Battery size

woodster · Apr 9, 2015

Matpearce said:
Hi I have just sorted out that my boat has come with two starting battery's not one starting and house
I know this is a bit of a open ended question but what size amp hour house battery are people running
I Use a small solar panel on board
Normally away on trips between 3 and 7 days Not sailing a ocean
Cheers mat

it would help us help you if you would be a little more open with your information ...as kind of boat and size and what you have on board in the way of 12vdc appliances and gadgets along with the lighting infor weather it be incandescent or led ...there are a lot of variables that determine what you may or may not need ...even how you will be charging those batteries and also what kind of batteries...agm,gel, and wetcell

Don S/V ILLusion · Apr 9, 2015

It's like asking how much water you need but not knowing how many people are onboard.
Also, no engine requires two starting batteries. Sounds like you have the boat designed to run all loads incl. engine from a two bank set of starters.

JK_Boston_Catalina310 · Apr 9, 2015

Mat,

Here are a couple of things that will help you.

First, here is a link to all of the electrical system upgrades I have documented on my blog. A lot of these are related to charging systems (solar, shore power, alternator, etc.) and batteries.

Here is a link to my power consumption worksheet. Your boat should be similar but probably not exactly the same. If you PM me your email address I can send you the excel spreadsheet versions so you can update it for your boat.

Here are two articles from Maine Sail's Site that you have to read before buying batteries: Installation & Orientation of Flooded Batteries; What is a "Deep Cycle" Battery.

Now some basics; you could find this info by searching through Maine Sail's forum here and his website but I will try to save you some time.

You DO NOT need a dedicated starter battery. Small diesel engines can be started just fine off of a deep cycle house bank. I have been doing it for several years on our C310 with no issue. Plan a large house bank with a small reserve bank.
You cannot fit 4 6V golf cart batteries and a group 24 battery in our battery area without compromising orientation.
You will likely need to upgrade your shore power charger. The factory one that came with my boat was a dumb Flyback, 20A charger. Bad news for your batteries if you want longer life from them.
Read Maine Sail's post here on the 1/2/Both/off switch if you want to upgrade your whole system to work better.
While AGM and Gel batteries are appealing due to the orientation issue, I recommend sticking with flooded batteries. Or being prepared to spend more time and money learning how to maintain your system. Here is a start if you want to go this way.
Learn the basics of flooded battery maintenance if you do not already know this: regular watering, checking the electrolyte levels, equalization, etc.

If I were in your position, I would probably look at either two 12V golf carts (155 Ah each) in parallel for a bank of 310 Ah or two 6V golf carts in series for a bank of 230 Ah. I estimate that we use around 50-120 Ah per day just hanging out on the boat. Running the alternator for about 1-2 hours a day should keep you charged enough for the type of cruising you listed. A group 24 will do fine for the reserve bank; go with the "deep cycle" not the starter or dual purpose.

Hope this helps.

Good luck and fair winds,

Jesse

JK_Boston_Catalina310 · Apr 9, 2015

Woody and Don,

Don't forget that Mat asked about what a Catalina 310 needs for batteries on a Catalina 310 forum. While I would agree that this question is too open ended in the "ask all sailors" or other sections of the page, it's not that open ended on this section.

Fair winds,

Jesse

KZW · Apr 9, 2015

Matpearce,

I have two 4D wet cell batteries, that appear to have been the standard C-310 fit. The PO installed them in 2013. I believe (not positive) they are in the 150 to 170 Ah range. When they die, I plan to go to four 6V golf cart batteries, two in series for each of the two banks yield 230 Ah each. It is my fondest hope they don't die for a considerable spell.

c130king · Apr 10, 2015

My boat has 2 x 4D batteries. They have 135 AH each. And the set up is that the battery switch selects either battery 1 or 2 and that selected battery powers everything including the starter. Do not have a dedicated starting battery.

On even days of the month I use battery 2. On odd days of the month I use battery 1.

Last set of 4D's...can't speak to the "quality" as I am not a battery expert...lasted about 5 years. I use my boat a lot...but mostly day sailing with occasional 3-5 days trips...but even then I am on shore power at least 1-2 of those days.

My batteries cost about $140 each. I do check water levels and specif gravity every month to hopefullly catch issues before they become too serious. Did have one battery lose a cell after about 2 years and I got a partial warranty payback applied to the new battery.

Works great for me. See no reason to change at this time.

Cheers,
Jim