Battery Box - REPAIR

[Galway Girl]

This spring as we were prepping for a new road trip, I noticed the battery box door seemed to be sticking out further than normal.
I thought I would adjust the latch to pull the door in a bit tighter.

What I found was that the battery box had started to tip forward away from the main hull as shown the pix below.
All the rivets up both sides and all across the top of the box had sheared and the box was tipped out about 1/2".

 

I contacted Oliver Support to understand how the box was designed, mounted etc. 

They cleared me for travel after having me check the support strut inside the trailer (under the pantry area) .

 

After some further consultation I was able to perform a repair.
Here's a sketch of how the battery box is installed in our Hull 505 (2019 Elite II) trailer.

 

 

The repair steps I took following Oliver instructions were:

1) Remove the batteries from the slide tray to get weight off the box.
2) Drill out all sheared rivets. (3/16" bit)
3) Release the 2 support bracket bolts inside the trailer under the pantry (one of which is adjustable).
   (This step is a pain and requires some long extensions for the ratchet wrench to make reaching nuts possible.)
4) Tip box back into position. (Check that the box base still has a slight outward tip for water drainage.)
5) Re-tighten support bolts.
6) Re-rivet all around the perimeter.
7) Clean seams and add a bead of boat life white sealant around the battery box seam. (See pix below).

Repaired Box Above:  Door closes with a good seal all around and the box sealed to the body.
 

We are going to keep an eye on this as we travel this next year, and make a trip to the Oliver factory for them to inspect and repair if necessary.

I'm not sure of the root cause or mechanism by which the box tipped out in the first place.

One concern would be that the box is putting too much pressure on the outer hull while bouncing down the highway.
I don't see any indications of cracking in the glass hull or box at this point.

Hope this helps if anyone else see's an issue.

Craig

Hull 505 

 

 

 

 

 

[mossemi]

Another excellent write up, thank you!  I have had my slide tray out for a re-paint after a battery leak, so I wholeheartedly agree with working the support bolts under the battery box is a challenging endeavor.  Four hands to make doable.

You detailed instructions will be help someone in the future, so kudos to y’all in the great northwest!

Mossey

[DavePhelps]

Trying to understand just where the rivet failed. Hard to tell from the pic, but it looks like it failed just under the head of the rivet?
If this is the case, then I would recommend 3 things.

1.Put a very slight countersink on the battery box rivet holes, just barely enough to break the sharp edge from the drilled hole. That sharp edge could wear away the rivet from vibration, especially if it's aluminum. If you removed the entire battery box, I'd soften that edge on both sides of the hole.
2. Use stainless steel rivets and not aluminum, they are stronger and I don't see issues with galvanic corrosion in this application.
3. Finally, back up your rivet with a washer of like material (if you can get to the back side of the rivet).
Just my 2 cents.

If I was designing this from scratch, I probably would have gone with rivet nuts (with backup washers), or a thru-bolt design, for a much more secure connection to the hull. But probably not able to use these as an after the fact repair. Looks like you did a good job. Hope it holds up for you!

Dave

 

Edited July 6, 2022 by DavePhelps
clarification

[Galway Girl]

36 minutes ago, DavePhelps said:

I would recommend 3 things.

Dave,

Thanks for the recommendations.  

It is amazing that fiberglass (key word glass) cuts through rivets.

I need to do the project again I'll implement your suggestions.
I'l also discuss your ideas with the factory when we close the ticket.

Close ups of how the rivet failed.  The factory had asked for these pix below.
I'd be interested in your thoughts on the failure mechanism of rivets in the pix.

[Rivernerd]

I note you have Lithionics batteries.  I wonder if the battery box door gets even more wear and tear on the road with heavier lead/acid/AGM batteries.

If that happens to our Elite II (once we get it), would stainless steel bolts and nuts with lock washers, sized to match the rivets, then secured with red Loctite, make a more permanent repair?

Thoughts?

[John E Davies]

As an ex aircraft tech, my comment is, those rivets simply do not belong there. Hollow aluminum pop rivets are really weak and not exactly reliable. I would prefer to have an aluminum backing plate bonded inside the hull flanges at the top and bottom. Install the box, drill through the hull and flange, install structural rivets like Cherry Max. Those won’t shear their heads like the ones pictured did. An even stronger setup would be countersunk machine screws and threaded inserts in the backing plates, as David mentioned above. I don’t think nuts inside would work, you can’t really reach the area very well, and they are buried in foil insulation. Putting blind rivets directly into fiberglass is not a great idea, they need a solid material to grab on to.

Some interesting reading:

“While on the topic of rivet stems, the ability of a rivet to retain its stem under conditions of high loads and heavy vibration separate aircraft rivets from their commercial cousins. A rivet loses much of its strength if the stem falls out. Many low-cost commercial blind rivets will not reliably retain their stems under difficult conditions. This is why they are generally never used for anything on an airplane that holds it together or keeps it running.”

https://www.kitplanes.com/best-practices-blind-rivets/

John Davies

Spokane WA

[DavePhelps]

John,

Thanks for the heads up on those Cherry Max rivets. Wicks Aircraft Supply sells them as well.
I sure don't see the rivet stems in Galway Girl's pics....

Yea, not the best place to employ pop rivets, especially soft, non structural aluminum ones. That box is heavy loaded up, and on the Elite2, since it is located right over the wheels, I wonder if that area may be subject to more vibration than other parts of the hull, just thinking out loud. The way those rivet heads broke off sure looks like a stress (vibration) related failure to me. Oliver may want to rethink this detail.  

Dave

 

[Frank C]

Are those vertical slotted holes on the support bracket? (see photo)

If the bolts weren’t tight, and probably even if they were, under loads from highway bouncing, that would allow the bracket to move up/inner portion battery box to shift vertically which would tilt the outer face out away from the hull as in your failure mode.   

Just curious if that’s a “before” photo because the bolts are fully at the top of the slotted hole?  And if so is the “after” position of the bolts different now that you’ve put the battery box back in the correct position    

[Galway Girl]

6 hours ago, FrankC said:

that’s a “before” photo

Frank 😄

yes that’s the before pix.  Only one bolt hole is slotted.  In the factory the second hole is drilled after alignment & adjustment of hhe box.  That means the brace is ridgedly bolted in the second hole as installed at the factory.

(Thus I wonder how it tipped out if the support brace is not really adjustable!)

 

 

[John E Davies]

FYI aircraft rivets like Cherry Max require a special gun to install. Your typical hand squeezer won’t do it. This isn’t a problem for a production line, but it makes it a problem for an owner, unless he has access to the special tool.

https://www.aircraftspruce.com/catalog/topages/cherryg28.php

I have never used one so I can’t comment on the necessary hand strength. I used to use a compressed air gun and it was a painless “kerchunk”.

Also, drilling these out is a pain, you drill the locking collar away, then use a small pin punch to drive the steel rivet pin out the back. Then drill the head off and drive the rest of the rivet out of the hole, hopefully while not wrecking the hole. Slightly oversized rivets are available, or go to the next larger standard rivet size.

John Davies

Spokane WA

 

 

[Mike and Carol]

16 hours ago, Rivernerd said:

I note you have Lithionics batteries.  I wonder if the battery box door gets even more wear and tear on the road with heavier lead/acid/AGM batteries.

If that happens to our Elite II (once we get it), would stainless steel bolts and nuts with lock washers, sized to match the rivets, then secured with red Loctite, make a more permanent repair?

Thoughts?

When I replaced my AGMs with lithiums I also had to do some repairs on the battery box.  I had several rivets that failed and I replaced them with stainless steel bolts and nuts/lock washers.  It’s doing fine after a year and a half but some of that is due to the significant weight reduction the lithiums afforded.  I think the 4 AGMs were just too much weight for the tray.  Mike

[Trainman]

Pop rivets can be a problem when too much pressure is put on them. Pop rivets in fiberglass and weight don't work out too well, if you could get a fender washer on the back side so the rivet it couldn't pull through and would add very much strength to the holding power and not pull through. Like Mike said, replacing them with stainless bolts and large washer is the correct way to go, but getting to the back side to get the nut and washer on is not always possible. 

trainman 

[Galway Girl]

This is a screen shot from a tour video showing how the battery box is internally mounted.

Once the trailer is assembled there is no way to reach the area where the battery box is joined to the sidewall of the outer hull.
After final assembly the box is buried deep under the pantry area of the trailer.

According to Oliver Service, after insertion, the box is supported by the outer hull by, by the wheel well and by a support arm that is bolted to the box on the top and the frame of the trailer on the bottom.

The only way to get backer washers, or backing plates onto the rivets (or bolts if desired) is during the manufacturing assembly process.  An owner cannot reach back into that space from the inside of the trailer.

For those of us experiencing sheared pop rivets, I'm not sure there's a much better solution than maybe stronger stainless rivets and perhaps some 3M 4200 Sealant/Adhesive to help hold the box in place.

I'll keep track of the repair and review it with Oliver the next time I get to Hohenwald and report back any updates.

Craig  - Hull 505

[Ralph Mawyer]

Keep an eye on your support bracket bolts. As reported previously, mine had either been removed and not replaced during the build or both(?) managed to back out and are living a life of freedom in the hull somewhere.  Caught it before I saw any damage, but think I need to check my rivets, given four lead batteries.

[Galway Girl]

In April  2024 (this year) I had the factory review the repair.  Jason said it all looked stable and they didn't see any further signs of fatigue or cracks.

I'm keeping my fingers cross and carrying a rivet gun and stainless rivets in the truck just in case.

Craig

 

[SNY SD UP]

On 7/7/2022 at 8:42 AM, Mike and Carol said:

When I replaced my AGMs with lithiums I also had to do some repairs on the battery box.  I had several rivets that failed and I replaced them with stainless steel bolts and nuts/lock washers.  It’s doing fine after a year and a half but some of that is due to the significant weight reduction the lithiums afforded.  I think the 4 AGMs were just too much weight for the tray.  Mike

Mike,
 

How did you access the nuts, whilst tightening the bolts, as mentioned above, that is a difficult location to get into?

 

Bryan

[SNY SD UP]

To all,

Do we just monitor, and if we see this happening, get ready to (re-)Rivet with stronger stainless rivets?

I will look at mine tomorrow, as we have taken some pretty hard jolts since 08/2020 pickup.

B~Out

[Mike and Carol]

11 hours ago, SNY SD UP said:

Mike,
 

How did you access the nuts, whilst tightening the bolts, as mentioned above, that is a difficult location to get into?

 

Bryan

Bryan, as I recall I just used traditional tools.  With the tray empty and pulled out it was not difficult to access.  Mike