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Posted: Mar 23, 2020

What is a Group 34/78 battery?

Car batteries come in different sizes...a LOT of different sizes. The DIN sizes actually make some sense, in terms of the numbers relating to the size- an H6 is bigger than an H5 and an H7 is bigger than an H6, etc... However, BCI group sizes can be very confusing, including the Group 34/78 battery size. The "34" number refers to a battery of specific dimensions with top terminals, while a "78" number also refers to a battery of specific dimensions with side terminals.

The physical dimensions of these two batteries, at least relative to their size without terminals, happens to be identical. As a result, batteries that share these physical dimensions can also have both top and side terminals, as is the case with our group 34/78 battery that comes in either a REDTOP or YELLOWTOP. The 34 references the top terminals, while the 78 references the side terminals. Now there are some applications where a group 78 battery will fit, but not a group 34 or group 34/78, because of height clearance issues with the top terminals. There are also some applications where a group 34 battery will fit, but not a group 78 or group 34/78 because of clearance issues with the width of the battery.

So if you need a 34 or a 78 or a 34/78 battery, which one do you choose between an OPTIMA REDTOP or YELLOWTOP? In the instances where you have a choice, select that battery that best suits your application. If your vehicle is relatively-stock from an electrical standpoint, a 34/78 REDTOP is a great choice. If your vehicle has significant electrical demands, which could include things like kids watching videos in the soccer field parking lot to winches, auxiliary lighting and aftermarket car alarms and stereo systems, than a YELLOWTOP designed for starting and deep-cycle use is a better choice.

Also, keep in mind, if you buy an OPTIMA battery from us and a Digital 1200 battery charger & maintainer at the same time, we'll ship them both to your door and add a year of warranty coverage to your battery.

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