Burned out alternator... Is it undersized??

C

CampionToba

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24431
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Last weekend I could smell sort of a sweet electrical burning smell, right around the time my alternator stopped pushing out 14 volts... I'm assuming it's cooked. Extremely hot to the touch. This is the second one in just over a year... The alternator is a Sierra 63amp, the house bank that this alternator charges is a dual battery setup with new Deep Cycles with the following stats: CA 1000, CCA 800, RC 136. Should I be running a larger alternator?

Very much appreciated!

Regards,

Chris
 
I don't know if this will contribute to anybody's answers, but... Are you charging your two batteries together (as the pair) or singly?
 
If you want to relieve the alternator and properly charge 2 different sized batteries I recommend installing a BlueSea ACR. The ACR is an automatic charge relay. It charges one battery 1st then it starts charging the second battery. They can be forced to charge or combine both batteries with the optional remote switch. You probably don't need to upgrade the alternator just fix or replace it 1st. Also make sure your ground wires and positive wires are properly sized from the alternator to the batteries.
Bill
 
A 63 amp alternator is not that big and, with your load your operating it near 100% all the time. Duty cycle is a term that applies to alternators as well as other power producing mechanisms. In the intended installation your alternator was designed and sized to charge up your originally installed battries and then supply the normal running needs of your engine and electronic loads. In other words it works hard for awhile then output(load)tapers off.

Your best bet is to install a larger unit sized to your current application and load. High capacity alternators are not too expensive. It will make your problem go away.
 
For the electrical gurus. Can an alternator be rebuilt to a higher capacity?
 
What is your DC draw? 63 amps while not large should be able to accomidate most power needs.
Installing a larger alternator would help. You should upgrade your battery and the alternators high current circuit at the same time. I'm assuming your primary feed off the alternator is the standard #6? If so I would check to see how hot the alternator output wire is getting. I'd guess it's also getting hot and heat = a voltage drop.
Bill
 
Alternator output can be upped by a competent (re)builder, to an extent. I don't know what effect doing that has on that Duty Cycle aspect. I tinkered with cars with a young body builder friend. He told me "You can build a small man up to be stronger than a big man. But not stronger than a built up big man."
 
Increasing the capacity of that alternator will probably make the problem worse. Inadequate coling is the primary reason for failure and more amps will make that worse. OHB is correct that duty cycle is key. No standard alternator is designed for high duty cycle.
 
Just to clarify, the two house batteries are about 2 months old and are charged by port-side alternator. I tend to run a small fridge off a 700 watt inverter, and a windlass for the anchor. Very little draw otherwise...
 
quote:
Originally posted by pdecat

Increasing the capacity of that alternator will probably make the problem worse. Inadequate coling is the primary reason for failure and more amps will make that worse. OHB is correct that duty cycle is key. No standard alternator is designed for high duty cycle.

Click to expand...


Absolutely correct. Cooling is everything. Recently a manufacturer of aviation alternators came out with a line of dual fan equipped alternators without changing the output and their failure rate dropped so dramatically, the units are considered essentially bullet proof.
 
Agree with Bruce

The ACR suggested by BillyIII will allow either or both alternators to charge all the batteries, yet keep the batteries separate when not charging. Works well, but depending on you layout you might need more than one.

IMO I'd take the existing alternator into a shop and have it rebuilt while I checked out the wiring. I can't help thinking there may be a problem other than the alternator.
 
The start bank is connected to the stb engine. Different type of battery. Both sides are completely separate. Is it ok to join the alternator charging systems?

Very much appreciated
 
I don't think connecting "starting" and "deep cycle" is a problem. It's my understanding that if they're all wet-cell, or all AGM, you can connect them but not to mix wet-cell with AGM. Others may have better info.

In an emergency situation, I'd do it anyway.

My house battery and starting battery are connected through an ACR, the starting battery is about 5 years old, house batteries over 3, but they're all wet cell. Primary charging is solar, the single alternator runs backup.
 
Is the ACR the same idea of a voltage sense relay? Will this work on a dual engine setup?
Again, thanks very much!
Chris
 
I'm pretty sure they are the same; another name is "battery combiner". I think they're intended for dual engine setups. I use mine on a single, but I have two charging systems; alternator for the start battery and solar for the house bank. The ACR/VSR/combiner allows either charging system to charge all batteries.

I'd google the manual for the relay you're considering, that should answer all your questions.
 
I am a little confused on this one. Part way thru it sounds like this is a twin engine. Since I do not know the type or setup this may not be applicable. If you have a counter rotating engine the alternator fan has to be reversed or at least universal flow. Air should flow from the diode end thru the alternator and out the front. An alternator will "electrically" work in either direction but is subject to early burn out without proper air flow.
 
You would need a pair of ACR's to use both alternators to either both charge a battery bank or to charge 2 different banks from a single alternator depending on how you wire them. Yes they are charge or voltage sensing solenoids.
Bill
 
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