Carver 325 Battery Setup Help

[tonyp444]

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!

[g36]

I use 6 trojan 105s has my house bank with my 405 they do make a good house setup and mine are mounted in the engine room between my engines along with the other batteries on board. A couplie things to note. Using 4 as you mentioned you will only have. 450 amp total house not the 900 you think. Wiring in series the voltage doubles but capacity is not. The parralel part will double your capacity to apx 450. So useable at 50% is 225 amps. Get a battery monitor, like a victron bmv 712 etc. This will let you know the stste of charge. There will lots of opinions but to keep things simple. You could set the house bank up on one side of the battery switch. It will charge from the engines when running. I see no reason you cant do what your wanting to do.
In my previous boat a Trojan F32 I ran. 4 T105s . I did have a genset. But batteries took care of a day out on yhe water with no problem. I could have gone more but usually every night we would as I do now run my ac to cool the boat and prepare dinner. Thus also charging the batteries too. You can start with your 4 battery bank and if it doesn't meet your expectations add additional. But I really dont see you needing to do that

[tonyp444]

Source of the post I use 6 trojan 105s has my house bank with my 405 they do make a good house setup and mine are mounted in the engine room between my engines along with the other batteries on board. A couplie things to note. Using 4 as you mentioned you will only have. 450 amp total house not the 900 you think. Wiring in series the voltage doubles but capacity is not. The parralel part will double your capacity to apx 450. So useable at 50% is 225 amps. Get a battery monitor, like a victron bmv 712 etc. This will let you know the stste of charge. There will lots of opinions but to keep things simple. You could set the house bank up on one side of the battery switch. It will charge from the engines when running. I see no reason you cant do what your wanting to do.
In my previous boat a Trojan F32 I ran. 4 T105s . I did have a genset. But batteries took care of a day out on yhe water with no problem. I could have gone more but usually every night we would as I do now run my ac to cool the boat and prepare dinner. Thus also charging the batteries too. You can start with your 4 battery bank and if it doesn't meet your expectations add additional. But I really dont see you needing to do that

Thank you, this is really helpful. I wasn’t thinking about the fact that having the house batteries wired in a 2x2 series/parallel would effectively make it a bank of 2 12v 225 ah batteries, so it’s half the capacity I was originally thinking. I like the idea of starting with 4 and adding a couple if necessary. I think if I end up adding a couple, I should do that within the first 6 months or so, to make sure the batteries are all approximately the same age, right?

[km1125]

I'll come back and elaborate later (because I'm short on time right now), but here's my thoughts.

You really don't need "two 1000 CCA lead acid starting batteries in parallel" for the start side. You certainly CAN do this, but to me it's mega-overkill. I'm guessing you have 300HP gas motors, which might specify 800CCA for a battery. 2000CCA would certainly be much more than you need (not a bad thing to have, but IMO, overkill).

I'd MUCH prefer to put a dedicated battery to each engine. Perhaps dedicating each of those 1000CCA batteries to an engine. That way there's complete isolation, but you can add a "paralleling" feature for jump-start assistance. That takes the house bank completely out of the starting circuit, even for backup purposes. You never have to worry about the A-B switch being left in the 'wrong' position.

Then, for the house bank. For what you describe, even just TWO golf-cart batteries in series would likely do fine for your application and provide quite a bit of power for running stuff for 12 hours. I used two like his on a 36' for over a decade, using it in a similar manner as you describe. Having four as the house bank would also be great too if you have the room. Mounting in the engine room is acceptable, as that is typical with most boats. Putting the batteries in a cooler spot is desirable if possible, but on most boats it's just not an option.

[tonyp444]

Source of the post I'll come back and elaborate later (because I'm short on time right now), but here's my thoughts.

You really don't need "two 1000 CCA lead acid starting batteries in parallel" for the start side. You certainly CAN do this, but to me it's mega-overkill. I'm guessing you have 300HP gas motors, which might specify 800CCA for a battery. 2000CCA would certainly be much more than you need (not a bad thing to have, but IMO, overkill).

I'd MUCH prefer to put a dedicated battery to each engine. Perhaps dedicating each of those 1000CCA batteries to an engine. That way there's complete isolation, but you can add a "paralleling" feature for jump-start assistance. That takes the house bank completely out of the starting circuit, even for backup purposes. You never have to worry about the A-B switch being left in the 'wrong' position.

Then, for the house bank. For what you describe, even just TWO golf-cart batteries in series would likely do fine for your application and provide quite a bit of power for running stuff for 12 hours. I used two like his on a 36' for over a decade, using it in a similar manner as you describe. Having four as the house bank would also be great too if you have the room. Mounting in the engine room is acceptable, as that is typical with most boats. Putting the batteries in a cooler spot is desirable if possible, but on most boats it's just not an option.

Thank you. This all makes sense. I agree what you described is a better setup, but at this point I have a pretty strong preference to keep the stock battery switch and charging system as is. I may eventually go this route, but right now I’d rather not deal with having to rewire chargers, add switches, change out the cable runs to the 12v panel, etc., especially because this is my first project of this type. I’d rather keep it as simple as possible and maybe I bite off a bigger upgrade project next time around. I’d just like to make an improvement over what we have today. Your point about the starting batteries being overkill is a good one. My thought was that we have room for 2 batteries in the compartment where they’re currently located (if I put the house bank elsewhere) and having more juice is better than less. But I think 800 CCA is fine with our engines. If I go with what I described, two 800 CCA starting batteries in parallel is probably still way more than enough. I guess I don’t really see a downside to having 2 starting batteries instead of 1, aside from the cost and the additional weight. I think 2 starting batteries would be nice for peace of mind.

[bud37]

Imo...your plan is fine. Larger start batteries may be overkill a bit, but remember if your engines are controlled by an ecu they will be more happy. The reason being, that circuit needs to have your windlass on it as well as some bilge pumps. It is good to check these draws first and realize which switch position they are drawing thru.

The house bank will be fine on lets say switch POS. #2 but check your wiring/cables. Good idea about the shunt.

Off gassing from lead acid batteries should always be minded. I built a battery box to house the house bank with a lid. Attached a vent hose to the lid and connected it to the discharge side of the bilge blower line. Hydrogen is light so will passively vent when being heavily charged.

Find out what boat loads are on what switch position before you decide. I have done the same and it works fine, only caveat is it is all manual, label the main switch , that may not be a bad thing though....

[tonyp444]

Source of the post Imo...your plan is fine. Larger start batteries may be overkill a bit, but remember if your engines are controlled by an ecu they will be more happy. The reason being, that circuit needs to have your windlass on it as well as some bilge pumps. It is good to check these draws first and realize which switch position they are drawing thru.

The house bank will be fine on lets say switch POS. #2 but check your wiring/cables. Good idea about the shunt.

Off gassing from lead acid batteries should always be minded. I built a battery box to house the house bank with a lid. Attached a vent hose to the lid and connected it to the discharge side of the bilge blower line. Hydrogen is light so will passively vent when being heavily charged.

Find out what boat loads are on what switch position before you decide. I have done the same and it works fine, only caveat is it is all manual, label the main switch , that may not be a bad thing though....

Thank you. This is probably a dumb question so please excuse my ignorance but when you’re talking about the draws and which position they’re on, you’re referring to draws that can bypass the main battery switch, right? For example, for safety reasons the bilge pumps will operate if the float is tripped even if the battery switch is turned off. In order to do that, they are hard wired. That hard wired circuit that bypasses the switch for the auto bilge pump operation is presumably wired to battery position 1 or 2. I know there is a separate fuse/breaker for each of those hard wired circuits next to the main battery switch. My understanding is that if the bilge pumps are manually activated by turning on the bilge breaker(s) on the 12v panel and flipping the helm switch, they will be powered by whichever battery position is selected on the main battery switch at that time, and I don’t think that’s what you’re talking about. So I should check to see which position those hard wired circuits are on? And would the answer to that question determine which position I would want to use for my “start” vs “house” banks? Apologies if I’m misunderstanding.

That’s a good idea on venting the battery box with a hose vs just having the hydrogen gas floating around in the engine compartment. How did you splice it into the blower exhaust hose, and is there anything special you need to do to prevent the fumes that the blower is extracting from backing into your battery vent hose?

Thanks again, I greatly appreciate all the help!

[bud37]

Yes....you just have to find out which bank these hard wired draws are pulling from including the big one, the windlass....that is the circuit I chose to call start.....then the other would be house. I think you have got the idea.
The switch position does not control those hard wired draws. You just don't want the windlass on the house bank, still a good idea to check cause ya never know what someone has done before ......

You could just run the small hose up to the discharge vent to let it passively clear....easy enough.

Hope this is clear as mud now......

[Viper]

Nothing wrong with the way you want to approach this. Knowing that the setup isn't ideal is good to know, at least you know that and can take measures to ensure it won't affect your boating and that it's something you can improve upon at a later date as you reassess your needs or get some other projects out of the way first. As long as you manage that battery switch properly, you should be good.

Installing the batteries in the engine compartment is acceptable as long as it's done right, you have proper ventilation, and that all your hardware in that engine bay is ignition proof. Mount them low, secure them properly, use marine cable and connectors, and cover the terminals. Having them in trays is okay, as long as they are properly strapped but putting them in boxes also affords the ability to contain battery fluid should the battery crack for any reason.

[tonyp444]

Source of the post Yes....you just have to find out which bank these hard wired draws are pulling from including the big one, the windlass....that is the circuit I chose to call start.....then the other would be house. I think you have got the idea.
The switch position does not control those hard wired draws. You just don't want the windlass on the house bank, still a good idea to check cause ya never know what someone has done before ......

You could just run the small hose up to the discharge vent to let it passively clear....easy enough.

Hope this is clear as mud now......

Got it, all makes sense. Thanks again!