Advice Needed On Altenator Purchase

[Snotter]

I recently took my 90 amp altenator into an autoparts store to have it tested. It was no good. I put on my spare 42 amp altenator which tested good at autoparts. It didn't work on the boat either. I suspect that the external spacreek controller and/or diodes may be bad, regardless, the wires look under-rated and the metal corroded. Also, the tachometer doesn't work.

I don't wish to spend the time trying to diagnose and fix the old equipment. I would like to upgrade to a 70 - 90 amp altenator (I don't wish to upgrade the belt size and pulleys on the engine) with a smart controller. (The spacreek controller required the current to be manually adjusted with charge time to keep the batteries from over or under charging.)

When I searched defender.com for an appropriate altenator, I got overwhelmed with the choices. However, the search did reveal that I can buy a controller and altenator as a package, reducing the risk of mis-match. Can anyone recommend what I should buy? Do I want an internal or external regulator and or bridge rectifier? Which is easier to install? I suspect that a 90 amp altenator should utilize 4 or 6 gauge wire.

My boat is an old Morgan 41 Out Island. The engine is a Perkins 60 hp 4-154. I have 3 battery banks: 2 big semi-tractor batteries in bank 1; 3 group 27 or 32 deep cycle 12 volt batteris in bank 2; and, a dedicated semi-tractor battery for the engine in the 3rd bank. Also, the battery charger is a new 4-stage 60 amp cpu controlled model. (I heard that too large of charger could burnout the rectifier diodes.)

Help is always appreciated from this group.

 

[Stu Jackson]

Hi, I went through the same issues you have a few years ago, seems like we're a dying breed of Auto Mac operators! I worked with the author of the linked article to write this a few years ago. It includes a source for plug & play alternators for a very good price (up to $160 now from $120 or so). I bought a Balmar MaxCharge but an ARS5 would work just as well. #6 wire is way too small for the alternator output which could be 50A on a depleted bank. I used #2 wire because #4 was a tad too small and they don't make #3 wire!

http://www.c34.org/wiki/index.php?title=Catalina_34_Electrical_System_Upgrade

I heard that too large of charger could burnout the diodes on an altenator.

That doesn't seem proper. One has nothing to do with the other, they're not on at the same time The alternator output should be run to the house bank. I would suggest you consider grouping your disparate banks into the largest house bank you can and keep the small battery as your reserve. See this post from the C310 Forum last week: http://forums.catalina.sailboatowners.com/showthread.php?t=104505&page=2

I suggest you review the links in those threads, too.

 

[Rich Stidger]

It sounds like you have the classic multiple-problem situation- A bad 90A alternator and a bad Spacreek controller.

In addition to Stu's good advice, I would also suggest that you take your 90A alternator to a local electric motor repair shop for further evaluation. The issues with the alternator may be relatively minor and the Spacreek device may have gone bad first and taken out the alternator with it. In any event, a rebuild of the alternator may be much less expensive that buying a new one.

A good repair shop can totally rebuild the alternator and it should then be like new. Check that the alternator will connect easily to a multiple stage external controller (like the ARS5 or equivalent) and you should be good to go.

Don't forget the wire size upgrade from the alternator to the batteries- this is very important with a large bank that can be deeply discharged. Also, with your new external controller, be sure to get the alternator temperature sensor that will throttle back the alternator if it runs too hot.

 

[Stu Jackson]

Also, with your new external controller, be sure to get the alternator temperature sensor that will throttle back the alternator if it runs too hot.

Another way to deal with this may be the Small Engine Mode. Please see: http://c34.org/bbs/index.php/topic,4669.0.html

Lotsa ways to deal with it, but knowing your system is one of the surest ways to understand the issues. I have never had a hot battery, but can understand alternator overheat. Others have had different experiences. More safeguards never hurt - they're there for a reason.

A good repair shop can totally rebuild the alternator and it should then be like new. Check that the alternator will connect easily to a multiple stage external controller (like the ARS5 or equivalent) and you should be good to go.

You'll have to get them to provide you with a plug to match the regulator wiring harness plug - female on the alternator end. Newer alternators come with the plug built in.

Here's a link to the wiring of those puppies: http://c34.org/bbs/index.php/topic,4548.0.html

 

[Snotter]

After reading the link that stu provided, I realize I have some research to do. Also, the link made me realize that the the unit mounted on my engine-room bulkhead might be a battery isolator. Specifically, the unit looks like a long rectangular diode mounted on a heatsink. It has four lugs, one of which is connected directly to the altenator. At first I thought it was the diodes that rectify the altenator output. Aren't altenator diodes always mounted internal to the altenator? If the unit is a battery isolator then that would give me yet another reason to trash it in favor of an echo charger.

 

[Bill Roosa]

Embrace the horror

By Nigel Calder's "boatowner's mechanical and eledctrical manual. Much cheaper than throwing away perficly good stuff just because you don't know what it is!!!
Alternator diodes are in the alternator. The item connected to the alternator output is most likely an isolation unit. It should have two other terminals and they should connect to the house + and start + batteries directly. There is a difference between the two terminals which preferentially charges the house. You also need to run the regulator's battery voltage sensing wire to the house + not the alternator as is common. The isolation diodes drop the voltage from the alternator by almost a full volt. Given that 12.6 is fully charged and 11.6 is pretty much dead this is a BIG item to get right.

BTW rebuilding alternators is very easy. If the bearings and windings are good the only other thing that can go wrong is the brushes ($0.50) or the diodes ($~3.00 each at digiKey).

 

[Snotter]

Re: Embrace the horror

The isolation unit should be trashed since it prevents fully charging the batteries. The SpaCreek controller should be trashed because it requires a constant manual intervention if you want the batteries to charge quickly. I think I will bring the old 90 amp altenator into an automotive electric shop and get an estimate to repair it, assuming that matching the altenator to a smart controller wouldn't be an issue.

I was dissapointed with Nigel Calder's Diesel Book on the subject of altenators and their associated equipment. Don Casey's 'This Old Book' was better but not great. I need to buy Calder's Electric book.

I really like the approach documented in Stu's link. I wonder how the approach could be modified to accomodate 3 banks; perhaps 2 echo chargers? I am affraid if I hooked the altenator output to the 1-2-B switch that I would fry the diodes if I accidently started the engine with the 1-2-B switch in the off position.

 

[Bill Roosa]

Isolation does allow batts to charge...

IF and ONLY IF you connect the battery voltage sensing wire from the EXTERNAL regulator to the batteries and not to the alternator. The regulator will then be regulating AFTER the isolation diodes and bring the alternator up oneish volt to compensate for the diode oneish voltage drop.
That is the real reason I don't prefer to use isolation devices with diodes. You spend your fuel making extra voltage just to burn it up as heat in the isolation diode.
If you have an internal regulator then you need to tap the regulator to port out a voltage sensing wire to run to the batteries.

I understand the desire to make things less cumbersome from an operational viewpoint but switching a 3-way is not that complicated. Leave it on both unless you are sailing with the motor off or at anchor. Then leave it on the house batteries. After a deep discharge of the house batteries, try to start with them first and if that fails, switch to start (not both). Don't want to take a good battery down trying to charge a dead one. Once started, switch to both.

engine on = both
engine off = house
engine start = house or start as needed with house being preferred and start as a backup.

I really don't see what the big deal is.

 

[Snotter]

I understand the desire to make things less cumbersome from an operational viewpoint but switching a 3-way is not that complicated. Leave it on both unless you are sailing with the motor off or at anchor. Then leave it on the house batteries. After a deep discharge of the house batteries, try to start with them first and if that fails, switch to start (not both). Don't want to take a good battery down trying to charge a dead one. Once started, switch to both.

engine on = both
engine off = house
engine start = house or start as needed with house being preferred and start as a backup.

I really don't see what the big deal is.

I have 3 Banks--not two. Also, Don Casey put the fear of God into me when he said that dis-similar batteries connected in parallel can set up large circular currents which can result in acid explosions. I don't want to hook the large tractor batteries in parallel with the group 32s (or are they 27s). If it weren't for bad luck, I would have no luck. I don't want to take the gamble.

Right now I am leaning towards two battery combiners because, if done right, there would be no way to accidently fry the diodes.

 

[Bill Roosa]

OK so you have 3 banks

Are the banks of different types of batteries? Not tractor, car and airplane but wet cell, gel cell or AGMs
I'm going to bet that all/most of your 3 banks have wet cells so there is not much of a problem with circular currents. And acid does not explode, the hydrogen gas may but you would have to have a spark.
If all your banks are the same type then the best use of your system is one electrically large (possibly located in several parts) house and a smaller starting battery. There are lots of reasons for this.

More on "circular" currents. The three types of batteries have slightly different voltages when fully charged. That is the primary reason you don't want to mix-n-match them in one system. It is very difficult to get one alternator and regulator to charge both correctly at the same time. So you should stick to one type. Given that they have different voltages, the first time you connect them together they will equalize. The one with the higher voltage will "charge" the other till the higher voltage battery voltage drops to the lowers fully charged voltage. The current then stops and you will never see it again until you charge one independently of the other. But given that you only have one battery charger and one alternator you will always be charging whichever one you choose at that battery charger or alternator voltage. You can set it up for one type OR another but not both.
A quick check on how much current will flow between a wet cell and an AGM (the worst case)
Wet cell 13.6
AGM cell 13.9
Difference in voltage 0.3 volts
The batts are "shorted" together so there is almost no resistance in the wiring but batteries have internal resistance and a completely charged batt has something like 3 ohms
Mr. Ohm says V=IR or I=V/R or I=0.3/3=0.1 amps flowing from the wet cell to the AGM. YAWN I can see that this is going to be a big deal and ...........
Don't believe everything you hear on the internet.

BTW; wet cells have little screwy things in the top that you take off and add water to. The other two types don't.
Tractor batteries are most likely wet cells
Group 27 is not a type it is a size so could be any type.

 

[Snotter]

Re: OK so you have 3 banks

Bill, Casey, in 'This Old Boat' specifically cited that even wet cell batteries that are of different age should not be connected in parallel for any duration. However, I will admit that before reading that I always kept the 2 tractor batteries and the 3 group 32s in parallel. The 5 batteries, though different sizes, are only a year old or so. I would prefer to convert my 3 battery banks to just 2 banks if there were no risk of shortening the lives of the batteries.

I find it interesting that the group 32s require the need to add water much more often then the tractor batteries. I guess some wouldn't find this surprising since the tractor batteries hold a heck of a lot more water. Since I live aboard and keep my 12v refrigerator running 24/7, I add water every 2 weeks.

 

[Bill Roosa]

batteries working together

As a general rule I'd agree that batteries of different ages should not be used together. That's not because they will not work but because the older ones go bad and take the newer ones out too. By replacing all your batteries at once you get max time on the bank. Draining a battery till it is dead removes a significant portion of their life. So when one cell in an older battery shorts internally it takes the whole bank down to 0% charged and that causes the new ones to not last as long. That is why you want to cycle banks as little as "shallow' as possible. By making one big bank you increase the Ah in it and make the cycling less often and shallower for a given set of loads or usage.
There is not a significant "danger" in connecting old and new but there is a financial cost.

 

[Stu Jackson]

2 banks or 3?

I really like the approach documented in Stu's link. I wonder how the approach could be modified to accomodate 3 banks; perhaps 2 echo chargers? I am affraid if I hooked the altenator output to the 1-2-B switch that I would fry the diodes if I accidently started the engine with the 1-2-B switch in the off position.

Why three banks? If you've "digested" my links, two banks are all that's required. If you want three, either another relay or a manual switch. For paralleled house banks, use a combiner to get full current flow, an echo charger only to current limit to the reserve bank. It can be done easily.

BUT, most importantly, get the AO off the 1-2-B switch to the (a ? one of your ?) house bank and once started you could turn the switch off and the engine would continue to run with no damage to the alternator, 'cuz as Maine Sail and I keep saying, there's always a load on the AO : the house bank.

You could do what you say in your last sentence above and NOT damage anything.

I fully agree: ditch the isolators. It was the very first thing I did on my boat when we bought it.

Re Bill's No. 8 Reply, I can't agree on the switch positions because it all depends on how it's wired and I haven't seen a wiring diagram.

I agree with the concept, which was expressed quite well in Maine Sail's points in one of the links I included before. House bank for everything, reserve for just that off a 1-2-B switch. If you want two house banks, it's just another switch and recognition of how to operate WHATEVER choice you make to for charging each bank - auto or manual.