We recently purchased a 1996 Carver 325. One of the many projects I’d like to work on while the boat is in storage this winter is upgrading the battery system. I’ve done some reading on this forum to see what others have for battery setups and have an idea of what I think I’d like to do, but I’m looking for some guidance.

Here is some background on our situation:
- Our boat does not have a generator.
- It is currently equipped with two dual purpose batteries located behind an access panel in the aft cabin, and the stock 1/2/both/off switch that came from the factory. Haven’t checked manufacture date, but the batteries are at least a couple years old. One appears to be group 31, 800 CCA and the other is smaller, 600 CCA. A bit odd that they’re different, but the previous owner did more than few things that have left me scratching my head. I’ll feel better about it if we get new batteries and start over fresh.
- 90% or more of our trips will be day trips. When we’re on the hook it will almost always be 12 hours or less. I’d like to have a battery bank with enough juice to run the refrigerator (previous owner put a cheap residential mini fridge in, which I will be replacing with a new Vitrifrigo 12v dc / 120v ac fridge shortly), stereo, and a few 12v accessories. I may add a small dedicated pure sine wave inverter in the salon for an LED tv and other small electronics that shouldn’t consume a lot of power.
- We’re on the western side of Lake Michigan which has pretty limited calm spots for overnight anchorage. On any overnight trips, we will likely be docked at a marina and on shore power, so I’m not worried about needing a generator or large amounts of battery capacity.
- I’d prefer to keep this to a relatively simple project. I’ve entertained a LiFePo4 bank for the house but I don’t think we need it at this point. Maybe I take the plunge when I replace the next round of batteries but not now.

I’m currently thinking of doing the following:
- Leave the charging system and stock battery switch as is.
- Instead of having two dual purpose batteries, one on each position, convert one switch position to a dedicated start bank of two 1000 CCA lead acid starting batteries in parallel (located where the two current batteries are) and convert the other position to a house bank of four 6v lead acid deep cycle golf cart batteries (Trojan T105 or similar) in series/parallel to make a 12v house bank with something like 900 total ah / 450 usable ah. Location tbd.
- I realize this setup requires remembering to change the switch position when you’re on the hook, and may not be ideal, but it seems like it will be relatively easy to reconfigure and should meet our needs just fine.
- We have an aft deck hard top and I’m considering adding solar at some point in the future, but I’d like to see how this goes first. We may not need it.
- I’d also like to add something like the Victron Smart Shunt for monitoring the house bank.

A few questions:
- What are your thoughts on this setup based on our needs? I’m reasonably handy but very inexperienced when it comes to this stuff so it’s very possible I’m overlooking something obvious. Anything I’m missing?
- Any suggestions for location of the house bank? We have a lot of room in the engine compartment because of the lack of a generator. I know that may not be ideal to put them in there because of the heat, but is it safe/acceptable? Based on the owners manual, it appears the stock setup was to have the generator battery in the engine compartment for the boats that came equipped with that option. The battery switch is under the stairs from the aft deck to the salon, and I’d like to keep the cable run as short as possible. I don’t think there is room in the aft cabin to put the house bank unless I put it under the vanity between the beds, which isn’t a terrible option but would eliminate some nice storage space. If engine compartment is a bad idea, I suppose I can sacrifice that storage space and put it there.
- Do I need to worry about off-gassing wherever I put the house bank? As long as it’s vented it should be ok, right?

Any and all feedback is greatly appreciated. Thanks!