Dual alternators, one regulator?

[EngineerRetired]

twin engine / alternators, single regulator. $270 https://www.westmarine.com/buy/balma...ecs-_-DY-_-PDP

[MatthLE]

Hello;

Former operator of Nuclear Plants both civilian and naval. I LOVE redundancy, it is our friend and often our saviour if it can be accomplished. One regulator = single point of failure.

Respectfully.

[EngineerRetired]

Originally Posted by MatthLE

Hello;

Former operator of Nuclear Plants both civilian and naval. I LOVE redundancy, it is our friend and often our saviour if it can be accomplished. One regulator = single point of failure.

Respectfully.

I would agree but you can not charge the same battery bank at the same time with two independent alternators.

[Bycrick]

Sound bites make for poor engineering dictum. Redundancy isn’t always better. Ask pilots about twin vs single engine planes. Adding more of something is inherently less reliable; there’s more to break and go wrong. "The man who goes to sea with one watch always knows what time it is. The man who has two watches is never sure." Multiple charging sources for a single battery, whether it’s multiple alternators, or multiple battery chargers or solar or wind work just fine as long as their properly set up. I doubt that 1 boat in 100 has a single system that intelligently integrates ALL possible charging sources. And if it did, then you’re really back to the single-point-of-failure argument.

[dfelsent]

Originally Posted by EngineerRetired

I would agree but you can not charge the same battery bank at the same time with two independent alternators.

If the two alternators share a regulator you certainly can charge one bank from two alternators.
The question is how independent are the two alternators? Do they share a regulator? Do they share an engine?
The solution depends on the answers to those questions but you can charge one bank from two alternators.

[Sailmonkey]

Originally Posted by EngineerRetired

I would agree but you can not charge the same battery bank at the same time with two independent alternators.

Oh? Pray tell why?

[Bycrick]

It makes no difference whatsoever how many charging sources one has connected to a single battery (bank). The battery itself, based on chemistry and state-of-charge, determines how much current it will accept at a certain voltage. If there are multiple chargers, they’ll share the current. Will they share it equally? No, but who cares?

[EngineerRetired]

Originally Posted by dfelsent

If the two alternators share a regulator you certainly can charge one bank from two alternators.
The question is how independent are the two alternators? Do they share a regulator? Do they share an engine?
The solution depends on the answers to those questions but you can charge one bank from two alternators.

I will stand by my words. "can not charge the same battery bank at the same time with two independent alternators".


Doing so is certain to burn one or the other out. Without a common control one will always produce a higher voltage than the other and that leads to a ton of issues.


With that said, wire your boat anyway you think is right.

[belizesailor]

Im not sure on the BALMAR, but the old NextStep regulators by Ample Power had a 1 regulator to 2 alternators option. Unfortumately they are out of business.

My boat had this configuration orginally, but when the original regulator failed, I went to dual regulators for redundancy.

[belizesailor]

Originally Posted by EngineerRetired

I will stand by my words. "can not charge the same battery bank at the same time with two independent alternators".


Doing so is certain to burn one or the other out. Without a common control one will always produce a higher voltage than the other and that leads to a ton of issues.


With that said, wire your boat anyway you think is right. [emoji2]

Demonstrably, yes you can, provided each independent alternator (or other charge source) has its own regulator...or a common regulator which can properly handle two alternators.

[belizesailor]

Originally Posted by witzgall

Chris from Balmar here. The MC-612 Dual is designed to drive the field for two alternators on a single engine charging a single battery bank. It has the additional connectors for the second alternator.
https://balmar.net/product/regulator-mc-612-dual-h/

And the manual: https://www.balmar.net/wp-content/up...For-Review.pdf

Chris, thanks for chiming in!

The MC612 is specified for single engine applications. Why is that?

The "Center Fielder" product is specified for twin engines. Right?

https://www.boundlessoutfitters.com/...ii-cfii-12-24/

[EngineerRetired]

Originally Posted by belizesailor

or a common regulator which can properly handle two alternators.

Exactly what I said originally

[hzcruiser]

Originally Posted by EngineerRetired

Exactly what I said originally

But somewhat contrary to the first part of the response which you left out in the quote?

Just two alternators and two regulators that don't know about each other. Both will try and put out say 13.8V but the batteries are pulling that down, depending on their SOC and acceptance rate. Hence they both work at full current until the bus voltage rises and the current from both tapers down.

They might never put out the same current and they might not stop charging at exactly the same point, but I absolutely don't see a reason why one would get damaged!?

So please explain... (without quoting hear-say or one-off experiences, please)

[Morrissey]

I've been running 2 x 200A alternators managed by one Balmar 612 Dual regulator for over 8 years. Set-up by the Shipwrights CoOp in Port Townsend. No issues.

I've seen as high as 360A feeding into a somewhat depleted large house bank, but nothing higher than that. Not sure why, but it has never worried me since that's a good amount of juice anyway. I always see in excess of 300A charge rate once above engine idle after an overnight anchoring.

Sure, these days the Balmar documentation says the alternators should be on the same engine. But mine are on seperate engines, of identical HP, that typically run with less than 10 rpm difference on the digital tach. So "almost" like they are on one engine......

[JC Reefer]

Originally Posted by Bycrick

Redundancy isn’t always better. Ask pilots about twin vs single engine planes. Adding more of something is inherently less reliable; there’s more to break and go wrong.

Good points BUT not sure the plane analogy is one I would have included. Being on a plane where ONE engine failed I was content with the other doing the job. [emoji6]