three battery banks

[limacina]

I have a 1974 40' sport fisherman with twin 3208 cats. Currently it has a couple 8d starting batteries running into heavy duty battery switches and the house load isnt that much because it had an 8kw generator to run indoor lights, fridge, micro and so on. The geni is in my garage getting a rebuild and I opted to take the time to do a better battery system.
My plan is to keep the starting batteries on the engines and add a house bank (space and weight isn't an issue) I'll determine the size of the house load when I decide on an inverter and what I expect the inverter to do (a future post I'm sure)
I'm interested in doing a http://bepmarine.com/Twin-Inboards,-Three-Battery-banks-180-1466.html You can see the wiring diagram at the bottom of the page.

I have a couple issues though...
I'm worried the engine switches in this cluster aren't big enough for big diesels.
The spec calls out that this cluster is for when its not practical to have both engine alternators in parallel because of the types of regulators, not sure what this means.

My gut feeling is to buy a VRS and use my existing heavy duty switches, buy a third heavy duty for the emergency cross over, and a regular on off switch for the house.

Any thoughts?

 

[seabob4]

Re: three battery banks

Your "latter" suggestion will work just fine and probably be cheaper. I like the BEP systems, we use them on gas outboards, simalar to the inboard setup.

Since the BEP cluster is stated for use on inboards, I would have to assume the cluster is designed to handle diesel starting loads as well as gas. Contact them and ask.

I also don't know the issue of alternators wired in paralell. Try a google search?

 

[seabob4]

Re: three battery banks

The "alternators wired in parallel" seems to have something to do with the voltage regulators on each, and the apparent "fighting" between the 2 alts to control the voltage of the system.

Silvertip, any ideas?

 

[Silvertip]

Re: three battery banks

Yamaha does not recommend it and it is simply not a good idea unless the regulators are designed for that type of service. You have two regulators fighting for control of what amounts to a single output. If that output (battery bank) happens to have some sensitive electronics on it, you may have some spikes that they will not tolerate. Why not put the house loads on just one of the engines along with its starting battery. Very simple, easily switched or VSR'ed and none of the complicted and potentially problematic wiring to deal with. If both alternators were isolated ahead of the regulator and single regulator used, then the system would be fine.

 

[seabob4]

Re: three battery banks

You have two regulators fighting for control of what amounts to a single output.

From my reading, that's the idea I got...

The voltage regulators will control charging output based on the state of the battery. But with 2 VR's trying to charge 2 batts basically all in one system wired in parallell, I can see a lot of confliction...

 

[DianneB]

Re: three battery banks

Being in the electrical/electronic business I will comment on "alternators in parallel"....

Whichever alternator has the highest (regulated) voltage, that alternator will carry the majority of the load unless resistance is wired in series with each alternator (a waste of power).

Much better to have alternators change their own bank rather than trying to match alternator voltages.

 

[seabob4]

Re: three battery banks

Being in the electrical/electronic business I will comment on "alternators in parallel"....

Whichever alternator has the highest (regulated) voltage, that alternator will carry the majority of the load unless resistance is wired in series with each alternator (a waste of power).

Much better to have alternators change their own bank rather than trying to match alternator voltages.

I think in the case of a single engine alternator trying to charge 2 batts, there would be no issue. The same with twins each charging their respective batts. But for 2 alts trying to charge 2 batts and everything connected "as one", well, that probably wouldn't be a good idea...

 

[limacina]

Re: three battery banks

It does look like BEP is suggesting charging the house load on only one engine and each engine charging its own starting battery. The question for them (i'll call them soon) is whether their inboard switch cluster can handle a big diesel starter load. I need to get this into a drawing so i can think visually because i'm thinking it'd be worth being able to switch the house load (either/or, not both) between engines. In case I have an alternator or engine failure. I can limp back home on one engine, but I need to be able to make my cup of coffee and microwave my eggs ;o)

In the end, buying a bank of house batteries and an inverter and all the wiring may cost as much as me finishing the rebuild on my westerbeke genni. I'm guessing $1200-1500 for parts there and 8kw in the end is truly the right solution.
I'll continue my research... Any comments are appreciated.