Third battery for 34/35

dmax

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Jul 29, 2018
969
O'Day 35 Buzzards Bay
I would like to add a 3rd battery (2 house, one starter) and wondering where people who have done so put them. So far, the best options look like right next to the fuel tank on the port side (which is basically unused space) or in the lazarette next to the water heater. Any preferences?
 
Oct 7, 2008
378
Oday Oday 35 Chesapeake Bay
I have my starter battery in the port side Lazzerette. I also have 4 six volt golf cart batteries in front of my fuel tank.
 

dmax

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Jul 29, 2018
969
O'Day 35 Buzzards Bay
Wow - you wouldn't happen to have a picture of them would you?
 
Oct 7, 2008
378
Oday Oday 35 Chesapeake Bay
I looked back in my picture but can’t find one. I think I posted something related to this in the past with a picture. You could do a search on my posts. I’m going back to the boat on Monday. I’ll get one then.
 
Aug 17, 2010
311
Oday 35 Barrington
I have a house bank of two Group 29 Duracell batteries (120 AH each for a total of 240AH) and a Group 24 start battery (it's PLENTY of power) mounted under the aft quarterberth. I built a mounting platform out of G10 which I tabbed into the hull to keep them level and to provide support for the retaning straps. I love that I can check the electrolyte level without having to crawl into the lazerette, or open the door into the engine compartment. This also allowed me to mount the batteries so that they would be better positioned to keep the plates submerged in electrolyte when heeling. Each battery sits in a battery box, and is strapped down.

The picture below shows them disconnected from the boat's electrical system (and connected to a Battery Tender) for winter storage. There are covers over all of the positive terminals when the boat is commissioned.
2018-12-23 10.51.56.jpg
 
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May 6, 2010
472
1984 Oday 39 79 Milwaukee
When we had our 34, I moved the two house batteries to a location under the starboard settee, and put the reserve battery in the engine compartment in front of the fuel tank. Part of the reason was to balance some of the weight on the port side - water heater, range, head...
 

dmax

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Jul 29, 2018
969
O'Day 35 Buzzards Bay
Thanks rajhsn, I looked through your posts (14 pages of them! lots of interesting stuff) but couldn't find the battery pictures.
Eherlihy, that looks like a great place to put the batteries.
 
Aug 17, 2010
311
Oday 35 Barrington
Many people that I have encountered seem confused by the "Start Battery" concept, or worse, have no idea what they are doing when they use the battery switch.

I explain that on my boat the start battery is used like the spare tire, I don't use it unless necessary. I normally start the engine and run all of my house loads (lighting, charging phones and small VHF radios, propane solenoid, 12VDC refrigerator) from the house bank. My start battery is automatically maintained by an echo charger, or when I switch the battery switch to "BOTH" when motoring.

I also maintain a schematic diagram of my 12 volt system as a living document that I keep aboard. Here is an older version as a JPG to give you an idea.
 

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dmax

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Jul 29, 2018
969
O'Day 35 Buzzards Bay
Thanks eherlihy, great diagram, that's basically what I want to do. My plan is to use the house bank like you say, only using the starter battery when the house bank is low.
 
Aug 11, 2011
857
O'day 30 313 Georgetown MD
This is a great subject. I currently have a starter (#2) and a house bank (#1). I am using #1 for everything all the time. #2 is kept topped up with the solar panel. Once in a while I will use it, just to make sure it's in good health.
In anticipation of doing some cruising, the installation of a third battery is on my list of upgrades. To reduce my energy usage I have changed out every light bulb to LED. However there is much equipment which still uses a lot of Amp hours. Interestingly, I recently watched Lady K You Tube video on Amp hours, and now I understand the concept much better. But as always there is a negative side. Having listened carefully, I may need another 100w of solar panel. Ha Ha.
 
Oct 22, 2014
20,989
CAL 35 Cruiser #21 moored EVERETT WA
always there is a negative side.
Now now... That will also need to be a positive side...

Think of the good you will be doing in a micro economics sort of way. You will be increasing the level of consumerism in your local solar panel environ. You maybe stimulating an ecological economy in your area. Such should be prased.
 
Aug 7, 2015
97
Oday 34 previous, O’Day 40 current Annapolis
Two Trojan T-104 in front of the fuel tank ( had to relocate the fuel filter) & starter battery starboard side under the berth.
LouK
 
Aug 11, 2011
857
O'day 30 313 Georgetown MD
Hmm. How would the third battery be switched? On my two battery set up, the switch is #1 or #2, both or off. Is there a Perko set up for three batteries.
 
Aug 17, 2010
311
Oday 35 Barrington
I can think of no reason to have three seperatly switched batteries on an O'day, and I can think of several reasons not to do so. You should simply combine multiple batteries into one house bank, and have a seperate start battery for emergencies... see post #8.
 
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Aug 7, 2015
97
Oday 34 previous, O’Day 40 current Annapolis
Correct, 2 @6 volt batteries. The 6 volt batteries in series allows you to produce 12 volts w/225 ah. Typical parallel installation of 2 Group 24 (75x2=150 ah) or 2 Group 27 (90x2=180 ah) yields ~20% less overall capacity. Since you don’t want to discharge more than 50-60% of your total capacity, the Number of useable ah is far less. This is pretty typical of what many cruisers do.

Battery switch doesn’t change; still use a single 12 v Group 24 for starting & battery #2 is for the house.