die Hard is capable of 5000A of current into a short. 5000A for just one battery!!!! If you have a bank of four, 400Ah, this is 20,000A. Your alt is still only 140A into a dead short........ The batteries are not self limiting and can easily exceed the capability if the wire, the alternator can not exceed this..

My understanding of circuit protection is, as you say "the protection is for the wire.", yet the fuse you recommend seems to ignore the 15' of cable.

This wire is fully protected and the fuse is required to be at the battery end. There is no fuse required for self limiting devices. This means that entire circuit is best protected at the "source end" or within 7" of the battery bank as he has already done and as is required under ABYC E-11 for house banks..

Even more confusing is your statement "The best protection for the alt is to run it direct to the house bank with its own dedicated fuse. This way no load dumps via the 1/2/BOTH switch are possible."

If your recommended dedicated fuse blows - then the alternator will see an open circuit and will suffer a load dump just as it would with a 1/Both/2/Off switch since the blown fuse exactly duplicates a Off switch.

It is not confusing when you realize that the #1 reason I see for blown diodes is a battery switch moved through the OFF position with the engine running. A properly sized fuse will not and should never blow unless there is a catastrophic short. If you have a short the blown diodes are the cost of sloppy wiring or what ever caused the short. If you have a short, and do not have this fuse, the cost to you is a BOAT FIRE. I think sacrificing an alt is the safer and much less expensive option / approach. I have even seen a starter solenoid fracture and the wire dangle and short to the engine block. If you believe a Zap Stop works feel free to add one but I have seen a number of them toasted and the alt diodes still blown when the battery switch dumped the load.

What am I mis-understanding here?

19 years ago I wired my boat as suggested with a direct path from my 135 amp alternator to my 625 amp hour house bank and do use an echo charger. The system has worked flawlessly through years of cruising and live aboard. But, I am still puzzled by a couple of your answers.

It sounds as if you are missing the proper fusing for your alt circuit at the battery end. Remember these fuses are for emergency situations and protection of catastrophic shorts to prevent the wire insulation from melting and starting a fire. You've been lucky you've not had a short.

55% of all boat fires are electrical in nature (source ABYC). This when we have millions of gasoline powered boats as well as LP gas on-board etc. etc..

 

[Maine Sail]

I will be installing the Balmar MC-614-H external regulator hoping it will work on MY system the way it is wired.

It will work but will not work as well as direct wired due to voltage drops. The systems performance you paid for simply won't be nearly as good as direct sensing the house bank.

Will work and best performance and not the same. Even a 3% voltage drop at 14.4V results in just 14.0V at the battery terminals. This means slower charging.

So yes it will work but just won't work the best that the system can.

I understand running alternator straight to house bank but still confused as to what would happen if there is a short in that run. Fuse would blow at battery bank but now what would stop power running from the alternator to the short. Hence my concern for alternator damage or possible fire.

You lose the alt. The concern for fire only arrises if you opt to not have a fuse on that circuit. What's a worse outcome from a short? Losing your boat and potentially endangering your family with a boat fire or sending the alt out for a re-build? I'll pay the $150.00 every time...

Most all alt diode issues I come across are from battery switch load dumps not shorts in that circuit and a fuse blowing. Remember the alt is "self limiting" with wire sized to handle its full output. Your battery bank is not self limiting...

 

[nautikaljeeper]

The recommended fuse is to protect the large GA battery/starter/alt cables. A wire chafing, loose terminal etc. creating a dead short is what these are for. Your "loads" should never exceed the fuse. If they can the fuse is sized improperly. They are there for catastrophic shorts in the large gauge wiring and to protect this wiring from the batteries..



The fuse..



How would it not see ground if that is where it grounded to..? The banks are always connected to grnd/earth/eng to complete the circuit. If you short the battery cable to ground it is shorting to ground....




Even if the alt continued to work it can not exceed its rating. This is called a "self limiting device. The wire is sized to handle 140A continuously so the wire can handle all the alternators current safely and no fire. The max allowable ampacity of 2/0 wire, inside an engine space, and under ABYC E-11 is 420A @ 150% and 280A @ 100%. So the alt can't even touch with wires max ampacity with its 140A.

What the wires can not handle is the short circuit current that can be created by an AGM battery bank. With some AGM batteries this can approach 5000A of short circuit current for each parallel wired battery. As single group 31 AGM by Odyssey/Die Hard is capable of 5000A of current into a short. 5000A for just one battery!!!! If you have a bank of four, 400Ah, this is 20,000A. Your alt is still only 140A into a dead short........ The batteries are not self limiting and can easily exceed the capability if the wire, the alternator can not exceed this..



This wire is fully protected and the fuse is required to be at the battery end. There is no fuse required for self limiting devices. This means that entire circuit is best protected at the "source end" or within 7" of the battery bank as he has already done and as is required under ABYC E-11 for house banks..



It is not confusing when you realize that the #1 reason I see for blown diodes is a battery switch moved through the OFF position with the engine running. A properly sized fuse will not and should never blow unless there is a catastrophic short. If you have a short the blown diodes are the cost of sloppy wiring or what ever caused the short. If you have a short, and do not have this fuse, the cost to you is a BOAT FIRE. I think sacrificing an alt is the safer and much less expensive option / approach. I have even seen a starter solenoid fracture and the wire dangle and short to the engine block. If you believe a Zap Stop works feel free to add one but I have seen a number of them toasted and the alt diodes still blown when the battery switch dumped the load.



It sounds as if you are missing the proper fusing for your alt circuit at the battery end. Remember these fuses are for emergency situations and protection of catastrophic shorts to prevent the wire insulation from melting and starting a fire. You've been lucky you've not had a short.

55% of all boat fires are electrical in nature (source ABYC). This when we have millions of gasoline powered boats as well as LP gas on-board etc. etc..

Quote by Maine Sail "Even if the alt continued to work it can not exceed its rating. This is called a "self limiting device. The wire is sized to handle 140A continuously so the wire can handle all the alternators current safely and no fire. The max allowable ampacity of 2/0 wire, inside an engine space, and under ABYC E-11 is 420A @ 150% and 280A @ 100%. So the alt can't even touch with wires max ampacity with its 140A".

This is the answer I was to question I was asking. Thank you Maine Sail and thank you TacomaSailor for for chiming in. I understand the functions of my 1/2/both switch VERY well and there will be nobody but me using that switch. My thought is by combining my house bank and starter bank is a larger bank to draw from and

 

[nautikaljeeper]

The recommended fuse is to protect the large GA battery/starter/alt cables. A wire chafing, loose terminal etc. creating a dead short is what these are for. Your "loads" should never exceed the fuse. If they can the fuse is sized improperly. They are there for catastrophic shorts in the large gauge wiring and to protect this wiring from the batteries..



The fuse..



How would it not see ground if that is where it grounded to..? The banks are always connected to grnd/earth/eng to complete the circuit. If you short the battery cable to ground it is shorting to ground....

Even if the alt continued to work it can not exceed its rating. This is called a "self limiting device. The wire is sized to handle 140A continuously so the wire can handle all the alternators current safely and no fire. The max allowable ampacity of 2/0 wire, inside an engine space, and under ABYC E-11 is 420A @ 150% and 280A @ 100%. So the alt can't even touch with wires max ampacity with its 140A.

What the wires can not handle is the short circuit current that can be created by an AGM battery bank. With some AGM batteries this can approach 5000A of short circuit current for each parallel wired battery. As single group 31 AGM by Odyssey/Die Hard is capable of 5000A of current into a short. 5000A for just one battery!!!! If you have a bank of four, 400Ah, this is 20,000A. Your alt is still only 140A into a dead short........ The batteries are not self limiting and can easily exceed the capability if the wire, the alternator can not exceed this..



This wire is fully protected and the fuse is required to be at the battery end. There is no fuse required for self limiting devices. This means that entire circuit is best protected at the "source end" or within 7" of the battery bank as he has already done and as is required under ABYC E-11 for house banks..



It is not confusing when you realize that the #1 reason I see for blown diodes is a battery switch moved through the OFF position with the engine running. A properly sized fuse will not and should never blow unless there is a catastrophic short. If you have a short the blown diodes are the cost of sloppy wiring or what ever caused the short. If you have a short, and do not have this fuse, the cost to you is a BOAT FIRE. I think sacrificing an alt is the safer and much less expensive option / approach. I have even seen a starter solenoid fracture and the wire dangle and short to the engine block. If you believe a Zap Stop works feel free to add one but I have seen a number of them toasted and the alt diodes still blown when the battery switch dumped the load.



It sounds as if you are missing the proper fusing for your alt circuit at the battery end. Remember these fuses are for emergency situations and protection of catastrophic shorts to prevent the wire insulation from melting and starting a fire. You've been lucky you've not had a short.

55% of all boat fires are electrical in nature (source ABYC). This when we have millions of gasoline powered boats as well as LP gas on-board etc. etc..

Lets try this again. Were are having problems with the internet service at our marina.


This is the answer to my question I was asking. Thank you Maine Sail and thank you TacomaSailor for for chiming in. I understand the functions of my 1/2/both switch VERY well and there will be nobody but me using that switch. My thought is by combining my house bank and starter bank there is a larger bank to draw from and depth of discharge per cycle is much less. You might ask why I don't take one of the start batteries and add it to the house bank? They are not the same group size. Originally I was going to isolate the starter banks and house bank with switch for drawing loads but my theory of minimizing depth of discharge is what led me to my reasoning.

 

[nautikaljeeper]

Here is some backup material to help you wire the alternator output to the house bank. Add a switch in the output line to be able to work on the engine and avoid a "live" alternator.

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

Thank you Stu for posting this info. I was hoping I would get feedback from both you and Main Sail. As I said I fully understand the function of the 1/2/both switch as well as the HEF.

 

[Stu Jackson]

nj, you're welcome. I think the issue we may be having a tad of an issue with is "My thought is by combining my house bank and starter bank there is a larger bank to draw from and depth of discharge per cycle is much less."

With a healthy house bank, there's really no reason to do so. Which we "covered" in the links provided. As Maine Sail has posted repeatedly, starting an engine takes all of maybe 1/2 ah out of any battery bank.

I DO think you do know how to operate your switch.

Please, let us know if there's anything else.