Author Topic: Alternator setup for AGM?  (Read 279 times)

Offline Wes

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Alternator setup for AGM?
« on: November 04, 2017, 07:53:59 AM »
Folks - has anyone installed a proper alternator/regulator setup for AGM batteries, particularly on a 27 with the original Universal M12 engine?

I’d like to do this, since I’ve read that a conventional alternator (with internal regulator) will cook the AGMs. I believe I need an outboard regulator with multiple charge profiles. But the ones available from Balmar seem intended for larger alternators, around 70 amp and higher. Putting such an alternator on my little engine would require changing out the pulleys for a larger belt, and seems like it would also rob power from my none-too-ample 11 HP.

Thoughts?

Wes
"Sophie", 1988 CP 27/2 #74
"Bella", 1988 CP 19/3 #453
Bath, North Carolina

Offline moonlight

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Re: Alternator setup for AGM?
« Reply #1 on: November 13, 2017, 09:09:42 PM »
Unless you're doing extensive cruising wherein the AGM's are getting depleted and then running a 6 hour motor cycle to recharge them; you're overthinking this.

Check alternator output voltage with fully charged batteries.  Then find a way to deplete the bank 50% to 12.4V, start the engine, and check alternator output voltage.  If you get 14.6V both times you're fine.  If you get less, no harm done unless scenario in sentence 1 is true.

If you're daysailing 90~95% of the time, your shorepower charger will handle the conditioning.  Which for the common sailor is overthinking it anyway.  AGM's, 5-7 years and they're done no matter what you do.  Same with all Lead Acid variants (in this case, the acid is just "adsorbed").

Call me off-line if you want to talk Lithium, 30-year batteries...

Offline redfishnc

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Re: Alternator setup for AGM?
« Reply #2 on: November 26, 2017, 06:57:21 PM »
Wes, what did you end up deciding about the batteries.  Awhile back I was going AGM and still had the original charger from 1993 (18hp Westerbeke).  Since I was going to have to replace batteries and charger I decided against it. (I do use AGM batteries on my flats skiff for trolling motor batteries.) Ended up buying wet cell  batteries and a new charger with 3 charging banks to enable a 2nd house battery to help power my Engle 45qt fridge.   Battery prices suck.

Wes /Moonlight - Interested in your thoughts and why??

Wayne
Sea Witch
Wilmington, NC

Offline Wes

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Re: Alternator setup for AGM?
« Reply #3 on: November 26, 2017, 10:13:05 PM »
Have not pulled the trigger yet, but need to do so soon. I plan to call Trojan tech support tomorrow and discuss this with them. Will keep you posted!
"Sophie", 1988 CP 27/2 #74
"Bella", 1988 CP 19/3 #453
Bath, North Carolina

Offline moonlight

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Re: Alternator setup for AGM?
« Reply #4 on: November 29, 2017, 10:31:28 PM »
Full disclosure, I am an ABYC-certified Marine Electrician (among other things) and provide a wide variety of marine electrical and mechanical services primarily to pleasure craft in the Gulf Coast region.

I only sell West Marine AGM batteries; with exceptions for custom lithium battery projects and the very rare wet cell battery.

First and foremost, people that pay me to do their electrical work do not check the water in the batteries. So they need a truly maintenance free battery. Vessels of the size and category that I primarily work on are coastwise vessels and usually stay in the water. In the rare event that warranty service is needed, West Marine supports their product exceptionally and is open 7 days a week. You won't get that with other brands.

The Sea Ray Dealer near me loves NAPA batteries; try to find that on a Sunday!  Another horror story, years ago I tried to help a young lady who wound up with the boat her dad could no longer maintain and her brother the residential electrician had started to rewire. They had a under warranty Walmart battery on board that had failed and in the attempt to save them money we tried to do the exchange, under warranty. Of course Walmart was farther away than West Marine.  And Walmart had to go through their own process which included overnight charging of the battery. So it was an hour to drop it off ( with time waiting in line); an hour the second day ( again with time waiting in line) to find that Jose forgot to charge it overnight; a repeat of that the third day, and finally on the fourth day they agreed the battery had prematurely failed and gave a warranty replacement. At that point my time which I didn't charge could have bought them two batteries.

Back to the topic, AGM batteries better tolerate the abuses the boaters put upon them; which is lots of idle time and seldom use. Rarely do you find people that actually cycle batteries or even get involved with depth of discharge other than trolling motor batteries. 

This crowd (Com-Pac forum) is different because you're all sailors. So depth of discharge is better than what we find with power boaters.

But to our own detriment as Sailors, who know that the wind is free, think that everything else should be. But cheap batteries don't provide first-class service.

So for first class service you have to start with first class batteries and then maintain them in a first-class fashion. 3 years is a minimum life, 5 is typical, and 7 to 9 is possible but again if you're not cycling them and keeping them charged you're still losing capacity. And even if you're doing depth of discharge calculations, you will be lucky to have 50% at 5 years whether you're using wet cell or AGM lead technology.

To do lithium batteries, you need to be even more involved, more educated, but these things can easily give you 3000 Cycles compared to 500 for lead variants. They will cost you 50% to 100% more depending upon system design and interlocks but since the design life and cycle life is 6 times the factor they're not real hard to sell.  Of course further elaboration of this is outside the scope this post but I'd be happy to help anyone through the process... Send me a PM, email, or call.

Offline tmw

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Re: Alternator setup for AGM?
« Reply #5 on: November 30, 2017, 04:01:04 PM »
At that point my time which I didn't charge could have bought them two batteries.

I need to keep telling myself this, and go out and spend money/time on the boat, and less time researching to find the best option.

Thank you for sharing your perspective, good to hear.