Considering adding a third house battery

[Chris_P]

I have checked the archives and there are tons of threads on batteries, but I couldn't find anything on this issue .... I have a 330EC and currently have 2 deep cycle series 31 house batteries.  We plan to do a fair bit of over night tips this summer on the hook.  Will I see a noticeable difference with an extra house battery?

I have an Intelli-power electronic charger with the digital display.  I cant recall the exact model or the AMP rating but it was installed last summer after the factory installed one died. 

I have read many threads about the current draw of the two fridges I have on board so I'm a little worried that I may not have enough power and will have to run the genny constantly.  Any advice would be greatly appreciated.

[Sea Dumpster]

If you have a genset, I am sure that you will be ok, however, if I had a boat your size, I would have 4 group 31s for house power especially with 2 fridges. I have 2 31's and a 29 on my 270 and I would have no less. The 31's power a 2KW inverter and I have an ACR to bridge them with the house battery.

Paul

[Dream 'Inn]

The only thing I will say is that adding another house battery at this point, you will not get full life out of it because of the age of your other batteries...assuming you are connecting it in parallel with the other two?

I'd be surprised if you have issues with only the two 31 batteries.  The real key is to keep your fridges turned down a bit and turn them way down at night.  They don't need to be cranked up all the time.  It will just continuosly run and wear the batteries down quick.  I have two 27's, that are 115-amp-hour rated and I have no problems for 3 or 4 nights on them, just running the generator once in the morning for 1-2 hours and once in the evening for the same.  When the genny is running, I then crank the fridge up. 

I'd say see how it goes this year, since you have a generator.  Then, if you need to, go with 3 new ones next year.

[Chris_P]

Thanks for the replies !  The two 31s are fairly new, they were installed midway through last season under warranty as the ones that came with the boat weren't holding a charge.  I put no more than 20 hrs on them last season.

I will probably go with your advice and give it a try this season with my two 31s and replace next year if necessary.

[Stodge]

I have 2 group 31s for my house.  No inverter, just 1 fridge and I can run the stereo, fridge and lights for the weekend without issue.  I also have a separate battery for each engine as starters.

If your alternators charge your house batteries you may want to look at their capacity.

[themaniam1]

To save energy I replace all my lights including the nav and deck lights with LEDs.  They use a fraction of what the halogens do.  I then turned them all on and they lasted for two weeks straight on the two house batteries.  It was in the garage for the winter so I wanted to do some testing to help with the long winter.  The shore power was not plugged in.  I am sure if I ran the fridge that it would have drained them much sooner but the point is that the LEDs do make a huge positive difference.

[Herm]

I did a little math here and with your setup now you are good for about 30 hours with your set up maybe more or less depending on how you use the lights and stereo and how often you open the fridges. To get your batts back up to full all you need to do is devide 200 by what ever your charger is rated, so if your charger is rated at say 30amp hours you will need to run your gen for atleast 6 hours to get them back to full if you have depleted them.