Odd sized battery conundrum

[weinie]

My boat came from factory with three odd sized batteries. The batteries are Exide ER350 model and apparently they fall under the Group D26 category. They are each 80Ah "dual purpose" batteries with 2 in parallel for the house bank and 1 for the starter.
They are arranged in a plywood framed battery box as shown in the attached picture. My problem is that these batteries are an odd size. Each one is 10.24" long x 6.89" wide x 8.88" high. As you can see in the picture there is no room whatsoever to go any larger here without doing carpentry work or relocating one of the batteries completely.

The boat is kept on a mooring and I throw on a 50w solar panel (and controller) on the house bank to keep it topped off for weekend. The starter battery is maintained by the alternator only. My sailing is mostly day sailing with some weekend cruising so I'm not looking to live off these batteries. I keep the fridge off so the use is mostly electronics and LED lighting.

At this point I have no real need to redesign the whole system at this time. My concern is that should my batteries need to be replaced, I will not be able to source these european sized batteries here and I can't find a flooded or AGM battery here that would fit in the same space!
I am wondering if anyone has any ideas of how I could get at roughly the same amount of power in the same size volume of space!

 

[rpwillia]

Are they lead acid or something else? I found this online http://shop.advanceautoparts.com/p/autocraft-automotive-battery-group-size-26-450-cca-26-2/2070030-P

 

[Benny17441]

I would do some carpentry work when the time comes to fit Group 27 size batteries. I would also replace all three with deep discharge batteries of around 105 Ah each. Would keep one as a starter and two for the house bank connected by a 1,2,All,Off switch. Dual purpose batteries will not offer the same number of discharge/charge cycles for the house bank and at 80Ah you are giving away 20% capacity. I favor flooded batteries as for me it is important that if I need to replace a battery while on a trip that I can go to the nearest retailer along the way and be able to use what they may have in stock. I also will not feel as guilty ($$) if I need to abuse them at any given time.

 

[Gunni]

Dedicate that box to House batteries and place a small starting battery in a secured box near the engine. Retain the ability to combine the batteries for emergency starting, yet isolate the starting battery as Plan B. AGM's can be oriented at odd angles to fit the space.

 

[weinie]

I thought about that but the problem then is still the height. You can see in this picture that the cover actually has cutouts to fit the battery posts!

 

[Gunni]

You have lots of room in the compartment holding your charger. If you moved the divider out 2-3 inches you could install 3 Lifeline GPL 31T batteries, possibly GPL 31XT's. Try blocking that cover .75" and see if you even notice with the cushion installed. That would give you between 315 - 375 Ah's. That seems more appropriate for a boat your size.

AGM's would be the only battery I would place in my cabin.

 

[weinie]

Gunni,
I figured that was the way I was going to have to go, though I was hoping for a more "plug and play" approach at this point.