The MGB battery arrangement changed at the introduction of the rubber bumper car in 1974. Chrome bumper cars from 1962 used twin 6-volt batteries wired in series to produce 12 volts, located in battery boxes under the tonneau floor behind the seats and accessible through a joint cover panel.
The standard battery type was Lucas SG9E until June 1966, when BT9E batteries without external bus-bars were introduced. Single-fill batteries followed in June 1969.
From the start of rubber bumper production, a single 12-volt battery was fitted in a new battery box on the right-hand side of the tonneau floor. In February 1976, the original screw-fixing helmet-type battery terminals were replaced by cables with clamp fixings. The distinction matters practically, single 12-volt batteries are widely available through general motor factors, but 6-volt batteries have become increasingly difficult to source through non-specialist channels. The 6-volt battery is available individually or as a pair, with the link cable available separately.
Battery clamp kits are available for both 6-volt and 12-volt applications in standard and stainless steel finish. Battery condition is the correct starting point for any electrical diagnosis on the MGB. A half-charged battery will produce symptoms across the entire electrical system that can be mistaken for component faults elsewhere. The full battery cable set is available as a complete loom, with individual cables available separately.
A standard battery master switch and an FIA-specification master switch are available for security, fire safety, or competition use. Bat-Aid terminal treatment is available for preventing and reversing terminal corrosion.