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Old 12-08-2009, 20:07   #1
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Running Two Alternators

I'm trying to figure out best practices for running two engine driven alternators. Is it best to parallel the fields and run a single regulator? I know Balmar is coming out with a two alternator regulator but how have folks been doing it up to now.
N.B. the two I'm thinking of are not matched (same make, different sizes) but they'll be feeding a common bank.
Thanks!
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Old 12-08-2009, 20:31   #2
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How big an engine do you have?

Alternators are a big hog of HP on an engine
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Old 12-08-2009, 20:49   #3
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I would keep the regulators separate and use the device Balmar calls Centerfielder for controlling and balancing out the two alternators outputs. Keeping two regulators is for redundancy reasons in case either alternator regulator fails.

Call Balmar about this. Their tech support is really good.
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Old 12-08-2009, 21:22   #4
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How big an engine do you have?

Alternators are a big hog of HP on an engine
Westerbeke 65A (70 hp @ 2600) I'm replacing my W58
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Old 12-08-2009, 21:26   #5
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I would keep the regulators separate and use the device Balmar calls Centerfielder for controlling and balancing out the two alternators outputs. Keeping two regulators is for redundancy reasons in case either alternator regulator fails.

Call Balmar about this. Their tech support is really good.
I've called them, They say that'll work but recommend their new system. I'm thinking of going to LiFePO4 batteries ( courtesy of wotname -maybe I'll start a thread on that) and the voltage requirements are out of spec for Balmars. In spec regulators arent set up to run them seperately.
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Old 12-08-2009, 21:44   #6
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Not sure I understand. Why cant you run one alternator if the other fails? You should be able to do this for your own good. If Balmar says you cant with their system then go with someone else.

Personally I would stay with standard lead-acid batteries because chargers and alternator regulators for them are very common and easy to get...and so are the lead-acid batteries themselves easy to get.
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Old 12-08-2009, 23:14   #7
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Well, I have been puzzled with this years ago but my situation was a little different.... we have three alternators on our Yanmar 4LH-HTE: the standard Hitachi 60A and two additional Lestec Brute 220A big guys. The Hitachi is just kept standard and charging the starter batteries and the two Lestec's charge the house batteries.

There was a really old fashioned Lestec regulator that served both alternators and they broke often (with previous owner, found a whole bunch of burnt out ones aboard). My research turned up two regulators that could do this: the Ample Power SARv3 and a Balmar one. Balmar acquired Lestec I think and their regulator would be the thing I had, which I didn't want. So I went with Ample Power and we're very happy with it (no more failures and smart charging).

But these two alternators are the same. Their combined field current can go as high as 14A and this was the big problem for finding a regulator. The fields are connected in parallel.

With two different alternators what you basically get is that one will win the battle for highest voltage output and that one will do all the charging while the other does nothing. I think the solution is what is used for boats with two engines (think that Centerfielder thing is for that too) and Ample Power has a solution for that too.

Or, you use one alternator for the starting batteries and the other for the house batteries (each it's own regulator). This will automatically solve the issue.

Like ChiefEngineer said: they take a bit of hp from the engine. Put some switches in so that you can shut them off if you want/need all hp from the engine. If I remember well, our two Lestec's can take 14 hp when at full output current so that would be around 3.5 hp for each 100A alternator output.

cheers,
Nick.
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Old 13-08-2009, 01:34   #8
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The best way is to have each alternator stand alone, charginh a different bank of batteries. Regards, Richard.
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Old 13-08-2009, 06:58   #9
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The best way is to have each alternator stand alone, charginh a different bank of batteries. Regards, Richard.
that 's my brother's suggestion. Start circuit is completely seperate: Lead acid battery . At least it'll get you home he says.
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Old 13-08-2009, 07:01   #10
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I think one of the most over-looked issues in setting up multiple drive belt systems, is the amount of belt contact on the driven pulley. As the alternators or compressors get bigger, this becomes more critical to belt life.
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Old 13-08-2009, 07:58   #11
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Double alternators = triple complexity. Why do it? Unless you really need the additional charging power -- as Jedi apparently does on his 64-footer -- why not go with a single large alternator? Keep an identical spare if you must.

If the alternator is over 100A or so, you've gotta go to either double-belts (more problems) or a serpentine belt system (better solution).

Separate alternator to charge the start batteries? NO, this is just a waste. Start batteries require VERY VERY VERY LITTLE charging in most cases (unless someone has hung a power hog load on the start circuit). Replacing the energy used to start your engine takes MINUTES, after which the alternator is just doing nothing. Why have a 60A alternator which is doing NOTHING 99% of the time? Much better to use a device like an EchoCharge or a DuoCharge to keep the start batteries topped up.

But, if you really must go with two alternators to charge a single bank, the Balmar Centerfielder was designed for this purpose and works well. It's commonly used in two-engine, two-alternator systems, but will do the job fine with a single-engine/two-alternator configuration.

Keep in mind that the simpler the system, the easier it is to understand, to monitor, to maintain, and to troubleshoot. And, if you size things correctly, I believe there's little reason for failure. Your system can be very robust AND very simple.

In things electrical on a boat, KISS is a very good principle to respect.

Bill
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Old 13-08-2009, 08:01   #12
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Not sure I understand. Why cant you run one alternator if the other fails? You should be able to do this for your own good. If Balmar says you cant with their system then go with someone else.

Personally I would stay with standard lead-acid batteries because chargers and alternator regulators for them are very common and easy to get...and so are the lead-acid batteries themselves easy to get.
The idea being that I want to run them in parallel.The charge acceptance rate for these would be (a LOT) more any any one alternator could put out.

To your second point, I don't mind being the guinea pig since I'm stuck on the Lakes for the forseeable future. If all else fails and i have a seperate start bank, I'm no more than 2 days away from a port. They've been used for some of the singlehand ocean races and on the Open 60's, so they're not completely untried.
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Old 13-08-2009, 09:18   #13
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S&S;

I assume you are looking at the Thundersky LIFEPO4 cells? Have you considered the Sky Energy Cells? They charge at 3.6v a cell, and float at 3.4 Multiply that by four, and you are very close to Balmar's settings for AGM cells. Here is what Balmar sent me when I asked them:

Chris – Thank you for contacting Balmar. The voltage figures you give a fairly close to our standard default regulator settings for AGM batteries with a 14.38Vdc bulk charge and 13.38 float charge. Our MC-612-H regulator is programmable so both modes can be adjusted. The bulk charge setting can be adjusted from 14.1Vdc to 14.8Vdc. The float voltage can be adjusted from 13.0Vdc to 13.8Vdc. This regulator sells for $429.95 with the harness and $409.95 for the regulator alone. You can find the three stage MC-612-H online at prices from $275 to $325. We also have a 24Vdc version of this same regulator.


You would still need a BMS for balancing, and over/under voltage protection at the cell level.

The largest they make is a 180ah cell (that I know of, bet they are working on larger) I would suggest having more than once battery pack anyways, as if the BMS trips because of under voltage for a single cell, you will lose that battery's power at that point. It would look just like a short in a single cell for an traditional battery, as the voltage for the pack will drop 2 volts instantaneously as the cell is brought off line. Or the BMS will shut down power completely, depends on how the thing is programmed.


Chris



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I've called them, They say that'll work but recommend their new system. I'm thinking of going to LiFePO4 batteries ( courtesy of wotname -maybe I'll start a thread on that) and the voltage requirements are out of spec for Balmars. In spec regulators arent set up to run them seperately.
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Old 13-08-2009, 10:05   #14
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S&S;

I assume you are looking at the Thundersky LIFEPO4 cells? Have you considered the Sky Energy Cells? They charge at 3.6v a cell, and float at 3.4 Multiply that by four, and you are very close to Balmar's settings for AGM cells. Here is what Balmar sent me when I asked them:

Chris – Thank you for contacting Balmar. The voltage figures you give a fairly close to our standard default regulator settings for AGM batteries with a 14.38Vdc bulk charge and 13.38 float charge. Our MC-612-H regulator is programmable so both modes can be adjusted. The bulk charge setting can be adjusted from 14.1Vdc to 14.8Vdc. The float voltage can be adjusted from 13.0Vdc to 13.8Vdc. This regulator sells for $429.95 with the harness and $409.95 for the regulator alone. You can find the three stage MC-612-H online at prices from $275 to $325. We also have a 24Vdc version of this same regulator.


You would still need a BMS for balancing, and over/under voltage protection at the cell level.

The largest they make is a 180ah cell (that I know of, bet they are working on larger) I would suggest having more than once battery pack anyways, as if the BMS trips because of under voltage for a single cell, you will lose that battery's power at that point. It would look just like a short in a single cell for an traditional battery, as the voltage for the pack will drop 2 volts instantaneously as the cell is brought off line. Or the BMS will shut down power completely, depends on how the thing is programmed.


Chris



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Thanks Chris. ( it was you not wotname (sorry!)).

Genasun makes a BMS that has been used in a marine environment. They also make a regulator. Alex over there said that the Balmar regulators are +/- 3% which may be too much out of spec for these. I'll call them again as I still need a send from the BMS to tell the regulator to cut the field before any contactors open (genasun's does this already). I'm looking at the Sky energy cells but I'd like to use less (larger) cells for simplicity's sake.

Who's BMS are you using?
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Old 13-08-2009, 10:11   #15
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Yes, I would separate the banks and charge each with a sep alternator and regulator. Ample Power makes good stuff and has a two alternator system... or did. If there is room on your engine, I think having two could be great, it will help load up your engine properly while you are just charging at anchor. Another advantage if you can put the alternators on separate sides of the engine is the loading of the pulleys/bearings etc isnt all to one side.
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