mlb75

I've got a new boat being built with twin outboards and need to see how they are supposed to be wired. I've talked to a couple people and what they describe doesn't make a lot of sense so if someone has a diagram I'd appreciate it.

In order to keep up with the stereo in the boat I'm thinking I may end up with 4 batteries and so need to figure out the best way to get them all charging properly.

FullAuto9

I've got a couple of diagrams, but I think you are looking for the schematic for two cranking batteries with switches and one auxillary battery charged by two alternators. I posted a pic of how the batteries are set up in my 32. Let me know if you still need the diagrams and I will fax them to you.

FullAuto9

mlb75

FullAuto, thanks that looks like about what I'm trying to do I'd just have another battery tied in parallel to the third. I guess my question is though if you can feed a battery via both alternators why in the world do you need three switches. Why not simply have a single switch and A starter battery on position 1 and a BANK of 1-14 battteries on position 2? A single battery is more than capable of starting either motor (obviously) and the position 2 would just be the house bank. I understand the risk of getting stranded with dead batteries is a little higher but I'm willing to take that risk rather than deal with a battery switch puzzle every time I want to go out. It would be much nicer to just be able to tell anyone to switch to battery position 2 when we're at the cove or dock then when we get ready to fire the engines switch it back to 1 or both.

That way worst case scenario you'd switch to bank 1 to start the boat then once everything is running switch it back to back 2 to charge the others. That way you wouldn't have to be afraid of bank 2 bleading charge off of the starter battery in position 1 etc.

Hopefully this makes sense. BTW the reason I'm interested in doing this is I don't want to have 3 or 4 battery switches if I don't have to but I need the battery power to run the stereo while we're just sitting around. The stereo is ~5500 watts so it'll drain a single battery pretty quick but I've had good luck running similar setups for longer periods as long as its fed off a couple batteries in parallel.

TIA

US1 Fountain

iTrader: (1)

Just run your stereo (house) batterys off one of your starting batteries thru an ACR. Simple and easy. No switches to ever have to switch back and forth, fully automatic.

DynojetResearch

Here's a diagram I made up a while back. The only thing missing is a ON/OFF switch on the house bank.

mlb75

US1, what do you mean when you say an ACR? Are you talking about an isolator? If so the only issue there is would the stereo battery be charged by both alternators?

DynoJet, thanks for the feedback but couple questions. How does the stereo bank get charged? Also the motor portion is a little sketchy it appears the batteries are attached to the output and position 2 of the left switch and the output and position one of the right switch. Then it looks like port motor is connected to position one of the left switch and the strbd motor is connected to position 2 of the right switch. That doesn't make any sense to me...

To me if you were to use two switches then the port motor would be connected to the output of the left switch a battery would be connected to position 1 and position 2 would be tied to position two of the right switch. Then the strbd motor would be connected to the output of the right switch and another battery would go to position 1.

Assuming that is correct and you could run the boat with both switches in the 1+2 position then I don't see a reason you couldn't just use a single switch with the output connected to both motors and a single battery on position one and a bank of 2 or more batteries in parallel connected to position 2. Is there a reason I can't do it that way? The only thing I can think of is that the alternators may not like working together.

Thanks

mlb75

I'll try and draw both of those out later this evening and post to give a visual.

US1 Fountain

iTrader: (1)

ACR, Automatic charging relay. Look at the Blue Seas web site http://bluesea.com/productline/docs/387 Works similar to an isolator, but more efficient and easier to install. An isoltor will work just fine too, it's just old school.
No switching of battery switches needed. Hook your stereo to your stereo battery, install the ACR paralleled between that battery and 1 of your start batteries, run a small gnd wire from ACR to ground. Done, enjoy.

The stereo battery would be charged by the motor that you connect the ACR to. No chance of the alts working against each other.

mlb75

US1, thanks that is essentially what I thought it was but the main limiting factor there is that it's only charged by one alternator. With them only being 60amp to begin with I'd like to be able to charge via both if its possible.

This is my understanding of the way they are normally wired.


Why can't they be wired like this



The only reason I can come up with is that the alternators aren't supposed to be run together but that doesn't really make sense. Especially when if you put both switches in 1+2 they would be doing exactly that anyway. Or is that ability there for emergency use only ie if you lost one alternator. There again that doesn't make a lot of sense though as there are quite a few setups that team alternators ie large trucks.

TIA