Engine/Transmission (1998.5 - 2002) why is there a difference in CCA for a AGM battery and Lead Acid battery of same size

[JCyrbok]

been looking at new batteries to replace my 10 year old Optimas and have noticed that there is a difference in CCA of AGM batteries and regular Lead Acid batteries of the same size.



For instance I was looking at a 34/78 AGM Duracell and a standard 34 Duracell and the CCA's were 775 for the AGM and 850 for the regular lead acid.



A quick check of what else was on the rack and it seemed the same for other group sizes too.



I like the advantages of the AGM batteries, particulary the no leaking acid but for more CCA for less money also seems attractive too.



Any idea's, lol



J-

 

[AH64ID]

Look at the Sears Platinum's, AGM with 850 CCA's. They are a re-branded Odyssey which is about as good as it gets.

 

[JR]

If Im not mistaken, an AGM is more of a deep cycle battery than the traditional lead acid battery, hence the lower cca number. Doesnt necessarily mean it has any less capabilities, they just dont discharge as high as the lead acid.

 

[AH64ID]

Not necessarily, there are plenty of AGMs that are pure starting and do not like being deep cycled.

 

[JR]

AH, looking back at my earlier post it was quite misworded. When I said they are more like a deep cycle what I was referring to was the AGM batts are better suited for heavy duty cycles, more like a deep cycle.

I think (and I could be wrong), the traditional lead acid batteries which are designed for delivering quick bursts have thinner plates whereas the AGM typically has slightly thicker plates which allows for a deeper or longer discharge but not quite as fast a discharge, as the op is seeing in his search for batteries.

 

[AH64ID]

It all depends on the design of the battery. The yellow and red top Optima's are both AGM, but one (red) is designed for fast draining for starting and the other is like you said.

The reason Optima's are often lower rated is because they don't make a battery for every application, but have a one size fits many with hold down adapters.

For the most part the AGM's are ± a small number of CCA's, and like my AGM's sometimes a lot more.