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post #1 of 23 Old 09-27-2012 Thread Starter
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Alternator Output Wire

In the DC wiring diagrams, I see the mention of Alternator Output wire, but I cannot find this wire on my engine.
In the Westerbeke wiring schematic the AO goes to the starter, so I assume the alternator output wire is connected to the starter solenoid and the heavy starter wire is the one that I connect to the battery for starting and charging? Or, do I need to have a separate cable from the Alternator to the battery?
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post #2 of 23 Old 09-27-2012
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Re: Alternator Output Wire

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Originally Posted by SVTatia View Post
In the DC wiring diagrams, I see the mention of Alternator Output wire, but I cannot find this wire on my engine.
In the Westerbeke wiring schematic the AO goes to the starter, so I assume the alternator output wire is connected to the starter solenoid and the heavy starter wire is the one that I connect to the battery for starting and charging? Or, do I need to have a separate cable from the Alternator to the battery?
That is the path to the batteries on many "factory wired" engines. A dedicated wire direct to the house bank is preferred by many. One benefit is that it eliminates the possibility of frying the diodes by turning the batt switch off with the motor running. On the drawback side a fuse now has to be added close to the battery bank and a "service switch" or other means of easy disconnect should be available so you don't get zapped with the battery switch off and the alt still "powered"..

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post #3 of 23 Old 09-28-2012 Thread Starter
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Re: Alternator Output Wire

Thank you Maine Sail. My plan is to make the Battery Switch a use switch as per your recommendation on “1/BOTH/2/OFF Switches Thoughts & Musings” post – to quote you:
“To make your 1/BOTH/2/OFF a "USE SWITCH" simply:

1- Make your house bank #1, or "primary"
2- Make the start/reserve battery #2 or "back up/secondary"
3- Install an Automatic Combining Relay (VSR) or an Echo Charger to charge bank #2.
4- (Bonus Option) Feed alternator output directly to the house bank.”

What I am trying to accomplish is to wire the alternator/starter directly to the battery, bypassing the switch - making the house bank the engine starting battery and make the charging “always on” with a VSR to the reserve battery.
Since my alternator output and starter share the same cable, can I route this cable that is now starter/alternator directly to the house bank to comply with your item 4 above?
Else I would have to find a way to wire a separate alternator output wire to the battery.
Thanks
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post #4 of 23 Old 09-28-2012
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Re: Alternator Output Wire

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Originally Posted by SVTatia View Post
What I am trying to accomplish is to wire the alternator/starter directly to the battery, bypassing the switch
While a battery disconnect switch is only an ABYC requirement for batteries with a CCA greater than 800 amps, I strongly suggest NOT bypassing the switch and connecting your battery directly to the starter. A potentially huge safety issue in my opinion.

Eric
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post #5 of 23 Old 09-28-2012
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Re: Alternator Output Wire

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Originally Posted by fairbank56 View Post
While a battery disconnect switch is only an ABYC requirement for batteries with a CCA greater than 800 amps, I strongly suggest NOT bypassing the switch and connecting your battery directly to the starter. A potentially huge safety issue in my opinion.

Eric

I suspect he only meant running the alt direct to the batt bank but typed starter... I agree 150% that a starter battery should ALWAYS have a switch. Never understood why less than 800CCA would not burn your boat down or was any safer than 801CCA...? Course I also fuse most starter circuits too especially on small AUX engines.

This happened with FAR LESS than 800CCA and with no fuse and no switch there was no way to stop the electrical fire....

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Last edited by Maine Sail; 09-28-2012 at 10:05 AM.
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post #6 of 23 Old 09-28-2012
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Re: Alternator Output Wire

Tatia, here's the WHY of how the boats were wired with one wire from the 1-2-B switch C post to the alternator and starter. When you route your AO to the house bank, you need to use a NEW wire, and disconnect the small wire between the starter and alternator.

OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

It was also discussed in Maine Sail's article.

Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
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post #7 of 23 Old 09-28-2012
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Re: Alternator Output Wire

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Originally Posted by SVTatia View Post
Thank you Maine Sail. My plan is to make the Battery Switch a use switch as per your recommendation on “1/BOTH/2/OFF Switches Thoughts & Musings” post – to quote you:
“To make your 1/BOTH/2/OFF a "USE SWITCH" simply:

1- Make your house bank #1, or "primary"
2- Make the start/reserve battery #2 or "back up/secondary"
3- Install an Automatic Combining Relay (VSR) or an Echo Charger to charge bank #2.
4- (Bonus Option) Feed alternator output directly to the house bank.”

What I am trying to accomplish is to wire the alternator/starter directly to the battery, bypassing the switch - making the house bank the engine starting battery and make the charging “always on” with a VSR to the reserve battery.
Since my alternator output and starter share the same cable, can I route this cable that is now starter/alternator directly to the house bank to comply with your item 4 above?
Else I would have to find a way to wire a separate alternator output wire to the battery.
Thanks
It's a great setup, I moved to this configuration this season. I used the blue sea ACR (Relay). If I did it over I'd use an echo charger simply because the echo limits current and can be wired to the start/reserve bank with smaller wire - wrestling battery cabling around is a huge pain.

On the other hand the battery switch provides connections to both banks in one place already so if the relay is mounted in that area its leads can be small. Also the Blue-Sea ACR has an indicator LED output which tells me when it (and the alternator) are working properly. I don't know if the echo has this nice output.
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Re: Alternator Output Wire

Maine Sail, Fairbank56, Stu Jackson, asdf38

Many thanks for your responses – you have removed the doubts and I am now clearer about how to do this. Thanks for the link Stu.
Great education - you guys rock!
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post #9 of 23 Old 06-04-2013 Thread Starter
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Re: Alternator Output Wire - what size?

I had to revive this post because I am now actually doing this.

The alternator output post a #8 screw where the 10awg wire is connected with a ring and routed to the starter - a very short run.
When I wire this to the battery, the distance is about 12 feet, and I was planning to use 4awg cable.
I am not sure how I will attach a lug or ring to this 4# cable to connect to the much smaller #8 bolt on the alternator. Any ideas?

Thanks
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post #10 of 23 Old 06-04-2013
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Re: Alternator Output Wire

Lugs for 4 awg are available with holes as small as a #10.

Brian
Living aboard in Victoria Harbour
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