Batteries not charging

Hi

I just bought a 76' Newport 28 with a "later" model A4. Before the boat went in this summer, I gave both the acc and the cranking battery a good 48hr trickle charge. After being out for a few nights it was apparent that the batteries were not charging/holding a charge. The first things I did were check the battery’s fluid, which was good, and checked the voltage off of the alternator, which read ~15.4vdc, and cleaned the battery terminals, which were filthy. The batteries still didn’t seem like they were holding much of a charge, so I put them back on a charger (two days ago), as I thought perhaps they just needed a little help to get topped up (as I only really motor <45 minutes on any day, so far).

One thing I did notice was that my amp meter was not reading anything, while engine is cranking, nor when running. I downloaded the wiring diagram that D. Moyer posted, and it almost looks to me that since the amp meter is in line between the alternator output and the batteries, if the amp meter was "open" then there would be no power getting to the batteries. Am I correct?

Thanks in advance
Eric Morin
Saint John, NB

[dtinder]

Eric---You might check your voltage at the + terminals of your batteries---with engine running vs. not. The 15.4v you noted might be a bit on the high side--but not to worry. Be sure and check the position of your batt selector switch when measuring the voltage at the terminals themselves. A fully charged 12v batt is actually 13.2v (depending on where you went to school and whether or not you missed that day). It is possible that your 12v batt reads more than 13.2v---but lets not go there. The real test of the batt's is a load test. These meters are not in the average guys tool box, so you might have to look a bit for one. Be sure and follow the directions for testing. If you get carried away---by holding the switch too long---you'll really zap your batt. The point is: Even though the initial voltage reading is "OK"----it may be only a superficial plate charge---and when the batt is put to work---it quickly gives up!! Re the ammeter: I'll leave that one to Mr. Don. Best of luck----this problem IS solvable.

[Don Moyer]

Eric,

You're correct to assume that all charging current flows through your ammeter (it being wired in series with the charging circuit), so if the ammeter were to be open, no current would flow through the circuit.

That being said, ammeters are shunted, meaning that they can (and usually
do) provide a path for current even though their gauge mechanisms may be faulty.

The suggestion of the previous poster regarding the checking of battery voltage directly at the battery posts while the engine is running is a good one. If your 15.4 volts survives all the way to the battery posts, the alternator as well as the entire charging circuit (including the shunt in the ammeter) is OK.

If you do not read 15.4 volts at the battery posts, you will have to check for a loose connection somewhere within your charging system. Since your ammeter is apparently inoperative, you may as well connect your alternator output directly to the big battery terminal on your starter solenoid and install a voltmeter in the cockpit in place of the ammeter. You didn't report what model of boat you have, but the Catalina 30 fleet (with 6 quick disconnect terminals in the charging circuit) is notorious for loose connections in their charging circuit.

If you do read 15.4 volts at the battery posts, it would of course leave unanswered why your batteries are depleting, and at some point we would have to question the condition of the batteries themselves. I couldn't find where you mentioned the age of your batteries, but the manufacturer of our aftermarket alternators continue to stress to us that old batteries develop high internal resistance which can drive an alternator regulator into a max output, which in time can damage an alternator.

Therefore, if your voltage checks good at the battery posts during engine operation, I would follow through with the previous poster's suggestion to check the batteries through an actual load test (the most reliable way), or at least by monitoring them individually with your voltmeter for several days to watch how fast their voltage decays (less accurate, but workable in case you can't find a load tester). Good batteries should hold close to a full charge (12.6+ volts) for up to a week. Be sure you disconnect each battery from your electrical system and/or check for a small short to rule out any drain from a small "trickle short" to ground.

Best regards,

Don