Battery box mount.

[AP0196]

I want to relocate the 12v battery on my sailboat to it’s original location under the companionway step, and I want to build a low tray to put the battery box in so it doesn’t slide around. Probably a wood frame that I’ll glass over and attach to the bottom of the hull with fiberglass. Is this overkill? Otherwise Whats a good way to secure the battery box without drilling holes, which id prefer to avoid.

 

[jssailem]

I want to build a low tray to put the battery box in so it doesn’t slide around. Probably a wood frame that I’ll glass over and attach to the bottom of the hull with fiberglass.

This is a perfectly acceptable method. You will want to include straps that hold the battery down in the box should your boat take on a heel while sailing.

 

[jssailem]

Welcome to the Forum. Congrats on your new to you boat.

 

[Project_Mayhem]

Yep, that'll work. You can do tabbing instead of glassing the whole thing. I highly recommend ratchet straps instead of the typical battery straps. Much much easier, faster and in my opinion, more secure. Put a pad eyes on the wood to hook the strap to

 

[AP0196]

What is tabbing? On second that could I just adhere the wood frame to the hull and install eye straps for the battery? It would have to be a pretty small ratchet strap. Maybe bungee cords?

 

[Project_Mayhem]

What is tabbing? On second that could I just adhere the wood frame to the hull and install eye straps for the battery? It would have to be a pretty small ratchet strap. Maybe bungee cords?

Tabbing is strips of fiberglass cloth that bonds one object to another. Very simple. Your C22 has tabbing between different parts of the hull. You want something stronger than a typical adhesive as you're dealing with a 40lbs object filled with acid, lead and will happily act as a welder when shorted.

I've used 1" wide ratchet straps in the past. I put it on, then cut the long tail off. Take a lighter to the end so it doesnt fray if you'd like. Bungy cords wont stop a battery from flying if you're healed over enough

Tabbing here is done with a simple strip of fiberglass cloth to join the wooden bulkhead to the hull

 

[jssailem]

As @Project_Mayhem states: "Bungy cords won't stop a battery from flying if you're healed over enough."

You want the battery to be solid in place, no matter what the boat is doing. The box should stop lateral motion, and the strap stops vertical motion. A 1" strap should hold a group 24 or 27. If you have a group 8D, then you will need several straps.

 

[AP0196]

Sweet! Good info! And I do intend to heel! I guess I will add tabbing to my list if skills to learn!

 

[Project_Mayhem]

Sweet! Good info! And I do intend to heel! I guess I will add tabbing to my list if skills to learn!

It's really easy. Here's how I'd go about this:
1. Assemble your box outside of the boat. Standard wood screws will outlast the boat in the Midwest. Do not paint it yet!
2. Sand the paint off the area you'd like to put the box so the resin can properly adhere. An electric palm sander works well (use a half or full face respirator, not a disposable mask!)
3. Place your box in the boat
4. Use EPOXY resin such as TotalBoat or West Systems. I'd recommend TB. You wont need much for this project. You'll probably want three layers of run of the mill fiberglass tape (can someone please specify the weight?) or one layer of 1708. Regular tape will likely be easier to work with for a beginner. I personally like to brush a little bit of resin on the hull and wood. It helps saturate the cloth and makes it stay in place. You'll want to work the resin into the cloth until you start to see the the strand/weave disappear (see youtube for further details on this). Your next layer will need less epoxy than the first to get it saturated
5. Let it cure overnight and then paint if you'd like

I would recommend putting some fiberglass over the area that you're going to screw the pad eye into. Through bolt it if you can

PS - I'm not the expert in fiberglass but have done my fair share

 

[FastOlson]

Making a sturdy mounting place is vital, but do not lose sight of the ABYC requirement to have it inside a liquid/acid proof container with a lid to protect the terminals from anything touching and shorting them. And then... secure that container down firmly.

 

[Project_Mayhem]

To meet these requirements you can make your box/tray large enough to accommodate plastic battery boxes. At some point it will catch some battery acid. I'd also recommend cargo D rings over pad eyes. They are available painted and in stainless. Much easier to through bolt and guaranteed to work with ratchet straps

 

[AP0196]

It's really easy. Here's how I'd go about this:
1. Assemble your box outside of the boat. Standard wood screws will outlast the boat in the Midwest. Do not paint it yet!
2. Sand the paint off the area you'd like to put the box so the resin can properly adhere. An electric palm sander works well (use a half or full face respirator, not a disposable mask!)
3. Place your box in the boat
4. Use EPOXY resin such as TotalBoat or West Systems. I'd recommend TB. You wont need much for this project. You'll probably want three layers of run of the mill fiberglass tape (can someone please specify the weight?) or one layer of 1708. Regular tape will likely be easier to work with for a beginner. I personally like to brush a little bit of resin on the hull and wood. It helps saturate the cloth and makes it stay in place. You'll want to work the resin into the cloth until you start to see the the strand/weave disappear (see youtube for further details on this). Your next layer will need less epoxy than the first to get it saturated
5. Let it cure overnight and then paint if you'd like

I would recommend putting some fiberglass over the area that you're going to screw the pad eye into. Through bolt it if you can

PS - I'm not the expert in fiberglass but have done my fair share

Okay so build the box. Originally I was gonna make it without a bottom, just the four sides as a frame, but now I think I will. Sand the bottom fiberglass of the boat where the box will go. Put box in the boat. Use the fiberglass tape around the outside of the box to seal it down? With one side overlapping the box and the other the hull?

 

[Project_Mayhem]

Exactly! Put a divider between the two battery boxes that goes up roughly 3/4 of the way. This way you can use one strap for both batteries (it'll hold and I did a LOT of healing and heavy weather sailing) without the lids smashing together. It will also save a tiny bit of time when you need to access the batteries. I believe I just tossed a 2x4 between the two boxes. Experiment with yours to see what works

 

[AP0196]

I only have one battery right now. Might add a second later on if I do more serious voyages.

 

[JBP-PA]

It's really easy. Here's how I'd go about this:
1. Assemble your box outside of the boat. Standard wood screws will outlast the boat in the Midwest. Do not paint it yet!
2. Sand the paint off the area you'd like to put the box so the resin can properly adhere. An electric palm sander works well (use a half or full face respirator, not a disposable mask!)
3. Place your box in the boat
4. Use EPOXY resin such as TotalBoat or West Systems. I'd recommend TB. You wont need much for this project. You'll probably want three layers of run of the mill fiberglass tape (can someone please specify the weight?) or one layer of 1708. Regular tape will likely be easier to work with for a beginner. I personally like to brush a little bit of resin on the hull and wood. It helps saturate the cloth and makes it stay in place. You'll want to work the resin into the cloth until you start to see the the strand/weave disappear (see youtube for further details on this). Your next layer will need less epoxy than the first to get it saturated
5. Let it cure overnight and then paint if you'd like

I would recommend putting some fiberglass over the area that you're going to screw the pad eye into. Through bolt it if you can

PS - I'm not the expert in fiberglass but have done my fair share

For step 3, I would epoxy the box in with thickened epoxy and create some fillets so the inside corners are not sharp. This makes it easier (and stronger) for the glass to fit in the corners. You don't need to wait for this epoxy to cure, but you should let it kick (start to get stiff) so you don't mess up your nice fillets.

For step 4, stagger the strips so the long edges are not all in the same place, this makes a smoother transition. I put one 1/3-ish to the left, one in the center, and one 1/3 to the right. Others use 3 different widths of tape.

 

[Project_Mayhem]

I only have one battery right now. Might add a second later on if I do more serious voyages.

It'll be much easier to add a second battery spot now than later. If you end up not using it, you'll have some extra storage space

 

[AP0196]

It'll be much easier to add a second battery spot now than later. If you end up not using it, you'll have some extra storage space

Not sure there’s enough room for them side by side. I’d have to measure.

 

[FastOlson]

I'm not sure if it's relevant, but I recall that when I added an emergency bank, I was able to use a tray rather than a full box. This was approved because I was using an AGM battery. This does make the whole install go somewhat easier. You still need strong tie-downs, tho. And rubber "covers" for each terminal bolt.

 

[Silvercreek]

I asked this exact question not long ago. Here’s what I ended up with. (Commentary welcome)

Best approach to attach plywood base to v-shaped hull? - Cruisers & Sailing Forums

I'm looking to add a new base to mount a pair of Group 31 batteries near the bow of my fiberglass boat . I have a good location selected right at the centerline of the boat along the bottom hull .

www.cruisersforum.com

 

[marcham]

Making a sturdy mounting place is vital, but do not lose sight of the ABYC requirement to have it inside a liquid/acid proof container with a lid to protect the terminals from anything touching and shorting them. And then... secure that container down firmly.

If ... it's a spillable battery electrolyte.... not required for lithium, AGM, etc... as the ABYC standard refers to "consideration to the type of electrolyte". Venting of hydrogen must also be considered for flooded batteries (permit discharge from the boat)... thus why most OEMs use AGM batteries, as there is no venting during normal use.

Refer to ABYC E-10 for installation of batteries. Getting short term access to all their publications is about $50....

Usually, battery straps are sufficient to keep the battery boxes in place, up to a group 31. After that, addtional fastening would be required to limit lateral movement and ensure the battery does not become dislodged if the vessel is tipped on it's side or , worst case, inverted.

Consider as well that flooded batteries shouldn't be installed below electrical equipment.