MGB Tips – 12V Battery:

I regularly get asked for advice about selecting the most appropriate 12V battery to convert an early MGB from twin 6Volt starting batteries.

The placement of two 6V batteries behind the seats of an MGB is an ideal solution to enhance weight distribution across all four wheels. Unless the car’s originality is important to you, these batteries are now becoming expensive, making one 12V battery a smart option.

The trick is finding a battery which is powerful enough, that’s also small enough to fit into the battery carrier.
It needs to be tall, rather than long and wide because it’s not going under a low bonnet like it would in other cars.

Car battery model names are fairly universal across many brands and they represent the dimensions, terminal position & style and battery rating, which I won’t go into at this time.

For an MGB, you should be looking for – NS40ZSMF or NS40ZLSMF because the terminal position won’t matter in an MGB, you just rotate the battery 180° in the carrier to suit the location and length of your battery leads.

Century Yuasa brand batteries in these models are rated at 330CCA and 40Ah with dimensions of 196mmL x 127mmW x 202mmH, which might need the front edge of the battery carrier base to be pushed down a little so the battery will fit in more comfortably.

This is the minimum rating you should be using in an MGB and this is only suitable for cars equipped with an Alternator. MGBs with Generators might struggle with this lower specification battery, especially in winter when lights, wipers and heater fans are on. The Repco branded version is now priced at $159.

For Generator equipped MGBs, and ones fitted with Alternators, a better option is battery model NS40ZLSXMF which is rated at 410CCA and 42Ah and has a similar footprint to the lesser battery but it’s taller at 220mm. The Repco branded version is currently priced at $176. For the small difference in price, every MGB owner should really opt for the more powerful unit.

Personally, I use an Odyssey brand battery, model PC1200. This battery is much more powerful at 550CCA and 44Ah. It does however have two disadvantages, it has a different battery terminal style which requires different ends to be fitted to the battery leads, and also it’s about three time the price!