Re: Replacement Grp 31 Batteries in the Bow

Bill Kinney


we use firefly batteries as our main house batteries and are very happy with the performance and value. Certainly, they would work well in your application, but…  you will be paying a steep premium over flooded batteries for cycle life and partial state of charge performance that will never be used in the bow thruster only application.

They also have some particularities that might need addressing in the existing charging system.  When not being used, they prefer to NOT be connected to a charger in float mode, rather they should just sit. They also have a different charging voltage profile than standard batteries. Lastly, to get maximum performance and life span they need to be charged rather quickly, at 0.2 to 0.5 C. Can your existing charging system handle these needs? 

If the existing type of batteries have worked for you, I expect they will be the most economical choice in both the long and short run.

Bill Kinney
SM160, Harmonie
Hilton Head, SC, USA

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