Battery charger question

[Captnkev25]

I have a 1984 Catalina 25 that has two batteries. I also have a 1994 Johnson outboard with electric start and an alternator to charge the batteries up. My question is can I hook up my regular old Sears battery charger to the batteries while at the dock using one of the 110 outlets on my boat while hooked up to shore power? Do I have to disconnect the batteries to do so? This would be rare and just to top them off. They are both starting batteries and I was going to replace one with a dual purpose this year. If I do need to disconnect them what is the sequence for doing so. I also have a off, 1, 2 or both switch. What position should that be in when charging ( I'm assuming off). Any guidance is appreciated.

 

[Stu Jackson]

Yes, you can connect your charger to the batteries. The position of the switch makes no difference if you connect the shorepower charger to the batteries.

As far as your 1-2-B switch is concerned, and your engine, you need to find out how it's wired. Most likely, the output of the engine alternator goes to the C post of the 1-2-B switch. This means that the switch performs two functions: when the engine is running the switch determines which battery gets the charge, and when the engine is off it determines which bank (battery in your case) provides the power to the boat.

 

[Don S/V ILLusion]

You should be fine as you described the process. Depending on the charger voltage, it is probably wise to shut the battery switch to off so as to avoid putting a high voltage on whatever electronics/electrics you have assuming the only thing connected directly to the batteries is the float switch/bilge pump.
Depending on how the outboard alternator is wired (internally), it is conceivable you could blow the alternator if you run both the charger and engine simultaneously.

 

[Captnkev25]

Running the engine AND the charger at the same time should not be an issue seeing as this would only be done while tied up at the dock with the shore power cable plugged in. My main question was do I need to disconnect the battery to charge it. I'm pretty sure my charger can only do one battery at a time so I didn't know if I needed to isolate each one to get a proper charge. This won't be done often as I do have the alternator to charge them so it wouldn't be a big deal even if I did have to.

 

[Bill Roosa]

1) The charging voltages of a battery charger are the same no mater how you power it. An alternator is a battery charger, and the charging voltages have not blown anything yet so any other type of battery charger will be fine also. that means you do not have to disconnect the batteries from the boat to charge them.
2) You have one set of terminals so it would appear that you can only charge one battery at a time. But wait, you have a 3-way switch which connects the batteries POSITIVE TERMINALS together when put to the "both" position. That means you can connect to one battery as normal and set the 3-way to "both" and it will charge both batteries at the same time.
Don't leave the charger pluged in as a "non-marine" charger does not isolate the ground from the neutral and leaving it pluged in and turned off but the shore power cable pluged in can result in some interesting rusting of metal parts attached to the motor.

 

[Stu Jackson]

Bill's right, but what it really is saying is that you NEED to do some more homework on electrical systems. We all started out as new sailors and learned as we went along, by asking questions, buying books and reading internet forums, and then contributing.

The basic 1-2-B switch is rather simple, but has been incorrectly installed by boat builders forever. The reason is in Reply #11, here: http://c34.org/bbs/index.php/topic,4949.0.html

Whether your have just an outboard or an inboard engine with an alternator, the concept is the same.

So, spend some time with a good book, there are literally hundreds out there, go to a chandlery and find a few, pick one that you feel comfortable with, and learn about electrical systems and charging. As you learn, you'll find yourself more comfortable with your systems, and heck, who can argue with confidence?

You also have the resources of the Catalina 25 Association website, great guys over there, too, as here.

 

[Bill Roosa]

I am constantly amazed at what I have forgotten over the years.
"BOTH is not a terminal on a 3 way switch"

 

[FourPoints]

Whether your have just an outboard or an inboard engine with an alternator, the concept is the same.

I am actually planning to wire in a 1-2-B switch this weekend, but my outboard uses a single set of wires for starting and charging, so I cannot attach the start and alternator outputs separately. How would you suggest I wire in this case?

Attached is a diagram of how I plan to wire my electricial, the only question is do I hook up the engine wires (not pictured, and remember single wire is both start and charge) to the spot labled A or B in blue?

 

[FourPoints]

bump... hooking this up today, got everything ready to mount yesterday (had to put up a piece of 3/4" plywood and epoxy it to the bulkhead because I couldn't screw into the bulkhead where I want everything mounted)