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MG MGB GT V8 Factory Originals Technical - Those twin batteries

Now that the twin 6-volt batteries are getting harder to source and left behind by more modern sealed batteries, does anyone have any experience of using more modern sealed batteries - either twin six-volts as before or a 12-volt that actually fits in one of the vacant battery compartments? I'm on the cusp of replacing my old-style units, and would prefer a less prehistoric and lower-maintenance solution!
David Knowles

Hi David,

I bought a single 50 D20R battery back in January from Latchmere Motor Spares in Battersea 020 7228 3907. This fit straight into one of the twin boxes and worked fine all through the cold weather that we had in Jan/Feb when i was using the V8 as a daily driver. Don't know what the make is offhand (I've got the receipt in front of me which I kept for the 2 yr guarantee) cost 45


Philip Shingler

I use a single 12 volt battery mounted in the front RH of the boot. I bought a battery tray & clamp from an accessory shop & bolted it to the "shelf" that runs across the front of the boot.This way you can use any size battery you like & it's very accessible. I ran in a new cable(2 mtrs long),but you could possibly use the original cable & join a new piece by using a battery switch as a connector. Moss sells or used to , plastic inserts for the original battery trays ,so that these can be used for storage. I lined mine with plywood panels for the same reason but so far have never used them because of the inaccessibility. HTHs Barrie E
Barrie Egerton

Many other threads on this in the Archive. To paraphrase myself, I've replaced the twin 6 volts with a single 12V. It was a "063" size battery, mine is an Exide, grey in colour with blue clip-over terminal covers. It has a 450 Cold crank amp capacity, the biggest CCA I could find in that size. It cost 45-49 can't remember now. Only creative input required is you have to trim the mounting "feet" with a knife, and devise how to secure it in the hole.
Phil Hill

On the MGOC bbs there also was talk on this subject. I replaced my 2x6V with...two new 6 V items! Not only by far the cheapest solution (around 27,5 Pounds inc VAT a piece), but also easiest. And highest Amp rating. They are sealed units, just like modern batteries, and from reputable brand (in Holland, that is); Boogstein Accu Firm from Leerdam (small town). I could drop them of when I hop over end May, should you want to; I heard these 6V's are more expensive your side of the channel?


My V8 has the single 12v anyway, but when I went to replace the single 12v with twin 6's on the roadster found I couldn't get the battery out, it was too big to go through the hole! The carrier had had some welding done, and had been modified to make the base slightly bigger, so I wondered whether 'they' had got the battery in first then welded it up. At one point I was contemplating whether to cut the top or the carrier as the only means of getting it out, but something made me realise that by turning the battery over onto one end while it was still in the box, I could get out out of the top opening! I only mention this as a possible way of getting a sealed large 12v battery into a 6v box, assuming the framework underneath is big enough to take the battery on its base.
Paul Hunt

Since 1976 I have used 1 12volt battery in my 1964 MGB. It is from a VW Kombi and I think fits some Fiats. It is faily square and fits either battery box perfectly. It has now been powering the V8 for 4 months and 2,000 miles without any problems. On occasions I have cranked for a long time with it. However there is one little trick. There is a retaining lug at the bottom of the battery on both sides which needs to be removed with a hacksaw or tenon saw so the sides are smooth. This does not effect the integrity of the battery case. Takes 5 minutes. My batteries last me 3 to 5 years and they are quite cheap here. I am sure the same version is available elsewhere even though the catalogue numbers may be different. In reality you could run 2 of these in parallel.
Another big plus is there does not seem to be the corrosion problems around the terminals.
I will even measure my battery if anyone would like the dimensions. It is handy having the other battery box for fuel filters, non standard fuel pump and pressure regulator.
Ian Buckley


I wonder how many amps your battery gives; 12V units give normally less amps than 6V units. You'd have to use 2x12V to get anywhere near. And then I wonder if it's worth it, because you to buy two batteries and do something with the wiring.


The big question for reliably starting a large engine is surely the capacity of the battery. This is, I understand, confused by the different methods of measuring this in different parts of the world (one of the websites has a rundown on this - apologies to whoever posted it if they are listening - great site). I accept that there are many variables here, apart from the measurement methods, like weather, frequency of usage and age of battery. Nevertheless I would be interested to know how little capacity people get away with as these smaller batteries which fit the orig. trays must have a lower capacity. I use a big boot mounted unit of over 600 CCA (cold cranking amps)and do wonder if it is bigger than I really need.
ian thomson

Single 12V provides all the "current" you need, as Ian T says, different people/countries measure the capacity in different ways. As I mentioned above, I have a 450 CCA single 12V battery which will happily turn over a very little used V8 with 10.5 compression no problem. It's not like the MG is a modern car with electric everything (mirrors, roof, windows, power-steering, seats etc) so the major loads are starting and the cooling fans....... I do have a battery isolator and do cut the battery before I leave the vehicle anywhere, but I haven't had to re-charge it yet. It fits into the existing body holes on the existing frames once the feet are cut off. Sounds the same format case as various US posters in the achive (case size 63 in UK, 26 in US ?? Aus ??) and as Ian B from Aus.
Phil Hill

I think there is a good response from Phil. I left out 2 factors. I have had a battery isolator for over 20 years and would not be without it for the security and fire advantages. The car was a 4 cylinder til I contracted this current disease that you all know about. When I put the V8 in I installed a gear reduction starter; IMI brand, from the US I believe, obtained from a supplier here is Aus. The main reason I went for this starter was clearance. I can remove it in 10 minutes but I am getting away from this thread.
Of course this is a warm climate, but I can crank for a very long time with my one battery, described in my earlier post.
Ian Buckley

Sounds like the perfect opportunity to convert to single 12V. It leaves one hole open for tools, smuggling those Norton parts, ale4picnic, GPSpu ect.

This thread was discussed between 29/04/2002 and 04/05/2002

MG MGB GT V8 Factory Originals Technical index

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