New Electrical System Questions

[Frankly]

I actually have a BS maxi fuse block that I was planning to install in series with that jumper. More I thought about it more I decided just didn't make any sense.

Maybe I will put it in before I put Cbreeze on the market in 30 or 40 years.

By the way the NEC (not that the NEC has any standing on boats) has provisions for tap conductors. The 10 ft tap rule is allowed: If the tap will carry the load (as determined by downstream overcurrent protection 36 amps) and the upstream current protection is not more than 10 times the rating of the tap (10% of 250 is 25 amps).

Bear in mind that overload protection could be placed anywhere along the protected conductor (by definition the load is at the load end of the conductor), and the current is the same along the circuit (according to some guy named Kirchoff), the short circuit/ ground fault condition is what drives the protection back to the feed source (where the wire size is typically reduced).


And that my friends is all I am going to say about it.

[Maine Sail]

Originally Posted by ramblinrod

A better way is to have a dedicated start battery connected directly to the alternator, and the house bank combined via a diode isolator, 1/2/both switch, or ACR (in order of lowest to highest preference).

With a diode isolator you would wire direct to the input stud not the start bank but very, very few competent techs in the industry are even using these today, for numerous reasons, not just the voltage drop issue..

With the ACR you may want to investigate relay cycling, something I fix and correct for a fair number of times per year. This is always due to folks not understanding how to correctly wire an ACR into a boat with a large deep cycled house bank and small start bank.

In the case of two unequally sized banks wire the alternator & other charge sources straight to the house bank, the bank that needs it most, and do your voltage sensing here too as this will give you the most optimal charging performance.

Wiring the charge sources to the house bank also avoids running the high charging currents, needed for the cycling bank, across the relay. The relay will now only need to pass a few amps to the start battery, cake walk for the relay, and thus any voltage drop across the wiring and relay will be greatly minimized, as will the issues of relay cycling.

Originally Posted by ramblinrod

This way, the starting battery is dedicated to starting and used (successfully tested) every time the vessel is started. When (not if) the start battery fails, the house bank can be switched over to start the engine (assuming it is wired to do so).

With a 1/2/BOTH switch there really is no dedicated starting battery. You can select bank #1 or bank #2 but neither are really a dedicated starting battery just two banks...

The only way to get a dedicated start battery with a 1/2/BOTH is to add more switches such as a second ON/OFF switch. I do this quite often, when going with three ON/OFF switches is out of the budget, or space does not allow..

There is nothing wrong with using a dedicated start battery, I actually prefer it, but many thousands of boaters do everything on their house bank and keep the second bank charged and in reserve. There is no rite way or wrong way on this. While I generally prefer a dedicated starting battery with its own switch, when I can wire it that way, I am not going to suggest to a customer that he needs to change anything, in that regard, if he is happy starting off the house and using the other battery as an reserve / back up. I do remind them to start off the second bank at least once every three to four weeks to ensure it is still performing but a battery kept at full charge and not used often stays pretty darn healthy.

Originally Posted by ramblinrod

It really doesn't make sense to have an isolated start battery, but to keep it as a back-up and use the house bank to start. (At least, I can't think of a valid, practical reason for doing so.)

This is likely because the vast majority of boats ship, even today, with a 1/2/BOTH switch. To make it easier to charge both banks many owners will add an Echo Charger, battery to battery charger (B2B) or VSR/ACR/Combiner between the banks to avoid the need to manually rotate the switch. When you go with an Echo Charger, Duo Charger or other battery to battery charger all charge sources need to be wired to the house bank anyway.

They usually add these devices to avoid switching back and forth, which can lead to blown diodes or all the batteries on-board drained, if not careful. These owners simply get to the boat, switch to the house bank and enjoy life.

Some owners install the Blue Sea Dual Circuit Plus switch, but that switch really gives you very little options in the way of isolation in the event of a bank malfunction. In the case of an internally shorted battery the only option with that switch is to parallel the shorted bank with the good bank. I generally only install the DCP on small fishing boats with equally sized banks..

Originally Posted by ramblinrod

I recommend connecting the alternator to the starting battery, and the house bank via an ACR. This way, the dedicated starting battery is tested every time you start the engine. When (not if) the starting battery fails, you can manually combine the house bank, to get you out of trouble.

The Blue Sea SI-ACR (start isolator) is the one I recommend to customers.

The Blue Sea ACR's are excellent products, as are the Yandina Combiners. I also use the Blue Sea ML-500 ARC's too which offer both manual and automatic operation and are rated for up to 500A continuous..

I would still urge you to seek out Wayne Kelsoe's excellent tech bulletin on relay cycling. Blue Sea Systems does not suggest wiring an alt direct to a start battery if the other bank is a large deeply cycled house bank.

Here is Blue Seas own diagram for when you have two unequal sized banks. Note that all charge sources are wired direct to the house bank not the start battery. The instructions supplied with the ACR are for boats with two equal sized banks, such as a center console fishing boat...

[Maine Sail]

Originally Posted by ramblinrod

Well, I'm gonna disagree. I should not have stated "instantly". But if those 8 gauge wires the max current they can, they will get hot. Maybe a dead short will trip a fuse, but higher impedance short will not, and they most definitely will light up.

Per ABYC every branch circuit off a main circuit having lighter gauge wires, requires independent current limiting, if the main circuit current limiting capability is too high for the branch circuit wiring. In this case, 250 A into 2 x 8 AWG ~ 3" wires, is too high. They will get hot and burn.

"E-11 - July 2015 - Over Current Protection

11.10.1.1.2 Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection within a distance of seven inches (178 mm) of the point at which the conductor is connected to the source of power measured along the conductor (see FIGURE 14).

EXCEPTIONS:
1. Cranking motor conductors.

2. If the conductor is connected directly to the battery terminal and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box or enclosed panel, the overcurrent protection shall be placed as close as practicable to the battery, but not to exceed 72 inches (1.83 m).

3. If the conductor is connected to a source of power other than a battery terminal and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box or enclosed panel, the overcurrent protection shall be placed as close as practicable to the point of connection to the source of power, but not to exceed 40 inches (1.02 m).

4. Overcurrent protection is not required in conductors from self-limiting alternators with integral regulators if the conductor is less than 40 inches (1.02 m), is connected to a source of power other than the battery, and is contained throughout its entire distance in a sheath or enclosure.

5. Overcurrent protection is not required at an alternator if the ampacity of the conductor is equal to or greater than the rated output of the alternator

6. Pigtails less than 7 inches (178 mm) in length are exempt from overcurrent protection requirements."

[Terra Nova]

The reason it is preferred to charge the start battery, first, is that this battery tops off very quickly, soon allowing all charge to go to the house bank, which may rarely come up to full charge. And to insure you always have full voltage available for starting.

[transmitterdan]

Originally Posted by Terra Nova

The reason it is preferred to charge the start battery, first, is that this battery tops off very quickly, soon allowing all charge to go to the house bank, which may rarely come up to full charge. And to insure you always have full voltage available for starting.

That's precisely why it is better to charge the house first. If using a charge relay like Blue Sea or others when the start battery reaches the "connect" voltage it isn't fully charged. But the discharged house bank will reduce the voltage often below the "disconnect" voltage. There is usually a timer to prevent the relay from oscillating as fast as it can. But it will still oscillate at the timer rate and take literally forever to charge the house bank.

Starting does not discharge a start battery much. You can start a typical sailboat diesel 50 times without recharging. There is no compelling reason to be paranoid about charging it before the house bank.

If the engine requires 60 seconds of cranking to start that is a different problem not related to batteries.

[Maine Sail]

Originally Posted by transmitterdan

That's precisely why it is better to charge the house first. If using a charge relay like Blue Sea or others when the start battery reaches the "connect" voltage it isn't fully charged. But the discharged house bank will reduce the voltage often below the "disconnect" voltage. There is usually a timer to prevent the relay from oscillating as fast as it can. But it will still oscillate at the timer rate and take literally forever to charge the house bank.

Starting does not discharge a start battery much. You can start a typical sailboat diesel 50 times without recharging. There is no compelling reason to be paranoid about charging it before the house bank.

If the engine requires 60 seconds of cranking to start that is a different problem not related to batteries.

I have a rather sophisticated Midtronics tool that allows me to measure the cranking system performance and includes the loaded to unloaded starter duration.. The average cranking time across perhaps 85+ vessels that I have used it on has been between 3/4 of a second and about 3 seconds.

This is:
Averaged voltage during starting (this was a house bank)
Averaged amperage during starting
Loaded to unloaded starter duration

Do the consumption math on 0.765 seconds at 286A....

[Nicholson58]

The best solution to the motor start issue I know was on the Heritage One-Ton I raced from the late 70s. It had a 2-cylinder 35 HP diesel with compression release. You could easily release the compression, spin it up and engage the compression. Started every time, no power needed. Is this feature still available?




On our boat, we have two pretty large house banks with a bat-1, bat-2 switch, a combiner and two-bank variable charging system. I alternate starts using either bank and keep both charged. The battery monitors tell us if a bank is not at full or is in trouble.

[mitiempo]

Originally Posted by ramblinrod

I recommend connecting the alternator to the starting battery, and the house bank via an ACR. This way, the dedicated starting battery is tested every time you start the engine. When (not if) the starting battery fails, you can manually combine the house bank, to get you out of trouble.

The Blue Sea SI-ACR (start isolator) is the one I recommend to customers.

Ramblin Rod

Whether he has a start battery that is used for every start or a battery that is kept in reserve it makes no sense to run the alternator to it rather than the house bank. The house bank will always be the most in need of charging current. Why run that through the start battery first?

[ramblinrod]

Originally Posted by Maine Sail

"E-11 - July 2015 - Over Current Protection

11.10.1.1.2 Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection within a distance of seven inches (178 mm) of the point at which the conductor is connected to the source of power measured along the conductor (see FIGURE 14).

EXCEPTIONS:
1. Cranking motor conductors.

2. If the conductor is connected directly to the battery terminal and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box or enclosed panel, the overcurrent protection shall be placed as close as practicable to the battery, but not to exceed 72 inches (1.83 m).

3. If the conductor is connected to a source of power other than a battery terminal and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box or enclosed panel, the overcurrent protection shall be placed as close as practicable to the point of connection to the source of power, but not to exceed 40 inches (1.02 m).

4. Overcurrent protection is not required in conductors from self-limiting alternators with integral regulators if the conductor is less than 40 inches (1.02 m), is connected to a source of power other than the battery, and is contained throughout its entire distance in a sheath or enclosure.

5. Overcurrent protection is not required at an alternator if the ampacity of the conductor is equal to or greater than the rated output of the alternator

6. Pigtails less than 7 inches (178 mm) in length are exempt from overcurrent protection requirements."

I don't believe exception 6 is applicable in this case, for the following reasons:

1. A buss bar is not a DC power source. A DC power source is a battery, generator, alternator, etc.

2. Per Definition 11.4.19, Pigtails - Conductors provided integral to an electrical component or appliance, for the purpose of connection to external circuits.

The conductor connecting the Blue Sea Fuse Block to the positive buss bar is not a pig tail, it is a conductor.

Anyway, the risk of that jumper burning in the event of a short on the Blue Sea fuse block positive connection side, could be eliminated by placing an appropriately sized fuse in series.

Ramblin

[ramblinrod]

Originally Posted by jongleur

Do you disagree with this:

1/BOTH/2/OFF Switches Thoughts & Musings | SailboatOwners.com Forums

No serious disagreement with anything, except the "reserve" bank concept.

For a 1/2/B/OFF switch, my preference is the last illustration example, but with the alternator, starter, and start battery connected to the "2" post, without the separate on/off switch.

This way, the alternator is always connected to the start battery, regardless of battery switch position.

Benefits:

1. The start battery is normally isolated and will not be killed by house loads.

2. The start battery is charged by the alternator, regardless of battery switch position.

3. Going to or through "OFF, won't hurt the alternator.

In this case, the battery switch is used as follows:

- "OFF" to disconnect the DC panel (house loads) from any battery, such as when leaving the boat.
- "1" - "Normal", the DC panel is connected to the house bank, such as when sailing or at anchor.
- "B" - "Combine", for charging purposes, or to start if the starter battery is flat.
- "2" - "Service" (connects DC panel to start battery for isolating and servicing the house bank).

(BTW, many 1/2/B/OFF switches have an alternator field disconnect so that if one passes through OFF it won't hurt the alternator in all other wiring configs, but on many boats this was never wired. Go figure.)

[Maine Sail]

Originally Posted by ramblinrod

No serious disagreement with anything, except the "reserve" bank concept.

For a 1/2/B/OFF switch, my preference is the last illustration example, but with the alternator, starter, and start battery connected to the "2" post, without the separate on/off switch.

By doing this you have just removed any sort of battery switch from the starting circuit. The ability to 100% isolate a failed battery or a wiring issue should ideally be considered in any good DC system design. The ability to 100% isolate a battery is always key to my designs for cruising customers.. It is really safe to not have a battery switch at all for the start circuit and no way at all to isolate the battery from the system wiring or starter? You were concerned about parallel 8GA wires that are about 3" long and reside under a Lexan panel yet do not seem to be concerned about entirely removing a battery switch from a battery bank, a bank that does not even require OCP under ABYC standards.....? I am confused..?

If you've ever seen a starter solenoid stick, I have on a few occasions, one time where the owner called me on his cell phone in the middle of nowhere in a panic. He told me the only way he could shut off the motor was to kill the battery switch then pull the stop lever. "The engine is making an awful sound and I could not shut it off. It kept turning over so I shut off the battery."

Had the battery switch not been there he would have had no way to stop the starter motor until it murdered itself, which could have resulted in a fire.. Turned out to be a stuck start button that he was able to free up with some WD-40, by removing the rubber cap. This got him from the boonies to a harbor with services & parts. What if he had not had a battery switch for the start battery? While pretty rare, this is not an isolated case, and I have seen it more than I would care to..

This same sort of issue has also happened on our club launches because they get started sometimes 40-60 times per day. The first time this happened the launch driver destroyed both the flywheel and the starter and started a small fire $$$$. The second time it happened all drivers had been trained to immediately kill the battery switch then motor. The launch drivers now know to immediately hit the battery switch and call another launch for a tow back to the dock where our water front manager can fix it..

Even small batteries can be dangerous. This was a single group 24 with no battery switch and no over current protection. The engine starting wires shorted and started this fire.

Originally Posted by ramblinrod

This way, the alternator is always connected to the start battery, regardless of battery switch position.

I still don't see the need to do this nor do Blue Sea, Balmar, Xantrex, Nigel Calder, Charlie Wing etc.... Why do you feel the need wire the alt to start bank?

Originally Posted by ramblinrod

Benefits:

1. The start battery is normally isolated and will not be killed by house loads.

Unless of course the owner forgets and leaves the switch on BOTH.... You also do not have an isolated start battery you have a direct wired start battery with no way to isolate it. Can we also guess, no over current protection if connecting to the #2 stud?

Originally Posted by ramblinrod

2. The start battery is charged by the alternator, regardless of battery switch position.

Why? The start battery is already essentially full.

Originally Posted by ramblinrod

3. Going to or through "OFF, won't hurt the alternator.

It won't when you wire it to the house bank either, just as Blue Sea, Xantrex, Balmar, Wing, Calder etc. recommend on boats that cruise...

Originally Posted by ramblinrod

In this case, the battery switch is used as follows:

- "OFF" to disconnect the DC panel (house loads) from any battery, such as when leaving the boat.
- "1" - "Normal", the DC panel is connected to the house bank, such as when sailing or at anchor.
- "B" - "Combine", for charging purposes, or to start if the starter battery is flat.
- "2" - "Service" (connects DC panel to start battery for isolating and servicing the house bank).

But you have just given up any ability to isolate a bad bank (internal short etc.), stop a wiring short or stop a stuck starter... It is also an ABYC requirement that you have a battery switch, for most of the boats we are discussing.. Heck even my small work skiff has a battery switch & OCP with its single group 24 battery..

Originally Posted by ramblinrod

(BTW, many 1/2/B/OFF switches have an alternator field disconnect so that if one passes through OFF it won't hurt the alternator in all other wiring configs, but on many boats this was never wired. Go figure.)

People don't wire the AFD because most factory alternators do not provide the ability to cut field without doing surgery on the alt to tap into the field wires. When folks add a high performance alternator it is almost always direct wired to the house bank so the AFD feature is not necessary.

You can always wire how ever you want to, but this is not something I would personally consider. I always strive for full isolation capability and over current protection, even for starter circuits.

[Terra Nova]

It is rare to see boats with their start circuit fused. But is essential to have an on-off switch.

[ramblinrod]

Originally Posted by Maine Sail

By doing this you have just removed any sort of battery switch from the starting circuit. The ability to 100% isolate a failed battery or a wiring issue should ideally be considered in any good DC system design. The ability to 100% isolate a battery is always key to my designs for cruising customers.. It is really safe to not have a battery switch at all for the start circuit and no way at all to isolate the battery from the system wiring or starter? You were concerned about parallel 8GA wires that are about 3" long and reside under a Lexan panel yet do not seem to be concerned about entirely removing a battery switch from a battery bank, a bank that does not even require OCP under ABYC standards.....? I am confused..?

If you've ever seen a starter solenoid stick, I have on a few occasions, one time where the owner called me on his cell phone in the middle of nowhere in a panic. He told me the only way he could shut off the motor was to kill the battery switch then pull the stop lever. "The engine is making an awful sound and I could not shut it off. It kept turning over so I shut off the battery."

Had the battery switch not been there he would have had no way to stop the starter motor until it murdered itself, which could have resulted in a fire.. Turned out to be a stuck start button that he was able to free up with some WD-40, by removing the rubber cap. This got him from the boonies to a harbor with services & parts. What if he had not had a battery switch for the start battery? While pretty rare, this is not an isolated case, and I have seen it more than I would care to..

This same sort of issue has also happened on our club launches because they get started sometimes 40-60 times per day. The first time this happened the launch driver destroyed both the flywheel and the starter and started a small fire $$$$. The second time it happened all drivers had been trained to immediately kill the battery switch then motor. The launch drivers now know to immediately hit the battery switch and call another launch for a tow back to the dock where our water front manager can fix it..

Even small batteries can be dangerous. This was a single group 24 with no battery switch and no over current protection. The engine starting wires shorted and started this fire.






I still don't see the need to do this nor do Blue Sea, Balmar, Xantrex, Nigel Calder, Charlie Wing etc.... Why do you feel the need wire the alt to start bank?




Unless of course the owner forgets and leaves the switch on BOTH.... You also do not have an isolated start battery you have a direct wired start battery with no way to isolate it. Can we also guess, no over current protection if connecting to the #2 stud?



Why? The start battery is already essentially full.



It won't when you wire it to the house bank either, just as Blue Sea, Xantrex, Balmar, Wing, Calder etc. recommend on boats that cruise...



But you have just given up any ability to isolate a bad bank (internal short etc.), stop a wiring short or stop a stuck starter... It is also an ABYC requirement that you have a battery switch, for most of the boats we are discussing.. Heck even my small work skiff has a battery switch & OCP with its single group 24 battery..



People don't wire the AFD because most factory alternators do not provide the ability to cut field without doing surgery on the alt to tap into the field wires. When folks add a high performance alternator it is almost always direct wired to the house bank so the AFD feature is not necessary.

You can always wire how ever you want to, but this is not something I would personally consider. I always strive for full isolation capability and over current protection, even for starter circuits.

I certainly do not suggest the on/off battery switch is bad design, for all the reasons stated.

Per ABYC, 11.6.1.2.1, a battery disconnect switch is not required if the battery CCA is less than 800 Amps. (According to Calder, this is because a stuck starter motor will kill the battery before it overheats and catches fire.)

I disagree with your statement, "But you have just given up any ability to isolate a bad bank (internal short etc.), stop a wiring short or stop a stuck starter."


Another way to disconnect a start (or any battery) in an unusual event, is to remove the battery terminal. This is an effective (albeit slower response) to a possible but highly unlikely occurrence.

I too prefer all battery banks be current limited, which prevents the risk of fire in the event of a battery short circuit.

So installed, if such an occurrence takes place, the fuse blows and battery is disconnected, long before the user ever gets to an on/off switch or battery terminal.

So IMHO, the on/off switch is a convenience feature, but not required (except for ABYC compliance for start batteries greater than 800 CCA).

Anyway, great discussion, but I hafta get to work now.

Ramblin

[exMaggieDrum]

Ramblin - I think I just seconded an opinion you had on another post but I am 100% against what you just posted about not having a start battery switch - very cheap insurance and a nice way to isolate the battery for wiring and starter work, and earlier, about wiring your alternator direct to the start battery. Nothing personal, just a difference in opinion. But this was hashed out previously but I feel pretty strongly about this, as I sense you do about your suggestions.

[ramblinrod]

Originally Posted by mitiempo

Whether he has a start battery that is used for every start or a battery that is kept in reserve it makes no sense to run the alternator to it rather than the house bank. The house bank will always be the most in need of charging current. Why run that through the start battery first?

Again, there are numerous ways to skin a cat.

Connecting the alternator to the start battery is the most fool proof solution. The start battery gets charged even in the event of an ACR or wiring failure.

If the ACR drops out due to low voltage when the alternator is combined to the house bank, possible solutions are:

a) Connect the alternator to the larger bank (and risk a flat start battery if the ACR or associated wiring fails). (My least preferred solution.)

b) Use a Blue Sea Battery Link ACR. This will hold them combined down to 12.25V. In the event this still isn't enough, the "Priority" connection can be made, to hold the house bank combined to the starter battery, as long as the engine switch is in the "Run" position. (An OK solution.)

c) Advise the customer to avoid excessive house bank discharge (below 50%), and install a proper sized alternator for the house bank. (My preferred solution.)

Ramblin Rod