Isolating Batteries to Create a Start and House Bank.

[DavidM]

My original post to this thread suggested a group 24 battery dedicated to the genset. That gives you another level of redundancy. Start the genset and let it run to charge up the discharged start battery.

To repeat my setup for a single on the Pilot 34: 1) A single G31 for starting, 2) A pair of GCs for house, 3) A single G24 for the genset. For your twin engines, just wire both engines to the same G31 start battery.

David

[kwmeyer13]

David,
More than likely that’s the route I will wind up going. To start, I will stick with my 4D’s and add a gen set battery. Plan out the changes needed to be done on my system, assemble the necessary items, and when time is right hinge the rest of the setup. Once again many thanks to you and every one else who took the time share information.

[FlyWright]

Originally Posted by CMS

Use one switch for HOUSE BANK & One switch for START BANK

Put all master panel loads on HOUSE (panel under rear cockpit hatch)

Use one START BANK for both engines and the genset

Feed all charge sources to HOUSE BANK other than start banks engine alternator

One alt still feeds direct to HOUSE BANK (bigger of the two, if one is)

One alt feeds START BANK

Install a Blue Sea ML-ACR 7622 between banks on the load side of the switches. This allows for emergency manual cross-connect (use house for everything with start off/isolated, or start for everything with house bank off/isolated). This will also allow both alternators to charge both banks, automatically, thus doubling your bulk charge capability into the house bank.

Keep it simple there is no need for more than two banks on a 34' Mainship.

Without a diagram of how it is actually wired at this point in time it's impossible to say how you do this in the most efficient manner..

Short and sweet! This is how my twins are set up except I use a Yandina combiner instead of the Blue Seas ACR. I can parallel the batts with the Perko Switches for extra engine start oomph if needed.

Works well with no need for throwing switches in normal ops.

[kwmeyer13]

Which bank(s) are best for the windlass and bow thruster? Right now mine are off the house/port start battery. Seems to me since both items are most likely to be used when the engines are running they should be hooked into the start bank.

[FlyWright]

Originally Posted by kwmeyer13

Which bank(s) are best for the windlass and bow thruster? Right now mine are off the house/port start battery. Seems to me since both items are most likely to be used when the engines are running they should be hooked into the start bank.

That's how I have my windlass, on the start battery, b/c it's only used when the engines are running. If I had a 12V thruster, I'd probably do the same.

[dhays]

Originally Posted by kwmeyer13

Which bank(s) are best for the windlass and bow thruster? Right now mine are off the house/port start battery. Seems to me since both items are most likely to be used when the engines are running they should be hooked into the start bank.

Keep in mind that CMS suggested that the larger (if one is larger) of the alternators should be feeding the house bank. So while you are are maneuvering one of the alternators will be feeding the bank you would be using for the thruster/windlass. Of course, at idle I don’t know how much help it would be.

[john61ct]

When the engine's running, the ACR is closed, so the alt current should be charging all banks.

So as long as alt output and ACR capacity are higher amps than what the high-current load is pulling, the batts aren't being touched anyway, so it doesn't matter.

But if you need to run that big consumer when the engine is off and the banks/circuits are isolated, it should IMO be running off the much larger House bank.

[ranger58sb]

Originally Posted by djmarchand

Yes, two group 31s will fit on one side but not in the 4D/8D boxes. You will have to use new boxes and turn the batteries 90 degrees. But why?

If two would fit that way, could three also work on each side? Mostly just trying to illuminate options... but also partly because we had good success with banks of 3x Odyssey PC-21050s... without changing any boat wiring.

Originally Posted by djmarchand

And two GC batteries will fit in the existing box.

Does it follow from above that four GC batteries could be fitted each side, using different boxes and/or different orientation?

Another thought: some of the taller traction batteries (e.g., Trojan's L16) fit in the same horizontal footprint as regular GC2 golf cart batteries... and offer even more capacity. If vertical space isn't so tightly constrained. IIRC, it's 300-Ah for a pair of L16s or Lifeline's AGM equivalent.

Originally Posted by FlyWright

One 8D box can fit 3 GC batteries. My house bank of 6 GCs fit into 2 8D boxes.

Ah. Thanks for correction. I was having a brain phart when I said 4 might fit in each 8D box.

FWIW, when I converted one of our banks to GCs, I also wanted a box instead of open trays... but finally found some that would hold 2x or 4x GCs. Inserting the box actually turned out to be more work than the batteries, just because of the stuff in the way of getting the box into place.

-Chris