12 vdc Eletrical Question-gctid342294

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Got a Replacement kicker off of Fleabay, probably paid too much for it, but I could not resist it because it was 15HP 2 Stroke Long Shaft Merc and is ELECTRIC START and CHARGES THE BATTERIES WHEN TROLLING. Dallas at Anchor Marine is going through it now to give it a once over, i.e, new water pump, gearcase lube change, general check up. Then I got to thinking which is not too smart for a COF, the wiring is two heavy duty cables, one for positive and one for negative, just like it's BIGGER partner the 150HP Main motor. Das Boat has two batteries that are connected via a Perko Switch (1, 2, both, Off). Here's my question; will one motor's charging system interfear with the other motor's charging if both are running at the same time????? Or do I have to "Isolate" them from each other????

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my kicker and main motor are both hooked up to the same battery and i have never had a problem???

[johnrupp Seasoned Member Find all posts View Profile Close johnrupp]

The simple answer is yes they can interfere with one another. Generally one alternator will work at max while the other will put out very little. There are products out there that allow you to run both without them interfering with each other. Balmar makes a product called the Centerfielder that will take care of your problem.

http://www.balmar.net/centerfielder.html

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Is that really necessary for a kicker motor? For the limited amount of time that the 2 motors run at the same time?

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Ofishal wrote:
Is that really necessary for a kicker motor? For the limited amount of time that the 2 motors run at the same time?

No it is not necessary and as you pointed out it will not hurt anything running as is. My point was in order to get the max charge rate you should use something like the centerfielders.

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Ah I see, it would be a good addition to a twin setup.

[johnrupp Seasoned Member Find all posts View Profile Close johnrupp]

Ofishal wrote:
Ah I see, it would be a good addition to a twin setup.

Yes it is, especially where you want both alternators to charge a large house bank.

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How things work actually depends on the batteries' state of charge and the altenators.

MOST altenators (not sure about the kicker, sometimes they are really simple) produce current into the battery to maintain a certain voltage level. At that level they stop producing more current. As the batteries charge it takes less and less current to reach the voltage.

The battery doesn't know where the current is coming from and doesn't care.

Each altenator will produce current into the battery according to it's error amplifier circuitry gain. It comes down to this:

If one alt output maxes out, and the battery requires more current to meet the voltage level desired, the other alt will produce more current to increase the voltage to the desired level.

They will likely share the current contribution to the battery somewhat. In this situation each will be under less load than if running by themselves.

In some extreme case the alt feedback control systems could oscillate with each other, but I highly doubt this will occur.

The large cables are for starting aspect; I'd guess your kicker alt. maxes out at 15A or so, and will never need that big of a connection for charging.

No isolation needed.

Chay

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johnrupp wrote:
The simple answer is yes they can interfere with one another. Generally one alternator will work at max while the other will put out very little. There are products out there that allow you to run both without them interfering with each other. Balmar makes a product called the Centerfielder that will take care of your problem.

http://www.balmar.net/centerfielder.html

I don't think he can use Centerfielder on his outboard. He would need to change the voltage regulators on both the main engine and the outboard, and be able to feed excitation back into the outboard. Not impossible but terribly impractical.

Just go ahead and connect the kicker's cables to the existing main boat's start battery.

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Thanks for the replies everybody, the consensus & the Mechanic at Anchor Marine sez hook'em up, no problems. About the only time they will be running at the same time is warm up at the dock, and when it is time to quit trolling & head on in, i.e., leave the kicker running until the big motor fires & starts to warm up for the run in. I just didn't want to fry anything electrical in either motor.

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JohnQ wrote:
............. Das Boat has two batteries that are connected via a Perko Switch (1, 2, both, Off). Here's my question; will one motor's charging system interfear with the other motor's charging if both are running at the same time????? Or do I have to "Isolate" them from each other????

I think that the answer to both questions is NO.

johnrupp wrote:
The simple answer is yes they can interfere with one another. Generally one alternator will work at max while the other will put out very little.

Twin engine owners interface alternators via an ACR or VSR quite often. Apparently these guys are not having any issues.

How often will the kicker and one or both main engine(s) be operating simultaneously? Or in your case..... the kicker and the main engine?????

Unless I've missed something here, I don't think that I'd be overly concerned.

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