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Discussion Starter #1
I made a video ... may be simpler+faster to just watch it:
https://youtu.be/BzgpzcdaySI

However, I'll also try to describe the situation in words.

1979 Tartan 37. As far as I can tell, it originally had 2 batteries. A previous owner upgraded to 4 batteries by adding 2 to the storage compartment under the quarterberth.

The problems with the current setup are:
* Old battery box hides one battery underneath a panel that makes it difficult to service the battery
* New battery location interferes with access to the engine (particularly in the way when trying to change the oil filter)

I'm considering moving the 3 house batteries up under the settee. This will involve a lot of rewiring and modifications to the new compartment. I'm leaning heavily toward doing it, but looking for input in case there's some angle to this that I'm missing.
 

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I believe the battery system would be a lot more efficient if all the cables were the same length, which it sounds like your new plan would achieve. Keep in mind that when a battery out-gasses those fumes are explosive, so proper venting of the compartment (under the settee in this case) is a must.
Anything on a boat that is easily serviced is going to be serviced more regularly, which is a good thing.
 
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You can buy remote battery filler system so you can fill batteries without having to pull them out to do it. 2 of my four batteries are buried under furniture. To even check the liquid level had to pull out two batteries and then slide the other two into view. The remote fill system has taken care of that and made servicing the batteries a pleasure. https://www.rvupgradestore.com/RV-Battery-Watering-System-p/55-8752.htm
 

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bell ringer
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I feel the battery cable length thing is an "on paper" item with the low loads boaters place on batteries. I also feel that gassing is a minor thing if you are charging properly and not running a big load like an inverter. Just saying, not fighting.

Far as moving the batteries, only the OP can say whether the work is worth it in the long run to him. But I would say it is based him asking the question.
 

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Also consider what moving that weight will do to the trim of the boat... permanent list? Can it be offset by moving other items typically stored?
 

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Bill, I have no idea what a T37 looks like inside. But what does that entire compartment look like when reassembled? Is there anything structural or functional about it, or could you literally just remove the current battery compartment and rebuild that area with something that allows the installation of batteries all in the one place. Presumably there's no usable space on the other side of the engine either?
 

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Discussion Starter #8
Bill, I have no idea what a T37 looks like inside. But what does that entire compartment look like when reassembled? Is there anything structural or functional about it, or could you literally just remove the current battery compartment and rebuild that area with something that allows the installation of batteries all in the one place. Presumably there's no usable space on the other side of the engine either?
The port side is my diesel tank, so there's not usable space there (except for storing diesel ... obviously).

Ripping out the existing stuff that the batteries mount to doesn't help me much, as far as I can see. Basically, I can't come up with a more efficient way to store the batteries than is already there. That compartment is oddly shaped because the bottom is the outer hull (and thus curved). Moving the batteries forward where I actually have a square compartment seems like better use of space to me. I can then tear out the existing battery supports and have more space for smaller items.
 

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Discussion Starter #9
Also consider what moving that weight will do to the trim of the boat... permanent list? Can it be offset by moving other items typically stored?
I doubt it will have any effect on the list of the boat ... they'd be moving from the port side to the port side.
 

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Discussion Starter #11
How old are the batts you have now?
They're fairly new ... should have a few years of life left in them, assuming I take proper care of them. Given all the other work I'm doing on the boat, I'm avoiding replacing them this year. I want to save up and go with the best battery chemistry available when I do replace them, and that's going to be a strain an already strained budget this year.
 

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They're fairly new ... should have a few years of life left in them, assuming I take proper care of them. Given all the other work I'm doing on the boat, I'm avoiding replacing them this year. I want to save up and go with the best battery chemistry available when I do replace them, and that's going to be a strain an already strained budget this year.
My 1st thoughts...
Leave it in place because you are going to 'something new' later/2 yrs?, plus you have many other things you will be doing in the interim.
Many things on the boat won't be what you really want later, or 'think' you will want later, but you probably have tons of real projects needed and other ideas on improvements that can be addressed.

If it works now, maybe look at other things that...bother you more.

If it ain't broke...find something else that is...

...edit: 'later on' you will prob need 1/3rd of the batt space you now have to meet your needs
 

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Best battery chemistry?
You might want to hide your credit cards and then define "best". Right now that would be lithium, if best means "performance". That would also give you well more than double the power capacity in the same space--meaning the existing box would be big enough.
If "best" means most economical...wet lead still does that, short term. If the amusing claims for number of cycles for lithiums are correct, they'd come out as "best" for long term price, too.
It was just unclear from the pix whether removing the woodwork might clear up enough odd space to allow for more batteries in the same larger space. And then, if you can shelf out over the curve of the hull, that might also expand things. Or, dare I mention that AGMs have their pros and cons, but being installed off-level is one of the big pros.
And if your starting battery is really just used as the "who left the stereo on?!" emergency starting battery, it can be surprisingly small and light, so that also opens alternatives. House banks really don't mind engine starting as a routine duty.

Moving the batteries all forward (and that means all, if you want them all to charge at the same voltage) means heavy cables, or compensating for voltage drop in the cables, and of course running a vent hose out someplace. Not impossible, just would seem "better" if you could keep them by the engine.
 

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Discussion Starter #14
Best battery chemistry?
You might want to hide your credit cards and then define "best". Right now that would be lithium, if best means "performance". That would also give you well more than double the power capacity in the same space--meaning the existing box would be big enough.
If "best" means most economical...wet lead still does that, short term. If the amusing claims for number of cycles for lithiums are correct, they'd come out as "best" for long term price, too.
It was just unclear from the pix whether removing the woodwork might clear up enough odd space to allow for more batteries in the same larger space. And then, if you can shelf out over the curve of the hull, that might also expand things. Or, dare I mention that AGMs have their pros and cons, but being installed off-level is one of the big pros.
And if your starting battery is really just used as the "who left the stereo on?!" emergency starting battery, it can be surprisingly small and light, so that also opens alternatives. House banks really don't mind engine starting as a routine duty.
All good advice.

Given that the existing batteries have been functioning well so far, I'm planning to hang on to them for the next few years for a few reasons. One of those reasons being that I've only used the boat as a weekender so far, and once I live aboard full time, I assume my power usage patterns will be different, so I can't really be sure exactly what I need in terms of battery until I have some experience.

AGMs, Fireflys, lithium ... these are all things I've been keeping my eyes on. I'm no expert yet, and the technology is liable to change over the next few years anyway.

But right now, I have the current refit that I'm working on, and I'm trying to figure out what it makes sense to do in the short term.
 

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Solid thinking. sounds like you have a handle on it. So much, so fast...

Maybe slide to the back burner for a while...then look at it again later...
 

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There has always been a "miracle chemistry" in development. I think the latest one may be from Toyota with an equally (arguably) reputable partner, not one of those "Investors click here" companies. Supposedly two or three years out, although that often turns into dog years.
Looking around when your batteries are going into their "this will be the last" year, absolutely a good way to go.
Me, I've been waiting around since 4th grade, when Reddy Kilowatt promised us all we'd have domestic nuclear reactors the size of home hot water heaters, and never need to buy electricity again.
 

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AGMs, Fireflys, lithium ... these are all things I've been keeping my eyes on. I'm no expert yet, and the technology is liable to change over the next few years anyway.
It's usually better to assume battery technology will not revolutionize in the next five years. Lithium Ion (LiCo) batteries got all their patents wrangled out in the late 1980 and went into commercial production in 1991. Not "announced". Not "coming real soon now". Commercial production, as in you could just order some and they'd show up, in pallet-load lots, ready to be encased in whatever your product was. 20 year later or so, you start seeing widespread people putting them in boats because finally everybody knows enough about them to actually build working reliable power system around them and how to make them last for years and years. Lithium iron phosphate (LiFePO4, LiPO) batteries got their patents wrangled out in mid 2000s, and as of about 2013, they've been in commercial production for a few years. So you'll start seeing those getting widespread adoption on boats in like... 10-15 years. And that's the most PROMISING replacement, with much more charge-cycle life, steady voltage output through almost the entire charge range, safer when physically mishandled than "regular" lithium ion, at a cost of (currently) slightly lower energy density and avoiding over or under charge situations being a "Avoid this, it will cause fires" circumstance rather than the "Avoid this, you'll wreck your battery, no really" of AGM and LiCo, and the "Avoid this, you'll take months off the life of your battery" of flooded acid.
 
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