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Need help deciding on batteries

Mar 31, 2017
7
Catalina 27 2633 Racine, WI
Just purchased a 1976 Catalina 27 with an Atomic 4. Not sure of the age or status of the batteries so I'm planning to replace them. However it's maddening to figure what's the best way to go. The boat has a Motorola alternator that produces 37 amps. I am new to the boating world but it seems that some batteries need a larger alternator. What would make the most sense for the boat. Any and all help is appreciated!
 
May 20, 2016
2,883
Catalina 36 MK1 94 Everett, WA
To answer your question we would need to know how you plan on using the boat. Around the bouy Friday nite racing only or long cruising and acchoring out. Additionally what you energy budget looks like

While 35A was good in 70's with iceboxes and alcohol stoves and maybe a sounder and water speed. Today's electronic world demands more juice, so what do you have or plan to have consuming electrons while you are having fun???
 

Joe

.
Jun 1, 2004
6,897
Catalina 27 Mission Bay, San Diego
My Catalina 27 has 2, 12 volt, group 27, deep cycle batteries. Their rated at around 100 amp hours apiece. They are charged through a 10 amp smart charger that is hardwired to my 110 volt shore power system. It takes quite a while to charge them up... but I have very low power needs.

Check out the WestMarine Advisor articles... Inspect the top label on your batteries to get an idea of size, capacity and type. A lot of budget mined sailors get their deep cycle lead acid batteries from Costco or WalMart.
https://www.westmarine.com/WestAdvisor/Selecting-a-Marine-Storage-Battery
https://www.westmarine.com/WestAdvisor/Sizing-Your-House-Battery-Bank
https://www.westmarine.com/WestAdvisor/Marine-Wire-Terminal-Tech-Specs
https://www.westmarine.com/WestAdvisor/Installing-a-Second-Battery

According to the second article, your 37 amp alternator is matched up to approx. 200 ah battery bank.
I highly recommend you acquire a copy of "The 12 volt Bible" by Miner Brotherton.
 
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Dec 16, 2008
57
Pearson 422 FL & CT
Will second the recommendations from Leslie. Before you buy batteries you need to determine what your electrical requirements will be. I'm guessing the boat doesn't have refrigeration but what about lights? Are they incandescent and will you be weekending on the boat? Anchor light? Electronics?

First step is to work up an energy budget, then determine how much battery capacity you will need to supply that budget and then how to keep those batteries charged.
 
Mar 31, 2017
7
Catalina 27 2633 Racine, WI
For this year mostly just day sailing. We do not have a refrigerator, hot water, or tv. I guess we'll be sailing like they did in the 70's...except for charging digital devices.
Eventually we would like to sail to various destinations around Lake Michigan but I'll be happy with a solution for this year alone. Thanks!
 
May 24, 2004
6,068
CC 30 South Florida
What could be important is the power draw of that vintage gasoline engine starter motor. A "starter" battery rated in cranking amps is designed to handle large and quick loads while a deep discharge battery rated in Amp Hours is better suited for house functions of slow deep discharges. Being that a sailboat spends most of its time underway with the engine off having a deep cycle is of importance so perhaps it may be advisable to have one battery of each dedicated to each function. Like Leslie indicates the size of the alternator depends on the intended use for the boat and the size of the battery banks. No reason to upgrade alternator until you get familiar with your setup and have a need to do so.
 
May 20, 2016
2,883
Catalina 36 MK1 94 Everett, WA
At this point I would recommend adding another battery in a one bank configuration. Get to know your boat and how you use it. Flooded lead acid FLA) will hold up better than gell or AGM given the chargers you are most likely using. FLA can also handle not being fully charged better. You don't mention if or what other chargers you have (shore, solar, wind...) but they will play a role in ultimately designing a system.

In addition to the WM links. Maine Sail (a featured contributor here) maintains a web site that has lots and lots of great info on batteries and chargers MarineHowTo.com

Les
 
Dec 16, 2008
57
Pearson 422 FL & CT
My preference for any boat that relies on a battery to crank the engine is two batteries, isolated from each other. One cranking batter, one deep cycle. One problem not many (or any?) true deep cycle batteries in 12V and small to mid size but there are heavy duty 12V batteries that would work.

Also, for your application I would stick with plain old flooded, lead/acid batteries. Most bang for the buck and generally take abuse better than other types.
 
Jan 18, 2016
517
Catalina 30 Dana Point
The starter on a A4 takes very little power - probably could start it with 8 D cells. (heck, that's funny enough I may try it and make a youtube of it)

A 27' boat with not a lot of electrical loads - two 'deep cycle' 12v batteries that fit in the boxes as long as they're bigger than G24s.

Some reasoning.... I have an "everything" (house) bank, and an "emergency" or reserve bank. Just worked out a bit easier than start/house and I kept my A/B/both/off switch. I really didn't have the room for the right switchgear to go with a dedicated start configuration although I agree that's the optimal setup. House is a pair of GC2s that fit in the original location. The reserve is a small G24 that I have actually never used - it's only there in case I draw the house down to nothing and it's kept charged with a tiny battery maintainer. So I start my A4 off my house. I charge the house from the alternator, charger, and 120w of solar. If I didn't have room for the reserve battery I would have just kept one of those little jump starters on board. I can go 3 days or so on the hook (I have refrigeration) with just the solar and still be able to start the engine fine and keep the beer cold. With the fridge off, I could last forever off the solar.

Without refrigeration, your power needs aren't gonna be too much. You can get 200AHish capacity with a pair of G27s. Or 225AHish with a pair of GC2s wired in series (if they'll fit). Your alternator will not charge quickly. Mine sure doesn't. But it'll keep up with the autopilot and plotter when motoring.

There is absolutely no reason for you (or almost anybody) to go the extra $$$ for AGMs, gels, LiFePO, carbon foam, etc... Plain old FLA is fine for your use. Buy em anywhere but west marine. (Costco/Sams are the bargains, particularly for GC2s). A G27 isn't generally as 'good' as a deep cycle battery as a GC2, but you'll likely never know the difference unless you put in a fridge or a 200 watt stereo or something.
 
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May 20, 2016
2,883
Catalina 36 MK1 94 Everett, WA
One more thing if planning on a new alternator be sure and get marine grade they are not too much more and are required and safer than an auto alternator (no sparking) /- especially important with gas engine. Stay under 100A because of single 3/8 belt

Les
 

Ward H

.
Nov 7, 2011
2,578
Catalina 30 Mk II Barnegat, NJ
However it's maddening to figure what's the best way to go
For your first year with the boat, follow the KISS principle. (keep it stupid simple)
QUOTE="Karcher, post: 1369136, member: 137613"]For this year mostly just day sailing.[/QUOTE]
Why not take the batteries to a local auto store and have them tested? If they test fine, that will buy you the year of day sailing. It also buys you the time to learn all your options and plan your electrical system upgrade.
If they are shot, replace with same size & type you have now.
 
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Aug 23, 2011
89
Hunter 31 Georgetown, MD
Welcome to a great sport and hobby
I agree with what Ward says.
For starting out, if your batteries have a date label over4 years or test out dead, replaced with like batteries. Our Hunter 25.5 had two group 24s with a selector switch. For day sailing even our outboard kept them up as we motored in and out of the marina and river.

Our local independent battery warehouse store always has a spring sale of Deka (East Penn) marine batteries with more "bang" (Amps) for your "bucks" $ Costco or Walmarts!

Mike
 
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Nov 7, 2012
678
1978 Catalina 30 Wilbur-by-the-Sea
Get a decent solar panel and charge controller. We purchased our current boat 4 years ago and the batteries were low so I installed said items and we are still running the same hodge podge 200ah+ group of cells that she came with after 4 years. Expect them to die at any time but there seem happy being at a nice float most days and we only use the boat on weekends, never a worry. Also we do not connect to shore power so less concern about stray currents and electrolysis.

If the batteries are shot I would just get some deep cycle cell from Sams or Costco as mentioned above.
 
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Mar 31, 2017
7
Catalina 27 2633 Racine, WI
Wow....thanks for all the input. It seems 2 flooded deep cells is the way to go for now. I'm sure I'll have more questions as we go along. Nice to know so many are willing to take time to help out us novices.
 
Mar 27, 2016
21
Catalina 310 NAS Pensacola
I went the 6 vdc in series golf cart battery route. Easy to handle, two banks of 6v in series, cranks great.
 
Aug 13, 2012
519
Catalina 270 Ottawa
Get a decent solar panel and charge controller.
Don't skimp on the controller. Do your research and pick a good one. you will be happy later.
If you go this way, Genasun or Morningstar are good starting points.