Separate Yanmar 3JH5E Alternator and Starter Motor

[delmarrey]

Then why is it that Yanmar, that uses ABYC standards, doesn't put a fuse link between the alt and starter.

B/c if the alt is over charging it'll boil the battery not burn the wire. I've worked on auto electrical systems since 1973 and have yet to see a burned (unfused) alt wire. And can't remember ever seeing a fused alt wire, for that matter.
Got any pictures???? I do!!

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[DeepFrz]

The fuse should be at the battery end of the cct. so why would Yanmar put a fuse between the alternator and the starter. It is also best practice, although not required, to put a fuse at the battery end of the starter cct. If you don't believe it is necessary check out this link to Maine Sail's article.
Battery Bank Fusing Photo Gallery by Compass Marine at pbase.com

[delmarrey]

That's a battery terminal, not and alt wire.
Battery term'ls need to be fused in case they start arching or get over loaded. that's what causes boat fires, like a loose starter cable, for instance.

LOOK AT THE USCG DRAWING! Most likely the internal voltage regulator would burn up before the alt wire and battery.

[mitiempo]

Originally Posted by steve_roach

Hi,


My main concern, though is the Alternator. Seems there are two opposing opinions and it's a matter of choosing the right devil...

- If it's fused and the fuse blows while under load, the Alternator probably burns itself out.
- If it's not fused and it over-currents, the cable may catch fire.

Would no fuse and ensuring a cable far in excess of the Alternator output be the way to go. The Alternator is rated at 80A.

TIA

Steve

The proper fuse will not blow under load. Alternators are self limiting. The reason for the fuse is not the alternator but the battery. Balmar recommends a fuse that is rated at 140% of alternator output. As long as the fuse is lower than the wire's current carrying ability this will not be a problem. Use either an ANL fuse or a MRBF on the battery post. An ANL fuse will handle about 150% of its rating under load for over 8 minutes anyway, but will blow in a short circuit event in milliseconds.

[DeepFrz]

It is also best practice, although not required, to put a fuse at the battery end of the starter cct. If you don't believe it is necessary check out this link to Maine Sail's article.

This is what I was referring to.

However, I believe it is best practice to also fuse the alternator cable and sense wire at the battery end of the cable/wire.

[mitiempo]

I agree it is best practice to fuse the starter circuit on a sailboat with a smaller diesel. Not on a powerboat with larger diesels as it is not practical though. I have fused starter circuits on many diesels up to about 50hp or so and have not had a nuisance blow. The problem is that most factory installs used wire that is too small a gauge. The appropriate fuse for 4 gauge doesn't cut it. But upgrade the wire to 1/0 or 2/0 and fuse it properly and it isn't a problem. The bonus is quicker starting as well.

[smac999]

if you fuse the alternator wire at 150% load, which is normal for charging wires. it'll never blow unless that wire is damaged or shorted.

any fuse in a cirucuit should never blow unless something goes wrong. if you are randomly blowing fuses you're wiring job, wiring size choice, and fuse sizing was poor.

I fuse 95% of starters too. I get a bit leary once the engine is about 8' long. blue sea makes anls up to 750a which I've yet to have an engine blow.


and yes most alternators connect to the starter post. and this is a very good and efficient way to do it. you are utilizing the large starting cable which otherwise has no current once the motor is started. so you have a few feet of small alt wire to a large battery cable. if you run the alt cable all the way to the batteries you need another large wire.

once you start getting into large alternators and large banks you start to change things.

[smac999]

Originally Posted by steve_roach

Hi Guys,

Thanks for that. I have attached the full circuit - with mods assuming separating the alt and starter motor. I guess, given this and some of the comments here, I would have to always have the On-Off-Combine switch to On or Comb while the engine is running to ensure somewhere for the charge to go. Either that or tie the Alt directly to the starter battery.

Cheers

Steve

the vsr needs to go battery to battery before any switches otherwise it causes weird issues. best to put on its' own fuses. the charging sources also needs to go before any switches otherwise they will try to directly power loads when the switch is off. your switching setup looks ridiculous and over complicated. get a blue sea add a battery kit. one switch, one acr. leave the alt on the starter post unless it's over 80-100a. in which case it it straight back to the house bank with large wire and own fuse.

if you want better control over which one starts it beside just combining you can do it with 2 swtichs. but they are still both after the acrs and charging sources

use an on / off all for the starter. run cable from each battery to that switch. then jumper the house battery from that input switch post to a reg on/ off switch for the house. now you can start from either battery separately or combined.

[delmarrey]

Originally Posted by smac999

the vsr needs to go battery to battery before any switches otherwise it causes weird issues. best to put on its' own fuses. the charging sources also needs to go before any switches otherwise they will try to directly power loads when the switch is off. your switching setup looks ridiculous and over complicated. get a blue sea add a battery kit. one switch, one acr. leave the alt on the starter post unless it's over 80-100a. in which case it it straight back to the house bank with large wire and own fuse.

if you want better control over which one starts it beside just combining you can do it with 2 swtichs. but they are still both after the acrs and charging sources

use an on / off all for the starter. run cable from each battery to that switch. then jumper the house battery from that input switch post to a reg on/ off switch for the house.

The down fall to this idea is if you have to shut your "1,2, both" switch off, it'll burn up the alt, unless you buy the "Alt Field Disconnect" type of switch.
e.g. 281477 >>> PERKO Battery Switches at West Marine

With the alt wire directly to the battery(s) the motor can still run if the switch is off. And if you have an engine room or panel fire you'll want to turn off the switch. If you're out in a rough sea using your motor, the last thing you'll want to do it go idle. You'll get tossed around like marbles in a box.

[mitiempo]

Originally Posted by smac999

and yes most alternators connect to the starter post. and this is a very good and efficient way to do it. you are utilizing the large starting cable which otherwise has no current once the motor is started. so you have a few feet of small alt wire to a large battery cable. if you run the alt cable all the way to the batteries you need another large wire.

once you start getting into large alternators and large banks you start to change things.

I disagree. This is the way a manufacturer wires it trying to save money. The alt output should go directly to the house bank, the bank that needs the current the most. With a VSR (ACR) there is no reason to keep charging manual. Yes it adds the cost of a wire but well worth it.

[mitiempo]

Originally Posted by smac999

get a blue sea add a battery kit. one switch, one acr. leave the alt on the starter post unless it's over 80-100a. in which case it it straight back to the house bank with large wire and own fuse.

The Add a Battery kit is for boats with equal size banks - small sports fishing boats for example. It only allows for combining the banks, something to be avoided when one bank is too weak to start from. If the start battery is too weak for a start you want to switch to the other bank by itself, not combine.The ACR is a great product, the switch not so much.

Because you already have the VSR (ACR) I think, it wouldn't make sense to buy another anyway.

[steve_roach]

Hi Guys,

I must say, I'm getting a bit confused with all the options. Where there is disagreement, I just don't have the knowledge to make a call. There is also a part of me that thinks; well, if there are experienced people making different calls, there must be a similar amount of differences in real installations in the wild and, as most floaty things are still floating, either option would probably do and we are seeing preferences rather than high risk alternatives.

Anyway, considering all of the posts - and, don't get me wrong, this is all very good stuff - I have made another update to my circuit. I guess the salient points are:

• I have a 200A fuse close to each battery as a fire-stopper.
• I have moved the VSR to the battery-side of the switches.
• Likewise the charging sources are before the switches (each has its own switch).
• The bilge pumps are also before the main switches (each pump has its own switch in the sub-circuit).
• The Alternator has been connected to the Charging Sources busbar and is fused to 150% of its rating at the busbar-end.
• All charging sources are on the house battery-side of the VSR.
• SW1 allows starter battery, house battery or both to be connected to the starter motor.
• SW2 isolates the remainder of the boat.
• I have somewhat simplified the wiring.

Please continue to comment, especially if I have done something I really shouldn't have.


Cheers

[CharlieJ]

Post 27 is functional and in compliance.

[CharlieJ]

Post #16- Take the cited diagrams in context. The top picture shows that an OCPD is required at the device for a non-self limiting DC generator. The middle picture shows that an OCPD is required at the equipment end of the output conductors of a non-self limiting AC genset.The bottom picture shows, that in contrast, the self limiting alternator does not require an OCPD at the alternator end of the conductors.

[delmarrey]

Originally Posted by steve_roach

Hi Guys,

............... either option would probably do and we are seeing preferences rather than high risk alternatives.

There it is in a nut shell. These are mostly preferences. Every boat will be wired differently. The main thing is not to over load a circuit and make sure your connections are good quality. And if you follow the ABYC/USCG regulations no one can dispute the results. Over kill is an option.