Is my alternator dead ?

[junaido]

So those who have been following the saga of our A4 (started in Bellingham but now is in Seattle). We finally got everything hooked up on the exhaust side and took her out for a spin. The engine ran very well over a couple of hours. Water temp varied between 120-180 depending on throttle setting. It is SO much nicer not to have to hang off the transom everytime you want to start the motor or adjust throttle.

One thing I noticed is that the ampere gauge on the panel showed 0 (the dial goes +25 to -25). Does it mean the alternator is not working ? What is the "normal" value I should see on it when it is running ? I did not test the voltage at the battery terminals. I have 2 group24 batteries, one is brand new, other is old and probably dead. Battery selector switch is on "Both".

If I am using shore power to charge the batteries and just day-sailing, does it matter if the alternator is dead ?

Junaid

[edwardc]

Your alternator may not be dead. The automotive style regulators that are used in alternators with internal regulators are notorious for undercharging. Unlike the smart chargers & smart regulators, they cut off strictly based on voltage, so they tend to start charging hard, but then back off very quickly to zero.

Also, they often do not generate enough voltage to charge at idle or low rpms, and will show zero then too.

And lastly, of course, your ampere gauge may just not be functioning.

[ArtJ]

Try racing the engine up to around 1500 rpm or so momentarily to start
the marine alternator charging . This is common to need to do this in order to
begin charging.

Regards

Art

[lat 64]

More power!

Your alternator may not be dead. The automotive style regulators that are used in alternators with internal regulators are notorious for undercharging. Unlike the smart chargers & smart regulators, they cut off strictly based on voltage, so they tend to start charging hard, but then back off very quickly to zero.

Also, they often do not generate enough voltage to charge at idle or low rpms, and will show zero then too.

And lastly, of course, your ampere gauge may just not be functioning.

Ed,
Do you have one in particular that you can recommend?
I'm learning so much about how insufficient my original alternator setup was from you guys. I think this is an area to get a "best practice" plan from the forum to follow as an upgrade. Starting with the mods some of the guys have done to improve this and a bit o' theory too.

[sastanley]

quick & dirty boat charging 101

Junaid, what Ed said.

I'll throw in some of my opinions (or three ) as well. If you know a battery is dead, don't set the switch to BOTH. The regulator, if it is working, is dumb..it can't charge a good battery & a bad battery at the same time. What happens is the good battery can get sucked down while the amps go into the bad battery. If you have batteries that you suspect are in widly dissimilar states, keep them isolated. Because of the phenonenon that Ed mentions, (no charging at idle) it is usually safe to switch from one battery to the other, as long as you NEVER GO THRU "OFF", and charge them independently. A good battery will take 15 or so amps for a few minutes after starting to replenish the amps pulled by the starter. If a battery is in good condition, it should noticeably be on the (+) side of the gauge, but only taking a few amps.

A bad battery may exhibit the same behavior...the regulator is dumb because it can't sense anything..only the voltage of the battery and adjusts amps accordingly, based on voltage alone..a bad battery will come up as long as you keep dumping charging amps into it, so the regulator will move closer to zero after a while, but when no longer being charged, the battery voltage drops again quickly. Bottom line, IMO, if you only have one good battery, use it, and isolate the good one from the bad..the bad will kill the good in no time.

The easiest way to tell if your alternator works is to put a voltmeter on the battery post & check it before you start the engine, and then check the battery again when running (but not at idle as Art already noted) and see what the voltage is. A good battery at rest (no charge or load for 24 hours) should show 12.6volts, & a charging battery should show 13.8-ish volts on stock Motorola alternators. You can also check the output voltage of the alternator at the alternator post to see if it is spitting out volts (should be the same 13.8v with an engine running above idle)..The post should be right on the top of the alternator with a big red (or sometimes orange) cable attached. Be mindful of the spinning fan & belt on the other side!!

There are quite a few threads on this forum about batteries and charging. It can make your head spin if you want to learn more, and most of the discussion in this forum is specific to our engines & limited alternator/regulator choices and the general older boats we have with less electrical demands. Wait until you get into newer boats and double belt alternators (Hanley excluded ) and multi-battery banks, and/or double alternators - - Anyway..we'll hold off on that...it is over my head too.

[joe_db]

You guys are missing something - This is a CENTER 0 ammeter. If connected correctly, it is on 0 when the load is being supplied by the alternator and the battery is just coasting.
I personally *hate* these things. Cessna uses them and the difference between +5 and -5 is about a needle width and you don't know anything is wrong until the radios act funny 9500 feet over Orlando at 0100.
Get a voltmeter. Anything over 12.6 or so means something is charging and over 13.8 is good.

[ArtJ]

A voltmeter is good. Especially if it has marking for positive and negative values
so that some of us don't have to remember that 12.x is charging while 12.y is
discharging. I bought a analog center zero meter from Blue Seas a number
of years ago which is labeled Green when in charging zone and Red when
in discharging zone this is mounted at the nav station.
Although I have added a current shunt and a digital blue seas meter to
the cockpit firewall, I still like the convenience of the other analog voltmeter.
The problem with the digital meter is that it can't easily be viewed in
sunlight, but is great for knowing how much charge is going into the
batteries. This job was formerly accomplished by the old fashioned plus
minus 30 amp meter which did not have the umph to carry 60 to 100 amps
for the high current alternator I added to charge my 4 battery bank
for the Freezer. Not only that, but the wiring could not handle the
current either with the old traditional ammeter.

Best Regards

Art

Best Regards

Art

[edwardc]

Ed,
Do you have one in particular that you can recommend?
I'm learning so much about how insufficient my original alternator setup was from you guys. I think this is an area to get a "best practice" plan from the forum to follow as an upgrade. Starting with the mods some of the guys have done to improve this and a bit o' theory too.

I can't recommend one yet, but on my "to do" list is a plan to get my 55 Amp Mando alternator modified to bring out the field winding connection, and install an external smart regulator/charger. I've been looking at the Balmar ARS series, and I picked up an old used ARS-1 at a flea market to see how it performs.

Meanwhile, after going thru all the details (current, temp, time since last charge, chemistry, etc) that affect the battery voltage, and finding that these factors can have a larger effect on the exact voltage than the difference between full charge, and 50%, I've decided the only way to go if you REALLY want to know your state of charge is to install a battery monitor. These do all the arcane measurements & calculations for you and give a "gas gauge" type of readout. It's not going to be cost effective, or even necessary, if you only day sail or overnite, but I think its a recommended addition if you plan to do any extended cruising without access to shore power.

[joe_db]

Some fun with cheap FleaBay meters.

[sastanley]

You guys are missing something - This is a CENTER 0 ammeter. If connected correctly, it is on 0 when the load is being supplied by the alternator and the battery is just coasting.
I personally *hate* these things. Cessna uses them and the difference between +5 and -5 is about a needle width and you don't know anything is wrong until the radios act funny 9500 feet over Orlando at 0100.
Get a voltmeter. Anything over 12.6 or so means something is charging and over 13.8 is good.

I am with Joe on this & he's right.. These gauges have such a large scale in such a short sweep, 5 amps is easily the width of the needle. I ditched my ammeter a couple of years ago & yanked the long charging run, and then tapped the voltmeter into the other gauges.

[lat 64]

Thanks Ed, et al.
I am finally getting the fog to lift on my brain about batteries.
I have Nigel Calder's book, and am studying that slowly so that I don't sprain something in my head. Can't wait 'til I have some money to buy some cool gauges. I want to make a master plan and float it by the committee late this summer.

Cheers,
Russ

[joe_db]

THe voltmeters in my photo are about $12

Thanks Ed, et al.
I am finally getting the fog to lift on my brain about batteries.
I have Nigel Calder's book, and am studying that slowly so that I don't sprain something in my head. Can't wait 'til I have some money to buy some cool gauges. I want to make a master plan and float it by the committee late this summer.

Cheers,
Russ

[Mark Millbauer]

$12.00!!! Seems like a deal. Where might another Afourian find such a deal?

mark
C27

[sastanley]

local home improvement store

Mark, My 'fancy' ($30) digital gauge was reading bad...You can get a $12 analog meter at Lowe's. Ok..well..mine mighta been $16..I think the brand is GreenLee.

[joe_db]

http://stores.ebay.com/Elite-element/Doesnt-require-POWER-/_i.html?_fsub=2803756012&_sid=897140872&_trksid=p4634.c0.m322

$12.00!!! Seems like a deal. Where might another Afourian find such a deal?

mark
C27