What Does Battery Group 34 78 Mean?

The Group 34/78 (sometimes referred to as a 34 78 or 34-78) battery is a standard BCI group size. In OPTIMA batteries, the Group 34/78 battery measures 7.88 inches tall, 10.06 inches long (the longest dimension) and 6.94 inches wide. These batteries are slightly wider than Group 34 batteries, because 34 78 batteries have side terminals in addition to the top terminals, whereas Group 34 batteries only have top terminals.

The numeric designation of 34 78 batteries indicates in this standard size, the batteries have both top (34) and side (78) terminals. OPTIMA offers these batteries in both REDTOPs and YELLOWTOPs. Another common battery size that utilizes both top and side terminals is the Group 75 25 (also sometimes referred to as 75/25 or 75/25). It's a mystery to us, why those batteries reference the side terminals first, while the Group 34 78 batteries reference the top terminals first, but the battery numbers that start with a 7 do indicate side terminals, while those that start with a 2 or 3 (like 25, 27, 35 or 34) reference top terminals.

These side terminals are designed & intended to deliver short bursts of power for starting applications, so if you want to connect a winch or aftermarket stereo system to a 34 78 battery or any other dual terminal battery, it's a good idea to make those connections directly to the top terminals.