Alternator New or Rebuild

[Bruce Alker]

Hi All,

 

The alternator on my 6bt5.9M Cummins has blown diodes and I need to have it rebuilt or else get a new one.  I live in Oxnard/Ventura area and was wondering if anyone has experience with a good alternator rebuild shop?

The alternator is a Delco Remy 15SI style P/N 10479925 105A output.  It was rebuilt about 8 years ago by PO and during the rebuild it was converted to external regulation and a Balmar ARS-5 external regulator was installed.  It appears that the Balmar regulator is OK in that it is delivering about 3.3amps to the field windings in the alternator.    The alternator/Balmar combo only has about 400 hours on the setup so it seems a little premature for the alternator to fail but that is the way it goes with boats.

My dilemma is,  all new alternators appear to be internal regulated so if I did buy a new one I would still need to bring it to a reliable alternator rebuilt shop to have the new one disassembled and modified—this seems counter productive.  I would appreciated any advice regarding how to handle the internal vs. external regulation issue if I decide to buy a new alternator. 

 

Thanks,

 

Bruce

 

Topic

[Bruce Alker]

OK, I have installed the rebuilt alternator, added the temp sensor to Balmar external regulator, programmed belt manager to B-4, set the temperature limit to 92C in the advanced programing option——- fired it up and so far everything runs the way it should.  More than adequate current from alternator and it is not overheating.

 

Thanks everyone for all you help.

[Bruce Alker]

Yes, I have the temp sensor in hand and it will be installed.  And, I will reprogram the Balmar belt load feature to 75%.  It was set to “belt-0” which is no reduction in alternator output.    <br /><br />

I will post the results when I get finished.

Thanks again.

[JimmyK]

I bet they just plain screwed up the test.

Re-install once it is rebuilt and add the temp probe and de-rate to 75% using the belt manager and I think you’ll be good.

[Bruce Alker]

The Saga continues.  I picked up the alternator today and the shop foreman said that after they cracked it open they did in fact find that the diodes were toast—which was my original assumption, now the normal forward drop in one direction and open in the other is present from B+ to ground  The shop tested the original diodes individually but I did not get a detailed description of how many diodes had failed.   So the diodes have been replaced and we will see how it performs when I get it installed.

This leads us to wondering why the alternator seemed to be good when tested in the shop.  If all the diodes were in fact open circuited then the load test in the shop would not have produced measurable current.  But, if the right combination of diodes had failed the rectifier assembly could look like a half wave rectifier and not a full wave rectifier.  So maybe when loaded with a carbon pile load (I guess that is what the shop would use) you would see current from either the positive or negative portion of the cycle but not both.  This may produce enough current to look good on a carbon pile load but would not generate enough voltage (or current) when loaded with a large house battery bank to achieve a voltage level that would buck the battery voltage and deliver current to the batteries.  Just speculating, but I will post the results of the reinstall when I get things back together. 

Thanks for all the comments.

[JimmyK]

My best guess is you have the worst type of problem–an intermittent one.  Personally I would put the alternator back in the way it was and re-test it as a next step.  I’d honestly hope that it didn’t work (again) so I could spend more time troubleshooting.  However, my guess is that it will indeed work fine, leaving you to wonder what the root cause was and when it will return.

I say this because based on your test results and methodology I would have guessed bad alternator, but based on the shop’s testing, I would now change that to intermittent alternator (sticking brushes, possible bad connections, etc?).

It could also be something with your test methodology was off that isn’t coming through with your description.  I’m not trying to nitpick but I would have full-field tested the alternator in situ before removing it to confirm it was bad.  It doesn’t sound like you need the warning, but ensure you do not have the alternator connected to the boat’s electrical system when full-field testing.

[Bruce Alker]

When I started sliding down this slippery slope two weeks ago the first thing I did was to conduct the “Regulator” test and “Alternator” tests that Balmar publishes.  The results were that the Regulator was OK but the alternator never raised the level on its B+ terminal above battery voltage of 12.4 volts.  So this is why I concentrated on a defective alternator.  

The field output of the regulator (blue wire) was at a steady state of 12 volts during the original testing.  The blue wire in the regulator harness terminates in a spade connector within 6 inches of the alternator.  I opened this connection and inserted a DVM set to the amps scale.  When the regulator was power up I observed that field current started at 2.2 amps and gradually increased to about 3.5 amps, this process took about 15-20 seconds .

Since the Balmar field output is a pulse-width-modulated signal I next connected my oscilloscope to the field  terminal (amp meter was removed and field connection restored to its original configuration).  What I observed was an initial 50% duty cycle pulse train of 4 millisecond duration.   The duty cycle decreased gradually over the next 20 seconds and settled down to a continuous pulse train with negative going pulses of 25 microsecond duration occurring at 4 millisecond internals.  So that is why the field voltage appears as a 12 volt level when measured with a DVM.  I communicated this observation to Balmar tech support and they confirmed that this was normal.  During all these test the alternator output voltage at the B+ terminal never increased above battery voltage.  So this is why I suspected the alternator.

Thanks for your inputs they ae greatly appreciated.

[JimmyK]

How did you measure the field current?  Did you actually measure the output voltage at the alternator?

Balmar has a very good step by step troubleshooting guide.  I suggest you download it and follow it step by step.

[Bruce Alker]

OK, now I am really confused.  The alternator rebuild shop called this afternoon and said the alternator is perfect, with 100+ amp solid output so does not need to be rebuilt.  Before I removed the alternator from the engine the field windings tested OK, the regulator was providing proper field current but the output diodes appeared to be open circuited.  By the time it got to the shop everything was A-OK.  I am at a loss as to what is going on.  The only thing I can hope for is that the shop finds some intermittent connection in the internals of the alternator–they will start the investigation tomorrow.    I guess it is possible that the regulator was doing something strange that is not obvious, or maybe there  is a high impedance connection in the wiring from the alternator back to the battery B+ that was preventing the alternator from delivering current to the batteries?

Has anyone had an experience like this?  I would love to hear about it. Thanks, Bruce  

[JimmyK]

Yes, what I wrote is the same as what I see in your quote.  Note that they refer to the condition that will initiate the field reduction as a ‘catastrophic over-temperature condition…’

This is markedly different than what is implemented in the MC-618 which uses the alternator temperature as an input to the PID controller to proactively maintain the alternator at a safe temperature before there is an over-temperature condition.

Said a different way, the ARS-5 includes alternator temperature sensing as a means to react to a failure or fault state.  The MC-618 includes alternator temperature sensing as a means to proactively control alternator temperature at or below a preset point.

If you’re going to keep the ARS-5 for $$ reasons (totally get it), I would add the temp sensor for sure, but also adjust the belt-load manager setting to reduce the maximum output of the alternator.  I have found most alternators can sustain about 75% of max output without frying themselves, so something at or below this threshold should increase alternator life substantially, although it is alternator and install dependent.

[Bruce Alker]

 

Thanks very much for the comments about the Balmar external regulators.  Ideally I would get the Balmar MC-618 regulator as I like the ability to program it without poking it with a screwdriver and the realtime monitoring of charging parameters, but the boat is leaking money at every turn so not sure if I want to replace my current regulator, the ARS-5, which is functioning OK.

Based on the following quote (see paragraph below) from the Balmar ARS-5 manual I was under the impression that the ARS-5 would in fact limit and/or stop alternator output based on temperature extremes from the alternator or batteries. 

From Balmar ARS-5 Manual:

“When used in conjunction with optional MC-TS-A and MCTS-B alternator and battery temperature sensors, the ARS-5 features the ability to monitor and respond to a range of ambient temperature conditions, including reduction or discontinuation of charging voltages, should a catastrophic over-temperature condition occur at the alternator or the batteries.”

JimmyK has indicated that the ARS-5 only flags the overtemp condition as an error and does not limit the alternator output.  So I was wondering if the Balmar manual is incorrect or I am misinterpreting the manual?  Any comments would be appreciated.

Thanks

[JimmyK]

I agree, with a battery bank that large you need external regulation with alternator temperature monitoring.  That said, ditch the ARS-5.  It is old technology and while it has an input for alternator temperature, it was designed only to identify over-temp as a fault condition, not as a way to moderate alternator output to keep temperatures stable over the long term.  Newer external regulators, such as Balmar’s MC-618, are designed to use alternator temperature as an input to proactively adjust alternator output and keep temps in check.  In addition to the MC-618, you can check out the regulators from Wakespeed and the new Zeus regulator from ARCO.

In addition to being able to actively adjust alternator output to maintain a safe alternator temperature, these newer regulators will also allow you to monitor key alternator parameters such as temperature in real time.

[Bruce Alker]

Part 2:

In addition to all the charging related add-ons and modifications the boat as tons of instrumentation that sucks up a lot of power from the batteries.  I won’t get into that since the list is too long.

So back to internal vs. external regulation; here is where I am today.  Based on Tony’s great recommendation I brought the alternator into Saticoy today for a rebuild and it will keep the external regulation.  It just seems to me that with the power demand of the boat it needs to have a definite control mechanism, which the Balmar external regulator offers, to reduce alternator output when the loads get overly demanding.  Of course when I get it back I will add the alternator temp sensor that it should have had from the get-go.  Also, the Balmar has the option of limiting the max current that the alternator can output in order to control heating and belt loading.  The large size of the house bank can demand a huge amount of charge current to keep it satisfied, in the order of 160 amps, which the alternator cannot produce so it is necessary to limit the alternators continuous output so it does not self destruct, hopefully the Balmar can do this.  The AGM batteries like to see a variable charging profile and the Balmar offers that option. 

Sorry this was so long and boring.

[Bruce Alker]

Part 1:

 

Thank you everyone for your inputs and suggestions.  Since the alternator has failed I have been investigating the charge and power distribution on our boat to a greater extent.

The boat has extensive add-ons which affect the power requirements of the vessel.  The boat has a bow thruster (stock unit) and a stern thruster added on several years ago.  Both thrusters are Side Power units and “if” they are activated together they will draw about 700 amps from the house batteries.  The house battery setup is 6 Lifeline GPL-6CT 6V golf cart style batteries for a 900AH battery bank when they were new (they are a little tired at the moment).   The start battery for the Cummins 6bt5.9M is a, Lifeline GPL-4DL and is charged via an echo charger.  Cold cranking amps for these seven batteries are more than sufficient to drive the thrusters assuming the batteries are at a decent state of charge and not depleted.   

The boat has a Xantrex Freedom SW2012 Inverter/Charger with 2000W inverter and 100Amp charger respectively. 

Regarding monitoring, there are three analog voltmeters and two digital volt meters.  The digital meters are integrated into a XANBUS system control panel and a Xantrex Linklite battery monitor.  So we do have some monitoring of the charging system; Tony has indicated how important that is.  Current, via a ground shunt, and AmpHours are monitored with the Xantrek Linklite.

We use the boat on a regular basis for trips about the vicinity of the Channel Islands off the coast of Ventura county.  When not on the water the boat is connected to shore power so the batteries are always very happy before we leave the dock.  On the last multiday expedition the house back suffered because of the failed diodes in the alternator since the alternator is the only source of charging when away from the dock.

Eight years ago the Delco 15SI 105A alternator was converted to external regulation by the PO and a Balmar ARS-5 external regulator was added to control alternator current output via the field input of the alternator.  The fact that the diodes failed in the alternator is a concern to me because I can foresee it happening again.   The shop that did the conversion years ago did NOT include a thermistor to sense the case temperature of the alternator.  This is a definite prerequisite to ensure that the alternator is not driven to heat extremes.  Balmar is even emphatic about using the temp sensor with their regulator to shut down or limit the alternator output to prevent heat damage.

 

[Francis Valerio]

I dont know how complicated your DC system is BUT if it is a fairly simple system I would recommend keeping it as simple as possible.

Less connections the better and I think internally regulated is a more simple setup.  Personally I have a very simple system on my boat and I like to run internally regulated and self exciting alternators.

Just in my opinion and personal preference.

Maybe share a little insight on what you are running for a DC system and how many batteries and banks etc… inverters etc… someone on here might have better advice.

 

[Tony Athens]

I am full of opinions on alternators and the likes, but all it centers around understanding your DC Power distribution system and how it is monitored. From experiences workings  on lots of different boats, and looking at some very overly complex DC power distribution systems, I’d say most leave out what matters most–Measuring / Monitoring Battery Terminal voltage…………….External or internal voltage regulation works –It’s a full understanding of what you want to accomplish that matters.

 

 

 

[Bruce Alker]

Thanks for the references Tony.

Do you have an opinion regarding external vs. internal regulation of these marine alternators?

 

[Tony Athens]

Unit II  in Saticoy?   

http://www.unit2inc.com/Welcome%20to%20Unit%20II/About%20Unit%20II.html

Or, next to Taylor Steel in Oxnard?  Not sure of the places name

[Author]

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