Hello, I noticed your conversation and wanted to offer some assistance. I can answer a lot of battery questions, but I'll never be able to explain why the Battery Council International (BCI) picks the number designations they do for automotive batteries. Group 27 batteries are larger than Group 34 batteries and Group 31 batteries are larger than both Group 27 and Group 34 batteries. You can view all the specification on our BlueTop batteries
here.
In deep-cycle applications, reserve capacity is generally a more important consideration than cranking amps, with more reserve capacity equalling more run time. I also want to stress that trolling motor batteries should be designed for deep-cycle use. Our Group 34M BlueTop with a black case, is the marine equivalent of our RedTop starting batteries and is not designed for deep-cycle use, including trolling motors. Additionally, anytime multiple batteries are run in series or parallel configurations, they must be identical in age, size and type (AGM or FLA). If anyone has any questions about our batteries, I'll do my best to answer them.
Jim McIlvaine
eCare Manager, OPTIMA Batteries, Inc.
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