Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - 6 volt to 12 volt battery

I am doing a few jobs at the same time as from my previous post ie rocker cover..still on going..
On this update I am replacing the 2 x 6 volt batteries to 1 x 12 volt..
I have the new 12 volt battery ready to go in, but have read various post on the best way to proceed.
My MGB GT is 1800 1974 one o f the last Chrome bumpers to be made.
I am wary on placing a new 12 volt battery in when I have two spare leads..( how do I deal with these?) plus earthing the is this done..?
Any good clear advice would be appreciated, I am no mechanic but I want to try and update and modify as much as I can get my head round before handing it over to a garage if you get my drift..just trying to keep the costs down on.
Thanks again

J Giddins

I assume you are putting the single battery in the driver's side bin. That way the positive cable that comes from the starter motor should be just fine for the positive side of the new battery.

You will have to transfer the negative cable over from the other bin. It is simply bolted to the body - look in the bin and you will see. Unbolt it and drill a new hole in a similar position inside the driver's side bin. Clean the area so that the terminal on the lead is firmly bolted onto nice clean metal. Connect the battery, positive cable first, then negative.

The cable that went across the tunnel between the original batteries is redundant. Either take it out or tuck it away out of harms way.
Mike Howlett

Jim. Mike is correct. The only point I would make is that I would recommend removing the connecting cable from the system. Regardless of how well it is tied out of the way, there exists a potential for it coming loose. At that point, it can short out the single battery, wrap itself around the propshaft, drag down and catch on something under the car, or some permutation of these things. When you install the ground cable to the chassis, a little grease between the clean chassis and the cable end will help keep corrosion from developing. Rust is not your friend.

Les Bengtson

There have been several posts on this subject, usually with the age old question about which battery to use. Which 12V battery have you bought and does it fit without any modification?
Richard Coombs

Richard Hi,

I have managed to pick up a Varta Blue B18 440 battery from Tayna batteries..this is the same as a 063 which other MGB owners have recommended..

J Giddins

Some have had to modify this battery type. Have had to?
Richard Coombs

Not as yet, still haven't fitted it, what modifications are we thinking?
J Giddins

Some have to cut the lugs off the bottom of the case (used by modern car battery clamps) to get it in, be aware that this will almost certainly nullify the guarantee if you have to take it back and they spot it. You also have to rejig the clamp arrangements, do *not* leave it to bounce around inside the cradle, shortening its life, and possibly shorting out on the bottom of the lid.

Speaking of catching on the propshaft I replaced mine for some reason but couldn't get the original armoured one. A few weeks later something made me take it out and have a look at it and I found it had been resting on the propshaft as I hadn't attached it to the clip that holds it off the propshaft underneath the panel that is above the batteries, and it had worn half-way through the insulation! Tied it up out of the way. More recently I had to replace it again because of corrosion of one of the connectors, but this time was able to get an armoured cable. Tentatively tried undoing the nut that held the central clip and was amazed it came undone as sweet as, well, a nut! Almost certainly hadn't been touched since Abingdon. The clip was also perfectly reusable after I had peeled the old bit of original armouring out of it.
PaulH Solihull

Ok..I think it may need a Tayna batteries recommended this in regards the 063 for MG's..certainly work a quick call..

J Giddins

Spoke with Tayna, and they said they will honour the Guarantee, if it needs trimming or they will replace with like for like..They know of the problem with MG's and fitting, just the case of not cutting through to the battery cells...
J Giddins

I'm also looking at this. I've tried a 063 type battery and it just fits if you flatten back the lip of the circular orifices in the battery compartment. Otherwise you can't get it out again!. The battery I tried was 207 mm across. Exide do one this width and I think Varta do too. SOme 063s are 212mm which may be too wide. Varta also do another battery which is 175mm wide which looks like the Bosch S2000 (or was it 4000) which has been mentioned on this site as another possibility.
Steve Church

It's the Bosch S4000, but I've yet to buy one.
Richard Coombs

What battery would anybody reccomend to replace two six volts in a V8 I would like to put in one 12v. Vehicle is a 1974 chrome bumper factory V8.
a goldup

Just copied this from the MGC Archive it was my last post on the subject. 1 x Yuasa Elite as I suggest below, I am sure will start your MGB V8.
The mini ratchet strap from Halfords straps round the bottom cage and over the top of the battery and saves
all the fiddling etc with hook bolts.
Also the lugs have to be cut off the battery and yes
this wont effect the Yuasa warranty.
One last point Yuasa are the manufacturers of Lucas batteries.

best of luck


Hi Chaps

Just finished the jobs on FRX & TGT.
I followed Brians Hutchinsons advice on battery choice
Yuasa Elite 12V Battery part no YAB063T. After cutting the end lugs off they just drop straight in.
Anthony Allens advice for fixing with the mini ratchet strap. FRX (positive earth)already had a battery cut off switch so the wiring was dead simple with the terminal positions. TGT (negative earth) just fitted a new battery cut off switch and put the battery in the oposite way round. a job well done
and thanks again for all your suggestions.
'C' You at 'C' Day.
Tim Hodgkinson

I work for Unipart and Yuasa supply our batteries. I think I will go for a GBA4063 as it is a higher AH than the standard GBA3063 at EN 425 A/hr 47 and i believe is listed for a RV8 but will have to check this tomorrow.
Is it best fitted into the right hand box behind the driver.
a goldup

"Is it best fitted into the right hand box behind the driver."

Yes, because the 12v cable is already there. It is much easier to move the earth cable across to that box than extend the 12v cable the other way. Some may say having the battery on the opposite side to the driver gives better balance, but if you compare the weight of the battery with the weight of the car the effect will be irrelevant.
PaulH Solihull

Thanks to all who replied to my query, just letting you now, new battery has been installed and the my MGB has it beat back. Fantastic sound of the engine put massive smiles on myself and Steve a great friend, as we finally got the engine to catch and roar its approval of its new transplant.

Just need the rain to stop, as the sun-roof leaks, before I can take it out for a decent run..

Thanks again


J Giddins

I know the subject has been dealt with and it was mentioned that you fit the battery into the box behind the driver, but for the sake of anyone else thinking about making the conversion I'll give you my slant on it for what its worth. I had just fitted a new high torque starter motor which required a slightly longer power cable, whilst at it I re-routed the cable to the box behind the driver's seat,and then running it thro one of the smaller holes I found that high up, in the transmission tunnel out of harms way was a metal loop which I ran it thro and into the opposite small opening in the box behind the passenger seat to be connected to the battery
+ and retaining the Negative cable in its usual position.To complete the job I cut and shaped sheet aluminium and covered in both boxes pop riveting the panels in place. My aim it to resite the fuel pump in the other box keeping it clear of the elements, and able to access with laying under the car. Peter
P Mayo

"and able to access with laying under the car"

With*out*, I presume you meant, and a good idea.
PaulH Solihull

yes 'WITHOUT" sorry Paul, must have been having a senior moment.
P Mayo

This thread was discussed between 15/08/2010 and 24/08/2010

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.