Alternator Issues

[Capt Don Q]

I just ordered a new 55 Amp API alternator from Moyer Marine, I called to verify my order and had a chat with Don and he asked me to relate this to the forum, so here goes. Be gentle.

Part 1:
I put my boat on the ground for the summer in April. At that time everything was working fine. When I launched it a week ago this is what happened:
1) First I charged all batteries for a couple of days on my new 30 amp charger.
2 Once the boat was in the water I put the selector switch to 1 (my group 24 starting Battery) and all it did was click and make a slight effort to turn the motor and then stop-dead battery.
3) I then put the selector switch on "all" and the engine started right up.
4) As I puttered around checking for leaks, I switched the selector switch back to "1" to try to charge the battery again.
5) After a few minutes I noticed that there were no "Amps" showing on my Amp meter and that the voltage stayed at 12.4 instead of climbing to over 13 volts as is usual when the engine is running.
6) I once again switched the Selector switch to "all" but still no alternator amps and no extra voltage.
7) I then switched the selector switch to off and the engine instantly stalled.
8) I rechecked all electrical connections again, cleaned them and reconnected them. The engine started right up on "All" but instantly stalled on "Off" position. Battery "1" showed 8 volts dropping quickly to the bottom off the scale.

My conclusion was that battery "1" had died completely and that it had then fried my alternator because it showed the alternator no load. The Diodes fried.

I bought a new 1000 cca Group 24 battery and installed it, but still no Amps showing from the alternator in any position. I then ordered a new alternator from Moyer Marine. One final note, I tested this battery under load before putting the boat away and it was fine. It evidently died during storage.

Here is the part Don wanted me to relay:

My wiring setup is as follows:
From the alternator the wire goes to an Amp meter then directly to the positive post on Battery 1. I did this because I often have children aboard and wanted to be sure they would not fry my alternator with misuse of the selector switch ("off" position while engine is running). Battery 1 is then wired to the "1" post on the selector switch and Battery "2" is wired to the "2" post on the selector switch. The common post is wired to the starting solenoid and the house "+" bar.
I did it this way so that
a) I could not fry my alternator through misuse of the selector switch
b) The engine would instantly start replacing the amps it took from battery 1 to start the engine (negligible but important)[I would always have a fully charged starting battery
c) I could then place the selector switch on "all" and use the engine to charge the house battery or go back to battery 1 if I needed all my horsepower for something (lee shore?)

So here are the questions:
1) Is it possible to fry the alternator with a completely dead battery?
2) Did I do something wrong with my wiring configuration?
3) Was my diagnosis of the problem correct? (replace battery and alternator)
4) Is it just coincidence that my battery and alternator went bad at the exact same time?

What do the experts think?

Don

[ndutton]

Don,
Follow-up question to part 1, item 3 above: did you read positive amperage and 14 volts when running on the house bank?

[CalebD]

In your wiring description you indicate: "From the alternator the wire goes to an Amp meter then directly to the positive post on Battery 1." which you did to bypass any problems with switching the battery selector while the alternator was creating a charging current, as Battery 1 now has a dedicated line to the alternator. The only problem with this idea is that battery 1 was essentially dead and could not accept a charge and all that current had nowhere to go. I would say that your dead Battery 1 undermined your wiring intentions which caused the alternator diodes to fry.
As I understand it you are not supposed to mess with the battery selector once the engine is running as even a momentary disconnection between the alternator and batteries can fry the diodes. There is more to be said on the switching mechanism in the battery selector switch about 'make before break' connections but I am not the one to talk about that.
I was wondering why you did not take your old alternator to an automobile alternator rebuild shop and have them replace the diodes? Maybe you wanted a higher amp alternator?
I am no expert but I have fried an alternator and had it repaired. The repair wasn't so cheap either but the alt. looked like new when I picked it up.

[Capt Don Q]

Alternator

No I did not read 14 volts, but the alternator amp meter flickered to 5 or 6 amps momentarily, then dropped off to about 2 amps.
I am having my old alternator fixed so that I will have a back-up alternator. I am also buying the 55 amp alternator from Moyer as the original was the lower amperage Motorola.
I could not guarantee that kids would not move the switch inadvertently, so this was my solution. I think the alternator would have fried even if wired the conventional way and battery 1 was selected only (and it was dead).

Don

[ndutton]

I’m not sure why the Group 24 engine starting battery was dead in the first place but having it constantly connected to the alternator is worrisome to me. Even the slightest current drain over a prolonged period will make pretty quick work of a battery. Regarding the reasoning behind your setup, I understand, but the first kid who messes with my battery switch gets a 30 second swimming lesson. Problem solved.

With the start battery at 8 volts (may as well be zero volts) switching from the good house bank to the dead start battery while the engine is running would be the same as moving the selector switch to OFF which would result in a current spike and finish off the diodes at the speed of light. Any observations/testing after that would show zero alternator output.

I don’t think it’s a coincidence that the battery and alternator failed simultaneously but rather the dead battery killed the alternator by switching to it with the engine running. If the start battery was a true deep-cycle battery there might have been a glimmer of hope in recharging it but I suggest it would have been healthier for the alternator if the battery selector had been switched to the ALL position (with engine running) for a while to bring up the dead battery before trying position 1 by itself. If it’s not a deep-cycle, at 8 volts it’s history, don’t even try to recharge it.

Regarding your new alternator, pay careful attention to the gauge of the output wire. At full output and depending on the length of the wire from the alternator to the ammeter and back to the battery, you should be using #6 gauge minimum, maybe bigger. My Catalina 30 was originally wired with #10 so the high-output alternator upgrade also required a wiring replacement.

[ndutton]

Don,
Instead of wiring the alternator directly to the battery, how 'bout a battery selector switch with a key lock? The switch would allow you to disconnect the engine start battery during periods of non-use and the key lock would keep little hands from mischief.

Something like this

http://www.nextag.com/Perko-8504DP-Medium-Duty-503042609/prices-html

I'm assuming the switch can be locked in any position which might not be the case.

[Capt Don Q]

Alternator/Battery drain?

In on of the previous posts it was suggested that hooking directly from the alternator to a battery will drain the battery when the engine is not running. is this correct and is this a problem? What would be the difference if the alternator was wired conventionally?

Don

[ndutton]

That was a concern of mine but not necessarily a fact. I don't know of any current drain through an alternator at rest under normal circumstances but with the battery connected even the smallest issue could be a problem. A piece of conductive debris in the wrong place could do it.

My practice is to have any battery wired directly to a battery switch. It allows me to isolate one battery for engine starting and to completely disconnect it when closing up the boat. Remember, something drained your starting battery during a prolonged period of non-use. The battery itself could have failed but if it didn't, something drained it. This possibility is eliminated with the battery disconnected.

[Dave Neptune]

Dead or Broken Battery

Don, did you check the battery for an internal short "cell by cell? If the battery has a cell with a bad connection (broken,cracked or weak inside the case) it will show no voltage gain as you move along the cells with the V/meter. If the offending cell is at one of the "posts" it may create a "make-n-break" situation which could fry the diodes. Frying the diodes is usually caused by the power surge that a "make-n-break" can cause.
Over the years I have replaced many diodes in alternators to repair them and it is surprisingly easy to do. There are 2 sets of them one positive and one negative and all they do is control the direction (+ or -) of the current to create DC voltage. The alternator makes AC current and it must be converted to DC, where as a generator makes DC which is why you need to polarize them when installing.
How about one of you "Sparky" electrical guru's stepping in for a little tutiledge here.

Dave Neptune

[67c&ccorv]

A $50.00 battery isolator would have saved a lot of re-wiring issues and expensive alternator repairs.