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MG MGB Technical - Battery Box

I am going to have to replace my battery box/battery holder on my rubber bumper MGB.

I note they are quite expensive for what they are.

Has anyone got a pattern to make one up out of sheet steel?

Also, I assume the old one is removed by drilling out the spot welds. Can the replacement be just bolted to the floor or does it need to be welded?



I made a new one for my car out of the 1" angle iron you can buy in B&Q or Homebase. I welded mine together, but a bolted box would be fine. It isn't a structural part of the car so welding isn't essential.

My car originally had twin 6v batteries, but I made one larger box to house a single 12v battery, and use the spare one for my fuel pumps, swirl pot and filter that I needed for the fuel injection. In my photo the top (right side) box is standard size and now houses the fuel components, the lower (Left side) box is extended for the 12v battery.

Mike Howlett

If you do get one of the plastic battery boxes, they will fit in your present battery box hole without any modifications being necessary. RAY
rjm RAY

I think the plastic ones are just an insert. They don't replace a rusty one.

I was hoping to make one out of sheet steel just cutting and bending it to replicate the original - I hadn't considered making one out of angle iron.

I haven't got any welding equipment however I have got access to a MIG welder should I need one but it is not local to me.


Have you been polishing your floors?
Dave O'Neill2

The lip, on the plastic battery boxes, holds the weight of the battery. No repairing of the factory battery box is required. The only reason that my '67 B still has the original battery boxes is because the PO didn't know that she had a pinion seal leak on the rear axle. It coated the boxes in 90W oil and preserved them mosquitos in amber. RAY
rjm RAY

"I think the plastic ones are just an insert."

They are also *supposed* to be used for an empty cradle as a storage area when you have converted from twin 6v to single 12v, they are not intended to put batteries in despite what vendors claim. You need to modify then for the cables and hold-down, and even then they will trap corrosive and explosive fumes if not feed them into the cabin. I can think of no good reason for putting batteries in them, only bad ones.
Paul Hunt

I agree with Paul. My battery frames are still in good nick and I still have twin 6 volt batteries so I've never even considered using the plastic boxes. I do suppose that they can be an alternative if your battery cradles are rusted away. Even so, some minor modifications will be requires for cable clearance and drainage. I once serviced a MGA that, when I took it out for a test drive, the engine died at forty miles an hour. I pulled over to the side of the road and noticed black plastic pieces of material all over the road. Both of the battery boxes had fallen apart from rust and the owner had cobbled together replacements out of scrap metal and old license plates. RAY
rjm RAY

After looking at the new Moss catalog, I see that they state that the top lip of the plastic battery box is designed to hold the weight of the battery. RAY
rjm RAY

I also noticed that the plastic boxes were designed to hold the weight of the battery without needing the steel frame.

Obviously it would have to be cut to allow cables etc to go through which would provide some ventilation, but I am not sure that the battery retaining clamp could be used.

Also, there is a bracket on the rear part of the battery box which supports the join of the flexi brake pipe to rear axle which is quite important to stop the rigid brake pipe from flexing and fracturing!

Never use an MGB with unsecured batteries, this from a motorway patrol police officer:

The (car) was totally destroyed following an accident on my section of the motorway. Unfortunately the driver died in horrifying circumstances which I believe to have been avoidable. I can now relate the circumstances as the inquest has recently been closed as I feel there are important lessons to be noted.
What happened was the car was travelling along the M6 at about 4am when, for reasons unknown, the vehicle left the road on the nearside and took out a traffic sign. The impact caused very severe damage to the underside of the car as the concrete base to the sign was at cross-member height. This impact also took out the fuel pipes. Now as we all know the electric fuel pump keeps on pumping until the electricity supply is cut. With the electrical circuits still open after the crash this is exactly what happened consequently soaking the underside of the car, which after the crash had come to rest on its offside. The driver had suffered serious but not fatal injuries - MGBs are strong cars - but however he was trapped by one leg.

When a passing motorist stopped shortly after the accident, he saw the driver was trapped and able to talk to him as he was conscious. At this time poor maintenance in the battery compartment then contributed to subsequent events. The battery was not of the correct size and was only resting on the battery tray - it was not secured. In the extreme circumstances of the heavy impact, the battery was able to move and short out on the metal body of the car because of the lack of secure fixings. Now remember the petrol pump was still running and pumping fuel out of the fractured fuel lines and tragically the arcing between the battery and metal body ignited the petrol vapour.

Now I do not have to go into the details but suffice to say the death of a conscious person by burning is one of the worst fates you could imagine and I have had the unfortunate experience of witnessing three such deaths in my service.

The moral is clear - secure your batteries properly (gravity is not enough!) and if possible fit an inertia switch as found on the current MG Efi models which would cut the power off from the fuel pump in events of a violent nature. Together these precautions would have prevented the death of this driver. Enough said. Incidentally the fire was so intense that most metal items in the area of the seat of the fire actually melted - including a whole spare wheel.

Paul Hunt

Just do what I did on my 67 BGT I fitted a small 12 Volt battery under the bonnet next to washer bottle great fit short cable to starter switch no cables under the car so no need for boxes or the overpriced plastic boxes from Moss!
I bought two square plastic boxes from Ikea supposed to be for kitchen waste. They are a great fit, just had to trim an inch or two off the top, a couple of self tappers to hold them in place, you can use them for storing tow rope spare parts etc.
Great job,
Cheers Jack.
Jack New Forest

On later cars, that area is taken up with the brake servo.
Mike Howlett

This thread was discussed between 14/08/2013 and 29/08/2013

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