Battery Choice - Group 75 or 78?

[C5Jim]

I need to look for a new battery since mine is 4 years old and the voltage is starting to fall below 12.5 volts.

My car takes a group 78 battery, but the group 75 (used in 2001 and up) is a bit smaller and lighter.

Provided it gives no less than 550 CCA, can I use the 75 in place of a 78?
I figure it should bolt right in.

Thanks in advance,
Jim

[c4c5specialist]

Hi there,
Always use the correct battery rating for your car.
Using a smaller one can be done, but a 78 is what is supposed to be there.
Both for electrical stability and correct usage of electrical features.
Allthebest, c4c5

[LT1driver]

ask a battery shop and they can ensure the smaller battery has correct volts, cranking amps etc. they are the experts ask them and they will tell you.

[c4c5specialist]

????? And we are ?????

They do NOT engineer the cars and if engineering thought the 75 class was enough, they would have put it in the c5, like they did the c4.

Allthebest, c4c5

[vettex2]

bigger is better

[LT1driver]

bigger is not always better.

[c4c5specialist]

Alright, lets get back to the facts.

Engineering originally installed 78 class in 1997 to avoid electrical systems issues due to battery usage.

It was found that 75 class batteries, under validation testing, may not always give enough CCA when they got older and tried to support the entire electrical systems function. That being said, look at column lock issues, that alone are mostly caused by ineffective batteries that are NOT capable of supporting the electrical system of c5.

There was ONE exception to this rule.

In 2001, the AGM or absorbent glass mat battery was engineered in a 75 class size but actually had the same amount of plates as the 78 class. This gave the CCA of a 78 class, but the size of the 75 to reduce weight.

Unfortunately, because of reasons unknown to us here, they stopped using the AGM 75 class and went back to the 78 class lead acid type battery.

Allthebest, c4c5

[@lien@ted]

Understood!

[vettex2]

Originally Posted by LT1driver

bigger is not always better.

I meant CCA not size if you are talking about batteries......

[LT1driver]

I agree with you c4c5, I was only trying to suggest the poster to check local so they could show him and explain in person why he should go with what factory put in, sometimes people need to be told/shown in person to make better sense of it...by the way I have the correct size in my 03 because I almost always believe in what the general did/does for us common non-mechanic trained folks.