alternator failure - mid cabin (assume it varies by model)

[BobCT]

will one alternator charge both batteries, enough to keep the engines running or are they completely isolated? Compared to other makes, people think it's odd we have no battery selector switch which I realize doesn't solve the alternator issue.

Mine are original and work fine (22 years, 800 hours) but I'm thinking of buying a new alternator, installing it and keeping the spare on board...or just getting both rebuilt. It's an easy road side swap and I have extra belts onboard.

If both engines can charge/run off one alternator then maybe I won't worry about it.

Bob

[koviak]

Bob, I have replaced both of mine in my 1989 mid cabin. I don't think you can run (1) alt. for both, charging amps would be too great. I purchased brand new ARCO products for mine. Charging became an issue for me after sitting at anchor all day with appliances running, they were only putting out 12 volt and not refreshing batteries. Don,t wait too long to replace as it will catch you at the worst time (ie: Murphys Law)

[prowlersfish]

One alt should take care of both With no issues ( as long as your not runnig a high load like a large inverter) The engine it self once started takes very liltle power . You will need a switch to combine the batteries . as far replacing the alt to be safe I would not as new is not always better .

[RWS]

My 1983 10 meter International has 3 batteries.

port engine, starboard engine nad genny.

The genny was hard wired into the port side for charging purposes.

After upgrading the factory batter y charger (2 battery system) to a modern Xantrex for three batteries, I put a battery isolator switch oin the genny battery.

This way in th e"normal" position the three batyteries can be charged by shore power OR the genny.

In the event both engine batteries run down I can either

1) strart the genny and charge all 3 batteries

or

2) turn the battery switch and combine th egenny battery to the port battery

or

do #2 above AND hit the emergency start solenoid, thereby tying ALL THREE batteries together to start an engine or the genny.

SOmething to think about re: the alternator issue.

RWS

[BobCT]

As far as I can tell, the start batteries are isolated to each engine unless the "emergency start" button is engaged.

I'm more concerned about losing an alternator underway and having an engine die as opposed to just getting them started.

If they are in fact isolated, then that would mean one alternator wouldn't have the option of charging both batteries. I think what you guys are saying is I need to add a battery combing switch.

I don't have a genny, one start battery for each engine and "one" (actually two 6v T105's) dedicated to the aft fridge.

Am I confusing the way starting vs charging works?

Bob

[ready123]

My 1983 10 meter International has 3 batteries.
port engine, starboard engine nad genny.
The genny was hard wired into the port side for charging purposes.
After upgrading the factory batter y charger (2 battery system) to a modern Xantrex for three batteries, I put a battery isolator switch oin the genny battery.
This way in th e"normal" position the three batyteries can be charged by shore power OR the genny.
In the event both engine batteries run down I can either
1) strart the genny and charge all 3 batteries
or
2) turn the battery switch and combine th egenny battery to the port battery
or
do #2 above AND hit the emergency start solenoid, thereby tying ALL THREE batteries together to start an engine or the genny.
SOmething to think about re: the alternator issue.
RWS

In all the genny setups I have seen ( my Onan and Northern lights) it is recommended (if not required) by the manuals that the genny battery only be charged by the genny when it is running.
Since the genny charges it's own battery when running if you have that genny battery also being charged by the battery charger being supplied 120V from the genny you are shortening the life of that genny battery!!

As the genny battery only starts the genny and is charged when the genny runs there should be no reason to charge it at any other time.... like shore power.
I would suggest you do some research and have the charger setup to charge all batteries other than the genny start battery.

I have a three bank Zantrex which charges each of my engine batteries and the house bank... either from shore power or genny power... the genny battery is charged by the genny when it runs.

[prowlersfish]

Some Gen set do not charge the batteries and and use the boats battery charger , not a set up I would want.



Back to bobs question . Bob I would install some battery switch's that would in able you start of or charge different batteries . they maybe one there already , I have a battery switch for the House where I can run the boat house electric off the port or starboard battery , if I switch it to all it "jumps" the 2 batteries so I could charge both off one engine . I also have a switch on the gen set so I can start it of its own battery or the port engine battery , can also be use in the same way .

[S.A.M.]

Bob,

The batteries are independent of each other. The port battery is charged by the port engine and also handles certain 12v systems. The same for the starboard. My third battery is dedicated to the genny.

I never have studied the wiring schematics to learn what 12v systems are powered by each side.

[RWS]

Bob,


I never have studied the wiring schematics to learn what 12v systems are powered by each side.

========================

Don't quote me, but I believe there is a system here.


On the main breaker panel there are TWO main mreakers at the top.

It is my UNCONFIRMED UNDERSTANDING (didn't veirify this with the schematic) that these two breakers conform to the port side electrical system and the starboard side.

Now, going down the panel below thyose two main breakers are a number of smaller breakers - (YES THESE ARE AIRPAX BREAKERS AND SNOULD NEVER EVER BE REPLACED WITH A PLAIN TOGGLE SWITCH EVEN THOUGH THEY DO LOOK LIKE TOGGLE SWITCHES)
inserted photo



Now tale a look at the rows of smaller breakers, each row has 5 breakers.

I do not recall which side handles the center row of breakers, but it would be really easy to confirm when you are on the boat.

Also what is true for the wiring arrangement on a 1983 International Express Cruiser may be different for different model years or build series.

The breaker issue is important as it's really easy to make the mistake of replacing those breakers with plain toggle switches.

It's a novice mistake and I know because I did it on several as did the previous owner.

Those breakers do become brittle and fail.

Be safe.

RWS

[S.A.M.]

Harris,

The panel in my '90 MC is the same. The breakers may go to different items.

The easiest thing to do would be to turn off the portside and see what 12v items turn off(lights, etc). And do the same for starboard.

[prowlersfish]

I don't belive there is any thing in that panel that could handle the amps of a alternator / or starter and would not be wired that way. In fact I will bet on it

[RWS]

I don't belive there is any thing in that panel that could handle the amps of a alternator / or starter and would not be wired that way. In fact I will bet on it

=============================

Agreed

I'm simply showing the split of the systems in regard to S.A.M. ' s earlier post.

RWS

[BobCT]

It sounds like my best bet is to install a battery switch. I (we) already have an emergency start switch on the mid cabin but that won't do me any good underway.

That way, I can bridge the two batteries together and get some charge to each and keep running.

I guess I could always just pick up a good/spare alternator and swap it out if needed.

Since my 3rd battery is only for the fridge, I need to be careful on the hook since I'm using my start batteries for the house.

BTW, you can fit two Trojan T105's in the middle of the battery box. You need to move the rubber catches to increase the height but they do fit. there's about a 2" gap height wise but at least there all inside the box.

For you guys w/o a genny, this is a pretty good option as it gives me about 3 days keeping the aft fridge cold. Plus with jumper cables on board, this is my back-up to the back-up in case I ran both my start batteries down.

Bob