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Group 24 vs. Group 27 Batteries
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Author:  M3eater [ Thu Jul 09, 2009 9:02 pm ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
I've never seen Maxx 31s at WalMart. The 29s are about $80. These are 125-AH (as I recall), at a discharge to a level of either 80% or 75% charge. Two of these is quite nice for overnight, they stay well above the 80% charge point (for our usage anyway). If you discharge a deep-cycle battery below 80% it will start to shorten its useful life cycle. That's why you want more AH capacity than just what you calculate as your usage over a period of time.

On the 268V, the starting battery is just running the engine systems. The CO monitors run off the house and are shut off when the breaker switch for the house systems is off (the toggle switch just above the battery switch). When you run the battery switch in the "on" position, just the engine systems are live.

Charging, be it alternator or the on-board charger, hits all of the batteries regardless of whether they are on or off.
Author:  cougarcruiser [ Thu Jul 09, 2009 9:08 pm ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
The systems in my 318 are isolated the same.

FW was gracious enough, however, to give me a single house battery (probably because I have a generator on board).

I need enough juice to safely overnight with 2 fridges, a tv or radio for a while, some lights, and the vaccuflush.

Will twin group 29's do it?
Author:  M3eater [ Thu Jul 09, 2009 9:17 pm ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
You are pretty much running two of my boats, when you're on the batteries. You may wish to use three, if you want to be assured of not having to run the generator (except for 120-v stuff), and keep the batteries in their upper charge range.

If your CO detectors ever start chiming, due to low charge ... you're at about 10 or 10.5 volts ...... way below the 75% mark.

I plan on adding one more 29 house battery, on the other side of the engine compartment, for a total of three (will help the balance as well), so that we have all the power we want, and I can also install an inverter for some A/C power. We don't have a gen.
Author:  firecadet613 [ Fri Jul 10, 2009 3:32 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
Have any pics of your battery set up Gordon?
Author:  millhaven_nice_guy [ Fri Jul 10, 2009 7:18 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
When I rewired my batteries last year I went with a single starting battery and wired the two group 27's in parallel for my "house" use. Ideally I want everything to run on either battery that is selected so I can use the "house" batteries when floating and have the starting bat as my complete and full backup. Unfortunately, the fridge was wired directly to the #1 battery lug at the switch so it always had power! It took me months to figure out what was constatntly draining my starting battery! I only found out because I went back to the fridge for something after I had turned off the bat switch and the light came on!
Author:  M3eater [ Fri Jul 10, 2009 7:31 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
Here ya go .... it's dirty ... :(
The one closest to the engine is the engine battery, the two house units are behind.

(you made me late for work ..... :wink: )

Image

Image

Image
Author:  cougarcruiser [ Fri Jul 10, 2009 8:13 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
2 Group 31 Optimas (D31Ms) will run me almost 400 bucks along.

Anyone have a good recommendation for a couple of good Group 31's that don't cost $200+ each?

Otherwise, I'm tempted to try a couple of 29s and see if that solves my lack of overnight capability...
Author:  Cap'n Morgan [ Fri Jul 10, 2009 8:36 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
Will your battery boxes accomodate a Group 31?

Sometimes Sears will have Group 31's at the store. If not these Group 29's should work.
http://www.sears.com/shc/s/p_10153_1260 ... le+battery

Also, try your local Napa, Costco or Sam's Club.
Author:  M3eater [ Fri Jul 10, 2009 9:23 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
29 & 31 are the same size, at the base (as I recall).
Author:  Cap'n Morgan [ Fri Jul 10, 2009 9:31 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
I found:
Group 29 = 13L x 5W x 8-15/16H
Group 31 = 13L x 7W x 10 H
Author:  cougarcruiser [ Fri Jul 10, 2009 9:47 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
The Optima D31m specs to fit in a Group 27 battery box.

Regardless, I would need to buy one new tray anyway - so I might as well just upgrade one of the other ones if I go that route
Author:  M3eater [ Fri Jul 10, 2009 10:57 am ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
Cap'n Morgan wrote:
I found:
Group 29 = 13L x 5W x 8-15/16H
Group 31 = 13L x 7W x 10 H


Thanks Cap ..... I had just recalled that the mount bases are typically sold as 29/31.
Author:  firecadet613 [ Fri Jul 10, 2009 7:51 pm ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
Thanks for the pics. How hard was it to install the extra batt and rewire everything? If I did this route, I figure I could get one group 29 for now, and leave the 2 24's to be house batts until I need to replace them, then go 29s. I do have a built in gen on this boat though...
Author:  cougarcruiser [ Fri Jul 10, 2009 8:01 pm ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
I don't think you will pair 2 different sized batteries on a single bank.

First question is how is your boat wired. If you have 1 isolated engine battery, and one isolated house battery - it's alot easier. If that's the case just run parallel battery cables from the house battery to the 2nd house battery. That should be sufficient?

If you are dual batteries wired on a switch that parallel's them when 'both' is selected - that may change things up a bit. I'm not sure how that would work other than setting up an isolated battery on a switch for the engine. Then use that switch to run 2 house batteries.

thoughts?
Author:  M3eater [ Sat Jul 11, 2009 12:09 pm ]
Post subject:  Re: Group 24 vs. Group 27 Batteries
Fire's boat will have the house batter on an isolated circuit and the engine battery on another.

Simply add the second house battery in parallel with the first one.

DO NOT put different sized batteries in parallel for the house (I don't think he was saying that's what he would do). This will not cause any safety issues, but will seriously hamper the capacity of the system. In very lay terminology, you would have two 24s (if you did a 24 and a 29, for example). It's not really that simple, but you can sort of look at it that way. And, the larger battery may not ever get fully charged.

Using two different sizes on the two different circuits (engine & house) is fine.

As for my set-up, I removed everything, cleaned up the area, sealed the original screw holes (from the battery mounting plates), and then mocked up the mounts, for fitment. Once I was sure all would fit (watch out for items in the back of the area (don't remember what they were), that may be clear on the mounting bases, but would hit the batteries once they are installed (measure the battery height as well as the foot-prints). Pay attention to how you will run the cables ... make sure the existing cables will reach the intended post locations. Figure out your positive and negative jumper cables. I made mine, so they were just right vs pre-made cables.

Make sure you don't get the engine and the house cables confused.

Once you're happy, mark the screw locations for the mounts and then drill them. Use stainless #12 self-tapping screws (fill the hole with sealer before inserting).
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