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MG MGB Technical - Battery Group Size

On my way to exchange a new battery based on some archive articles regarding battery "group" suggested. First, I have an 80 LE and measured all dimensions just now (should have done that before). Base area where battery rests is 8 inches by 10/3/8 inches. Top opening is 7 3/8 by 10 3/4 inches. No battery box is installed, thus purchased a group 26 per archive threads (8 3/16 by 6 13/16). When installed, it's readily apparent that "one bump" and the battery is cockeyed and leaking electrolyte to corrode the metal as well as weakening the battery. The inside dimension or "hole" that the battery could drop through directly to the underside of the car is 6 inches by 7 7/8. Thus, a group 26 battery won't drop through, but is insufficient in length and width to keep from dropping one corner into the opening.

A group 24 is 10 1/4 inches in length (same width and 1 1/8 inch taller), well within the opening tolerance and long enough to keep jolts and vibration from "tilting" the battery and losing its electrolyte. All battery group dimensions are from the BCI battery group size index.

There might be other sizes that fit better also, but if the length secures the fit, the width could be a little narrower to install a bunge cord to secure the battery from extreme bumps.

Please measure your area before purchasing a battery.
Rick Penland

The battery should be secured in place (bolted down). The battery shouldn't be allowed to jump around. Universal battery hold downs are available at most parts stores.
Kimberly

Hey Rick, what part of Missouri are you from?
william fox

The type 26 (63 in the UK) is used for converting the earlier twin 6v to single 12v, as it will fit into one of the battery boxes. The later cars which were fitted with a single 12v battery as standard, had a much larger battery box, hence your problem.

As Kimberly points out, the battery should be securely mounted.
Dave O'Neill 2

The Group 24 is THE battery to have in late RB cars. The person selling it to you will look puzzled as it looks way too big for the car (it came stock on things like the '70 Suburban with 7 liter V8) but it slides right into the holder like it's made for it.
Sam

I exchanged the group 26 for a group 34. The group 24s they had in stock were long warranty and higher priced. The group 34 fits perfectly, but doesn't have the strap to drop it in or remove it. I used a nylon strap to lower it and secured it with a short, heavy duty bunge cord until I get a nut and bolt style hold down of proper dimension.

Thanks for the comment about the different battery areas based on whether your car was made for a single 12V or dual 6Vs. I had a 70 MGB that ran the dual 6Vs, but don't recall what year they came out with the single 12V.

In reply to William about where I am in Missouri, southwest Missouri, between Springfield and Branson.
Rick Penland

Rick...

1974-1/2 was the introduction of the single 12v battery. (First of the rubber bumpered cars).
Rick Ingram

Thanks for the comments. I found some useful information on the internet under "BCI Battery Group Size". It gives all the dimensions and helpful to determine what you need before you go buy a battery. The group 34 that I opted for is exactly the same length and width as the group 24, but an inch shorter in height.
Rick Penland

This thread was discussed between 15/11/2008 and 18/11/2008

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