Battery health?

[Ajax]

Something interesting happened to me yesterday as I was motoring in from a short, afternoon sail.

The wind died, so I had a longer motor than usual back to my dock, so the batteries should have received a nice charge.

I have the original ammeter and no voltmeter. Original, 30 amp alternator. Normally when I start the engine, the ammeter jumps up to around 25 amps and tapers down quickly if I haven't been sailing overnight with lights and instruments.

This time, the alternator jumped to 30 amps and never dropped below 25 amps, all the way back to the dock. It acted as if the batteries were severely drained. The starter cranking sounded normal, and not lagging as if the batteries were low. The ammeter seemed to indicate low batteries, even when I arrived at my dock. Once back at the dock, I plugged into shore power and turned on my onboard, Guest battery charger. It jumped up to 10 amps output, and quickly tapered down to 2 amps, and would eventually shut off. This is what I view as normal.

The starting battery is of unknown age, and came with the boat when I bought it 3 years ago. It is a "starting" battery.
The house battery is only 2 years old or so, and is a deep cycle marine battery from Wal-Mart. I have never deeply discharged it, or abused it.

Do I have a regulator problem or a battery problem?

Oh, here's a variable: I just installed a Rigid (brand) 750 watt inverter, tied directly to the house battery (until I get a breaker for it). It was turned OFF the entire time, but could it present a parasitic load even while turned off?

[joe_db]

You *really really* need a voltmeter to solve this riddle.

[Ajax]

Well, I have a Fluke multimeter that I can manually put on the batteries to see what they're doing.

I'll check the resting voltages and the charging voltages when I get a chance.
I'm fighting a cold all of a sudden so it will be a few days before I get down there to fool around.

[sastanley]

Ajax, I would recommend keeping the AC charger out of the loop for a while until we get more data. Being plugged into the dock all the time always makes the batteries 'look' great when you come down to the boat.

Resting voltage will tell us a lot!

Also, if the batteries are flooded, which I suspect they are, the first check is a visual on each cell and make sure each is filled with (distilled) water just up to but not quite into the neck..I've read that just a perceptible air gap at the neck helps with venting gases during charging...and also almost any water in the neck usually overflows when you put the cap back on.

[JOHN COOKSON]

This time, the alternator jumped to 30 amps and never dropped below 25 amps, all the way back to the dock. It acted as if the batteries were severely drained. The starter cranking sounded normal, and not lagging as if the batteries were low. The ammeter seemed to indicate low batteries, even when I arrived at my dock. Once back at the dock, I plugged into shore power and turned on my onboard, Guest battery charger. It jumped up to 10 amps output, and quickly tapered down to 2 amps, and would eventually shut off. This is what I view as normal.
Do I have a regulator problem or a battery problem

Maybe you have an ammeter problem.
There could be a bit of corrosion that is causing the needle to stick inside the meter.
Since everything seems to be normal except the ammeter reading I wouldn't trust it until it's verified that it is working correctly.

TRUE GRIT

[Ajax]

Just to wrap this up:

The needle doesn't stick. It wiggles enough to prove to me that it's not stuck.
Apparently the batteries were simply drained more than I expected. After a full charge from my onboard charger, the ammeter is acting normally to charging the batteries.

I am interested in switching to a voltmeter to eliminate the long charging run. It's all a matter of cash and time.

[norahsark]

Re elimating long charging run with volt meter

I don't understand what you mean by that. Do you mean long charging time or long run of wire?

[ndutton]

Long wire run. Voltage drop is a function of three factors, wire length being one of them. Please see this post for a brief description.

[Ajax]

Yes, I was referring to the long wire run, not charging time.

I don't like the idea of pulling high amps through a long, skinny wire through the ammeter and back. Especially if I ever upgrade to a 50 amp alternator.

[JimG]

One of my non-A4 boats has a house bank of six 6 volt batteries. They were all six years old, and I just replaced them. Two of the batteries (one in each two battery pair) had a simple shorted cell, showing a steady charging current at barely 12 volts (when the shore charger was trying to do the 14.5 volt "acceptance" charge. Before taking the batteries over to Costco for the swap, I checked each pair to see where they stood, and one pair exhibited a new-to-me symptom. They would accept 25A indefinitely, while showing a charging voltage of 12.8v. Resting voltage then dropped to 12v. The two batteries were exactly 1/2 of both of those values. My guess is that they were sulfated in some way I'd never seen before.

The A4 turns over so easily, that I could start my A4 with several dead battery cells (just before I installed the Optimas).