Changing Batteries

Scott2

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Sep 26, 2008
58
Hunter 240 Hayward, WI
Greetings Fellow Sailors,

I bought a 1994 Catalina C270LE last year and would like to change the batteries. It's my first boat with a diesel engine and and shore power and I want to get it right. I also tried deciphering the Catalina 270 wiring diagram, but am still confused since it simply says "Battery 105AH Exide, Quantity 2". So here are my questions:

1. Given that the battery selector has a 1,2 and Both position, does the engine start off either/both batteries? If so, should they be both starting/deep cycle or one starting battery and one deep cycle? Or perhaps one or both combination starting/deep cycle batteries?
2. If one starting battery and one deep cycle, which position is which?
Thanks for your help. This Minnesota sailor can't wait to get on the water!
3. What protects the starter battery from draining too low to start the diesel?

Scott
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Correct on the 1/2/both switch. Deep cycle for both batteries. The idea is get two of the same, and check the mfg date and get as close together- if not the same. When you leave the boat, have only one battery on. When you go back to the boat, use that battery to start the engine and recharge the batt while motoring. Swap to the other battery while sailing then leave the second one on back at the slip. Do not leave "both" batteries on when you leave the boat, lest a battery go bad and drain both of them dead.
 

Scott2

.
Sep 26, 2008
58
Hunter 240 Hayward, WI
Thanks Ron, that makes a lot of sense and I hadn't thought of one battery draining the other. I had been leaving shore power on but both batteries off. I thought the system still charges the batteries when the battery switch is in the Off position.
 
Sep 25, 2008
7,077
Alden 50 Sarasota, Florida
You are generally correct assuming the charger is independent of a battery switch - however -

Don't assume anything. There is no certainty in what a previous owner may have done as evidenced by many stupid things people do particularly when it comes to boat wiring. The PO may have changed something you won't know until you trace all wiring to confirm the existing configuration.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
[QUOTE="Scott2, ]/// I thought the system still charges the batteries when the battery switch is in the Off position.[/QUOTE]

Agree with Don that you never know what a previous owner did. Ideally, if your charger has two outputs, you'd wire one to each battery. THEN, the switch in the off position will keep them isolated. You're on the right track, but trace wires and keep a diagram of your findings.
 
May 24, 2004
7,129
CC 30 South Florida
All above comments are on point but allow me to provide the simple logic that drives them. The boat's battery requirements can usually be divided in 1) house functions and 2) engine starting. A starting battery does not serve well in house functions as it is not fit for multiple deep discharge cycles but a deep cycle battery can more than adequately start the small diesel engines. The characteristics of the deep discharge battery allows us to bring in the element of redundancy into the system. By having two deep cycle batteries we can use one and leave the other in reserve for emergencies. Batteries can and do go bad (they don't all offer warranties for no reason) and electricity flows like water from a good battery to a depleted or bad battery. These deep cycle batteries have a finite number of charge/discharge cycles (manufacturers don't tell you how many because they have no clue) and in order to keep both batteries with a similar anticipated remaining service life you should alternate their use. What most do is use battery 1 this outing and battery 2 for the next outing. The battery switch is usually wired to indicate which battery is handling the loads and in addition which battery is receiving charge from the alternator. Switch to battery 1 and that is the battery that will supply the power and receive charge from the alternator, switch to battery 2 or Both and .......you get the idea. If there is an inboard battery charger it will usually charge both batteries irrespective of the position of the switch. By using the switch position Both you actually combine the batteries in parallel doubling the capacity of a single battery. It can provide a boost to a discharged battery for engine starting or it can double the capacity to perform house functions. Just understand that when you combine the batteries you are making a conscious decision to abandon redundancy. Not unusual that once the engine has started and is running to combine both batteries so that both receive charge from the alternator in a long run. Not unusual either to combine them just for engine starting and then isolate one of them. In other instances if you carry a third battery or staring battery pack then you can combine the two to double capacity for house functions. When isolated each battery is known as a single battery bank but when combined both batteries become also a single battery bank. It is good to know when batteries can be combined or not; a deeply discharged battery will suck the juice out of a fresh one perhaps leaving 2 partially discharged batteries unable to start the engine when the fresh one could have easily started it. As I rule I would first start the engine and then decide what I wanted to do. By this time you have probably figured out that there are different types of batteries with different price tags. I personally like the wet cell batteries for price and availability. Nothing like getting off the boat anywhere and finding an auto parts store and purchasing a replacement battery to substitute a fouled one. Or finding a Walmart to redeem a warranty replacement. Some boats because of sophisticated electronics and heavy load appliances do need to have high end type batteries and monitoring systems but for most simpler vessels the battery system with wet cell batteries perform just fine. as you become familiarized with your boat and your electrical needs you may improve your system in the future but for now I would recommend Two group 27 wet cell, deep cycle batteries with approximately 105Ah each. Batteries should be fresh so at purchase the manufacture date should be inside 60 days of manufacture. batteries that sit on the shelf for too long may have sulfating issues which may reduce their capacity and life expectancy. Look for a retailer that constantly moves their inventory. Good luck.
 
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Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
:plus:Way to identify clarity to the issue Benny.
"The best solution is usually the simplest that meets your specific needs"
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
Hi Scott,
Nice boat selection! Where will you be sailing? Your battery selection can vary depending upon your normal use. If you are day sailing on inland waters, you will probably be happy with 2 identical deep cycle batts wired independently to the 1-2-B switch. If you are going to keep your boat on Lake Superior and spend weekends anchoring in the Apostles, you might want to have 2 identical deep cycles combined on Bank 1 and a 3rd (smaller) batt for reserve on Bank 2. This will give you better battery performance (longevity) if you are typically using more amps during periods away from your charger.
I suggest that you read as much as you can from what is posted in "Featured Contributors", "Musings with Maine Sail" on battery topics. The education will be mind blowing! This is all within the SailboatOwners family of forums, and many of us contributed and learned from this site. You should do as much reading about the way you intend to us the batteries as you can, because there are several suitable ways to set up your DC power system to fit your needs and desires. Just because Catalina (or a previous owner) sets it up one way doesn't mean it is right for you. Pay particular attention to the way charging sources are organized and employed. Also, pay particular attention to the details of your shore power source. You may want to modify several or all of the components of your system (not just your batteries) to serve your needs.
Are you a Hayward native? My brother has a home on McClaine Lake.
I have 2 grp 27 wet cell batts for a house bank and I use a separate start battery that can also serve as a reserve, but my switching system is different from yours so that under normal circumstances my two banks are isolated when both are "ON" at the same time. This way, I always know that my house bank use will never affect my ability to start the engine with a charged battery. A battery monitor will also provide you with a useful tool to maintain and monitor your batteries.
I can combine the banks but don't have a need or desire to combine the banks (many believe that combining the banks is asking for trouble). With auxiliary switching, I can isolate either bank for combined starting and house bank functions, if I ever had that need due to a failed battery bank.
There is a ton of excellent information if you use the "search" function.
 
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Jan 19, 2010
1,169
Catalina 34 Casco Bay
If you do not replace both batteries at the same time, and the older is weaker ( naturally ) than selecting "BOTH" on a battery switch will cause the batteries to attempt to equalize. Same goes for charging. If one is older/weaker charge independently of the newer one. You can switch between 1,2, or both while the engine is running and charging. Always shut the engine down before turning battery selector to off, otherwise you can damage the alternator.
 
Aug 13, 2012
533
Catalina 270 Ottawa
The batteries on C270 are stored under the settee in the cabin. Therefore, you should use batteries that don't gas out during charging. There is not much venting available in the compartment. Probably a gel cell battery is the most appropriate (this is the type that was provided as OE).
If you have a standard setup, you should have two batteries of the same type. There is no room for a 3rd battery, unless the PO changed the boat inside.
 
Aug 1, 2011
3,972
Catalina 270 255 Wabamun. Welcome to the marina
What Marek said. There's no easy way to extend cables anyplace else, so likely only two batteries. It's a fairly short cable run up to the switch, and unless it's been modified, it's a 1 2 off switch.
 
Feb 26, 2004
22,760
Catalina 34 224 Maple Bay, BC, Canada
Nice boat, congratulations.


You may be interested in these links which come from this topic:
Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

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OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

This is a newer primer for boat system wiring design with a thorough digram: Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/in...dc-electrical-foundation.181929/#post-1332240

The Short Version of the 1-2-B Switch Stuff: http://c34.org/bbs/index.php/topic,5977.msg38552.html#msg38552 This is a link to the Electrical Systems 101 Topic, reply #2

What are ACRs, Combiners & Echo Chargers? (by Maine Sail)
http://forums.catalina.sailboatowners.com/showthread.php?p=742417
 

Scott2

.
Sep 26, 2008
58
Hunter 240 Hayward, WI
Scott T-Bird.... The sailboat is home ported at Lake City Marina on Lake Pepin. Almost all day sailing with a very occasional anchor out adventure.
 

Scott2

.
Sep 26, 2008
58
Hunter 240 Hayward, WI
Ahoy esteemed gurus of batteries :) After a plethora of due diligence, research and review, I am at a crossroads. What is your recommendation regarding either a deep cycle gel battery or the newer Absorbed Glass Mat (AGM) battery. Any advice? Thanks in advance. Scott
 

Johnb

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Jan 22, 2008
1,420
Hunter 37-cutter Richmond CA
Ahoy esteemed gurus of batteries :) After a plethora of due diligence, research and review, I am at a crossroads. What is your recommendation regarding either a deep cycle gel battery or the newer Absorbed Glass Mat (AGM) battery. Any advice? Thanks in advance. Scott
If you are basically a weekend warrior with occasional vacation trips I would keep as as simple as you possibly can.

The worst thing that can ever happen to you is you can't start your engine. That is why I have two batteries. Save one for starting the engine and use the other for lights, domestic water, TV and other "frivolous" uses. If you somehow manage to run it flat you can still start you engine with the other one and then you have power for running lights, depth finder and essential needs.

After I bought my boat in 1999 I put in two flooded deep cycle batteries in 2002 (total cost $160) which lasted until 2009. I then replaced them with another 2 the same (another about $160). 8 years later I am thinking I should replace them but either one can effortlessly crank the engine, even after we came back from 6 weeks vacation.

This time I will install a more elaborate system because we plan to go cruising next year, but the point is you can save yourself a lot of money and headaches by just getting what is adequate for your needs. On this site the anguish is never ending. Never have so many spent so much for so little - the story is pretty the same and goes "I spent 1/2/3 boat bucks 1/2/3 years ago and now its FUBAR".

I have a smart stand alone charger and about twice a month hook it up direct to the battery terminals and charge them overnight. Once a month I check the water levels and about every 3 to 4 months need to add water. Other than that we just use engine charging. That's it.
 
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Aug 13, 2012
533
Catalina 270 Ottawa
In a C270, you should use a sealed battery (gel cell or AGM). I don't think you will have much advantage from installing AGM batteries and your charging system may not be up to the task (AGM batteries require a bit different charging profile). Unless your charging system (both the alternator and the charger) have been upgraded, you risk of slowly murdering the AGM batteries.

In short, in your case (as in mine) I would install the gel cell batteries.

Marek
 
Mar 31, 2017
7
Catalina 27 2633 Racine, WI
Scott - That is a great idea! How are your house bank batteries wired? Series or parallel? Thanks!