Battery box build recommendations

I will be ripping out two very old and falling apart battery boxes in my engine room which house both my two start batteries, and my house batteries. The space in question is about 21" wide, and 64" long.

I have found many battery boxes online from all sorts of manufacturers that I could probably make work in some way, but they all would require modification, or group the batteries in smaller sections than I'd like.

I'm considering just building my own sectioned box-like long structure out of King Starboard but am curious if others have recommendations of materials, tips and tricks and the like when building your own.

I have 8x G31 LiFePO4 batteries for the house bank + fuses. The start batteries are G31 AGM batteries. Ideally I would like four G31s in a "section" to make two sections just to have more strength and blocking between them, although they are super light (31lbs each).

I also need a very strong cover structure because it is in between my two main engines, and where I walk/lay when working in the engine room.

Starboard will work fine to make your battery boxes from. As you probably know, Starboard doesn't glue well. There are some glues specially designed for Starboard but I have used 3M 5200 and it works ok.

Reinforce the joints with backing strips and put it together with screws. The glue/5200 is more for sealing.


But plywood with a couple of coats of CPE will last just as long and be lots cheaper.


David

Screwed and glued plywood with the inside of the box glassed.. You can then make it any size you need...By the way Steve I find your blog very informative, thanks for taking the time to publish it..

I agree with the plywood/fg construction... Not a good use of Starboard IMHO..

Have you considered the battery boxes from Dyno there in Seattle? I had one for the 4 L16's in my inverter bank and was very happy with it, as I could custom cut the cable ingress and egress, and ventilation, to suit my installation.

Worth giving them a call

Dyno Product 3

Keep in mind, though that AGM's and LiPo's don't need the same containment that classic FLAs do.

I love Starboard but not for this application. I would make the box out of plywood and fiberglass it so it will contain any leaking acid. 5200 doesn’t really stick well to Starboard and the special glue that does requires a special applicator. Also it would be easy to epoxy in the plywood box with thickened epoxy. And make the top out of 3/4” plywood and it will be strong enough to support several people’s weight.

Sean built a new battery box for me during the refit project. Coosa board with a couple layers of fiberglass on the inside and out. Plywood is ok; Coosa is forever. You can finish it as much or as little as you want. Mine is faired and gelcoated. Also has a very nice lid.

http://www.trawlerforum.com/forums/attachment.php?attachmentid=38120&d=1425964584

http://www.trawlerforum.com/forums/attachment.php?attachmentid=38121&d=1425964584

Ted

djmarchand said:

But plywood with a couple of coats of CPE will last just as long and be lots cheaper.

David

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Yeah that's why I was asking. I am terrible with wood stuff of any kind, and I prefer Starboard, but it is $$$

Ka_sea_ta said:

Screwed and glued plywood with the inside of the box glassed.. You can then make it any size you need...By the way Steve I find your blog very informative, thanks for taking the time to publish it..

Click to expand...

Thanks for the kind words on the site! Yes, the trend here seems to be what I expected - using plywood and fiberglass. While I do lots of projects on my boats, as you can see on the site, wood related stuff and anything like fiberglassing or finishing do not come up often, because I am....terrible at it!

Sailor of Fortune said:

I agree with the plywood/fg construction... Not a good use of Starboard IMHO..

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Thanks!

caltexflanc said:

Have you considered the battery boxes from Dyno there in Seattle?

Keep in mind, though that AGM's and LiPo's don't need the same containment that classic FLAs do.

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Ah I totally forgot about Dyno. They do have a nice box that looks like it would fit perfectly in my space and hold 4x GC2s. I could get 2x of those, and then another box for the G31s. And yes, I'm aware on the containment side - if I built my own box, I wouldn't need to deal with the FLA issue.

Comodave said:

I love Starboard but not for this application. I would make the box out of plywood and fiberglass it so it will contain any leaking acid. 5200 doesn’t really stick well to Starboard and the special glue that does requires a special applicator. Also it would be easy to epoxy in the plywood box with thickened epoxy. And make the top out of 3/4” plywood and it will be strong enough to support several people’s weight.

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Ah expoxying it in would be a good thing instead of some sort of other attachment point. I don't know whats under the existing boxes yet because I'm using the batteries/boat and haven't been able to rip them out. I think there is some glassed in marine plywood, but I am going to guess that needs to be replaced given the age.

O C Diver said:

Sean built a new battery box for me during the refit project. Coosa board with a couple layers of fiberglass on the inside and out. Plywood is ok; Coosa is forever. You can finish it as much or as little as you want. Mine is faired and gelcoated. Also has a very nice lid.

Click to expand...

Hey that's a nice box! I hadn't thought of Coosa board - it is expensive too, but very strong stuff.

Coosa board or eqv is easy to work with and would be a "forever" fix. Strong and light weight, cut it with a sabre saw, tack it together with 15 min epoxy, brush on a couple of layers of fiberglass, paint and you're done forever. Love the stuff.

When ya'll say add fiberglass to a plywood box... do you mean just the resin? Or do you mean layers of glass mat fiber cloth, too? Or...?

-Chris

ranger42c said:

When ya'll say add fiberglass to a plywood box... do you mean just the resin? Or do you mean layers of glass mat fiber cloth, too? Or...?

-Chris

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It would have to be mat to have any strength.
Build the plywood box.
Paint the entire box with polyester resin diluted 25% with acetone. That will allow the resin to penetrate the wood.
Then start laying up the mat/resin. you could staple the mat in place to make working the resin a little easier.
Do at least 2 layers of mat.
Then either paint or gelcoat.
That's how I would do it.

I built a box to fit 2 4D batteries from 1/2 inch exterior ply. I glued (exterior gorilla glue tube) and screwed the box together. Made the lid the same way. Then applied a few coats of fiberglass resin without glass fiber. The resin was only applied to the interior of the box and lid.The resin is only there for sealing the wood against battery moisture and acid spill. It has no structural integrity alone. It would be much more complex to build a solid fiberglass enclosure without wood and having structural strength. Also, bear in mind that the enclosure is not intended to be lifted with batteries inside. It is to provide an an outer protective cover for batteries and to prevent them moving when underway.

caltexflanc said:

Have you considered the battery boxes from Dyno there in Seattle? I had one for the 4 L16's in my inverter bank and was very happy with it, as I could custom cut the cable ingress and egress, and ventilation, to suit my installation.

Worth giving them a call

Dyno Product 3

Keep in mind, though that AGM's and LiPo's don't need the same containment that classic FLAs do.

Click to expand...

I used these for my house batteries and I am very happy with them. They fit 4 6vDC batteries.

I used 3/4” plywood for strength. Then epoxy coated it to seal the wood. I used thickened epoxy to filet the corners and also add more strength. Then painted it with Interlux Bilge Kote white paint. If you want strength from the fiberglass then I would use some 1708 biaxial fiberglass. You don’t want to use mat with epoxy.

Comodave said:

I used 3/4” plywood for strength. Then epoxy coated it to seal the wood. I used thickened epoxy to filet the corners and also add more strength. Then painted it with Interlux Bilge Kote white paint. If you want strength from the fiberglass then I would use some 1708 biaxial fiberglass. You don’t want to use mat with epoxy.

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Dave you may want to explain why.

Epoxy doesn’t wet out mat properly due to the binding that is used in mat to hold it together. Epoxy will wet out the mat layer in 1708 since 1708 uses stitching to hold the mat together instead of the binding that is used in regular mat. Something to do with styrene.

I built mine out of 10 mm (3/8") marine ply. I used 3/4 x 3/4" oak at all the seams to give the screws something to bite into and epoxied the lot inside and out before assembling and glued/screwed it together. No mat required as it has plenty of structural strength, although I've used mat with epoxy on plenty of other projects.
Installed with a hinged lid on the battery box with built in LED's. No paint required. I'm happy with the epoxy over wood look.

AusCan said:

I built mine out of 10 mm (3/8") marine ply. I used 3/4 x 3/4" oak at all the seams to give the screws something to bite into and epoxied the lot inside and out before assembling and glued/screwed it together. No mat required as it has plenty of structural strength, although I've used mat with epoxy on plenty of other projects.
Installed with a hinged lid on the battery box with built in LED's. No paint required. I'm happy with the epoxy over wood look.

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Yes, you can use epoxy on mat, but it doesn’t really wet out properly because there isn’t any styrene in the epoxy to break down the binder in the mat. Wet out the mat with polyester resin and compare it with mat wetted out with epoxy.

I would hot coat it (diluted as Jay Leanard suggested) But I would lay the mat up before cutting and assembly. Much easier to do it on the flat before cutting out and then just add strips to the joint corners. I'd be comfortable just building a plywood box glued,screwed and painted too.

I built one last summer to hold 4 gc2 batteries.
I used pine boards, sealed with epoxy and reinforced with fiberglass. I then paint it with bilge paint and primer. I could have used plywood too but the pine boards were exactly of the required size so barely no cut needed. Each battery space has a small space below the battery to collect spill if any.
Cost was less than 50$ all included.

L

Yes ,epoxy does not wet out as well as polly , the simple solution is thinner mat 3/4 oz or glass cloth , not roving.

Multiple sewn layers of glass are best left to the vacuum infusion folks.

Epoxy is a glue that sticks well to plywood , polly is for laminating , not a glue.

stevemitchell said:

I will be ripping out two very old and falling apart battery boxes in my engine room which house both my two start batteries, and my house batteries. The space in question is about 21" wide, and 64" long.

I have found many battery boxes online from all sorts of manufacturers that I could probably make work in some way, but they all would require modification, or group the batteries in smaller sections than I'd like.

I'm considering just building my own sectioned box-like long structure out of King Starboard but am curious if others have recommendations of materials, tips and tricks and the like when building your own.

I have 8x G31 LiFePO4 batteries for the house bank + fuses. The start batteries are G31 AGM batteries. Ideally I would like four G31s in a "section" to make two sections just to have more strength and blocking between them, although they are super light (31lbs each).

I also need a very strong cover structure because it is in between my two main engines, and where I walk/lay when working in the engine room.

Click to expand...

Marine plywood coated and assembled with laminating epoxy and 'super bond' epoxy glue in the joints .. Paint if wanted...but prime before any painting. Stronger and easier than Starboard. FG Coatings CO in ST Pete good source for epoxies.

Did anyone mention cheap, commonly available, Azak. It would be acid-
proof and it glues strongly with PVC cement not necessary but especially if corners are mitered for extra glue area. Azak sells their own glue as well. Stainless ring nails hold it while gluing. Works easily with hand and power tools.

stevemitchell said:

I will be ripping out two very old and falling apart battery boxes in my engine room which house both my two start batteries, and my house batteries. The space in question is about 21" wide, and 64" long.

I have found many battery boxes online from all sorts of manufacturers that I could probably make work in some way, but they all would require modification, or group the batteries in smaller sections than I'd like.

I'm considering just building my own sectioned box-like long structure out of King Starboard but am curious if others have recommendations of materials, tips and tricks and the like when building your own.

I have 8x G31 LiFePO4 batteries for the house bank + fuses. The start batteries are G31 AGM batteries. Ideally I would like four G31s in a "section" to make two sections just to have more strength and blocking between them, although they are super light (31lbs each).

I also need a very strong cover structure because it is in between my two main engines, and where I walk/lay when working in the engine room.

Click to expand...

I have two Todd Battery boxes that I just removed for a housebank redesign. I am also in the Seattle area. But, I believe they are roughly 21" Width x 12 1/2" Height x 24 1/2" Length. They are in great shape and have SOLID covers... If you're interested (or anyone else) $150 for both or $100 each.

Scottwb96 said:

I have two Todd Battery boxes that I just removed for a housebank redesign. I am also in the Seattle area. But, I believe they are roughly 21" Width x 12 1/2" Height x 24 1/2" Length. They are in great shape and have SOLID covers... If you're interested (or anyone else) $150 for both or $100 each.

Click to expand...

Sending you a PM

I rarely use fiberglass mat. I can get a pretty strong lay up using 3 layers of 6oz E glass cloth. I knock together boxes using scrap ply and 2x materials. I round over all the edges with a 1/2 inch router bit or sanding block. I wrap it with shrink wrap or cooking type cling wrap. I lay down a plastic drop cloth on my table and staple the ends down. I cut my cloth to the shape I need. Lay it out on my table and wet it out. Then lay it over the form and smooth it down with a metal fiberglass roller. I wrap a sheet of ply with plastic, lay it on the freshly laid up box, and weight it down. This gives a smooth flat bottom on the outside. After it dries, I pop it off the form using compressed air in a void at the top of the box edge between the plastic wraped plywood and the fiberglass box. Once it's off, I cut an inch off the top of the fiberglass box. I use this cut off to make the top. I wrap the cut off in plastic and put it back on the form. This gives the form the same size of the fiberglass box so the top, after laying up, can drop down over the new box and fit tight. Making the top is the same as the box except the cloth only needs to hang over the form 1.5 inches. The excess 1/2 inch can be cut off. Really you can make the top as deep as you want. I keep mine around 1 inch for tight spaces.



If anyone is curious, I use U.S. Composites epoxies. I find them easier to work with. Also a bit cheaper as well.


Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc.






I use horse stall mat to line the bottom of my battery boxes. It's cheap and can be bought anywhere there is a farm supply store like Tractor Supply, Farm and Fleet, or Rural King. I like those cable glands to seal the cable into the box. Any good closed seal weather stripping will work for the top to box seal. I use straps and metal rings to hold the top down. I always bolt my battery boxes down if possible.


Box straps.
https://www.amazon.com/Boat-Marine-...68518d592f273197483e4e9e693da2&language=en_US


Cable glands. I buy the size that fits the cable's measured diameter. I put my terminals on after they are trough the cable gland fitting.
https://www.amazon.com/s/ref=as_li_...972cac22a4f9b7a81b507e607e297e&language=en_US


And a nice video about fiberglass types from a long trusted source.

I'll cast a vote against Starboard. I believe it is not well-suited to this and many structural applications, where it is (over)used by builders, yards and DIYers. It lacks the necessary stiffness, it distorts easily under load, and it is dimensionally unstable with temp changes.

As others have noted, carefully glassed over plywood will work, and so will GPO3, while the latter is more costly, it will never rot or be affected by acid, it's stiff, stable and available in a wide range of dimensions. It screws and glues well.

I'll also use this opportunity to point out that while ABYC standards allow for up to 1" of movement for an installed battery, I believe there should be no movement, batteries should be completely immobilized.

This article may be helpful. https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Large-BatteryBank133_03-1.pdf

Keep in mind, there is no requirement for batteries to be in boxes. ABYC Standards call for "containment" taking into account the type of battery used. Thus, an AGM battery could rest in a liquid-tight tray and be compliant. My approach is to use boxes only for flooded batteries, otherwise, I prefer to install batteries in trays/cleats and use clamps to hold them in place, improving heat dissipation and making casual inspection, i.e. every time you walk by, far easier.

(In Xiamen, China at the South Coast Yard)

When I have a battery in a box that allows the battery to slide a bit, I cut a piece of Starboard to size and slide it down next to the side of the battery to shim out the extra space so the battery can’t slide at all. The Starboard won’t be hurt by battery acid. I don’t want any movement of the battery, over time it can loosen the cables.

I definitely will not be using Starboard based on feedback here. 10 of the batteries are LiFePO4 and 2 are Lifeline AGM, but I will most likely have the AGM in their own section or box.

I want a box or structure with a hard set of lids because these are between my main engines and act as a walkway/crawl-way and need to be sturdy because of my...bulk

ben2go said:

I like those cable glands to seal the cable into the box. Any good closed seal weather stripping will work for the top to box seal. I use straps and metal rings to hold the top down. I always bolt my battery boxes down if possible.

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It sounds as if you are trying to seal the box, to make it airtight, is that right?

(In Xiamen, China, at the South Coast yard)