darrylcf

Battery Ground Location

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Hello all, 

I just bought my first boat, a 1975 Sabre 28, and I'm trying to get everything squared away before it gets put in the water. The electrical system is what's throwing me for a loop though; I've read it's set up as a "floating system" unlike a car, and that's where my knowledge of electricity peters off a little bit. I work on cars a lot and understand mechanics admittedly way better than I know electrical systems, but I have car systems down pat.

With that, and with the knowledge I have in general of electrical systems, my thought is that I need the same gauge positive and negative cables coming off of my battery, and this is where the problem is. I've been trying to hook the two batteries up as they're supposed to be and I have my two positives coming off of my battery switch and the third going to the starter, so I've accounted for my red wires in the system, and then I have another red crossover cable which I found some black electrical tape on so I assume the previous owner was using that as a negative. So as I see it, I've got my whole system set with the exception of the ground for the system. Here's where the problem is: the only ground coming from the engine to the battery bay is a small like 10 or 14 gauge that's connected to the starter. When I use this as my main ground, I can get all the accessories to turn on in the cabin, but I haven't tried to start the engine that way because I don't want to start a fire or anything. There should be another 4 gauge ground somewhere attached to the engine block, right? Am I crazy? Or is there a principal of electricity at work here I'm not familiar with that allows for such a small ground? (Again, I'm only an amateur at best electrician, so that's a definite possibility!) If I'm correct, I was going to go buy a 4 gauge ground to run to the engine. Is there a specific spot it was designed to attach to with a bolt? On the Atomic 4 that is. I also plan on replacing the crossover cable with the correct color cable. If I were a wiser man, I would have taken pictures of this all yesterday when I was at the boat, but alas, I didn't think of it. Any help would be greatly appreciated, thank you very much!

Darryl

5853907_20160628133256177_1_XLARGE.jpg

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Isolated ground, floatinf system ... means a two pole system...two wires..one positive and one negative ..to every electric consumer.

 

the engine block ..or any piece of equipment is not a negative pole .

 

Do not ground it to the negative pole of the boat 

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2 hours ago, darrylcf said:

With that, and with the knowledge I have in general of electrical systems, my thought is that I need the same gauge positive and negative cables coming off of my battery, and this is where the problem is. I've been trying to hook the two batteries up as they're supposed to be and I have my two positives coming off of my battery switch and the third going to the starter, so I've accounted for my red wires in the system, and then I have another red crossover cable which I found some black electrical tape on so I assume the previous owner was using that as a negative. So as I see it, I've got my whole system set with the exception of the ground for the system. Here's where the problem is: the only ground coming from the engine to the battery bay is a small like 10 or 14 gauge that's connected to the starter. When I use this as my main ground, I can get all the accessories to turn on in the cabin, but I haven't tried to start the engine that way because I don't want to start a fire or anything. There should be another 4 gauge ground somewhere attached to the engine block, right? Am I crazy? Or is there a principal of electricity at work here I'm not familiar with that allows for such a small ground? (Again, I'm only an amateur at best electrician, so that's a definite possibility!) If I'm correct, I was going to go buy a 4 gauge ground to run to the engine. Is there a specific spot it was designed to attach to with a bolt? On the Atomic 4 that is. I also plan on replacing the crossover cable with the correct color cable. If I were a wiser man, I would have taken pictures of this all yesterday when I was at the boat, but alas, I didn't think of it. Any help would be greatly appreciated, thank you very much!

Darryl

You do seem to be missing a large ground (return) wire.

What you describe as a "floating system" is very unusual in a fiberglass boat, though not uncommon in an aluminum one. 

 

Sabre Yachts is still in business, most Maine manufacturers stand behind their products. 

Your alternator should be feeding your batteries through the Isolating switch, and there must  be a connection to complete the circuit. 

Most commonly this is through the metallic frame of the alternator --> engine --> ground wire --> batteries

similarly your starter would have it's power connection made through that same ground.

The 10 gauge wire to starter would not be sufficient in most cases, as it's a 30 Amp rating. 

I'd call the factory and have them walk you through it. 

there's also Moyer Marine who make Atomic 4 parts. 

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15 minutes ago, LionessRacing said:

You do seem to be missing a large ground (return) wire.

What you describe as a "floating system" is very unusual in a fiberglass boat, though not uncommon in an aluminum one. 

I'm probably wrong about the floating thing then, it's just something I read in a forum that wasn't specific to my boat. 

So as I understand it then, I should have my two positives of my switch to each battery's positive terminal, and then the third red coming out of the switch hooked to my starter battery. Then I should have a 4 gauge ground coming from the alternator to my batteries.

Is that right so far? So then do I need a 4 ga + coming from the alternator too connected to the batteries? Should there also be a 4 ga - coming from the starter? 

Thank you very much for the help! I'll give the factory a call if I'm still incorrect.

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8 minutes ago, darrylcf said:

I'm probably wrong about the floating thing then, it's just something I read in a forum that wasn't specific to my boat. 

So as I understand it then, I should have my two positives of my switch to each battery's positive terminal, and then the third red coming out of the switch hooked to my starter battery. Then I should have a 4 gauge ground coming from the alternator to my batteries.

Is that right so far? So then do I need a 4 ga + coming from the alternator too connected to the batteries? Should there also be a 4 ga - coming from the starter? 

Thank you very much for the help! I'll give the factory a call if I'm still incorrect.

While it's good that you noticed you are likely missing the ground cable, you really probably should look at a good schematic, there are books by Nigel Calder et al that would be a good start. From the question above, I am not confident of my understanding of what you are asking to give other than a very general answer. 

Your battery banks are generally considered as: starting and house. Some boats have multiple house banks, with one or more batteries in the bank (mine has bow and stern batteries to service the windlass and refrigeration loads) boats with multiple engines might have multiple starting banks.

The battery switch(es) are designed to enable you to feed your loads from either/both batteries. Usually you would have the breaker/fuse panel connected through a switch to your house bank(s) Usually you would have your starter connected through a switch to your starting bank. 

You can usually connect them in parallel, for example if your starting bank was low and you wanted to use the house bank, or conversely you had to use the VHF off the starting bank. 

Your alternator(s) and battery charger(s) can feed one or both, but you need to be careful to not put them in parallel without intending to.

There are devices made to charge one from the other within certain limits (e.g. duocharge) or to combine them with diodes etc. 

Many batteries have been ruined due to poorly wired charging circuits, and/or poorly wired distribution systems. I have had issues where my shore power was mysteriously disconnected and I lost house bank batteries.  

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41 minutes ago, darrylcf said:

I'm probably wrong about the floating thing then, it's just something I read in a forum that wasn't specific to my boat. 

So as I understand it then, I should have my two positives of my switch to each battery's positive terminal, and then the third red coming out of the switch hooked to my starter battery. Then I should have a 4 gauge ground coming from the alternator to my batteries.

Is that right so far? So then do I need a 4 ga + coming from the alternator too connected to the batteries? Should there also be a 4 ga - coming from the starter? 

Thank you very much for the help! I'll give the factory a call if I'm still incorrect.

On your engine...oil pressure, temp...sensors....isolated  earth will have two wires.  

                      On isolated  earth  the    Alternator will have two output wires..positive and negative

                      On isolated  earth the        Starter motor will have two  large diameter input cables....positive and negative.

 

take a voltmeter...connect the negative -  test leed to engine block, connect positive  + test leed  to hot terminal on back of battery switch ...if you read 0 volts your system in isolated ground... you have no negative on the engime block .....

if you read 12 v on the voltmeter your  engine block is Negative 

 

I dont know your battery switch ...normally a battery switch only interupts one leg...the positive leg.

 

the negative leg will be wired to a common buss bar...all negative conductors touch this bar..... the negative leg is  interrupted by  a knife fuse 

this is the common setup 

 

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Without further details of the battery switch - this is the standard primary electrical system for the era:  two batteries, negs common, and to engine block. Pos separate to a 3 position batt switch (off/1/2/both). Lead from output of switch to starter.. This was the simplest way to get two separate batt  'banks'. However, this set up only charges the batt the is selected on the switch. So normal use is start on one batt, then switch to 'both' while engine is running to charge both batts. When eng shut off, switch moved to '1' or '2' to power house while keeping one batt in reserve to start engine. So big wiring is: Pos - separate lead from each batt pos to switch '1' & '2' studs. SAME gauge lead from common stud to starter pos. Smaller gauge wire to breaker panel. Neg - both neg terminals connected, same gauge lead to engine block, smaller gauge to breaker panel. Alt pos output goes to pos stud on starter. Wire gauge calculated from max loads/length of wires - there are many graphs/calculators to determine gauge. Boats should be using AWG wire sizing. Use 3% voltage loss tables, the slight increase in wire size more than made up in actual performance of everything. Tables are made for perfect conditions, which are never met on boats.

Euro boats also have a cut off switch in Neg common lead, US boats almost never have this. But needed in metal boats for corossion control.

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17 minutes ago, longy said:

Without further details of the battery switch - this is the standard primary electrical system for the era:  two batteries, negs common, and to engine block. Pos separate to a 3 position batt switch (off/1/2/both). Lead from output of switch to starter.. This was the simplest way to get two separate batt  'banks'. However, this set up only charges the batt the is selected on the switch. So normal use is start on one batt, then switch to 'both' while engine is running to charge both batts. When eng shut off, switch moved to '1' or '2' to power house while keeping one batt in reserve to start engine. So big wiring is: Pos - separate lead from each batt pos to switch '1' & '2' studs. SAME gauge lead from common stud to starter pos. Smaller gauge wire to breaker panel. Neg - both neg terminals connected, same gauge lead to engine block, smaller gauge to breaker panel. Alt pos output goes to pos stud on starter. Wire gauge calculated from max loads/length of wires - there are many graphs/calculators to determine gauge. Boats should be using AWG wire sizing. Use 3% voltage loss tables, the slight increase in wire size more than made up in actual performance of everything. Tables are made for perfect conditions, which are never met on boats.

Euro boats also have a cut off switch in Neg common lead, US boats almost never have this. But needed in metal boats for corossion control.

Thank you, that sounds like exactly what I have! Last question though is where do I attach the ground to the engine at? Anywhere on the block I can make good contact or is there a bolt or and accessory I should attach to? 

Thank you everyone for the responses. Attached are the diagrams I've been looking at just for reference, but none of them show what I have exactly. The 1st is my hull number's "layout", but I have dual batteries and a 1-Both-2-Off switch, the second is the layout with the diesel in later years and looks like pretty much what I have, but obviously with the different engine. On a side note, what is being shown where I circled in red on the first diagram?

Thanks, Darryl

28-1.jpg

28 Diesel.jpg

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Circled is a common NEG connection point - all misc neg go to this point, then larger wire to batt neg post. Your first (atomic) schematic has a number of errors/things not done anymore for safety. Use the deisel schematic as a guide. Alt outputs cannot (in todays code) be run thru a ampmeter. Amp gauges must be fed by a sensor indirectly.

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1 minute ago, longy said:

Circled is a common NEG connection point - all misc neg go to this point, then larger wire to batt neg post. Your first (atomic) schematic has a number of errors/things not done anymore for safety. Use the deisel schematic as a guide. Alt outputs cannot (in todays code) be run thru a ampmeter. Amp gauges must be fed by a sensor indirectly.

Awesome, thank you! Are you familiar with the Atomic and where I should connect my ground or is it just anywhere secure on the block with good connection?

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For all ATOMIC questions MOYER MARINE is the first place to check. Generally, neg connects as close to starter motor as reasonable. Any large diameter bolt will work, but make sure that there is enuff thread still engaging after addition of cable lug. Clean off all paint under cable lug to bright shiny metal for good connection. After bolt is fully re-tightened, coat with something to prevent corossion around/under the connection.

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1 minute ago, longy said:

For all ATOMIC questions MOYER MARINE is the first place to check. Generally, neg connects as close to starter motor as reasonable. Any large diameter bolt will work, but make sure that there is enuff thread still engaging after addition of cable lug. Clean off all paint under cable lug to bright shiny metal for good connection. After bolt is fully re-tightened, coat with something to prevent corossion around/under the connection.

Awesome, thank you so much for the help!

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6 hours ago, LionessRacing said:

While it's good that you noticed you are likely missing the ground cable, you really probably should look at a good schematic, there are books by Nigel Calder et al that would be a good start. From the question above, I am not confident of my understanding of what you are asking to give other than a very general answer. 

Your battery banks are generally considered as: starting and house. Some boats have multiple house banks, with one or more batteries in the bank (mine has bow and stern batteries to service the windlass and refrigeration loads) boats with multiple engines might have multiple starting banks.

The battery switch(es) are designed to enable you to feed your loads from either/both batteries. Usually you would have the breaker/fuse panel connected through a switch to your house bank(s) Usually you would have your starter connected through a switch to your starting bank. 

You can usually connect them in parallel, for example if your starting bank was low and you wanted to use the house bank, or conversely you had to use the VHF off the starting bank. 

Your alternator(s) and battery charger(s) can feed one or both, but you need to be careful to not put them in parallel without intending to.

There are devices made to charge one from the other within certain limits (e.g. duocharge) or to combine them with diodes etc. 

Many batteries have been ruined due to poorly wired charging circuits, and/or poorly wired distribution systems. I have had issues where my shore power was mysteriously disconnected and I lost house bank batteries.  

Get Calder's books. Don't listen to Slug.

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Our Atomic 4 has the battery negative connected at one of the flywheel cover bolts.

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