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Battery Box Repair for MOT

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Evenin' chaps.

One of the failures on the MOT this year is as follows:

Nearside front (floor) Seat belt anchorage prescribed area is excessively corroded [5.1.B.6]

Looking underneath, the area he's circled with his white marker is the large hole in the bottom of my battery box. Last year I stuck in a piece of aluminium just to support the batteries as I wasn't too bothered with this non-structural area.

Seeing as he's failed it this year, I can only assume that it's because it's within 30cm of the outboard lower seatbelt mount.

Here you can see my issue, I have cut out the bottom panel (nasty job lying underneath with the grinder :() where most of the rot was. Don't quite know what to do about the bits at the side.

post-10578-127429698546_thumb.jpg post-10578-12742970006_thumb.jpg post-10578-127429701411_thumb.jpg

Anyway, I need to repair it before next Tuesday as it's booked in for the re-test at 9:00. Since I can't weld properly yet I was thinking of cutting a piece to the right shape/size and riveting or bolting it in. Does the panel think this would be satisfactory for the MOT?

Longevity is not really an issue as it will likely get removed and a new larger battery box fabricated later on in the year.


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My two pence worth.

The seat belt mount is not attatched to the battery box. It's hel by two bolts through the steel frame of the door apature and one bolt to the 'B' post...You can remove the battery box. Well the whole seat box and still mount the seat belt to the steel.

As far as I see the battery box has no structual value.

I would do as you suggest repair the hole and paint over the metal.


I made a larger battery box a couple of years ago. pictures are available if that would help you.

As I said earlier the battery box is separate from the seat box and the seat box separate fom the structual body fittings.

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That's what I thought Mike. There doesn't appear to be anything visually wrong with the actual seat belt mount point itself, so I assumed it must be this (granted very heavily corroded) non-structural area.

Might give them a ring tomorrow and see if I can get a chat with the tester, see exactly what it is I need to fix.

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The reason I can be so precise is I've ripped the storage box out from under the drivers seat on my Defender 110. So I've had the seat belt mounting off the body today.

I certainly think a call to the tester if not VOSA should sort things out.

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I failed my MOT due to a heavily corroded battery box and seat box ends.

That was all due to the proximity to the seatbox anchor points.

I fitted the yrm box and ends in a day and passed without a problem.

Just so you know the yrm box comes in a number of bits to make up the bottom and sides. If the rest of the box is ok then you may just want to fit the bottom section over your existing sections.

The seat box ends, contributing to the failure, had holes smaller than 1 pence piece and has absolutely no structural value but as it was close to the seatbelt mount it matterd.

Also, if you ring up yrm before 10am then they'll get the bits out super quick, mine turned up the next day, bloody good service

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Shoot me down if you like.... and I know that the fail was on the seat belt mount, but....... if the battery box was that gone would that not be a fail anyway as the battery was unlikly to be "secure" i.e. it could fall through the floor? so maybe he didn't get round to that.

So as you are doing would it not be best to replace it anyway?


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the YRM box appears to be made of aluminium, so welding is unlikely. a rivetted repair should be more than adequate.

That said, we did this Job on Oranges 90 earlier this year and it's not a nice one to do!


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Well I phoned the garage this morning and spoke to the tester chap. He said he failed it because it was corrosion in the area that the seat mounts to, and because the seat belt mounts to the seat this becomes a prescribed area. I wasn't aware that the seat belts mounted to the seats on Defenders....

Either way I need to replace the battery box, more so because I've cut a ruddy great hole in it now :P

I've ordered a YRM replacement box which should be here tomorrow, and I can hopefully get it fitted this weekend. They do rivet in apparently, but the lady said they are a direct replacement and not any larger than a standard box. The chap who builds them is going to phone me this evening to talk me through the fitting procedure :)

Looks like a fun weekend coming up. Seatbox might need to come out! :(

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Mine was riveted in and is quite easy to do.

The hardest part I found was making sure the back and sides were in the correct position in order to fit the bottom correctly but that could be my cack handed way of doing things.

With regards to the seat belts mounting on the seats, he's a bit inaccurate. The seat belt mount bolts through the seat box to the sill and door frame in that corner but not directly to the seats at all

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He was talking about the buckle on the inboard side of the seat. As far as I'm aware it bolts through the seatbox to a bracket on the chassis?

I need to replace the battery box anyhow, and it will give me a good opportunity to re-do the wiring through the top hole in the box, so I can block off the bottom ones.

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Well let's see them fail it on the battery box now ^_^

post-10578-127454733663_thumb.jpg post-10578-127454733944_thumb.jpg

Just the battery wiring to finish now, need to get some more M6 threaded rod to make a new mount. Tomorrow's job.

Replacing the battery box took me pretty much all day to do, but it's one of those things where I could probably do it in half the time now I've done one. Quite an involved strip down, one has to remove the sill member (plus the rock sliders on mine) which runs from bulkhead foot to tub, as the edge of the battery box is sandwiched between that and the seat box end flange. Suffice to say I have a lot of Hogmoor sand in my hair now!

The kit YRM supply is very well built, and seems to slot together very nicely. I put plenty of rivets in so it shouldn't be going anywhere for a while! Also re-routed the electrics through the top two holes rather than the bottom one, makes for less wires in the box and a tidier install I feel. I'm not going to bother blocking up the bottom hole, as it occurred to me that without some sealant this box won't be watertight anyhow. I think it's best to leave as is and then the water can get out once it gets in.

If you want somebody to weld it I will help out! :)

Very kind of you, thanks. All aluminium work today, but next time something steel gives up I'll bear your offer in mind :lol:

Thanks to all for the help :)

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Pukka looking job there!

There is a bit of irony available, if anyone wants it: you've replaced the spot welded OEM seat box structure with an aftemarket pop-rivetted mod - and now it'll pass. I do sometimes wonder at the blind adherence some MOT testers have to the "book"

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  • 6 years later...

I know it's from a few years ago but any helpful tips on doing this one? I've bought the parts from YRM and need to attack it in the new year!

Is the only part that needs drilling out the 9 rivets on top of the transmission tunnel alongside the gearbox?

Is it best to rivet the whole thing together first and then mount it, or assemble in place and rivet after?

Have you painted it with anything to protect it?

Any other tips that might save me some headaches?



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I've replaced both battery and tool box side on my seatbox with the YRM kit. If you're not planning on removing the seatbox then I'd imagine it will be easier to build the panels in one at a time as it may prove a bit unwieldy once riveted up. I used Cleco pins to do mine but some small nuts and bolts will allow you to loosely assemble prior to riveting 

This is the battery box assembled...


old one beside it...


Battery side Cleco pinned in place....quite easy to fit with nothing else around it as you can see.


I etched primed and painted mine as part of the rebuild and a few years on it still looks factory fresh. Seam sealer on the joints will help keep it dry too.

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I've installed the seat box ends and battery box from YRM on my 90.

I think it helps to do one end at a time to stop the whole thing going floppy. 

I did the joints with sikaflex and rivets so it's strong and waterproof.

Overall it's a great repair/mod and I simply don't understand why they didn't make them like this to start with.


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  • 3 weeks later...
  • 2 weeks later...

I made a start on this today and predictably hit a few issues...

1) I can't get the rockslider off, it's rusted solid in the rear bulkhead outrigger - does it need to come off to fit the battery box or can it be done in place? I can get to the bolts for the sill member behind it and should be able to drop that down a few cm without any problems, or does it need to come right off? I need to get the rockslider off at some point anyway as I've got some new ones to fit, but I'd like to try and get the battery box fixed first if it's easy enough to do with it in place.

2) I can't get the seat rails off as the two rear bolts are just spinning in the nuts - these are circular ones that are supposed to be attached to flat plates but they aren't attached any more unfortunately. Do I need to remove the seat frame to fit the battery box? I can probably dremel them off but will need to get some new nuts and bolts too - can anyone confirm what size they are?

3) I seem to have 2 earth posts top right of the attached photo - are they both needed or can I consolidate on one when the new bits get fitted?

4) Do I need to remove the black bolted strip at the back which holds the seatbox lid down to be able to drill out the rear plate, or is that where my Eberspacher is? Just need to work out how much more disassembly I need to do!



Battery Box.jpg

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Are you putting a new "end" panel on the seatbox ? I renewed mine as they were corroded but can't remember if it was part of the battery box kit....

There are three bolts that go down through the side panel and the return flange of the battery box and through the sill so you may not even need to remove your rockslider, chances are the bolts will shear off anyway!

As for removing the seat rail then yes as you need access to all the existing rivets to drill them out; it just makes it easier. The top filler panel at the door end on mine had the seat runner bolted through it so had to come off but it had the earlier two bolt style runners. The captive nuts available for the runners so you just need to rivet new ones in after cutting off the old bolt heads. The lid bracket needs to come off too.

Your earths can be consolidated, I'd be earthing on the battery though with it being there.

If you scroll up and look at my old and new side by side you can see the fresh drilled rivets its in the correct orientation as if your looking in the door so that should give you an idea of where and what needs drilled.


bolts are m8x25, captive nut is AWR4731

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Apologies Richard, I missed this thread popping back up.

My memory of the repair is pretty sketchy, however I definitely had to remove the rock slider things I had fitted at the time. It may be possible to slide the battery box flange out from between the seat box and sill member, but I'm not sure.

Your stuck seat rail bolts - if you remove the centre cover panel you'll be able to get to the nut on the inner one with a spanner. The outer one would be more tricky, if you can't get to it underneath you'll probably have to cut/drill the bolt head off.

I never got round to painting/sealing mine, which I now regret as there's a 1/4" layer of dried mud/silt from various off road excursions. It would be wise to seal up the joints at least - if mine ever comes apart again sufficiently I will take the opportunity to do it then.

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