Burning Alternators

Stu Jackson · Apr 6, 2009

Before we get into more details

do you have a battery monitor on your boat?

Also, how long do you use the two appliances you mentioned?

What alternator and what regulator do you have?

How do you manage your two batteries?

A bit more info would be a great help in helping us diagnose your problem.

U wrote: "This seems crazy, because the regulator should protect the alternator output."

What the regulator does is tell the alternator to produce, it is not to "protect" the alternator. If the batteries need a charge, the regulator says: "Go charge!" Most external regulators have a pre-programmed bulk, absorption and float setup, and most have a minimum 23 to 36 minutes bulk phase when they are started. This is a MINIMUM TIME, so the regulator, when started, always tells the alternator to put out the maximum current and the battery acceptance then takes over.

See the bottom of page 9, here: http://www.balmar.net/PDF/2005-mc-612-manual.pdf

Looking forward to your reply.

Tim C350 April IV · Apr 6, 2009

Heating appliances - like a coffee pot or sandwich grill - are huge electricity hogs and really aren't intende to be powered via boat batteries and an inverter.

The 380 has a great propane cooktop on it that will make short work brewing you some great coffee, and there are many options for grilling sandwichs on that cooktop.

Good Luck!
Tim Brogan
April IV C350 #68
Seattle

Maine Sail · Apr 6, 2009

Just some thoughts

Two 4D batteries are roughly 340 amp hours. Stock alternators on many engines are about 50 amps. Catalina usually supplies the standard alternator unless you order an upgrage.

If you have a 50 amp +/- alternator your alt is roughly 15% of your banks capacity. The recommended size of an alternator is 25-40% of the banks capacity. If you are careful, and never draw the bank down below 50%, a 50 amp alternator will do just fine because it is not running as hard or as long before the batteries acceptance backs its charge rate off and it can cool off.

It sounds to me like you are severely depleting your bank and this means the alternator with a depleted bank can run at full load for far too long because it may be undersized. This high amp output load will cause it to heat up and burn out if it runs that way for too long.

As Stu said we need more info and the above is just a likely scenario. With all that consumption or a relatively small bank you really are a great candidate for a battery monitor!!

If you have the Westerbeke 42B the stock standard alt is a 50 amp Mitsubishi alternator.

The Yanmar 3HJE has a stock standard alternator of about 55 amps.

Both companies offer upgrades but unless Catalina specifically ordered them it is unlikely you have anything bigger than a 55 amp..

Stu Jackson · Apr 20, 2009

jimberg said:
Stu,
...three alternator burnouts over the past two years and one inverter reset. We have battery monitors and the alternators are aftermarket "Prestolite 105 amp." ...One battery is dedicated to the inverter and the other starts the engine and runs the house. ...

That's the answer! Low house bank capacity with heavy inverter draw. You don't have enough house bank capacity. Period. The simplest, best, least expensive solution to your issue is to add a small automotive (read cheap!) separate reserve bank for using for engine starts as a backup, and tie your two existing 4Ds together as a larger house bank. Easy to wire, too. You will see extended life from the house bank because you will be reducing the % draw on the house bank with its doubled capacity even with the same daily load, and you'll stop burning out your alternators. For less than $100 you'll solve your problem. This is a relatively "standard" fix to the OEM Catalina factory standard which is poor to begin with, and why they don't do this for all their boats 27 feet and larger is (still) beyond me. All they get is unsatisfied customers when it comes to the electrical systems.

If you're interested in the whys and hows of it, try this, which discusses using (4) 6V golf carts, but just "replace" those with your existing (2) 4Ds: http://www.c34.org/wiki/index.php?title=Catalina_34_Electrical_System_Upgrade

Another wiring diagram which is our boat is reply #23, here: http://c34.org/bbs/index.php/topic,4623.15.html

Also read reply #31 here: http://c34.org/bbs/index.php/topic,4787.30.html
This is very important and it "closes the loop" on the first link related to the echo charge wiring in Jim's design.

Setup the house bank to do everything on your boat, don't dedicate any single battery of any kind to anything (except windlasses in certain cases) and run everything off the house bank, including starting your engine. Only use the reserve bank as a just-in-case emergency backup, which is why we stopped calling it a start bank and started calling it a reserve, backup, emergency bank. Do NOT dedicate your inverter to one battery, use the house bank. If you still have the old standard 1-2-B switch, when wired properly the reserve bank should be able to feed everything, too. With smart breaker operation you can run the boat if your house bank died by limiting the draw, and with your engine running you could get home OK. Limits would be: fridge off, VHF and instruments ON, etc.

Burning Alternators

jimberg

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Stu Jackson

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Tim C350 April IV

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Maine Sail

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jimberg

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Stu Jackson

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