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Old 11-29-2019, 04:17 PM   #1
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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.
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Old 11-29-2019, 05:07 PM   #2
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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.


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Old 11-29-2019, 05:20 PM   #3
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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..
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Old 11-29-2019, 05:49 PM   #4
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I agree with the plywood/fg construction... Not a good use of Starboard IMHO..
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Old 11-29-2019, 06:03 PM   #5
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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.
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Old 11-29-2019, 07:29 PM   #6
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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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Old 11-29-2019, 07:49 PM   #7
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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/a...0&d=1425964584

http://www.trawlerforum.com/forums/a...1&d=1425964584

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Old 11-29-2019, 09:50 PM   #8
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Quote:
Originally Posted by djmarchand View Post

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

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

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Originally Posted by Ka_sea_ta View Post
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..
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!

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

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Originally Posted by caltexflanc View Post
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.
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.

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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 doesnít 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 3/4Ē plywood and it will be strong enough to support several peopleís weight.
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.

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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.
Hey that's a nice box! I hadn't thought of Coosa board - it is expensive too, but very strong stuff.
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Old 11-29-2019, 10:39 PM   #9
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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.
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Old 11-30-2019, 07:34 AM   #10
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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...?

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Old 11-30-2019, 07:44 AM   #11
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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
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.
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Old 11-30-2019, 08:54 AM   #12
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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.
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Old 11-30-2019, 09:50 AM   #13
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Quote:
Originally Posted by caltexflanc View Post
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 used these for my house batteries and I am very happy with them. They fit 4 6vDC batteries.
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Old 11-30-2019, 11:36 AM   #14
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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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Old 11-30-2019, 01:39 PM   #15
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I used 3/4Ē 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 donít want to use mat with epoxy.
Dave you may want to explain why.
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Old 11-30-2019, 01:46 PM   #16
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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.
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Old 11-30-2019, 02:02 PM   #17
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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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Old 11-30-2019, 02:33 PM   #18
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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.
Yes, you can use epoxy on mat, but it doesnít really wet out properly because there isnít 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.
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Old 11-30-2019, 04:52 PM   #19
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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.
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Old 11-30-2019, 05:01 PM   #20
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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.

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