Alternator Overheating Problem

[crazyhorse77]

Hi,

In the last few days a few electrical problems have surfaced, first the cutoff domestics switch melted (now replaced) and now the charging systems are having problems.

Overview of Setup

• Stirling multistep regulator is installed for the charging system
• 80 amp alternator
• Durite charging spilter
• 3 * 100amp flooded lead acid batteries

Problem

Just recently the charging system will not sustain the charge and will drop from 50amps to 20 amps in 45 minutes. The alternator is too hot to touch for more then a second.

Things Checked

• Resistance from alternator to battery
• Bypassing charge spilter
• Disabling multistep regulator so charge rate drops (from 40 to 12amps when disconnected)

Really out of ideas, your help very much appreciated

cheers
Jarvis
http://crocbones.blogspot.com

[hellosailor]

Stirling? Do you mean Sterling Power?

Does the alternator have an internal regulator, and if it does or did, have you made sure that is correctly modified to use the external one instead?

Is the alternator designed to run at 100% duty cycle? Because 300AH of batteries could easily suck the entire output of that alternator if they are heavily discharged, in which case a conventional "automobile" alternator would overheat and if you are lucky, something would cut back on the output power to prevent it from burning out.

There's also the matter of cooling. In a marine installation you may need an alternator that has dual fans (front and rear) not the automotive single-fan type. And, an adequate supply of cooling air. If you don't have that, it will overheat.

[DeepFrz]

Dropping from 50 to 30 amps in 45 minutes doesn't seem out of the ordinary to me. What is important is the charge state of the batteries.

Holding your finger on the alternator for 1 sec. doesn't sound like hot unless you have a heavily calloused finger or high threshold of pain.

You really need to quantify some of your information.

What is the temp. of the alternator. Any higher than 195 f/ 90 c will damage the alternator over time and will severely reduce its output.

You can reduce the temp. of the alternator by ducting some air directly from the engine room intake ducts (you do have them right?) to the rear of the alternator.

And, finally, the alternator that you have is a little under rated for the size of your battery bank. 100 amp hot rated would be ideal.

[crazyhorse77]

Thanks gents for the replies.

The alternator was modified to use the Sterling external multistep regulator. If i disconnect the field control wire the output drops dramatically to around 12amps.

The batteries were less then 40% when the charging tests were done.

The engine room has ducting, yet doesnt have a blower fan to move the air around. I was looking at getting a inline blower that moves 240ft min ($50) to direct air directly onto the alternator. Do you think this would be ok.

I dont have anything to measure the temp of the alternator, so i put a few drops of water on the alt casing and it bubbled and evaperated in seconds. The alt had only be running 5 minutes at this stage, and outputing around 50-60amps. When i said i could tounch it for 1 second, i think i counted the one second extremely fast

The alternator is from a nissan car, i bought it in Barbados as our previous alt failed part way across the atlantic.

thanks in advance

Jarvis

http://crocbones.blogspot.com

Originally Posted by DeepFrz

Dropping from 50 to 30 amps in 45 minutes doesn't seem out of the ordinary to me. What is important is the charge state of the batteries.

Holding your finger on the alternator for 1 sec. doesn't sound like hot unless you have a heavily calloused finger or high threshold of pain.

You really need to quantify some of your information.

What is the temp. of the alternator. Any higher than 195 f/ 90 c will damage the alternator over time and will severely reduce its output.

You can reduce the temp. of the alternator by ducting some air directly from the engine room intake ducts (you do have them right?) to the rear of the alternator.

And, finally, the alternator that you have is a little under rated for the size of your battery bank. 100 amp hot rated would be ideal.

[DeepFrz]

This pdf might help you understand why you are having problems. You are over taxing the alternators and it is probably why the original failed half way across the Atlantic.

http://www.balmar.net/PDF/2009-12V-a...manual-web.pdf

I said above that a 100 amp. alternator would be ideal but that is only because going above that range will require other modifications to the pulley system. Dual belts, etc.

Balmar states that if using a thermal sensor and their regulator the output of the alternator will be cut to ~50% when the temp. reaches 200 deg f.

Maybe you can find a nissan replacement rated at 110 amps at an auto wrecker or they are selling on the internet for less than $100. new. Not including shipping of course. If you can adjust the regulator you have to keep the output at less than 100 amps you should be okay.
Good luck.

[Bash]

Originally Posted by crazyhorse77

The batteries were less then 40% when the charging tests were done.

!!! 40% !!!

There isn't an automotive alternator made that won't get hot to the touch trying to bring a 300AH bank back up from 40%. You're lucky it didn't melt down completely.

Yes, you are overtaxing your alternators. Significantly. We might even go as far as to say that you have been abusing them.

Two solutions:
(1) Don't ever let your house banks drop below 50%. Ever.
(2) Get a Balmar that's up to the job in terms of handling the heat.

[foggysail]

YEAH!!! Right on, just because one has an 80-100 ampere or higher alternator does not mean that output is continuous.

Alternators are wound with copper wire which has a positive temperature coeficient. That means, current flow generates internal heat which causes the internal wiring resistance to increase. The higher internal resistance causes more heat (losses) which causes higher internal resistance which..............

Also remember there is very little air being blown on a marine alternator other than that which is circulated by the altenator's fan attached to the pully.

[SV Demeter]

I would think a good external regulator with temp sensor should sort this problem out. Doesnt the sterling regulator have a provision for temp sensor? Maybe your solution is as simple as adding a $40 temp sensor so your regulator knows to play nice? Sure a 100amp balmar would be nice but thats a lot more dough than a temp sensor, or even a regulator with temp sensor like the balmar 614. Comments on limiting depth of discharge to 50% are of course valid as well but a 300AH bank at 50% will still take a pretty hefty draw if allowed to.

[crazyhorse77]

Thanks for your advice, at the moment we are tight for cash and after reading all the posts and looking for the most affordable solution we will try the below first. (I anderstand the below is not ideal)

The Plan:

1. I will buy a thermal switch to break the connection of the field control wire that goes from the ALT to the multistep regulator. So when the ALT casing reaches 100C the alternator will drop back to charging at 12 amps or less.
2. This morning I purchased a '4inch Inline Blower by Rule' to help cool the alternator. THis unit moves 240ft of air per minute. Install so the air is pulled in from the outside and position to blow directly on the Alternator
3. If the alternator is still running hot remove one of the batteries so the domestics is down to 200AMPS

Any comments or advice most welcome.

regards

Jarvis

Originally Posted by SV Demeter

I would think a good external regulator with temp sensor should sort this problem out. Doesnt the sterling regulator have a provision for temp sensor? Maybe your solution is as simple as adding a $40 temp sensor so your regulator knows to play nice? Sure a 100amp balmar would be nice but thats a lot more dough than a temp sensor, or even a regulator with temp sensor like the balmar 614. Comments on limiting depth of discharge to 50% are of course valid as well but a 300AH bank at 50% will still take a pretty hefty draw if allowed to.

[SV Demeter]

Originally Posted by crazyhorse77

Thanks for your advice, at the moment we are tight for cash and after reading all the posts and looking for the most affordable solution we will try the below first. (I anderstand the below is not ideal)

The Plan:

1. I will buy a thermal switch to break the connection of the field control wire that goes from the ALT to the multistep regulator. So when the ALT casing reaches 100C the alternator will drop back to charging at 12 amps or less.
2. This morning I purchased a '4inch Inline Blower by Rule' to help cool the alternator. THis unit moves 240ft of air per minute. Install so the air is pulled in from the outside and position to blow directly on the Alternator
3. If the alternator is still running hot remove one of the batteries so the domestics is down to 200AMPS

Any comments or advice most welcome.

regards

Jarvis

Dont take this the wrong way but, your thermal switch idea just sounds like a complicated Rube Goldberg solution. What about simply getting a temp sensor for your alt. regulator? Do you have one of these:

Sterling Power Products: Alternator Regulators

Yes the blower is probably not a bad idea but unless you have a good way of dialing back output the blower isnt going to be enough. Also if you dial the alt back to 12 amps how are you ever going to get your batteries charged?

[DeepFrz]

Maybe your solution is as simple as adding a $40 temp sensor so your regulator knows to play nice?

No, this is not the solution. The solution is to fix the problem so that the alternator never overheats. 100 c is to hot by at least 10 deg. But that is just a stop gap. As long as you realize that you can limp by. Cut back your energy usage, charge more often, etc. Don't let your bank get run down. Taking one battery off of your bank is also not the solution. It is really moving the wrong way. A better answer, for now, is to charge more often.

Any chance you can pick up a used solar panel. Even one that you mount on deck and move below while on passage will help.

You must think of your power generation and storage as a system. Once you decide what you need (energy use inventory) then you can start building toward the solution, one piece at a time if you have to.

[SV Demeter]

Why is his alternator overheating? Most likely it is because his battery bank is demanding everything the alternator can deliver all the time. My guess is he is wearing out belts quickly too. Pairing a 70 amp alternator with a 300 AH battery bank requires a temp sensor and an intelligent regulator or the alternator will live a short life. Even at a 25% dept of discharge without a temp sensor his alternator will likely be over tasked.

[saben]

I experienced alternator over heating. Balmar Series 7, belt slippage was not the issue. Alt was rated at 80 amps. Within 5 minutes of 60 amp output the Balmar regulator would decrease output to 50% through thermal temp switch and the alt would be hot as a pistol. A one second touch. And this was with engine cover removed and directing a fan at the unit. I hand carried the alt to Balmar in Arlington Wa. where they put it on a test stand and reported to me the unit puts out amps like advertised. Only problem was their shop was not equipped with a load that could sustain it for more than a minute due to heat dissipation inadequacies. Much heated discussions followed and the alt continued to over heat. That's my experience with Balmar. Very disappointing. Why do they paint the cases white? It looks nice but it also holds heat in. About that period in time I attended the Fisheries marine swap meet in Seattle and saw several Balmar alternators being off loaded by different sellers. Coincidence? In the end I cut my losses and purchased a refurbished Ample Power alternator and have never looked back.

[DeepFrz]

Why is his alternator overheating? Most likely it is because his battery bank is demanding everything the alternator can deliver all the time.

Absolutely agree. I just said that a temp. sensor is not the answer to his problem. Neither is cutting down the size of his battery bank. The temp. sensor should be used, I agree, but the problem is he has an alternator that is to small. Not to small for his battery bank, but to small for his electrical usage. Charge more often for a shorter period of time until they can upgrade the "system".

[Stu Jackson]

The alternator temp sensor is just a switch on the regulator taps that cuts the alternator output by half. It's easier to use the Small Engine Mode than it is to reprogram the regulator. An 80A alternator on a 300 ah house bank is what we have. It needs the Small Engine Mode after a day on the hook when the battery acceptance is very high, doesn't matter what kinda alternator you have.

Try this (and read the link in the last post on page 2): Alternator heat, Regulator Controls, Small Engine Mode