Need diagnostic ideas for house battery life

Stodge

Had our first weekend on the hook over Labor Day.  My brand new pair of group 31 deep cycle batteries could not keep the fridges running past the first night.  I plan to get in the bilge and check them to make sure I didn't lose a cell on one already.  Otherwise I'm running out of ideas for trying to figure out why they won't keep my fridges running for very long.  I didn't have the stereo on.  Very little is using the house aside from the LED lights in the cabin, and even those I kept on at a minimum.  I ran the genny a couple times for 30 minutes and had the battery charger on.  I also ran the engines for 30 minutes to try and juice them up.  That got me up to about 12.4 volts but they were down to 11.8 in a couple hours.

I checked and cleaned the battery terminals when I switched batteries.  I replaced the parallel jumper for the positive terminals as the old one was not in very good shape.  I've reached up to where the house connects up to the breaker on the battery panel and it's tight.  

Wide open to other ideas on figuring it out.

Dream_Inn

I'll say the first thing you want to do is keep the battery above 12.2 Volts.  That is around 50%.  Now, the way to do that.  When you run the genny (& battery charger), run it so that you are fully charged (over 13V).  From 50%, this will take anywhere from 2-4 hrs.  & if you want, while running the genny, turn those fridges up a bit.  When you are charged, shut down genny, put fridges at normal setting.  You should be able to get a solid 8-10 hours with the usage you are stating.

It's important to actually use the "deep" cycle part of your battery by getting fully charged and then taking it down to 50%, then charge all the way back up.

Here is a site that has some really good info (about half way down in the deep cycle portion).  

https://www.solar-electric.com/learning-center/deep-cycle-battery-faq.html/

This past weekend we were out for 4 days on the hook, I ran my genny for about 6-7 hours a day (morning for 2-3 hours, evening for 3-4hrs).  I don't adjust my fridges anymore, but I know it did use to help on regular batteries.  Now, my batteries are TPPL along with the newer charger, so they charge very fast and definitely hold much better than even regular AGM batteries.

Stodge

I looked up the specs on the fridge down below and my batteries.  After applying a little math it looks like I should only expect a maximum of 20 hours (more likely 12-15) of battery capacity for 1 fridge.  The cockpit fridge is smaller and "should" use less.  I guess my options are use 1 fridge and charge more often, or use both and charge a lot more often.  

Handymans342

How many amp hours are your batteries?

GMSLITHO

I shut my fridge off sometimes for a hour or so when Im out if your not in and out of it all day it keeps pretty cold

Stodge

Handymans342 said:

How many amp hours are your batteries?

Both batteries are 105 amp/hour according to the label.  So I'd expect 210 amp/hours total.  The galley fridge draws 4.6 amps.  Gonna guess the cockpit fridge is close, say 3 amps.   201/7.6=27.6 hours.

Dream_Inn

So, half that for 50% life.  13 hours with just the two fridges.  I can get a good 10 hours on mine and read 12.4V (usually in the morning) with just my fridges on over night.  You will have other things drawing a low amount of current (CO detectors, Mercathode, Generator - digital display for a bit & it's electronics) and radio takes quite a bit when on.

Michael T

As I have advised mt Rinker colleagues for years, if possible go TPPL......great choice DI!

If you have two series 31 AGMs hooked-up properly and charged  as per  DI's notes you will do well. 

That said, @Stodge.....want to really bump-up your battery run time?  Add a a third series 31 AGM. That will give you a geometric (as opposed to arithmetic) advantage.

Handymans342

Check out Battle Born lithium batteries. I will be installing these with a solar system. I am also looking at adding 2 Tesla batteries also. 

Stodge

Thanks for all the advice.  I'm also looking at 6V batteries in series.  I think I'll table any purchases till next season.

Liberty44140

I use two grp 29 deep cycle for house. They are not AGM/Gel. I am fine for 8-10 hours over night but similar to DI I would run the genny more often. 90 min in the morning, 60 min mid day, 60 min during cocktail hour, 60 min before bed....really whenever we are on the boat I run it for an hour to juice up and cool the cabin. 
Stodge - did you try turning the fridges off to check the voltage without load? When both fridge compressors are running the load makes my board guage say something much lower than reality.

Stodge

Liberty44140 said:

I use two grp 29 deep cycle for house. They are not AGM/Gel. I am fine for 8-10 hours over night but similar to DI I would run the genny more often. 90 min in the morning, 60 min mid day, 60 min during cocktail hour, 60 min before bed....really whenever we are on the boat I run it for an hour to juice up and cool the cabin. 
Stodge - did you try turning the fridges off to check the voltage without load? When both fridge compressors are running the load makes my board guage say something much lower than reality.

That's on my list of things to do.