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Old 15-02-2014, 17:00   #1
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New Small Boat Battery(s) & Alternator Questions

Looking at buying a new 27' daysailor from Catalina with a 2YM15 Yanmar (14hp) and SD20 saildrive. The battery is a single Exide group 27 dual purpose that barely fits under the salon seat. I may have Catalina keep the Exide as I'm not a big fan. The standard alternator from Yanmar is 60 amp and there is an optional 80 amp. Catalina has spec'd Yanmar to provide a 120 amp alternator. This seems awfully big. I assume all three are internally regulated.

The boat will be on a mooring from mid-May to mid-October so no shore power and I'm not planning on any solar, but there is a 12w Catalina option built into the anchor locker cover. Problem is that I expect it would be shaded about half the day and it may be custom sized, which could mean trouble down the road if it needs to replaced.

The expected use for the next 10 years will be to motor out of the harbor (5 minutes) and motor back in (0-4 minutes) anywhere from 1 to 2 times per week and maybe skipping a week because of bad conditions. The motor may need to run a bit longer to charge the battery(s) and certainly to break it in. The expected electrical use will be light (starting, stereo & very lightly used electric toilet). After 10 years, I may do some light cruising and need more reserve.

So this brings me to more questions than I have answers for. I initially feel that I should have a separate starter battery (group 34?). I know there are multiple options that I can go with especially if two batteries are involved, but I don't want over complicate a daysailor. So any help would be appreciated.

1. Should I after delivery convert this to a two battery system? I could keep it simple and just install a low voltage disconnect with a one battery system.
2. Flooded, AGM or both? Battery(s) will probably never be 100% charged until I pull the boat in October and bring them inside, so I expect the batteries will typically sit at 75-90% during the summer. AGM sounds better for the quicker charge and slower discharge, but am I going to damage them too quickly by not getting them 100% during the season?
3. Is the spec'd 120 amp alternator too big? I also have concerns the belt may wear quicker. If 120 amp is too big, then should it be the 60 or 80 amp?
4. Leave the internal regulator or convert to external?

It just seems like the more I research, the more complicated the system becomes and I start to wonder if I'm going overboard on such a small boat that is not being used for living aboard.
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Old 15-02-2014, 17:13   #2
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Re: New Small Boat Battery(s) & Alternator Questions

Your last paragraph is not really the question.

You've found a nice boat you like and you've identified the stock electrical as rudimentary requiring upgrades. That's not unusual, since many stock electrical systems have been found in need of upgrading for past handful of decades! You're NOT alone.

AGM batteries IMHO are a waste, not only for you but for most folks who install them UNLESS they REALLY know battery care & maintenance. I recommend standard flooded lead acid deep cycle batteries. Your choice of whether to use just a single larger house bank (say two) or two separate (old school). You could get a smaller "start" type battery for the engine.

In EITHER case, I would urge you to reconsider the solar. Indeed, a mooring location is THE perfect place for the application of solar. Why? The goal is provide a long life for the investment in lead. The best way to do that si to keep the batteries as fully charged as possible, and history shows that regardless of how long an alternator is run, it rarely is adequate, regardless of size, to charge the bank fully. That's where solar is such a great choice.

Millions of posts have been written about these issues. In lieu of rewriting what could be a book, I've assembled a series of links that you may be interested in reviewing: Electrical Systems 101 Electrical Systems 101

If it was my boat, I'd get two deep cycles for the house bank, and a separate small Sears/automotive battery for the reserve or engine start depending on how you wire it up or how the factory can provide it for you. Gerry Douglas should be able to help.

Then get a good sized solar panel, which actually can be purchase in addition to the factory panel.

IIRC, the Yanmar (Hitachi) alternators may not be able to be externally regulated, and if you read some of the links in the 101 topic, you'll see that external regulation isn't necessary if you get the larger solar panel. I'd get either the 60A or 80A depening on your energy budget and the battery acceptance based on the size of house bank you decide upon.

Good luck. Any questions, come on back.
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Old 15-02-2014, 17:20   #3
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Re: New Small Boat Battery(s) & Alternator Questions

Your last paragraph is not really the question.

You've found a nice boat you like and you've identified the stock electrical as rudimentary requiring upgrades. That's not unusual, since many stock electrical systems have been found in need of upgrading for past handful of decades! You're NOT alone.

AGM batteries IMHO are a waste, not only for you but for most folks who install them UNLESS they REALLY know battery care & maintenance. Your scenario as posted will KILL them rapidly.

I recommend standard flooded lead acid deep cycle batteries. Your choice of whether to use just a single larger house bank (say two) or two separate (old school). You could get a smaller "start" type battery for the engine.

In EITHER case, I would urge you to reconsider the solar. Indeed, a mooring location is THE perfect place for the application of solar. Why? The goal is provide a long life for the investment in lead. The best way to do that is to keep the batteries as fully charged as possible, and history shows that regardless of how long an alternator is run, it rarely is adequate, regardless of size, to charge the bank fully. That's where solar is such a great choice.

Millions of posts have been written about these issues. In lieu of rewriting what could be a book, I've assembled a series of links that you may be interested in reviewing: Electrical Systems 101 Electrical Systems 101

If it was my boat, I'd get two deep cycles for the house bank, and a separate small Sears/automotive battery for the reserve or engine start depending on how you wire it up or how the factory can provide it for you. Gerry Douglas should be able to help.

Then get a good sized solar panel, which actually can be purchased and wired in addition to the factory panel with a quality solar controller.

IIRC, the Yanmar (Hitachi) alternators may not be able to be externally regulated, and if you read some of the links in the 101 topic, you'll see that external regulation isn't necessary if you get the larger solar panel. I'd get either the 60A or 80A depending on your energy budget and the battery acceptance based on the size of house bank you decide upon.

Good luck. Any questions, come on back.
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Old 15-02-2014, 17:26   #4
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Re: New Small Boat Battery(s) & Alternator Questions

My situation is similar to yours; here is my experience. I have a 1987 Pearson 27, with a Universal 10 hp engine with a 55 amp alternator. Also light use, also on a mooring (no battery charger even if at the dock). I don't have an electric head, but I don't think that my usage is much different from yours.

The boat had two group 24 flooded deep cycles when I bought it. Last spring, I changed to a group 24 start battery(800 CCA/1000 MCA) and group 27 deep cycle (575/715). I remove the batteries in the winter and charge them occasionally at home. I have never had any problem keeping them charged with the stock alternator -- the 120 amp alternator sounds huge for your needs! The group 24 start battery starts my engine with ease. The 27 is an upgrade from previous and doesn't have to do very much: VHF, small chartplotter, stereo, depth/speedo, and a small Furuno radar that, well, if I need it, the engine will be on, too!

This past summer, I hardly used the boat. Occasionally I went aboard and ran the engine to give the batteries a little juice. I left them aboard until January (tsk, tsk) and got them off the boat with a dock line lowering them to the ground. I took them home and tested them and they were both at around 80%, and my fancy battery tester rated them both still over 100% of rated CCAs. They are all charged up now, and in the garage.

On the big boat, I have AGM 4Ds and thank heaven I do, as they are not easy to remove and it's not feasible to charge them while on the hard without babysitting the charger. The battery tester rated those at 95% in January, so I am a believer in that slow discharge thing.
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Old 15-02-2014, 18:03   #5
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Re: New Small Boat Battery(s) & Alternator Questions

Since I'm sure it costs money to go with the bigger alternators, I'd go with a small one and take the money difference and put it in solar. You said you weren't going to use the engine much so money in a big alt is wasted
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Old 15-02-2014, 18:18   #6
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Re: New Small Boat Battery(s) & Alternator Questions

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Since I'm sure it costs money to go with the bigger alternators, I'd go with a small one and take the money difference and put it in solar. You said you weren't going to use the engine much so money in a big alt is wasted
Very astute observation. My experience is that the battery acceptance is the limiting factor in these applications. My ~400 ah bank can only take 50A charging when @ 50% SOC anyway. But if he reads the link I suggested, there is a discussion of external vs. internal regulation which gets into this in more detail. A 60A or 80A alternator will NOT put out 60A or 80A because the battery acceptance will be less than that anyway. If he spends the $$ on solar, as you suggest, the 60A will be just fine for his intended use, now and in the future.
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Old 16-02-2014, 07:08   #7
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Re: New Small Boat Battery(s) & Alternator Questions

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Your last paragraph is not really the question.
No, the 1-4 numbered questions were my questions. The last paragraph was just a comment that I'm in a confused state.

Thank you for the link, I haven't seen that website before and it looks like I have a lot of reading to do.

Sounds like not to bother with AGM and use FLA. The only problem I see with FLA is that the space is so tight, I may have to unstrap the house battery and slide it just to check the level. Also sounds like two batteries at the minimum. Because of weight & size, I think I will go with a G27 deep cycle for the house and a G34 for the starter. In 10 years if I do light cruising, I'll add a second G27 for the house.

That being said, the size of the alternator is one of my pre-ordering concerns. I had made the assumption that 60 amp was stock and I had spoken to Gerry just to see if the 80 amp was an option. If so, I was going to research which one to choose. Then Gerry tells me they are installing 120 amp alternators, which seems like complete overkill for a single G27 FLA battery. But who am I to question one of the most successful sailboat builders? I'm not even sure if the 60 or 80 are an option. So now, I may be asking Catalina to install a special order Yanmar with a stock 60 or 80 amp alternator. So before I act like a "difficult" buyer, I better be at least sure of which alternator I should be requesting and why. If the price difference between the 60 and 80 is not an issue, do I go with 80 for the extra capacity or is 60 plenty if I ever expand to two G27 house batteries or for some reason shift to AGM?

Another pre-ordering concern is the solar, I initially really liked the idea of the recessed into the anchor locker hatch solar panel which is a Ganz GSP-12. But with trees in the early morning, adjacent masts in the late morning, my mast (and maybe boom) in the early afternoon, this just seems like it will not be as efficient as it should be (I'm tied stern and bow, so I'll always be in the same position). Also, I could have sworn that the panel at the boat show was a trapezoid shape and not the stock rectangle. Either way, if it needs to be replaced in the future and Ganz is no longer, now what? I have this recess in in the hatch that with or without a working panel is going to collect mold and dirt and just be another difficult place to keep clean. With no bimini and very minimal pulpits, a secondary panel is not really practical. It would probably make a more efficient head banger when getting in and out of the harbor dingy. This is the boat I'm working with (hopefully the image inserts):
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Old 16-02-2014, 17:36   #8
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Re: New Small Boat Battery(s) & Alternator Questions

if they are installing 120a alternators on boats with a single group 27 battery then they are retards... it'll probably only take about 20amps of charging anyways.

most boat builders don't know crap about electrical.

and I would definatly have at least 2 batteries. separate house / start. and a way to charge both from the alt. (acr etc)

if you boat is sitting not with a charger then you should have solar. if nowhere to perm. mount one. then maybe a temp one that is left on when the boat is moored and moved when used. so at least you'll have full batteries when you leave. and will charge back up during the week when you get back.
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Old 17-02-2014, 08:59   #9
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Re: New Small Boat Battery(s) & Alternator Questions

You don't need the larger battery for the engine, you need it for the house bank.
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Old 17-02-2014, 15:53   #10
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Re: New Small Boat Battery(s) & Alternator Questions

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You don't need the larger battery for the engine, you need it for the house bank.
A group 34 is about the same size as a group 24, but it is shorter so it actually has less amps than a group 24. You may be thinking of the the G31 which is bigger than the G27.

Any thoughts on what I should say to Gerry at Catalina when I try to convince him that a 120 amp alternator is too big? Also based on a future max of two G27 and a small G34 and if I'm not concerned about the additional cost of an 80 amp alt., will I still want the 60 amp Hitachi alt.?
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Old 17-02-2014, 15:59   #11
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Re: New Small Boat Battery(s) & Alternator Questions

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Any thoughts on what I should say to Gerry at Catalina when I try to convince him that a 120 amp alternator is too big? Also based on a future max of two G27 and a small G34 and if I'm not concerned about the additional cost of an 80 amp alt., will I still want the 60 amp Hitachi alt.?

I'd approach it from an engineering perspective. "Gerry, here's my energy budget, now and in the future. I really don't need or want a 120A alternator, what do you think?" Then you can get a dialog going with him as to why he's putting them on those boats.

If I had a choice between a 60A and 80A, I'd go for the 80A, since with the same load the alternator is working "less hard."

Good luck.
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Old 17-02-2014, 16:50   #12
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Re: New Small Boat Battery(s) & Alternator Questions

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A group 34 is about the same size as a group 24, but it is shorter so it actually has less amps than a group 24. You may be thinking of the the G31 which is bigger than the G27.

Any thoughts on what I should say to Gerry at Catalina when I try to convince him that a 120 amp alternator is too big? Also based on a future max of two G27 and a small G34 and if I'm not concerned about the additional cost of an 80 amp alt., will I still want the 60 amp Hitachi alt.?

I'm really surprised that Catalina is specing that Alt for that engine/battery config. I recently purchased a 355 and with a 3YM and 2 4D's it came with a 60A alt. Even though there was an option for an 80A alt, I chose not to upgrade since I planned on redoing the electrical system to my preference anyways. As Stu mentions, just ask Gerry about the stock Alt given your planned use.
As for the Exide, yes they are crap, but if you take care of them they should be good for several seasons; I think you will come out ahead only because Catalina will not give you much if any of a credit. Just replace with what you want when the time comes...good luck! That 275 looks like it should be a fun boat...
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Old 17-02-2014, 23:40   #13
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Re: New Small Boat Battery(s) & Alternator Questions

My 28ft'er has the same engine. The 80 amper is heaps, it's not going to rob the motor of shaft hp when you may need it.
I have a N70 wet cell in atm with provision for another. Plenty of power for 'stuff', I do run 180w of solar... so consider a panal, even a 20w er to maintain your battery at or above 14.2v.. loverly motor I might add..

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Old 18-02-2014, 14:11   #14
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Re: New Small Boat Battery(s) & Alternator Questions

I think a mooring sailed boat should have at least a small solar setup just to keep the battery topped. You mentioned your in a mooring field where they fix you fore and aft (I assume something similar to what they have in Camden Maine http://www.marinalife.com/images/featured/CAmden1.jpg
) if thats the case I would look at a panel that could be set up in the cockpit and has a quick release to something solid you could then orient it to the sun better than us with a free swinging mooring. I would than wire it to a deck plug (like a trolling motor plug) and just stow it away when your done. I have a fried who has a center console tied on an end slip with no power he sets up a similar panel on his fish box when he leaves and never has a dead battery when he gets back.
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Old 18-02-2014, 16:28   #15
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Re: New Small Boat Battery(s) & Alternator Questions

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I think a mooring sailed boat should have at least a small solar setup just to keep the battery topped. You mentioned your in a mooring field where they fix you fore and aft (I assume something similar to what they have in Camden Maine http://www.marinalife.com/images/featured/CAmden1.jpg
) if thats the case I would look at a panel that could be set up in the cockpit and has a quick release to something solid you could then orient it to the sun better than us with a free swinging mooring. I would than wire it to a deck plug (like a trolling motor plug) and just stow it away when your done. I have a fried who has a center console tied on an end slip with no power he sets up a similar panel on his fish box when he leaves and never has a dead battery when he gets back.
While the molded into the anchor locker option seems like a great idea, I also know that solar panel companies come and go and in ten years, will there be a panel that fits as well into the recess? That's why I'm hesitant to go that route. But I have been giving some thoughts to a flexible panel that I could shockcord around or stitch to the sail cover. Something like the Powerfilm at WM. Not as efficient, but it is at least something. I can even put the boom to the port side a bit to keep it the boom east/west. Thanks for the trolling motor plug idea, because I was trying to figure out what I could use to route the wire into the boat.

We have some moorings like Camden Maine and moorings that swing, but while my stern is tied to a can, the bow is actually tied to a school dock. I'm the 2nd can from the top (right). The dock is not really accessible and has no power. The posts behind my stern can is for the bows of a second row.
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