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steve_roach · 15-12-2013, 19:16

Hi Guys,

Looking at the circuit diagram for this engine, there is a positive cable between the Alternator positive and the Starter Motor. Bottom line - can I remove it. I would like a bit more control over which battery is powering the starter motor and where the charging current is going. If I separated them, could I break anything?

TIA

Steve

Albro359 · 15-12-2013, 19:35

That doesn't sound right.
How many battery banks do you have ? (separate start bank?)
The alternator circuit should be completely separate to the starter motor circuit.
The alternator positive (B+) should be a heavy wire going to your battery bank positive.
The positive on the starter motor should be going to one contact on the starter solenoid and a heavy wire from the start battery positive to the other side of the starter solenoid and some small wires going from the solenoid to a start switch button.
I think I'd need to see this cct of yours before going any further !!
Cheers
Alan

steve_roach · 15-12-2013, 20:26

Hi Alan,

OK. I have attached a detail image from the manual. 35 is the Starter Motor, 39 the Alternator. I have the single Alt option. The cable I'm referring to is labelled 10R (R = red) at the Alternator-end.

Here's a like to the whole document (warning - PDF): http://yanmar.com/product/marineplea...JHM-M00201.pdf

Cheers

Steve

delmarrey · 15-12-2013, 22:51

Steve,

Yes! The alt power lead runs to the battery terminal on the starter. I have the 3JH4E (2 years earlier). Just pull the alt lead off the starter and run an extension to a battery. Just make sure you always have power to the alt!!! Otherwise it'll go into full charge, as if the batteries were dead. Also, the alt needs power to even start charging.

I removed to wire on mine and ran it straight to the main batteries. From there I have combiners running to the house batteries and windlass battery. If the battery is more then 10 ft away, up grade the (red) wire to the next size.

Note:
If not already done, run your starter cable thru the main shut-off switch. If there is ever a fire due to a loose lead (arcing) you can shut down the amps. And with the power off, and the new set up, it won't hurt the alt and the motor can continue to run if need be.

Albro359 · 15-12-2013, 23:52

Quote:

Originally Posted by delmarrey

Steve,

Yes! The alt power lead runs to the battery terminal on the starter. I have the 3JH4E (2 years earlier). Just pull the alt lead off the starter and run an extension to a battery. Just make sure you always have power to the alt!!! Otherwise it'll go into full charge, as if the batteries were dead. Also, the alt needs power to even start charging.

I removed to wire on mine and ran it straight to the main batteries. From there I have combiners running to the house batteries and windlass battery. If the battery is more then 10 ft away, up grade the (red) wire to the next size.

Note:
If not already done, run your starter cable thru the main shut-off switch. If there is ever a fire due to a loose lead (arcing) you can shut down the amps. And with the power off, and the new set up, it won't hurt the alt and the motor can continue to run if need be.

Agree....
Seems a strange way to wire things up.....They must be assuming you only have one battery
Good luck
Alan

delmarrey · 15-12-2013, 23:57

Quote:

Originally Posted by Albro359

Agree....
Seems a strange way to wire things up.....They must be assuming you only have one battery
Good luck
Alan

Probably true for a small power boat. Plus, the motor will run right out of the box once a battery and fuel are connected.

steve_roach · 16-12-2013, 01:12

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

delmarrey · 16-12-2013, 01:59

It's not advised to put fuses between the battery and alt or battery and starter.

Starters can draw a lot of amps momentarily. And if a fuse blows with the alt running it'll burn up the alt.

If the alt is running thru the 1,2 switch, it can not be shut off with the motor running.

Although, Marine motors should be able to run with out power in emergencies, once they've already been started. Although, it would burn the alt if the wire were not attached to a good battery. The regulator needs feedback to adjust charge rate.

CharlieJ · 16-12-2013, 07:28

Quote:

It's not advised to put fuses between the battery and alt or battery and starter.

In the US an over current protection device (fuse or circuit breaker) is required at every attachment to a DC power source. The alternator is self limiting so there is no requirement for an OCPD at that end, however, an OCPD is required where the output from the alternator connects to the DC system. A Blue Sea Systems MRBF is perfectly suited for this application.

BTW, this wiring set-up is standard for most marine engine providers and the boat builders do not change it to the more functional system discussed in this thread.

delmarrey · 16-12-2013, 09:56

Quote:

Originally Posted by CharlieJ

In the US an over current protection device (fuse or circuit breaker) is required at every attachment to a DC power source.

Not!
See: CFR 33 Subpart I 183.455

Overcurrent protection: General.

Quote:

(e) This section does not apply to resistance conductors that control circuit amperage; conductors in secondary circuits of ignition systems; pigtails of less than seven inches of exposed length; and power supply conductors in cranking motor circuits.

Pictures right from the USCG manual.

.

CharlieJ · 16-12-2013, 15:21

delmarrey-
Sorry, but OCPD are required in all ungrounded conductors except for the starter supply as depicted in the diagrams that you provided. There are, as always a very few exceptions that were beyond the scope of the original discussion. BTW, the right hand diagram is directly from the ABYC E-11 Standard.

The fine points of a current limiting resistor are irrelevant to the OP's original question and as I was responding to a post that stated an OCPD in the alternator output is not desirable, your post was misleading.

steve_roach · 17-12-2013, 04:37

Hi Guys,

Thanks for the input. The information here is always good but, I must admit, this time I'm not sure which way to go - there seem to be conflicting opinions. I've done a couple of tweaks to my circuit design along the lines of what has been discussed. Because the circuit can use either (or both) batteries for the starter motor, I have removed the fuses from them. I have put one just before the House Busbar and I have also put one on the Alternator. The Charging Sources each have their own fuse or breaker and I'm pretty sure I have been advised to not put one on the Bilge Pumps as a blown fuse could result in a sunk boat. I'm still not sure about the Alternator one, though. Does it need protecting? If it blows under load, will the Alt burn out? Should I use one anyway and take that chance?

Is this circuit, in the forum's opinion, up to the job? I'm trying to build an adequate system to support a 38ft yacht and I just want it to be reasonably easy to use and not endanger the boat.

I am always happy to take advice from here so please feel free to take my design apart.

I have attached the latest incarnation.

Cheers

Steve

mitiempo · 17-12-2013, 06:40

One quick comment. Not fusing the bilge pumps does endanger the boat. All it takes is the pump to seize from rubbish and the wire can catch fire - fuse them with the manufacturer's recommended fuse.

Charging sources should be individually fused if their cables have an ampacity smaller than the rating of the main fuse.

steve_roach · 17-12-2013, 13:53

Hi,

Should have been a bit clearer here. Each bilge pump is fused through its own fused switch (http://3.bp.blogspot.com/-Wx8HrOoYCD...umpsSchema.jpg). It's just the common cable to the bank of switches that is not. An over-current in one pump will leave the others enabled.

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