26M - Battery Compartment?

[Idiotfool]

Greetings! I’ve finally gotten my motor lift repaired/replaced and I’m getting to be able to take the boat out, again. Weather isn’t cooperating, though, so I’m contemplating projects.

What does the battery compartment look like in your 26M? Mine had a little battery cushion, but the battery doesn’t have a box and the strap lets the battery move more I’d have expected. I’m curious what others have to keep things stable.

Also, I took the battery out to trickle charge in the garage... holy crap, that bugger is heavy!

[NiceAft]

I have two batteries in that compartment (a starter, and a house). I wedged sheets of styrofoam, between, and around to stabilize.

[adudinsk]

I glassed in 2 shelves of 1/2 " plywood, one under the aft kitchen table seat... and one under the aft hatch under the kitchen sink
This way the 2 batteries were balanced on each side of the boat. (yeah.. I measured it all out.)
Used larger batteries instead of the #24.. I went #26..just standard wet cell .. not AGM or other types. Friend owns a battery sales company.. said don't bother with AGM.. not worth the extra $$.. we will see..

I then installed a battery box and strapped in the batteries.. Although the cover was about 1/2 too big.. so no cover for the box.
Installed an A/B switch.. dual charger..bus bars..etc.etc. All the switches etc went under the entrance ladder where the old battery location was.


AD

[Be Free]

Assuming Flooded Lead Acid batteries, they should be in a box to prevent electrolyte spillage and the box should be fastened so that nothing moves around. It can be a home-made box as long as it will contain the electrolyte (acid). Glassing a piece of wood to the floor to level the spot where the battery will and maybe another small piece to attach the strap to is a good idea.

[JeffJuneau]

I have two group 24 batteries squeezed into that 26M compartment; the minimum required for a DF70A. As far as I can determine, I have the setup that came from Blue Water Yachts in 2009/2010. There are two stainless steel brackets that hold each battery in place against the headboard area of the rear birth. They are clamped in so securely that the batteries would not fall out if the 26M was inverted. I don’t see any evidence that there was any battery box with that original installation, though I am the 5th owner. With all the sloshing around and heeling, it would be nice to have some containment, but it would interfere with installing the batteries and getting access to the wiring. It is cramped enough in there to begin with.

[Be Free]

A full box is not required by ABYC standards but they do require that lead acid batteries be in an enclosure that will contain incidental electrolyte leakage taking into account the expected angle of heel or acceleration (more of a powerboat thing ).

[JeffJuneau]

Thanks for this information Be Free. I wouldn’t be aware of the existence of ABYC standards if it were not for this forum and that is just another example of how helpful Mac sailors.com, has been for me. It wouldn’t surprise me if my AC and DC electrical system is not compliant with ABYC standards in other areas too. I am acknowledging that I am stumped about how to solve the battery spillage containment risk in the 26M battery hold given the minimum cranking capacity and size of the lead acid batteries required for a DF70A. The length of the required group 24 batteries (side by side) exceeds the length of the opening of the battery hold. You have to put one battery in, and slide it all the way to the extreme side of that bilge area, to make room to insert the second battery. Then they are centered and clamped against the forward birth head-wall. I am not a good enough engineer or fabricator to know how to solve the problem of having two group 24 batteries in that space inside a fixed battery box without a lot of fiberglass work that I am not really up to. Maybe if someone made a perfectly fitted polyethene tray that would fit the whole area needed to slide the batteries around in the battery-hold and told me where to buy it, I could handle that. Did I mention that the height available is a problem too. From the top of the terminal-mount fuses on each battery, there is only 1/4” of vertical clearance left. No room to put a box or tray of any significant thickness in that space. Also, these batteries are insanely heavy, and I don’t want to replace them frequently. Many thanks to the person who started this thread, because I must not be the only one out there that has this engine in a Mac 26M, who would like to have two secured and spill-contained group 24 batteries. Jeff

[OverEasy]

Hi Jeff Juneau

The Mac26X isn’t much better it sounds like to your Mac26M for battery space.
We ran into a similar problem with our modification to a dual battery system on our Mac26X.
We solved our battery electrolyte spillage containment by using the bottom portion of two RV exposed location battery boxes similar to these:



The bottom boxes are just tall enough to reach slightly above the top of the battery.

We tossed the tops and trimmed the plastic molded strap loops off of each side of each bottom box. This allows the batteries to sit closer to each other.

In the case of the Mac26X the battery compartment is located in the single seat bench next to the galley.
We made a pair of fiberglass posts to mount a leveling support bar made from PVC 1 X 2 board on edge that matched the height of the ballast transfer tube that runs through that area. We then made a level surface with some trim Trex boards left over from a deck project that were screwed into the PVC board with 1-5/8 SST screws. A set of 3/4 X 3/4 (trimmed Trex) makes side to side rails to fit the battery box bottoms.

We use a web buckle belt to hold the batteries in place fore and aft. One end of the web is secured to the aft fiberglass wall of the compartment bench with a doubling of the web and a washer/bolt/washer/nut. The other web end is double screwed to the Trex deck.

We insert the 1st box bottom and then the aft battery. The two step shuffle slide moves the 1st combo aft then insert the second box then the second battery. After making the electrical connections, Adjust the strap halves and buckle together.

From what I recall of the Mac26M compartment you might be able to work with a 1/8 or 1/4 Starboard or other plastic that you can secure with fiberglass after modifying it to have side rails and web strap.

No easy solutions but might be workable.
One of the last things I wanted was loose liquid battery electrolyte sloshing around the bilges.

I’ve had battery casings crack and leak on cars and between the damage to structure and the mess cleaning it up I made it a priority to box and secure our batteries in Over Easy.

Hope this helps.

Best Regards,

[OverEasy]

Another trick is to make a thin (shoebox type) cardboard box with glue or duct tape then apply fiberglass and epoxy inside and out.
Smooth out the surfaces and edges.

I’ve done that approach to make specialized containers and plates.

Just a thought….

[Be Free]

I mention the ABYC standards only as a target to shoot for, not a rule to be blindly followed. There is no legal requirement that you use their standards. To quote the great maritime lawyer Barbossa, "...the code is more what you'd call 'guidelines' than actual rules. Welcome to the Black Pearl, Miss Turner." Maybe that last part does not apply.

ABYC has standards for just about everything. For the most part I consider them to be a good starting point when I'm working on the boat but I don't hesitate to vary from them if the situation requires it. Blindly following the standard will keep a boat surveyor happy but I prefer to understand the "why" behind the standard and fit it to my particular case rather than just checking off a list item.

The "why" behind the battery box standard is to prevent electrolyte from spilling into areas where it can cause damage. In your case that would allow it to get into the bilge. Not a good idea. It is unlikely that you will ever have any spills as long as you don't overcharge the battery or tip it over.

Every engineering problem has a solution and every solution involves a compromise between different design constraints. The "art" is in finding an acceptable solution that properly addresses the problem. Sometimes the only available solution is too expensive in relation to the problem so you just have to mitigate the effects of the problem instead of correcting it.

You mention that you have two group 24 batteries and that they are the minimum required for a DF70A. The DF70A requires a minimum of 650 MCA or 512 CCA in its start battery. That should not be hard to do with a single battery. There are lots of reasons to have more than one battery (I have five) but starting that engine is probably not one of them.

You can also change the size of the battery(s) if you want to. Just because it uses a group 24 now does not mean that you have to stick with that form factor if something else would suit your needs better.

Moving one or more of the batteries to another location is also an option. It's not trivial and takes some planning but a lot of us have done it.

Thinking outside of the box (pun only slightly intended) you can fabricate a containment in the bottom of the existing battery compartment.

Lots of things to consider.

[OverEasy]

Well said Be Free!

[JeffJuneau]

Hey, I just want to apologize to the fellow from Holmstead, Florida, who originally posted this whole question about 26M battery compartments; who probably just wanted to see some cool images of the type of boxes and setups used by people here; ended up having his post commandeered; and I haven’t heard a peep from him since. So… I apologize. For me, it has turned into an informative primer on why a battery acid resistant boxes are desirable, how some have installed them, and the quirky limitations of the basic battery space we have to work with in an M type. Be Free, I agree with you that there are probably enough ideas offered here that I should be able to find a way to construct something that would contain a small spill from a couple of group 24 batteries in my 26M. I have two interstate batteries ("marine" - whatever that means) that came almost new with my 2020-purchased Mac. I wondered why the PO needed two heavy batteries until I looked up the requirements for the DF70A and found the same requirements you cited. They meet the CCA requirement by having 550 CCA. Also, because of the type of poking around I want to do in remote areas of SE Alaska, I need to have a backup battery that can serve as a starting battery for that engine in case the starting battery fails. So I think the PO must have been trying to achieve the same goal, while having some limited ability to partially discharge these for use as a house battery. I also need some ability to run the house battery down a bit for the fan in a Wallas heater, communications, and for keeping a few things charged while I could be stuck in an anchorage for a few days. I suppose I will have to fabricate some type of box, like Be Free and OverEasy suggested. I have a question about battery acid and fiberglass resins. Is the polyester resin that our Mac’s are made of, resistant to battery acid? Is epoxy resin better, worse, or the same in terms of resistance to battery acid? Thanks again for this informative thread and your collective ideas. Jeff

[OverEasy]

Hi Jeff Juneau!

The plastic that the battery boxes referenced are specifically selected for long term chemical (and also for UV) stability.

Chemically Epoxy Resins are more acid resistant and less permeable than Polyester Resins.

Polyester resins have some resistance but will eventually degenerate sooner than Epoxy resins from what I have researched and seen over time. I haven’t seen a “side-by-side” comparative test as I suspect there are dozens of various proprietary formulas for both types of resins.

If I were to use polyester I’d make it a little thicker than I might with epoxy to make up the difference. In either case I’d make sure the glass was fully saturated, have multiple layers and an extra containment surface over coat of resin ‘just in case’.

When I’ve done the “shoe box card board type approach I’ve always gone ahead and used a thinned resin to fully saturate the cardboard before sealing it in between glass layers. (The cardboard only acting as a construct form.) I’ve never left the cardboard surface exposed.

Below is some basic technical information on polyester and epoxy resin sulfuric acid resistance:

POLYESTER RESIN





EPOXY RESIN




Specialty Epoxy Resin Designed For Acid Use Application




Sorry for the piecemeal post attachments but it’s the best I can do with an iPad (no PowerPoint to nicely splice the data sheets together)

Anyway, hope this helps you in your quest for a better battery containment box.

It sounds like you have some nifty adventures ahead of you up there.
It must be beautiful this time of year!

Down here in SC it has gotten oppressively HOT and HUMID .
Can’t spend more than an hour or two outside before I’m saturated in sweat .
Next week we haul out to get new bottom paint and both the hull and top deck polished/buffed.
(To be done at a local Marine Yard down here… I just can’t do that kind of stuff anymore with my back issues )
Then load Over Easy on the trailer & hull north to Lake Champlain in VT mid August to visit our daughter for a week.
Might be able to take a sailing course while up there……it would be nice to get some professional instruction before learning bad habits.
Then on to our home in NH and hopefully get our new Suzuki DF60AV in September or October.
While we’ve managed to get our old 2001 2-Stroke Tohatsu 50 up to snuff over the past several weeks we are looking forward to a newer, quieter, more powerful, more reliable, more fuel efficient engine for the start of our planned cruising of the ICW next year.


Best Regards,
Over Easy

[Be Free]

Jeff,

I see two Interstate batteries listed with 550 CCA. One is a "deep cycle", the other is a starting battery.

The M24DC is strictly a starting battery and will not do a very good job as a house battery unless you have very light electrical demands on it.

The SRM-24 is listed as a deep-cycle battery but with only 81AH it barely qualifies. Even true deep cycle FLA (Flooded Lead Acid) batteries should not be discharged more than 50%; 20% discharge is where they are happiest. A 50% discharge on this battery will "age" it quickly.

Assuming that you are holding one battery in reserve to be sure the engine will start in the morning, you have 40.5 AH at 50% and 16.2 AH at 20%. The original cabin lights drew 1.4A each; an anchor light (incandescent bulb) will be about .8A; a small laptop with an efficient 12V charger will be about 1.5A (running through an inverter will be more). At that rate 16.2 AH does not go very far.

The other thing to consider is that the 550 CCA is when the battery is new. That number will drop as the battery gets used. On the plus side, they they often test out above their label CCA when new so you have a little reserve. On the minus side, you don't have a lot of wiggle room between the battery capacity and the engine starting requirements. I can (theoretically) pull start my engine but I still carry a jumper battery pack just in case.

Just sayin'.

[OverEasy]

Those “jumper packs” are soooo cool to me!
Where were those things when I had my 8 year old 1969 Pontiac Catalina ???
I’ve seen those little jump packs turn over and start Truck engines multiple times on a single charge!
Gave one to my daughter. What a really nice piece of Tech!