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MG MGB Technical - Battery Box Problem

Just having a look over the car before I finally take it for an MOT I have noticed that the battery box has seen better days.

A colleague has mentioned that he has seen a pre-moulded plastic insert which drops into the aperture and bolts to the top of the rear deck. Sounds a brilliant concept with all the benefits of keeping the Great British weather away from the battery.

Anyone heard of this and no where I can get one from.


A I McGee


As these liners have to fit through the opening in the top they tend to be tight on space.

If you are bothered that the condition of the battery box will be an MOT issue fitting a liner will not solve your problem.

On my car I have fitted a small 12v battery in one of the 6v battery boxes. I have some alloy sheet and intend to use it to close the openings in the bottom, back and sides of the, now, spare battery box. This will enable me to use it for tool and spares storage. Just another job on my to do list.

You could do the same to keep the road mess off the batteries.

David Witham

Andrew, David is right in that a liner wont help the MOT situation. The 12v battery idea is a good one that I have used on both my 72 cars. I replaced both battery boxes on my roadster but you really only need to replace one if you are going 12v. Some people say to put the battery in the drivers side but I went for the NS as the pump protrudes into the drivers box. I would therefore avvise that you fit a new box which is an easy job. Take out the rear seat and the heelboard carpet. You can then see the spotwelds clearly. Dress the are with a wire brush to highlight them all then drill them all out and knock off the original battery box. Fit the new one and locate tightly with self tappers then weld through all the holes and dress and hand prime and paint the repairs.
Iain MacKintosh

Hi all.

If you do go for some sort of liner I would put some drain holes in the bottom (in case some water gets in) and allow some ventilation at the top to allow fumes to get out.


So for your MOT, your cars have to have all the original structure?
Bruce Cunha

"put some drain holes in the bottom (in case some water gets in) and allow some ventilation at the top to allow fumes to get out" which together with more holes for the correct clamps rather renderss the use of the box pointless. They also bring the battery connections closer to the metal lid, which has its own hazards, and can only accomodate a battery snaller than usual.

The boxes are not 'battery boxes' but 'battery hole boxes' for use when twin six-volt batteries hve been replaced by a single 12v, in the empty hole that is left, for additional storage.
Paul Hunt 2

Actually what I was after (or understood to have been manufactured) was a box that the battery could go into. On my race midget we have a battery box that is mounted in the front passenger footwell (made of heavy duty plastic resin), the terminal are sealed under the bolt down lid. I was wondering whether anyone manufactured one of these for the B.

thanks for all your comments.

A I McGee

Hi Bruce.

The UK MOT is quite tolerant of modifications, obviously provided that they don't compromise safety.
(I remember chatting to a Frenchman who told me that the French authorities will not accept modifications).

I would guess that Andrew was concerned that the MOT inspector would think that his battery was at risk of dropping onto the road, and the box would resolve this problem.


Actually the French *will* accept modifications, but you have to supply an example for crash-testing first! Which somewhat reduces the incidence of modifications. A friend who has had an MGB from new and converted it to V8 some years ago was gutted when he found there was no way of importing the car into France when he moved there to live.
Paul Hunt 2

Wellllllll, that's another reason I won't move to France :)
Mike MaGee

I don't understand why the plastic box won't solve the MOT concern? As I understand it, it is bolted to the deck and takes the weight of the battery so the old frame is redundant (isn't it?)

John Tampkins

Well that was my thought process anyway.

Will keep on looking!.

A I McGee

The ones I have seen aren't bolted to anything, they just sit in the hole. There is a narrow plastic flange sitting on the deck, which I wouldn't have thought was strong enough to take the weight of a battery bouncing around, and yes the bottom of the box does sit above the cradle.
Paul Hunt 2

I agree with Paul on this one, best use for the liner is as a tool box (or on my car for the fuel pump and swirl pot). An Optima battery will not fit in it, not sure what 12v will, and I wouldn't count on it to hold the battery up. But there's not much to that stock battery support and unless the sides have rusted away it should be a simple matter to replace the straps on the front and back bottom corners.

Jim Blackwood

My 12v is an Eco Deta 075 part no 85558.

It has 10% more cold cranking than the 2x 6v setup, requires minimal surgery to the box flanges, costs 44 + VAT and spins the engine like a Morris 1000.

Philip Hurst

I brought a plastic box for my rubber bumper GT (12 volt) from MGOC. Have not fitted it yet as current non-standard battery is too large. I would certainly not trust the plastic or the flange width to support the weight of the battery and intend to use normal clamps to hold everything in place.

V Todman

The previous owner fitted a 12V battery under the bonnet on my 1972 B. The original battery boxes are in good shape, and I have been considering returning the battery to the box in back of the passengers seat for better weight distribution, to properly route the oil cooler lines and have good access to the alternator. Having never seen the original set up, what would be the best place to ground the battery to if I move it back to its original location behind the passagengers seat?

There should be a hole in the floor or more likely at the top of the battery box. Clean the area and fit an earth strap connecting this to a proper battery post clamp of the split type and having a bolt on connection for the strap.
Iain MacKintosh

This thread was discussed between 24/10/2005 and 05/11/2005

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