Hot Alternator on Shore Power

[nuggetboater]

I just purchased a 2004 240 Sundancer. I brought the boat home and connected the shore power to my house to charge the batteries and have power while I cleaned it out. Initially the voltage of both batteries were about 11.6v, after about 24 hours of charging they now read 13.6v. While I was poking around the engine I accidentally touched the alternator and it was super hot, too hot to hold my hand on. Is this normal? I looked at the wiring schematics and it doesn't show AC power going to the alternator. The boat has a AC/DC Inverter and I thought that was what charged the batteries.

The next day I went out to continue cleaning and could smell a sulfur like odor, I assumed it was the grey water venting so I just opened up the canopy. Well come to find out both batteries, 550 CCA & 800 CCA Interstate, were almost dry, the water was down to about 3 inches from the bottom.

The boat has been in storage since OCT '14 connected to power and charging batteries.

Here are my questions:

- Does current flow through the alternator on shore power?
- What actually charges the batteries?
- Should I replace my batteries?
- Could there be a problem with the alternator?

Thanks for the help.:smt101

 

[Bt Doctur]

Does current flow through the alternator on shore power? No
What actually charges the batteries? The alt when the motor is running
Should I replace my batteries? Being cooked dry, Yes
Could there be a problem with the alternator? A bad diode causing to to back feed

Motor batteries should never be on a charger ,only house batteries. You found out why. They get cooked and go dead..
Your lucky you didn't start a fire

 

[sgs01]

So if I'm reading that right, you're saying that I should NOT connect my battery charger to my starting batteries? On my sea dancer, I only have 2 marine deep cycle batteries. I have a 4 position battery switch that can close either or both to the 12v bus. I don't have a dedicated house battery (not yet at least). So in my situation, how should I set up my battery charger?

 

[Jimmy Buoy]

My setup is one pair of 12vt batteries for the port engine/port house, and another pair of 12vt batteries for the stb engine/stb house, and one 12vt battery dedicated for the generator only. ALL of these batteries are charged (3 separate banks) by the battery charger. Never has there been an issue with the charger cooking batteries.

Not an expert in DC stuff, but I'd say the alternator is probably the issue… Take it off and get a shop to test it and repair if necessary.

 

[Lazy Daze]

Without knowing the full condition of the batteries before charging, we also don't know whether or not the charger is ramping down like it should and, instead, overcharging. It's probably a ProMariner unit? Call them and ask for the diagnostic procedure to verify if it's functioning properly... I don't remember it well enough to say.

There has been discussion about different ways to hook up batteries/chargers. Without taking anything away from BT's line of reasoning as I understand where he's coming from, I personally like having all batteries hooked up to the charger. For what it's worth, that's the way the factory does it. Not that that means it's the "only" way to do things, just offering that tidbit.

FYI, the "fire" part that BT is referring to can happen to any battery - not just a starting battery. I do not believe that he is saying otherwise - but based on his wording and your response, just wanted to mention it in case you were confused.

 

[sgs01]

That's what I thought. It might be that the OP's battery charger is boiling off the electrolyte in the batteries. We had that problem on my family's Bayliner 3788 with the old battery charger. It was promptly replaced with a new Newmark battery charger and we haven't had that problem since then.

 

[Bt Doctur]

My take on the engine batteries and chargers is that the owners never CHECK THE FLUID LEVELS. Be it engine , transmission, outdrive, generator or batteries. A good battery will never just discharge and go dead but a battery boiled dry will.
When you go on vacation for a week do you plug your car into a charger? Does the battery go dead. Nope.
You need engine batteries to start your engines , nothing else. You buy a twin for reliability but your electrical systems are tied together . No twin reliability. Keeping a battery topped off means it will never give you the hint its going bad from a slow crank indication. Get 60 miles off shore with dead batteries and you`ll learn real fast.
The factory dosent know shineola about wiring a boat. They do it as cheaply as possible . Save the cost of a switch and a battery cable for their bottom line. Dont give 2 ****s about the boat owner ,only his money.
If you have 2 batteries for a single engine, wouldn`t you have 2 batteries for the other engine too. Independent of each other.
That way if one does act up the other will still function.
The factory combines the alt charge leads so both alt are bucking each other or one alt charges the house and one alt charges the engine batteries. Not a true independent system .
But you say" I have the emergency crossover system" Dosent work with dead batteries, Sorry.
You want safety and reliability on the water ,leave your engine batteries alone and have independent electrical systems.

 

[nuggetboater]

Bt, thanks for the info on the alternator. I'll get it looked at.

The saga continues: I took both batteries to the local auto supply store, they are an Interstate dealer, to get them checked out. The cranking battery which was wired to bank #1 was at 13.6v and checked good, the deep cycle battery which was wired to bank #2 was completely dead. I was wrong about the fluid levels, couldn't quite see while they were in the engine bay, the cranking battery was topped off, the deep charge battery was a little low (I could see about 1/4 inch of electrodes). The guy at the store thought the charger was reading the dead battery and kept pumping in a charge, causing the good battery to overcharge. Thoughts on this?

Here is another strange discovery: The wiring for the banks were not labeled in the engine bay (or at least I couldn't find it) so to sort it out I wired up the new battery to one set and selected each bank separately to figure out which wires were for which bank. I figured it out but in the process found that when only 1 battery is wired to bank #2 the radio doesn't work, everything else came on. When 1 battery was wired to bank #1 everything came on, including the radio. When both batteries were in and I selected bank #2 the radio came on. Is this because the radio is hardwired to bank #1?

Also, at the store the cranking battery read 13.3v and the new deep cycle battery read 12.4v. After installing the batteries and selecting them individually I got 12.7 and 12.4 respectively. Could the cranking battery drop 0.6v just from turning on the radio for a few seconds or do you think it's bad?

Here is another round of questions:
- Why would the system charge one battery and not the other? When charging I had both batteries selected.
- Could the battery switch be bad?
- Should I replace the charging system?
- Is it time, already, to get this looked at by a pro?

Thanks

 

[ktcanuck]

Before you go too far with the alternators check whether the sense current is present when the ignition is off. You have three alternator wires. Two are the ground and charge current lines and one, a lighter gauge, is the sense. If you have voltage there when your ignition is off you have about 6 amps flowing through the alternator at all times. Mine was wired like that. I rewired it to get sense current from the fuel solenoid so it was only on when needed.

 

[Bt Doctur]

- "Why would the system charge one battery and not the other? When charging I had both batteries selected."

Most charger has dedicated feeds to each battery, you and the battery switch are not in the equasion.

"Could the battery switch be bad?"

Has no effect on how the batteries charge

"Should I replace the charging system?"

Only if it`s gone bad and overcharging the batteries

"Is it time, already, to get this looked at by a pro?"

If you are not confident in you ability to check/measure/ service it, Yes

 

[Bt Doctur]

kt, better check those wires. The typical alt used has a 12v sense, a 12v excite, and the main charge lead, plus a main ground lead.